Museum of Comparative Zoology HERPETOLOGY LIBRARY Ernst Mayr Library "^ I ) ■ i -> MuseuiTi of Comparative Zoolcgy Harvard University / O 3T-JM-.«Mi-^ t oJ^ftr\x» A HISTORY OF BRITISH FOSSIL REPTILES. BY Sill EICIIARD OWEN, K.C.B., E.R.S., Etc., FOEEIQN ASSOCIATE OF THE INSTITUTE OF FEANCE (ACADEMY OF SCIENCES). VOL. I. LONDON : CASSELL & COMPANY LIMITED, LA BELLE SAUVAGE YAKD. 1849—84. PUINTEil BY J. E. ADLAED, BAETIIOLOMEW CLOSE. This Work was on'p-hial/v issued ERRATA. Vol. I., p. 200. — The genus Polypiycliodon was found to belong to the order Saicropterygia : see p. 455. fi. p. 213. — The marine reptiles associated under the term Enaliosaitria were subsequently divided, as the number of discovered species increased, into the orders Ichlhyoptefjgia and Sauropterygia: see Vol. III., pp. I and 41. lb. p. 405. — The genus Cetiosaiwus was shown to belong to the order Dinosauria : see p. 577. lb. p. 426. — The suggestion at the foot of this page received the con- firmation given in p. 627. in Parts, by private ion of the Fossil ers of new species 'imens, led me to ■Is for the present ubinit them to the ich cannot be re- Six Parts pre- tlie IVoric uiill be to the Publishers. ^ /(J-L /y^ No. of this copy PEEFACE. At the date of the last (posthumous) edition of Cuvier's ' Rechcrches sur les Ossemens Fossiles,'^ descriptions and figures were given of a few fossil Crocodiles, to two Oolitic species of which Geoffroy St. Hilaire had given the generic names of Teleosaunis and Steneosaurus. To these follow descriptions of certain Tertiary Fossils of the order Chelonia, referable to the genera Testudo, Emys, Trlonyx, and, by a Cretaceous form, to the genus Ghelone. To the order Lacertilia Cuvier refers the gigantic extinct Reptile from the Maestricht Chalk, since termed Mosasaurus, and the genus from secondary marls near Monheim to which he assigns the name Geosaurus, not intimating thereby that the species was exclusively terrestrial, but " par allusion a la terre mere des geans" (p. 184, t. x.). Cuvier then gives a summary of Buckland's discovery and description of the remains from the Oxford Oolite, referred to the genus Megalosmirus, "quiparait tenir des Sauriens et des Crocodiles " (p. 185) ; also of Mantell's discovery of fossils from the Weald of Sussex which, after Cuvier's opinion on the dental character, were referred to the genus Iguanodon. Cuvier then proceeds to the description of Collins's and Soemmering's fossils of a volant animal which was determined by Cuvier to be those of a Reptile, and for which he proposes the name Pterodactylus. At that date no evidences of this genus had been recognised in secondary or other formations of Britain. The descriptions and inferences occupying pp. 215, 261, of the concluding volume of the ' Ossemens Fossiles ' are models of palfBonto- graphical work. Cuvier finally translates, with original remarks, the descriptions by Home and de la Beche of the Ichthyosaurus, and those by Conybeare of the Plesiosaurus ; the letterpress figures being limited to a single species of each of these Liassic genera. In conclusion, the immortal Founder of Palseontological Science, writes : — " J'avais aussi le projet de donner des chapitres sur les os d'oiseaux et de serpens ; mais — j'ai du renoncer a cette partie de mon plan " (tome dixieme, p. 475). 1 8vo, 10 volumes, edited by M. Feedebic Cuvieb, 1834 — 1836. ii PREFACE. After referring to the localities in which the remains attributed to birds (as those by Buckland from the Oolitic Slate of Oxford) had been found, Cuvier proceeds : — " Les os de serpens sont encore plus rares, s'il est possible. Je n'en ai vu que des vertebres des breches osseuses de Cette, et une seule des terrains d'eau douce de I'lle de Sheppey " (ib., p. 476). My determination of the Fossil Remains collected by John Hunter and described in the ' Catalogues of the Hunterian Collections ' then under my charge, together with the knowledge of other fossil remains of Reptilia with which holiday geological excursions and the transmissions by local collectors had made me acquainted, begat a conviction that the contributions of Buckland, De la Beche, Conybeare, and Mantell, were but the forerunners of other, probably much more extensive, acquisitions of evidences of Reptilian modifications of vertebral struc- tures from British strata. The application of a grant by the " British Association for the Advancement of Science," in aid of such research, enabled me to visit and personally explore the most promising localities of Reptilian Fossils, the results of which were communicated in two " Reports," published in the ' Transactions of the Association ' for the years 1841 and 1842. The foundation of the " Pal^ontographical Society," in which I co-operated with BowERBANK, Thomas Bell, and Searles Wood, gave subsequent opportunities of putting on record the characters of species of British Fossil Reptiles, at that time new to science. The contribution of such descriptions to the annual volumes was attended with the Society's permission to take, at my own cost, impressions of the plates, after their use by the Society, for the pui'pose of the present work. Its issue in " Parts " exhausted the materials at my command in 1854, and I thought that the new Fossil Reptiles, of which I received indications, would occupy a concluding part of like size and number of plates with its forerunners. But the acquisitions of fragmentary fossils, suggestive of new species or genera of Beptilia, beguiled me into procrastinating hopes of reconstructions which, in some instances have been fulfilled. In the excitement of such quests after draconic forms time passes swiftly, and conviction becomes imperative that it must have a term. Moreover, a Record of what may have been discovered of a given group or class of Natural Objects, especially of Fossil Remains, with figures aiding recognition and comparison, becomes a help and stimulus to rapid and extensive additions. The attempt to grapple with these and make them usefully known has absorbed year liy year such leisure as I could so devote after oflicial duties. The result is summarised in the Indexes to Volumes I and III of the present work. PREFACE. iii Another benefit flows from publication ; the correction, viz. of errors into which the author may have fallen. His acceptance, for example, of Mantell's and Cuvier's determinations of parts of the Iguanodon as the " tympanic bone '' and " clavicle " has been rectified ; in regard to the first, by the accomplished Professoi- Seeley's recognition of it as part of a vertebra of another genus and species ; and, in regard to the second, by Professor Leidy's reference of it to a part of the pelvis, as a pubic bone. The more recent discovery, in a Belgian locality, of an almost entire skeleton of an Iguanodon confirms these rectifications, and almost completes the restoration of that truly remarkable gigantic extinct form of phytophagous Reptile.' And here I cannot but gratefully notice the truly valuable additions to our knowledge of Dinosaui'ian fossils made by the personal labours, enterprise, and science of Professor 0. C. M.arsh, of Yale College, New Haven, Connecticut, United States. Such indications of the numbers of animal forms, which have existed during long epochs of our earth's past histoi'y, give an impression that the labours of an individual devoted to the fossil remains of a limited group can but leave a mere sketch of a fragment of the class — a sketch, however, which cannot fail to be filled in by the labours of successive generations of Palgeontologists. ^ These remains were discovered, in 1881, at Bernis.'sart, and their matrix was determined bv the accomplished Director of the Eoyal Museum of Natural History, Brussels, Prof. Edouaru Dupont, to belong to the Wealden Series ; the fossils are referred by Prof. P. G. Van Beneden to belong to the species Iffuanodon Mantelli. (' Bulletin de I'Academie Eoyale des Sciences de Belgique,' 8vo, 1881, p. GUO.) CONTENTS. PAGEINDEX. SECTION I. FOSSIL REPTILIA OF THE TERTIAUY FORMATIONS. Order— CHELONIA. § 1 • Structure and Homologies of the Carapace and Plastron § 2. Family — Marina. Genus — Chelone Species — Chelone breviceps . — longiceps . — latiscutata — convexa — subcristata — planimentum — crassicostata — declivis — trigoniceps — cuneiceps . — subcarinata Supplemental remarks on the species from Harwich Summary on the genus Chelone § 3. Family — Fluvialia. Genus — Trionyx . Species — Trionyx Henrici — BarbarcB . — incrassatus — marginatus — rivosus — planus — eircumsulcatus — pustulatus PAGE 1 7 10 16 20 21 24 25 27 30 31 33 37 40 44 45 46 50 51 55 56 58 59 60 VI PAGE-INDEX. § 4. — Family — V(tludinosa Genus — Platemys Species — Platemys BiiUockii — Bowerbankii Genus — Emys Species — Emys testudiniformis — leevis — Comjitoni — bicarinata — Delabecliii — crassus Platemys Boiverbankii ? PAGE 61 62 62 66 67 67 70 71 73 74 76 77 Order— CROCODILIA. Osteological Characters § 5. Genus — Ckocodiltjs. Species — Crocodilus toliapiciia — champsoides — Hastingsii § 6. Genus — Alligator Species — Alligator Hantoniensis § 7. Genus— Gavialis Species — Oavialis Dixoni . 80 112 115 120 126 126 129 129 Order— LACERTILIA. § 8. Genus — Lacerta Species — Lacerta eocena 133 133 Order— OPHIDIA. §9- § 10. Genus— Pal^ophis 139 Species — Palceophis typhceus — porcatus 139 144 — toliapicus — lonffus . Genus — Paleryx 146 149 149 Species — Paleryx rhombifer — depressus 150 150 PAGE-INDEX. vu SECTION II. EOSSIL EEPTILIA OE THE CRETACEOUS EOEMATIONS. CHAPTER I. Order— CHELONIA. § 1. Genus— Chelone Species — Chelone Benstedi . — pulchrieeps ■ — Camperi . — indeterminata § 2. Genus — Pkotemys Species — Protemys serrata . PA6B 155 158 162 163 166 169 169 CHAPTER II. Order— LACERTILIA. Tribe — Repentia 173 §4. Genus— Rapkiosaukus Species. — Rapkiosaurus subulidens 173 173 §i- Genus— CoNiosAURUS Species — Coniosaiirus crassidens 175 175 §6. Genus — Dolichosaurus Species — Dolichosaurus longicollis Tribe — Natantia 176 176 183 §7. Genus — Mosasaueus Species — Mosasaurus gracilis 183 . 185 §8. Genus — Leiodon Species — Leiodon anceps . 195 . 196 CHAPTER III. Order— CROCODILIA. § 9. Genus — Crocodiltjs Species — Saulii . § 10. Genus — Polypttchouon Species — Polyptychodon continuus — Mackesoni — inlerruptus 199 199 200 201 201 201 X Vlll PAGE-INDEX. CHAPTER IV. Order— EN ALOSAURIA. § II. Genus — Plesiosaxjrus Species — Plesiosaurus Bernardi — constrictus — Smithii — pachjnmus § 12. Genus — Ichthyosaurus Species — Ichthyosaurus campylodon PAGE 213 214 215 217 218 222 223 CHAPTER V. Order— PTEROSAURIA. § 13. Genus — Ptehodactylus Species^ — Pterodactylus Cuvieri — giganteus (conirostris) — eompressirostris 234 242 245 249 14. CHAPTER VI. Ordkr— DINOSAURIA. Genus — Iguaxodon . . . . Species — MantelU . . . . Concluding Remarks on Tertiary and Cretaceous Reptilia 259 266 272 SECTION III. FOSSIL EEPTILIA OE THE WEALDEN EOEMATIONS. CHAPTER I. Order- DINOSAURIA. § 1. Genus — Iguanodon Species — Iguanodon Mantelli § 2. Genus — Megalosaurus Species — Megalosaurus Bucldandii 275, 373 . 276 . 329 . 332 PAGE-INDEX. IX §3. §4. §5. Genus — HYLJiOSAURUS .... Species — Hylceosaurus armatus Genus — Iguanodon (Supplement No. I) Restoration of the hind foot (Section II, Scpplement No. 1.) Cretaceous Pterodactyles Order— PTEROSAURIA. Genus — Ptekodacttlus .... Species — Pterodactylus Sedgwickii — Fittoni page 355 358 373 373 379 379 379 381 §6. §7. §8. §9- § 10. § 11- § 12. CHAPTER II. Order— CROCODILIA. Genus — Streptospondylus Species^ — Streptospondylus major Genus — Cetiosaueus Species — Cetiosaurus brevis Genus — Pelorosaurus Species — Pelorosaurus Conyhearii Tootli of Cetio- or Poloro-saurus Genus — Poikilopleuron . Species — Poikilopleuron Bucklandii Genus — Goxiopholis Species — Goniopholis crassidens Genus — ^SUCHOSAUEUS Species — Suchosaurus cultridens (Section II, Supplement No Cretaceous Pterodactyles Genus — Pterodactylus Species — Pterodactylus sitnus — Woodwardi (Section II, Supplement No Cretaceous Enaliosaurs . 2.) 1.) Order— SAUROPTERYGIA. § 13. Genus — Polyptychodon . Species — Polyptychodon interruptus . 398 399 405 405 414 416 420 422 426 427 427 433 433 436 436 437 439 455 455 455 PAGE-INDEX. § 14 § 15. (Section II, Supplement No. 1.) Cretaceous Lizahds Tribe — Natantia Genus — Leiodon Species — Leiodon anceps (Section II, Supplement No. 3.) LiASSic Ptehodactyles Genus — Dimorphodon Species — Bimorphodon maeronyx PAGK 460 460 460 463 463 467 SECTION III {continued). § 16. Genus- — Iguanodon .... . Species — Iguanodon Mantelli (Bones of Forearm and Paw) — Foxii .... § 17. Genus — Hyl^ochampsa .... Species — HyltBochampsa vectiana 503 503 520 531 531 SECTION IV. MESOZOIC REPTILIA. Order— PTEROSAURIA. §1. Genus — Pterodactylus Species — Pterodactylus Baviesii — sagittirostris . 537 . 537 . 538 §2. Genus — Goloborhynchus . Species — Goloborhynchus clavirostris Pterodactylus Mansclii — Pleydellii — incertus — Kiddii — Buncani — Aclandi — Marderi . 542 . 542 . 544 . 544 . 544 . 546 . 545 . 545 . .548 Order— DINOSAURIA. § 3. Genus — Bothriospondylus Species — Bothriospondylus su_^ossiis 551 551 PAGE-INDEX. XI § 4. Genus — Omosaurus Species — Omosaurus armatus § 5, Genus — Cetiosaueus Species — Cetiosaurus longus § 6. Life and kinship of Dinosaurs Carpal spine of Omosaurus . § 7. Genus — Chondrosteosaurus Species — Chondrosteosaurus gigas Genus — Cardiodon Species — Cardiodon rugulosus § 8. Genus — Poikilopleuron Species — Poikilopleuron pusillus PAGE 556 556 577 577 595 620 622 622 625 625 , 627 , 628 Order— CROCODILIA. §9- Genus — Goniopholis Species — Goniopholis sitmts . — tenuidens 631 631 642 § 10. Genus — Petrosuchus Species — Petrosuchus leevidens 634 634 § 11. Life and kinship of Crocodilia 636 § 12. Genus — Bracuydecxes Species — Brachydectes major — minor 643 643 644 § 13. Genus — Nannosuchus 646 § 14. Species — Nannosuchus gracilidens Genus — Theriosuchus Species — Theriosuchus pusillus 646 650 650 Order— LACERTILIA. § 15. Genus — Ncthetes Species — Nuthetes destructor Dermal bones (or "granicones ") 655 655 656 CONTENTS. SYSTEM-INDEX. Order— CHELONIA. Family — Marina (turtles). PAGE Genus — Chelone ...... 7 — 155 Species — Chelone breviceps . . 10 — lonyiceps . . 16 — latiscutata . 20 — convexa subcristata . 21 . 24 — planimentum ' 25, 40 — crassicostata 27,42 — declicis . 30 — triyoniceps 31 — cuneiceps . . 33 — subcarinata . 37 — Banstedi . . 158 — pulchriceps . 162 — Camperi . . 163 Family — Fluvialia (soft turtles). Genus — Tbionyx . . . . . • .45 Species — Triony X Henrici . . 46 — Barbaree . . 50 — incrassatus . 51 — marginatns . 55 — rivosus 56 — planus . 58 — circumsulcatus . 59 — pnatulatus . 60 Family — Patud '.nosa (terrapenes or freshwater tortoises). Genus — Emys • 67 Species — Emys testudinifoiTnis . • • • • .67 Irevis . 70 SYSTEM-INDEX. XIII page Species — Emys Comptoni .... . 71 — bicarinata .... 73 — Belabechii .... . 74 — crassits .... 7(i Genus — Platemys .... . 62 Species — Platemys Bullockii . 62 — Bowei-bankii 66,77 Genus — Protemys .... . 169 Species — Protemys serrata .... . 169 Order— LACERTILIA. Tribe — Repentia .... 133—173 Genus — Lacerta .... . 133 Species — Lacerta eocena .... . 133 Genus — Raphiosackus .... . 173 Species — Raphiosaurus subulidens . 173 Genus — Coniosaueus .... . 175 Species — Coniosaurus crassidens . 175 Genus — Dolichosaurus .... . 176 Species — Dolichosaurus longicollis . 176 Genus — NUTHETES .... . 655 Species — Nnthetes destructor . 655 Tribe — Natantia .... . 183 Genus — Mosasaurus .... . 183 Species — Mosasaurus gracilis . 185 Genus — Leiodon ..... . 195 Species — Leiodon anceps .... 196,460 Order— OPHIDIA. Genus — Pal^eophis .... . 139 Species — Paleeophis typkcBus . 139 — purcatus . 144 — toliapicns . 146 — longus .... . 149 Genus — Paleeyx .... . 149 Species — Paleryx rhombifer . 150 — depressus .... . 150 Order— CROCODILIA. Genus — Crocodilus Species^ — Crocodilus toliapicns — champsoides — Hastingsies Genus — Alligator Species — Alligator hantoniensis Genus — Gavialis 112 112 115 120 126 126 129 XIV SYSTEM-INDEX. Species- Geuus — Species- Genus— Species- Genus— Species Genus— Species- Genus— Species- Genus— Species- Genus— Species- Genus- Species- Genus— Species- Genus— Species- Genus— Species- Genus— Species- Genus— Species Genus— Species- Genus— Species- Genus— Species- Geuus- Species Genus- -Gavialis Dixoni . Stkeptospondylus —Streptospondylus major -GONIOPHOLIS -Goniopholis crassidens — simus . — tenuidens •SUCHOSAURUS —Suchosaurus cultridens -Hyl,«ochampsa —HylcBOchampsa vectiana -Petrostjchus -Petruauchus Icevidens Brachydectes —Brachydectes major — tninor -Nannosuchus —Nannosuchus gracilidens -Theeiosucuus —Theriosuchus pusillus Order— DINOSAURIA ■Cetiosaukus — Ceiiosaurus brevis lungus -BOTHKIOSPONDYLUS —Buthriospondylus svffossus — longus — magnus -Chon'drosteosaukus — Chondrosfeosaurus gigas -Omosaurus — Omosaurus armatus — hastiger -Cardiouon — Cardiodon rvgulosus -Pelorosaurus — Pelorosaurus Conybearii -Htl^osaurus — Hylceosaurus armatus -Poikilopleuron . —Poikiiopleuron BucMandii — pusillus -Megalosaurus — Megalosaurus BucMandii -Iguanodon PAGE 129 398 399 427 427 631 642 433 433 531 531 634 634 643 643 644 646 646 650 650 405,577 . 405 . 579 . 551 . 551 . 657 . 658 . 022 . 622 . 556 . 556 . 620 . 625 . 625 . 414 416, 420 . 355 355—358 . 422 422—426 . 628 . 329 329—354 . 275 SYSTEM-INDEX. XV Species— Iff uanodon Mantelli — — (restoration ofhiiul foot) — — (restoration of fore foot) — Foxii (restoration of skull) Order— PTEROS AURI A Genus — Pterodactylus Species — Pterodactylus Cttvieri — conirostris — compressirostris — Sedgwickii — Fittoni — simus Woodwardii — Baviesii suyittirostris — Manselii — Pleifdellii — Kiddii — Duncani — Aclandi — Marderi Genus — Coloborhynchus . Species— Coloborhy7ichus davirostris Genus — CiiioKHYNCHUs Species — Criorhynchm simus Genus — DijiorphodOxN Species — Dinwrphodon macronyx PARE 27«— 328 . 373 . .i03 . 520 . 234 . 242 . 245 . 249 . 379 . 381 . 437 439—454 . 537 . 538 . 544 . 544 . 54ti . 547 . 547 . 548 . 542 . 542 437—550 437—550 . 463 4(i7, 548 Order— EN ALIOSAURIA. Sub-order — Sauropterygia. Genus — Plesiosaurus Species — Plesiosaurus Bernardi — ■ constrictus — Smithii — pachyomus Genus— PoLYPTYCHODON Specks— Polyptychodon continuus — interrnptus Sub-order — Ichthyoptkrygia . Genus — Ichthyosaurus Species — Ichthyosaurus campylodon • 213 214 215 217 220 . 218 200, 455 . 201 209 222 223 A HISTOEY OF BRITISH FOSSIL REPTILES. CHAPTER I.— Order CHELONIJ. TURTLES, TERRAPENES, AND TORTOISES. ^ 1. Introdadory BeDiarks on the Ilomolor/i/ of ihe Carapace and Plastron. The majority of the Fossil Chelonians, defined or descril^ed in my ' Report on British Fossil Reptiles,'* belonged to the marine division of the order, and as the species of this family depart least from the ordinary reptilian type in the modification of the -bones of the trunk, composing the characteristic thoracic-abdominal case of the order, I propose to commence with them the descriptions of the Fossil Reptilia which form the subject of the present Chapter. In order to facilitate the comprehension of the descriptions and figures of the fossil Chelonians, a brief notice is premised of the composition and homologies of the carapace and plastron, or roof and floor, of that singular portable abode, with which the reptiles of the present order have been endowed in compensation for their inferior powers of locomotion or other modes of escape or defence. In the marine species of the Chelonian order, of which the Chelone nujdas may be regarded as the type, the ossification of the carapace and plastron is less complete, and the whole skeleton is lighter than in those species that live and move on dry land: but the head is proportionally larger — a character common to aquatic animals, — and being incapable of retraction within the carapace, ossification extends in the direction of the fascia, covering the temporal muscles, and forms a second bony covering of the cranial cavity ; it is interesting to observe, however, that this accessory defence is not formed by the intercalation of any new bones, but is due to exogenous growth from the frontals (ii), parietal (7), postfrontals (12), and mastoids (s, see Pis. 1 1, and MA). The bony carapace is composed externally of a series of median and symmetrical pieces (fig. 1, cJi, f<\—s\\, pij), and of two series of unsymmetrical pieces (phs, m\ — 12) on each side. The median pieces have been regarded as lateral expansions of the summits of the upper vertebral (neural) spines,! the median lateral pieces as similar * Reports of the British Association for the Advancement of Science, 1841, p. \CM. t Cuvier, Lemons d'Anatomie Comparee, torn, i (1799), p. 212. B 2 BRITISH FOSSIL REPTILES. developments of the vertebral ribs (pleurapophyses),* and the marginal pieces as the homologues of the sternal ribs (h£emapophyses).t I must refer the reader to my Memoir, communicated to the Royal Society, Jan. 1 8, 1849, for the facts and arguments which have led me to regard these pieces, as dermal ossifications, homologous with those that supjjort the nuchal and dorsal epidermal scutes in the crocodile. Most of the bony pieces of the carapace are, however, directly con- tinuous, and connate, J with the obvious elements of the vertebrae, which have been supposed exclusively to form them by their unusual development ; the median pieces have accordingly been called " vertebral plates," and the medio-lateral pieces " costal plates." I retain the latter name, although with the understanding and conviction that they are essentially or homologically distinct parts from the vertebral ribs or pleurapophyses with which they are connate and more or less blended. But, with regard to the term " vertebral" plate, since the ribs {costaf) are as essentially elements of the vertebrse as the spinous processes themselves, I have been in the habit, in my Lectures, of indicating the median series by the term " neural plates," which term has the further advantage of removing any ambiguity from the descriptions that might arise from their being mistaken for the superincumbent epidermal shields, which are likewise called " vertebral plates" in some English works. § The term " marginal" is retained for the osseous plates forming the periphery of the carapace ; but the median and symmetrical ones, which seem also to begin and end the " neural" series, are specified, the one by the term " nuchal plate," the other by that of " pygal plate." The " neural plates" are numbered as in the classical Monograph of Bojanus.|| In the subjoined woodcut of the carapace of the loggerhead turtle {Chelone caouanna) (fig. 1), ch is the nuchal plate ; si to si l the neural piafes ; jjIi topis the costal plates ; and m 1 to m 1 2 the marginal plates. The carapace is impressed by the superimposed epideiTnal scutes or shields, which consist of a median series, called " vertebral scutes" v\ to vb ; * Ibid. p. 211. Rathke has recently supported this determination by arguments drawn from the mode of development of the carapace. See ' Annales des Sciences Naturelles,' Mars, 1S4G ; and ' Ueber die Entwickelung der Schildkroten,' -Jto, 1848, where he says, p. 10.5 : — " Ausser den Rippen und den horizontal liegendeu Tafein, zu welchen sich die Dornfortsiitze des zweiten uiul der sechs folgendeu Riiekenwirbel aasbilden, dienen bei den erwachsenen Schildkroten zur Zusammeusetzung des Riickenschildes noch eine oder mehrere Knochenplatten," viz. the "marginal plates." I have shown how Rathk6 was deceived by over-estimating the character of connation, in my ' Observations on the Development of the Carapace and Plastron of the Chelonians,' which conduct to a diiferent conclusion to that at which Cuvier and Rathke have arrived. (Philosoph. Transactions, IB^'J.) f GeofTroy, Annales du Museum, tom. xiv (1809) p. 7. X This term is used in the definite sense explained in my work on the '.\rchetype of the Vertebrate Skeleton' (8vo, V. Voorst, p. 49), as signifying those essentially different parts which are not physically distinct at any stage of development ; and in contradistinction to the term " confluent," which applies to those united parts which were originally distinct. § See Grifliths's translation of Cuvier, vol. ix, Synopsis of Regtilia, p. G — " fifth vertebral plates prominent." [| Anatome Testudinis Europceee, fol. 1821, tab. iii and iv. CHELONIA. Fie:. 1. Carapace of the Loggcrlicad Turtle (Chelone cuouamui). and of a lateral series of " costal scutes " there is also a peripheral series of " marginal scutes'" corresponding with and impressing the mar- ginal plates. The nuchal ])late [cJi) is remarkable for its breadth in all Chelonia, and usually sends down a ridge from the middle line of its under surface, which is attached by ligament to the summit of the neural arch of the first dorsal vertebra. The first true neural plate, si, is much narrower, and is connate with the summit of the neural spine of the second dorsal vertebra ; the succeeding vertebral neural plates, S2 — ss, have the same relations with the succeeding neural spines, but the ninth, tenth, and eleventh, like the nuchal {ch) and pygal {j}i/), plates are independent ossifications in the substance of the derm. The costal pieces of the carapace are supra-additions to eight pairs of pleurapophyses or vertebral ribs, those, viz. of the second to the ninth dorsal vertebrae inclusive. The slender or normal portions of the ribs project freely for some distance beyond the expanded and connate portions (" costal plates" of the carapace), along the under surface of which the rib may be traced, of its ordinary breadth, to the neck and head, which liberates itself from the costal plate to articulate to the interspace of the two contiguous vertebral bodies, (centrums), to the posterior of which such rib properly belongs. The woodcut (fig. 2) illustrates this structure : ch shows the inner side of the nuchal plate ; c\ is the first rib, articulated to the fore part of the body of the first dorsal vertebrae ; ph is the first rib of the carapace (the second rib of the dorsal series), connate with the first costal plate ; ph to jih, are the succeeding ribs and costal plates of the carapace, the interspaces between their own vertebral body, and that of the preceding vertebra luucr view of carapace of the Loggerhead (Chelone caouanna). The heads of the ribs articulate to BRITISH FOSSIL REPTILES. Fig. 3. The tenth vertel)ra supports a short pair of ribs in Chelone and in Enn/s, but not in Trionyx; and this vertebra is commonly reckoned as a " kuiibar" one. The eleventh and twelfth vertebrae have short and thick ribs, which abut against the iliac bones, and they are regarded as forming the sacrum. The remaining vertebrae belong to the tail, and are " caudal." The costal plates articulate with each other, and with the neural plates by fine dentated sutures. The free extremities of the ribs are implanted into sockets of those marginal plates which are opposite to them. The 1st, 2d, 3d, and 10th, are not so articulated in the loggerhead turtle. But all the marginal plates articulate with each other, and with the nuchal [ch) and pygal {'py) plates by sutures. The osseous basis of the plastron consists of nine pieces, one single and sym- metrical, the rest in pairs. The median piece, *, is the entosternal ; the anterior pair, es, is the episternal ; the second pair, hs, the hi/osternal ; the third pair, ps, the Jiyposfernal ; and the posterior pair, xs, the xiphisternal. With regard to the nature or homologies of these bones, three views have been taken. The one generally adopted, on the authority of Cuvier, Bojanus, and GeoflFroy St. Hilaire, is, that the nine bones of the plastron are subdivisions of a vastly expanded sternum, or breast-bone ; the second view is, that these subdivisions of the sternum are enlarged by combination with ossifications of the in- tegument ;* and the third view, in which Rathke stands alone, is, that they are exclusively dermal bones, and have no homologues in the endoskeleton of other vertebrata.f Since this opinion is given as the result of that celebrated embryologist's observations on the de- velopment of the Chelonian reptiles, 1 have tested it by a series of similar researches on the embryos and young of the Chelone mydas and Testiah indica, and have been led by them to conclusions distinct from any of the three theories above cited. The sternum, like the carapace, is, without doubt, a compound of connate endo- skeletal and cxoskeletal pieces ; but the endoskeletal parts are not exclusively the homologues of the sternum. For the details of the observations, and the special arguments on which these conclusions arc founded, I must refer to the description of PI. 1, and to my paper in the 'Transactions of the Royal Society,' 1849; the homologies of the endoskeletal parts of the plastron will require a brief illustration here from comparative anatomy. * Peters, Observatioues ad Anatomiam Cheloniorum, 1838. t Ueber die Entwickelung der Schildkroten, 4to, 1848, p. 122. Bonos of the plastron of the Loggerhead Turtle (Cliclone caouamid). CIIELONIA. GeofFroy St. Hilaire, whose views are generally adopted, was guided in his deter- mination of the parts of the plastron by the analogy of the skeleton of the bird : which analogy may be illustrated by the subjoined dia- grams of corresponding segments of the thorax of a bird (fig. 4) and of a tortoise (fig. 5). In both figures c is the centrum or vertebral body ; ns the neural arch and spine ; compressed in the bird, depressed and laterally expanded, accord- ing to Geoffroy, in the tortoise ; pi the pleura- pophysis, or vertebral rib, expanded in the tortoise, and with its broad tubercle articu- lating with the expanded spine ; h, li. in fig. 5, answers to h in fig. 4, and is the lipemapo- physis (sternal rib, or ossified cartilage of the rib) ; h, lis in fig. 5, is ha in fig. 4, i. e. exclusively a sternum, with the entosternal piece, hs , developed hori- zontally in the tortoise, and vertically in the bird. 'Yh.Q prima facie simplicity of this view has imposed upon most comparative anatomists : and yet there are other vertebrate animals more nearly allied to the Chelonia than birds, and with which, therefore, comparison should have been insti- Fis. i. Thoracic sej^meut of tlie skeleton of a Bird. Fig. 5. tuted before general consent was yielded to the Geoffroyan hypothesis. If, e. g. we take the segment of a crocodile's skeleton (fig. 6) corresponding with that of the tortoise (fig. 5), the comparison will yield the following interpretation : in both figures c is the centrum : ns the neural arch and spine, with d the diapophysis ; sc a median dermal bony plate (connate with ns in the tortoise) ; pi the pleurapophysis ; sc sc lateral dermal bony plates (connate with pi in the tortoise) ; h, U in fig. 5, answers to li! in fig. 6, an intercalated, semi-ossified piece between pd and k in the crocodile ; h, hs in fig. 5, answers to h, the haemapophysis in the crocodile ; and hs in fig. 5, exclusively represents hs, the sternum in the crocodile. h s lit Thoracic segment of the skeleton of a Tortoise. Fiir. (■). Thoracic segment of the skeleton of a Crocodili 6 BRITISH FOSSIL REPTILES. Such a comparison, in my opinion, guides us to a truer view of the homologies of the thoracic-abdominal bony case of the Chelonians, especially with regard to the lateral or parial pieces of the plastron, than the comparison exclusively relied on by Geoffroy St. Hilaire. The Plesiosaurus, by its long and flexible neck, small head, expanded coracoid and pubis, and flattened bones of the paddles, comes much nearer to the turtle than the crocodile does ; and its abdominal ribs, or hfemapophyses, are more developed than in the crocodiles ; a comparison of the ventral surface of the skeleton, such as that figured by Dr. Buckland, in his ' Bridgewater Treatise,' vol. ii, pi. 18, fig. 3, will show how clearly those abdominal ribs would correspond with the hyosternals and hyposternals of the turtle, if they had coalesced together at their middle parts, leaving their outer and inner extremities free. With regard to the marginal pieces m\ — «?12, figs. 1 and 2, although the comparisons illustrated by figs. 4, 5, 6, show that they answer rather to the intercalated piece // in the crocodile than to the entire sternal rib h in the bird ; yet the phenomena of their development demonstrate that they are exclusively bones of the dermal skeleton, retaining their freedom from anchylosis with the endoskeletal elements, hke the nuchal, pygal, and last three neural plates {ch, py, sg, s\o, and .s-il, fig. 1). This insight into their true nature teaches why they do not correspond in number with the vertebral ribs or pleurapophyses (ph — p/s, fig- 2). In the loggerhead turtle, for example, the first three and the tenth (?/?i, ni2, m's, and m\o) have no corresponding pleur- apophyses articulating with them ; and if even ci be supposed to correspond to ms, there are no rudiments of ribs answering to mi and ?«2. The marginal plates are not constant in number ; the Clielone mi/das has two less than the Chelone caouanna has. Some species of Trionyx {Cryptopua, Dum. and Bibron) have a greater number, but of smaller and less regular size, confined to the posterior part of the limb of the carapace; in other species of Trionyx {Gymnojms, Dum. and Bibron), and in Spharyis, the marginal part of the carapace retains its embryonic condition in all Chelovia, as a stratum of cartilaginous cells in the substance of the derm, forming the thickened, flexible border of the carapace. The rudiments of the hyosternals and hyposternals (PI. 1, fig. 2a) have originally the form of sternal or abdominal ribs ; extend transversely, and rise at their outer extremities to join those of the first and sixth pair of vertebral ribs, completing the hsemal, or inferior vertebral arch (ib., fig. 14), without the interposition of any of the marginal pieces, which are merely applied to the outer sides of the haemapophysis or sternal ribs. The expansion of the parts of the plastron, especially in the fresh- water and land tortoises, is due chiefly to the ossification of a layer of cartilage-cells in the substance of the derm, which ossified plates are connate with the more internal elements of the plastron, representing the sternum and sternal ribs. In the following descriptions of the fossil Chelonia, the terms ' entosternal, episternal, hyosternal, hyposternal,' and ' xiphisternal,' will be used as absolute designations of the combined endoskeletal and exoskeletal bones of the plastron, wdthout implying assent to the hypothesis that first suggested those names to Geofi"roy St. Hilaire. CHELONIA. 7 The scapular and pelvic arches, and the bones of the extremities of the Chelonia, are described and figured in the ' Ossemens Fossiles' of Cuvier ;* where, also, the figures of the modifications of the carapace and plastron, in the fresh- water and land tortoises, will sufiice for the purpose of ulterior comparisons with the fossils described in the present work, if they be understood according to the homologies above discussed, and which are illustrated by the figures 1 and 2 of the carapace, and fig. 3 of the plastron of the Chelone caouanna. § 2. Family Marina. Genus Chelone. With regard to the more immediate subjects of the present chapter, it must be admitted that the important generalizations of Cuvier and Dr. Bucklandf have been confirmed, but not materially extended, by subsequent observations on the remains of reptiles of the Chelonian order. Cuvier, after admitting that his results in regard to the tortoises were not so precise as those relating to the crocodiles, sums up his chapter on the fossil Chelonia in the following words : "Toutefois nous avons pu nous assurer que les tortues sont aussi anciennes dans le monde que les crocodiles ; qu'elles les accompagnent gcneralement, et que le plus grand nombre de leurs debris appartenant a des sous-genres dont les especes sont propres aux eaux donees ou a la terre ferme, elles confirmentles conjectures que les os de crocodiles avoient fait naitre sur I'existence d'iles ou de continens nourissant des reptiles, avant qu'il y ait eu des quadrupcdes vivipares, ou du moins avant qu'ils aient ete assez nombreux pour laisser une quantite de debris comparable a ceux des reptiles.";}: - Dr. Buckland also states, in general but precise terms, that " the Chelonian reptiles came into existence nearly at the same time with the order of Saurians, and have continued coextensively with them through the secondary and tertiary formations unto the present time. Their fossil remains present also the same threefold divisions that exist among modern Chelonia into groups, respectively adapted to live on land, in fresh water, or the sea."§ The remains of sea turtles ( Chelone) have been recognised in the Muschelkalk, the Wealden, the lower cretaceous formation at Claris, and the upper chalk-beds at Maestricht. Figures of Chelonites, as that in the Frontispiece to Woodward's ' Synoptical Table of British Organic Remains,' and in Konig's ' Icones Sectiles' (pi. xviii, -fig. 232, a and b), have been published ; but no true marine Chelonian, from Eocene strata, had been scientifically determined prior to the communication of my Paper on that subject to the Geological Society of London. || All the Chelonites from * Tom. V, pt. 2, pi. xii and .xiii. t Bridgewater Treatise (183G), p. 2.5G. X Ossemeus Fossiles, 4to, torn, v, pt. ii, p. 2-J9. % Bridgewater Treatise, p. 256. II Proceedings of the Geological Society of London, vol. iii, pt. ii, p. 570, December 1, 1841. 8 BRITISH FOSSIL REPTILES. Sheppey, described and figured in the last edition of Cuvier's ' Ossemens Fossiles,' for example, are referred to the fresh-water genus Emys ; and the statement in tlie earlier edition of the ' Ossemens Fossiles,' that the greater part of the remains of Chelonian reptiles belong to the fresh-water or terrestrial genera, is repeated. The aim of the Memoir, communicated to the Geological Society in December, 1841, was to show that the conclusion deduced by Cuvier, from an imperfect carapace from Sheppey, which might probably have belonged to a species of Emys, had been unduly extended to other Chelonites, which undoubtedly belonged to the marine genus Chelone ; and that this genus was represented, in the Eocene strata, by at least six species ; the remains of five of which were from the London Clay at Sheppey, and those of a sixth were tolerably abundant in the cliffs near Harwich. In the carapace of the fossil Chelonian from Sheppey, communicated by Mr. Crowe, of Faversham, to Cuvier, and figured in the ' Ossemens Fossiles' (torn, v, part 2, pi. xv, fig. 12), the author of that great work conceived that all the characters of the genus Emys were perfectly recognisable. He points out the proportions of the neural plates, which are as long as they are large ; and in the figure they are represented of nearly a quadrate form, and not rhomboidal. The fifth neural plate in the fragment figured (probably the eighth) is separated from the sixth (ninth) by a point, which is made by the mesial ends of the fifth (probably the seventh) pair of costal plates ; a structure which Cuvier says slightly recalls what he had observed in the Jura Emys of Solcure.* But Cuvier admits that the neural plates {jihufirs vert eb rales) are narrower than those of existing Emydes ; and that the equal breadth of the ribs is a character common to the Cliehnes with the Emydes. Now, in reference to the carapace figured by Cuvier, it is to be observed, that the margins are wanting ; and that the broad conjoined portions of the costal plates are not longer than they might have been, had the fossil belonged to a turtle {Chelone) ; and, consequently, that there is no proof that they were united together by suture throughout their whole extent, as in the Emydes ; but that they might have terminated in narrow tooth-like processes, as in the Chehnes. The narrowness of the neural plates is a character which, with their smoothness, undoubtedly approximates the fossil to the Chehnes ; and, without intending to affirm that the fossil in question does not belong to the family ^wyt/iVfe, which unquestionably existed at the time of the deposition of the Sheppey clay, its determination appears to me to be much less decisive than mio-ht be inferred from the remarks in the ' Ossemens Fossiles.' * Tom. cit., p. 2.34. This structure is not, however, peculiar to the geiuis Emtjs ; in the carapace of the Chelone caouaniin, iu the Museum of the Royal College of Surgeons, the seventh neural plate is separated from the eighth by the junction of the expanded extremity of the seventh rib on one side -with that of the opposite rib, and the eighth neural plate from the ninth by the same modification of the eighth pair of rib ;. A similar modification may also be seen in the carapace of the Trionyx Henrici, PI. 6. CHELONIA. • 9 Mr. Parkinson describes the plastron of a Sheppey Chelonite,* in which the hyosternal and hyposternal pieces are not united, but leave a vacancy in the middle, which he conjectured may have been filled up by membrane. This specimen must have belonged to a specimen at least four inches in length, exclusive of the head and neck. But Cuvier supposes that it may, nevertheless, have belonged to an Emys ; and that the vacancy of the bony sternum merely indicated the nonage of the individual. t The grounds on which Cuvier refers to the genus Emt/s, the imperfect and dislocated carapace and plastron of M. Bourdet's Sheppey Chelonite,;}: are not detailed ; but it is evident that the hyposternals in that specimen are in contact at the posterior moiety of their median margins only ; and that the margins recede anteriorly, leaving a median interspace ; which, as the plastron is nearly a foot in length, can hardly be attributed to the immature state of the individual. And if, as Cuvier supposes, this specimen belongs to the same species as those in the collections of Messrs. Crowe and Parkinson, the same objection to their belonging to a fresh-water tortoise holds good, as to the one figured by M. Bourdet. The question of the reference of these Eocene fossils to the fresh- or sea-water families of the Chelonian order, seems to me to admit of the safest determination by examining the crania of the Sheppey Chelonites ; since the differences in the extent to which the temporal fossse are protected by bone, and in the proportions in which the bones enter into the formation of that covering, are strongly marked in the genera Emi/-s and Chelone. But here Cuvier appears to have been unusually biassed in favour of the Emydian nature of the Sheppey fossils ; for in reference to the cranium, figured by Mr. Parkinson, the affinities of which to the turtle's skull will be presently pointed out, Cuvier obsei'vcs : " elle est probablement aussi d'une Emyde, bien qu'elle participe des caracteres de Tortues de Mer, par la manicre dont le parietal recouvre sa tempe ; mais nous avons vu que VEmys exjjansa differe tres peu de Tortues de Mer a cet egard, et la partie anterieure de la tete fossile ressemble d'avantage a celle d'une Emyde qu' a celle d'une Chelonce, surtout par le peu de largeur de I'intervalle des yeux."^ Now the most striking difference between the temporal bony vault of the Emys expansa and that of any known species of Chelone, is seen in the diminutive size of the post-frontals in this exceptional case among the Emydes, as contrasted with their large size and actual extension over the temporal fossse in the Chelones : — and this difference is accompanied by a proportional diminution in the breadth of the parietals in the true marine turtles. * Organic Remains, vol. iii, p. 268, pi. xviii, fig. 2. f Ossemens Fossiles, torn, v, pt. ii, p. 23.5. X Tom. cit., pi. XV, figs. 14-15. § Tom. cit., p. 235. C 10 BRITISH FOSSIL REPTILES. But the figure in Parkinson's work gives clearly the latter character ; whence also we may infer that it agreed more with the Cheloncs also in the size of the postfrontals ; although the anatomy of the skull is too obscurely delineated to demonstrate this fact. The following important affinities are, however, unquestionably indicated in Parkinson's figure :— first, the large size of the orbits, which are nearly six times greater than those of the Emi/s expanm ; secondly, their more posterior and lateral position ; and Ikirdh/, the greater breadth of the interorbital space : in all which characters the Sheppey fossil closely resembles the true Chelojies, and differs from the only known species of Emys {Podocnemi/s) expansa, in which the temporal openings are protected by a bony roof. That fresh-water tortoises have left their bony cuirasses in the Sheppey clay, will be subsequently shown ; but the evidence of the genus Emi/s, adduced by Cuvier, is incompetent to prove their existence ; and, it may be affirmed, that of the fossils cited by the founder of Palaeontology, some, with great probability, and others with certainty, are referable to the marine genus, Chelone. Without further discussing the question as regards these evidences, I shall proceed to describe the specimens from Sheppey which I have myself had the opportunity of examining ; and shall commence with those which belong undoubtedly to the marine family. Chelone breviceps. Oicen. Plates 16, 17, \1 A. Proceedings of the Geological Society, December 1, 1841; Report on British Fossil ReptUes, Traus. British Association, 1841, p. 1/8. Syn. Emys Parkixsonii. J. E. Gray. — DE Sheppey. FI. v. Meyer (I). Chelone antiqua. Kcenig (?). The first of the Chelonites, which led me to the recognition of this species, was a nearly perfect cranium from Sheppey (PI. \7A, figs. 1 — 4), wanting only the occipital spine, and presenting a strong and uninterrupted roof, extended posteriorly from the parietal spine on each side (figs. 1 and 4, 7), over the temporal openings to the mastoids (ib. 8) ; and formed anteriorly by a great development of the posterior frontals (figs. 1 and 2, 12). This unequivocal testimony of the marine genus of the fossil, is accompanied by similar evidence afforded by the large size and lateral aspect of the orbits (fig. 1, or), the posterior boundary of which extends beyond the anterior margin of the parietals ; and by the absence of the deep emargination which separates the superior maxillary (ib, 21) and malar (20) from the squamosal (27) and the tympanic bone (28) in the fresh- water tortoises, and especially in the Fodocnemys expansa. In general form, the skull of the present species of Sheppey turtle resembles that of the Chelone mi/das, Brongn. : but it is relatively broader ; the prefrontals (figs 1 and CHELONIA. 11 2, 14) are less sloping, and the anterior part of the head is more vertically truncate. The orbits are relatively larger, and extend nearer to the tympanic cavity. The frontals (ib. 11) enter into the formation of the orbits in rather a larger proportion than in Chelone mijdas. In the Chelone caouanna* they are wholly excluded from the orbits. The trefoil shape of the occipital tubercle is well marked (fig. 4) ; the depression in the basioccipital, bounded by the angular pterygoid ridges, is as deep as in most true turtles (fig. 3, 1) ; the lateral borders of the expanded parietals are united by a straight suture along a great proportion of their extent to the large postfrontals. These proportions are reversed in the Podocnemys expanm, in which the similarly expanded plate of the parietals is chiefly united laterally with the squamosal and tympanic bones. In other fresh-water tortoises the parietal plate in question docs not exist. The same evidence of the affinity of the Sheppey Chelonite in question to the marine turtles, is afforded by the base of the skull (fig. 3) ; the basioccipital (1) is deeply excavated ; the processes of the pterygoids (24), which extend to the tympanic pedicles, are hollowed out lengthwise : the palatal processes of the maxillary and palatine bones are continued backwards to the extent which characterises the existing OliL'hnes ; and the posterior or internal opening of the nasal passages, is, in a pro- portional degree, carried further back in the mouth. The lower opening of the zygomatic spaces is wider in the present Sheppey Chelonite, than in Podocnemys ew2Xt)isa. The external surface of the cranial bones in the fossil is roughened by small irregular ridges, depressions, and vascular foramina, which give it a wrinkled or shagreen-like character. The following are dimensions of the specimen described : Licbes. Lines. Length of cranium from the occipital condyle ... 2 9 Breadth of cranium across the malars (26) .... 2 7 Antero-po.sterior diameter of orbit ..... 1 0 The lower jaw, which is preserved in the present fossil, likewise exhibits two characters of the marine turtles ; the dentary piece (fig. 3, 32), e. y. forms a larger pro- portion of the lower jaw than in the land or fresh-water tortoises. The joint of the rami is completely obliterated at the symphysis, which is not longer or larger than in Chelone viydas. The species represented by this fossil, which is preserv^ed in the British Museum, and by a very similar one in the Hunterian Collection (PI. 1 7, figs. 1 — 5), is selected for the first of the Eocene Chelonians to be described in the present Work, because it is one of the few with which the characters of the carapace and plastron can with certainty be associated with those of the cranium. In the rich collection of Sheppey fossils, belonging to J. S. Bowerbank, Esq. F.R.S. * Ossem. Fossiles, torn, v, pt. ii, pi. xi, fig. 2. 12 BRITISH FOSSIL REPTILES. there is a l)eautiful Chelonite (PL 16, figs. 1, 2) including the carapace, plastron, and the cranium, which is bent do\\Ti upon the fore part of the plastron ; and which, though mutilated, dis2)lays sufficient characters to establish its specific identity with the skull of the Chelone brevicej^s just described. Both the carapace and plastron present the same finely rugous surface externally as the cranium ; in which character we may perceive a slight indication of affinity with the genus Trionyx, The carapace (PI. 16, fig. 1) is long, narrow, ovate, widest at its anterior half, and tapering towards a point posteriorly ; it is not regularly convex, but slopes away, like the roof of a house, from the median line, resembling, in this respect, and its general depression, the carapace of the turtle Chelone mydas. There are preserved the nuchal plate (fig. 1, e/<*) with ten of the neural plates {u\ — ?^lo*), only the eleventh and pygal plates being wanting. The eight pairs of costal plates {pl\ — -ph) are also present, with sufficient of the narrower tooth-like extremities of the six anterior pairs of ribs, to determine the marine character of the fossil, which is indicated by its general form.f The nuchal plate (fig. 6, ch) is of a transversely oblong form, with the anterior margin gently concave. Its antero-posterior diameter, or length, is ten lines ; its transverse diameter, or breadth, is two inches. The lateral margins are bounded by two lines meeting at a slight angle ; to the anterior one, the first of the marginal plates, «n, is attached; the posterior line bounds part of the vacant interspace between the first costal plate (jy/l), and the anterior marginal plate. The presence of this plate would prove for the genus Chelone as against Trionyx, were the characters of the cranium, the impressions of the vertebral scutes, and the sternum wanting. The nuclial plate in the Emydes is hexagonal, and nearly as long as it is broad. The Chelonite from the tertiary beds near Brussels, figured by Cuvier,:}: has the nuchal plate of nearly the same form as the present specimen from Sheppey. The neural plates in the Chelone breviceps axQ as narrow as in the Chclones generaWy ; and as in the Brussels Chelonite above cited. The first neural plate (.si, fig. 1) is four-sided; the rest, to the eighth («8), are hexagons of a more regular figure than in the existing Chelones, and are articulated to more equal shares of the contiguous alternate costal plates {ph — ph).* The first costal plate {ph) is directed more outwards, does not incline backwards, as in recent Chelones, and its anterior angle is less truncated than in them. (See fig. 1, p. 3.) The length of the second costal plate [ph) is one inch, nine lines ; more than half of the narrow terminal extremity of the connate rib is preserved ; the propoitions of * These letters refer to the parts in the typical carapace fig. 1, p. 3, by reference to which the cor- icspondiiig parts in the fossil will be readily under.stood. f In an Emijs with a carapace seven inches in length, the corresponding extremities of the ribs would have been united together by the laterally-extended ossification. X Osi-emens Fossiles, torn, v, pt. 2, pi. xv, fig. IG. CHELONIA. 13 the remaining costal plates correspond with those of the Chelone mydas, and Cliel. caouanna. The last pair of costal plates [ph) articulates with the eighth, ninth, and tenth neural plates, but does not overlap or supersede any of them. Not any of the costal plates articulate with those of the opposite side, so as to inteiTupt the series of vertebral plates, as in the carapace of the Chelone caouanna (fig. 1, p. 3), as in Mr. Crowe's Sheppey Chelonite, figured by Cuvier (torn. cit. pi. xv, fig. 12) ; and as is shov^ai in the view of the concave surface of the Brussels species (torn. cit. pi. XV, fig. 16). The ninth neural plate (fig. 1, sg) is the narrowest, as in the Chelones, and as in the Brussels Chelonite, figured by Cuvier, in loc. cit. pi. xiii, fig. 8, instead of beino- suddenly expanded, as in most Emydes. The tenth neural plate («io) expands to a breadth equal with its length ; the eleventh and pygal plates, as already observed, are wanting in the fossil. The vertebral or median ends of the costal plates present a modification of form, corresponding with that of the interspaces of the neural plates to which they are articulated. Only the first pair {pl\) present that form which characterises all but the last pair in the existing Chelones, and in the Brussels Chelonite ; viz., a straight line with the posterior angle cut off; the rest being terminated by two nearly equal oblique lines, meeting at an open angle, as shown in PI. 16, fig. \,pl'l — ph. This character would serve to distinguish the Chelone breviceps, if only a portion of the carapace, including the vertebi-al extremity of a rib, were preserved. The free extremities of the ribs are thicker in proportion to the costal plates, than in the Chelone caouanna, or the Chel. mydas ; and more resemble, in this respect, those of the Chel. imbricata, the species characterised by the size and beauty of the horny scutes, commonly called " tortoise-shell." More or less complete impressions of the five horny vertebral scutes {v\ — vb), and of four costal scutes on each side of the vertebral ones, show the forms and proportions of these characteristic parts, and especially of the median series, notwithstanding they were among the soluble and perishable elements of this ancient turtle of the Thames. The hexagonal vertebral scutes are characterised by the near equality of their sides, and the angle of about 100°, at which the two outer sides meet. The anterior border of the first vertebral scute, i^, has crossed and impressed the nuchal plate, ch, near its anterior border ; this scute has covered the rest of the nuchal plate, and more than half of the first neural plate. The second vertebral scute, v-, includes the rest of the first neural plate, the whole of the second, and almost the whole of the third neural plate. The third vertebral scute, ^;^ includes the hind border of the third neural plate, with the whole of the fourth and fifth neural plates. The fourth vertebral scute includes the sixth and seventh, and very nearly the whole of the eighth neural plates, and the outer angles of this scute terminate over the suture between the sixth and seventh costal plates. 14 BRITISH FOSSIL REPTILES. The plastron of the Chelone brcviceps (PI. 16, fig. 2), although more ossified than in existing Chelones, yet presents all the essential characters of that genus. There is a central vacuity left between the hyosternals {lis)* and hyposternals {ps); but these bones differ from those of , the young Emi/s in the long pointed processes which radiate from the two anterior angles of the hyosternals {hs), and the two posterior angles of the hyposternals {ps)* The xiphisternals [xs) have the slender elongated form, and oblique union by reciprocal gomphosis with the hyposternals {hs), which is characteristic of the genus Chelone. The posterior extremity of the right episternal {es) presents the equally characteristic, slender pointed form. With these proofs of the modification of the plastron of the present fossil according to the peculiar type of the marine Chelones, there is evidence, however, that it differs from the known existing species in the more extensive ossification of the component pieces ; thus the pointed rays of bone extend from a greater proportion of the margins of the hyosternals and hyposternals ; and the intervening margins do not present the straight line at right angles to the radiated processes. In the Chelone mi/das, and Chel. caouanna (fig. 3, p. 4), for example, one half of the external margin of the hyosternal and hyposternal, where they are contiguous, are straight, and intervene between the radiated processes, which are developed from the remaining halves, while in the Chelone hreviceps, about a sixth part only of the corresponding external margins are similarly free, and there form the bottom, not of an angular, but a semicircular interspace. The radiated processes from the inner margins of the hyosternals and hyposternals, are characterised in the Chelone breviceps by similar modifications, but their origin is rather less extensive ; they terminate in eight or nine ra3^s, shorter, and with intervening angles more equal than in existing Chelones. The xiphisternal piece, xs, receives in a notch the outermost ray or spine of the inner radiated process of the hyposternal, as in the Chelones, and is not joined by a transverse suture, as in the Emydes, whether young or old. Subjoined are dimensions of the plastron of Mr. Bowerbank's fossil : Inches. Lines. Shortest longitudinal diameter of hyosternal and hyposternal pieces 2 .5 Transverse diameter of ditto ...... 1 7 Total length of plastron ....... 6 0 The bones of the scapular arch, especially the coracoid, Cuvier has shown to afford distinctive cliaracters of the natural families of the Chelonia ; but the Eocene Chelonites described Jjy Cuvier, did not yield him this opportunity of thus testing their affinities. In the Chelone breviceps here described, the left coracoid (shown in fig. 2) is jireserved in nearly its natural position ; it is long, slender, symmetrical ; cylindrical near its humeral * These letters refer to the parts in the typical plastron, fig. 3, p. 4, by reference to which tlic homo- logous parts in the fossil will be readily understood. CHELONIA. 15 extremity ; flattened, and gradually expanded from its humeral third, to its sternal end; which is relatively somewhat broader than in the Chelonc mi/das and Chdonc caouanna. Inch. Lines. Its length is ..... 1 6 Breadth of sternal end ... 0 7 The characters thus afforded by the cranium, carapace, plastron, and by one of the bones of the anterior extremity, prove the present Sheppey fossil to belong to a true sea turtle ; and at the same time most clearly establish its distinction from the known existing species of Ch(?lone. On account of the shortness of the skull, especially of the facial part and of that which intervenes between the orbit and ear, compared with the breadth of the skull across the mastoids, I have proposed to name this extinct species, Chelone breviceps* By the characteristic shape of the median extremities of the costal plates of the carapace, I have been able to determine some fragmentary Chelonites which have afforded better ideas of the size of the species represented by Mr. Bowerbank's more complete but immature specimen of Chelone brevicejjs. A portion of the carapace of the Chelo-ne breviceps, including the fourth, fifth, sixtli, and part of the third and seventh neural plates, with a considerable proportion of the third, fourth, fifth, and sixth costal plates, is preserved in the museum of Mr. Robertson, of Chatham. The characters of the rugous surface of these bones, and of the equal- sided angles by which the costal plates articulate with the neural plates, do both, and especially the latter, point out the species to which the present fragment belongs. It has formed part of an individual double the size of the specimen above described, and figured from Mr. Bowerbank's collection, and therefore it had a carapace sixteen inches in length. Although the costal plates have been continued further along the ribs than in the younger example, the more complete state of the sixth rib, in Mr. Robertson's specimen, shows that they retained their longitudinally-striated, tooth-like extremities, which, in the sixth rib, is two thirds of an inch in length ; the length of the expanded part being four inches, and its breadth one inch nine lines. The internally prominent part of the rib is much less developed than in Chelone planimentim , and Chelone crassicostata, afterwards to be described. The right hyostcrnals and hyposternals are present, and they likewise preserve the character of the Chel. breviceps in their rugous surface and minor breadth, as compared with those parts in the Chelone lon(jiccps, the extinct species next to be described. Besides the specimens above described, on which the present extinct species of turtle * Proceedings of Geological Society, December 1, IS II, p. 570. Report on British Fossil Reptiles, Trans. Brit. Association, 1841, p. 178. 16 BRITISH FOSSIL REPTILES. has been established, remams of the Chelone hreviccps are preserved in the Hunteriau Museum, and in that of my esteemed friend Professor Bell, S.R.S. I know no other locality of the species than that of Sheppey, in Kent. Chelone longiceps. Owen. PI. 12 and 13. Proceedings of Geological Society of London, December 1, 1841, p. 572. Report on British Fosiil ReptUia, Trans. British Association, 1841, p. 177. The second species of Chelone, from the Eocene clay at Sheppey, which I originally recognised and defined by the fossil skull (PI. 1 2) differs more from those of existing Chelones by the regular tapering of that part into a prolonged pointed muzzle, than does the Chelone brevicejjs by its short and anteriorly-truncated cranium. The surface of the cranial bones is smoother than in the Chel. brcviceps ; whilst their proportions and relations prove the marine character of the present fossil as strongly as in that species. The orbits (PI. 12, figs. 1 and 2, o,) are large ; the temporal fossae (ib. fig. 3) are covered principally by the posterior frontals (fig. 2, 12), and the osseous shield completed by the parietals (7), and mastoids (s), overhangs the tympanic (28), ex- occipital (2), and paroccipital (4) bones. The compressed spine (3)* of the occiput is the only part that projects further backwards. The palatal and nasal regions of the skull afford further evidence of the affinities of the present Sheppey Chelonite to the true turtles. The bony palate (fig. 3) presents, in an exaggerated degree, the great extent from the intermaxillary bones to the posterior nasal aperture which characterises the genus Chelone ; and it is not perforated, as in the soft turtles {Trioni/x), by an anterior palatal foramen. The extent of the bony palate is relatively greater than in the Chelone mt/clas, and the trenchant alveolar ridge is less deep ; the groove for the reception of that of the lower jaw is shallower than in the Chelone mydas, or the extinct Chel. breviceps, arising from the absence of the internal alveolar ridge, in which respect the Chel. longiceps resembles the Chel. caretta. The Chelone lonjjiceps is distinguished from all known existing Chelones by the proximity of the palatal vomer (13, fig. 3), to the basisphenoid (5), and by the depth of the groove of the pterygoid bones (24),* and in both these characters in a still greater degree from the Trionyxes ; to which, however, it approaches in the elongated and pointed form of the muzzle, and the trenchant character of the alveolar margin of the jaws. The followinsr are dimensions of the skull described: Inches. Liues, 4 0 2 6 1 2 Length of the skull ....... Breadth of ditto across the zygomata .... Antero-posterior diameter of orbit ..... * The smaller figures are placed on the parts in Pis. 11 and 17^, by comparison with which the tor- responding bones of the present skull will be readily discerned. CHELONIA. 17 • In a second example of the skull of Chelone longiceps, two of the middle neural plates, and the corresponding costal plates of the right side, portions of vertebrae, with the right xiphisternal piece, humerus and femur, are cemented together, and to the cranium by the petrified clay. The neural plates in this specimen are flat and smooth ; the entire one measures one inch two lines in length, and nine lines across its broad anterior part :— this receives the convex posterior extremity of the preceding plate in a corresponding notch. A small proportion, about one sixth, of the anterior part of the external margin, joins the second costal plate ; the remaining five sixths of the outer margin forms the suture for the vertebral end of the third costal plate. In this respect, the Chel. longicqjs resembles the existing Chelones ; and differs, as well as in the smooth and flattened surface of the vertebral plates, from the Chelone breviceps. The length of the third costal plate, in the fragmentary example here described, is three inches ; the impression of the commencement of the narrow portion, formed by the extremity of the coalesced rib, is preserved. The marginal indentations of the vertebral scutes are not half a line in breadth. The transverse impression between the first and second vertebral scute crosses the first neural plate, nine lines from its posterior extremity ; the second neural plate is free, as in other Chelones, from any impression, being wholly covered by the second vertebral scute. The expanded ribs are convex at the under part, slightly concave at the upper part in the direction of the axis of the shell ; they slope very gently from the plane of the neural plates, about half an inch, for example, in an extent of three inches ; thus indicating a very depressed form of carapace. The xiphisternal bone, like that of Cltel. breviceps, is relatively broader than in the existing turtles, and both the internal and external margins of its posterior half are slightly toothed. A part of the notch by which it was attached to the hyposternal remains upon the broken anterior extremity of the bone. It measures one inch two lines across its broadest part ; its length seems to have been three inches and a half. The humerus presents the usual characters of that of the Chelones ; its length is two inches three lines ; its breadth across the large tuberosities ten lines. The radius and ulna extend in this Chelonite from beneath the carapace into the right orbit ; the radius is one inch and a half in length ; the ulna one inch, three lines in length ; portions of vertebrae adhere also to the mass, the state of which indicates that the animal had been buried in the clay before the parts of the skeleton had been wholly disarticulated by putrefaction. A mass of Sheppcy clay-stone supporting the ninth and tenth neural plates, and the expanded portions of the sixth, seventh, and eighth costal plates of the right side, exhibits the characters of the marine turtles in the great relative expansion of the D 18 BllITISH FOSSIL REPTILES. tenth neural plate ; and the tooth-like continuation of the rib from the posterior angle of the eighth costal plate. These portions of the carapace, from their smooth surface, the impressions of the homy scutes, the form of the vertebral ends, and the concavity of the upper surface of the costal plates, evidently belong to the same species as the fossil last described. A similar mass of Sheppey clay-stone, in Mr. Lowe's collection, supports a larger proportion of the hinder part of the carapace, including the sixth, seventh, eighth, ninth, and tenth neural plates, part of the fifth neural plate, more or less of the last four pairs of costal plates, with the impressions of the third and fourth ribs of the right side ; the impression of apparently the whole of the free, slender, termination of the third rib is preserved, and also that of the fifth rib, confirming the generic characters indicated by the skull. The smooth outer surface of the bones of the carapace, the forms of the neural plates, and the concomitant modification of the commencement of the costal plates articulated therewith, concur to establish the specific distinction from the Cliclone hreviceps, and indicate the specimen to belong to the present species, Cliehnc longiceps. The seventh, eighth, and ninth neural plates progressively decrease in size ; and the ninth presents a simple, quadrangular, oblong- form ; the tenth neural plate suddenly expands, and has apparently a triangular form, but its posterior border is incomplete. The indications of the comparative flatness of the carapace of the Chelone longiceps, (in this respect, as in the elongated and pointed form of the skull, approaching the genus Trio7ti/x,) which were derived from an examination of the foregoing fragments, and particularly of the portion preserved with the cranium on which the species is founded, are fully confirmed by the almost entire carapace and plastron (PI. 13) which, subsequently to the publication of my ' Report on British Fossil Reptiles,' where the present species is first noticed, I have had the opportunity of examining in the collection of Mr. Bowerbank. This carapace, as compared with that of the Chelone hreviceps in the same collection, presents the following differences : — it is much broader and flatter. The neural plates are relatively broader ; the lateral angle from which the intercostal suture is continued, is much nearer the anterior margin of the plate — the Cliclone longiceps, in this respect, resembling the existing species of turtle (see fig. 1, p. 3). The costal plates are relatively longer ; they are slightly concave transversely to their axis on their upper surface, while in Chel. hreviceps they are flat. The external surface of the whole carapace is smoother ; and although it is as depressed as in most turtles, it is more regularly convex ; not sloping away by two nearl)^ plane surfaces from the median longitudinal ridge of the carapace. The following minor differences may be noticed in the two Sheppey Chelonites : the nuchal plate of the Chel. longiceps (PI. 13, fig. 1, i) is more convex at its middle part, and sends backwards a short emarginate process to join the first neural CHELONIA. 19 plate (2) ; in which it resembles the Cliel. wi/Jas. The second neural plate (3) is pentangular, the left anterior corner being produced, and truncate to join with the first costal plate of the left side ; the right posterior corner of the first neural plate (2) being produced, and truncate, to articulate with the second costal plate of the right side. This structure I believe, however, to be an individual variety. In another carapace of the Chelone lon(jiceps, e. g. both posterior angles of the first neural plate are produced, and truncate to articulate with the second pair of costal plates ; and the second neural plate is quadrangular. But the characters of the species are exemplified in more constant modifications of the carapace. The succeeding neural plates to the seventh inclusive (4 — 7) are hexagonal, with the anterior lateral border much shorter than the posterior lateral border, as in Chelone mi/das, and not of equal extent, as in Chelone hreviceps ; they become more equal in the seventh (y) and eighth (9) neural plates, which also decrease in size ; the ninth plate (10) is very small, quadrangular, and oblong, as in Mr. Lowe's fragment. Only a small portion of the last neural plate is preserved in Mr. Bowerbank's beautiful specimen. The impressions of the horny scutes are deeper, and the lines which bound the sides of the vertebral scutes {vy — v-\) meet at a much more open angle than in the Chel. breviceps, in which the vertebral scutes have the more regular hexagonal form of those of the Chel. mi/das. Their relations to the neural plates are nearly the same as in Chel. breviceps. The plastron (PI. 13, fig. 2) is more remarkable than that of the Chel. brevicem for the extent of its ossification ; the central cartilaginous space being reduced to an elliptical or subquadrangular fissure. The four large middle pieces hyosternah {hs) and Injposternah (ps), have their transverse extent relatively much greater as compared with their antevo-posterior extent, than in the Chel. breviceps; and this might be expected, in conformity with the broad character of the bony cuirass indicated by the carapace. The median margins of the hyosternals (lis) are developed in short toothed processes, along their anterior three fourths ; the median margins of tlie hypiosternuls (ps) have the same structure along nearly their whole extent ; the intermediate space between the smooth or edentate margins of the opposite bone is ten lines ; the expanded end of the long coracoid is seen projecting into this space. The xiphisternals (xs) are relatively broader than in Chel. breviceps, or in any of the existing turtles ; and are united together, or touch each other, by the toothed processes developed from the whole of their median margins. The entosternal piece is broad, flat on its under surface, and is likewise dentated at its sides. The outer surface of each half of the jilastron inclines, as in the Chelone mydas, towards a submedian longitudinal ridge. The breadth of the plastron, in the specimen figured (fig. 2), along the median suture, uniting the hyosternals and hyposternals, is six inches : the narrowest antero- posterior diameter of the conjoined hyosternals and hyposternals is two inches nine lines 20 BRITISH FOSSIL REPTILES. The breadth of the plastron, at the junction of the xiphisternals with the hyposternals, is two inches six Hnes. The posterior part of the cranium is preserved in Mr. Bowerbank's specimen (fig. 1), withdrawn beneath the anterior part of the carapace ; the fracture shows the osseous shield covering the temporal fosste ; and the pterygoids remain, exhibiting the deep groove that runs along their under part. It is most satisfactory to have found that the two distinct species of the genus Chelone, determined, in the first instance, by the skulls only, should thus have been confirmed by the subsequent comparison of their bony cuirasses ; and that the specific differences, manifested by the cuirasses, should be proved by good evidence to be characteristic of the two species founded on the skulls. Thus the portion of the skull preserved with the carapace first described (PI. 17, fig. 6), served to identify that fossil with the more perfect skull of the Chelone breviceps (PI. 17, yl), by which the species was first indicated. And, again, the portion of the carapace adhering to the perfect skull of the Chelone longiceps equally served to connect with it the nearly complete osseous buckler (PI. 13, fig. 1), which, otherwise, from the very small fragment of the skull remaining attached to it, could only have been assigned conjecturally to the Chel. longiceps ; an approximation which would have been the more hazardous, since the Chelone breviceps and Chelone longiceps are not the only turtles which swam those ancient seas that received the enormous argillaceous deposits of which the Isle of Sheppey forms a part. Chelone latiscutata. Owen. Plate 24. Proceedings of the Geological Society of London, December 1, 1841, p. 574. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 1/9. A considerable portion, measuring three inches in length, of the bony cuirass of a young turtle from Sheppey, including the first to the sixth neural plates (PI. 24, fig. 1, il — a'G), with the corresponding pairs of costal plates i^ph — ^^/g), and the hyosternal (fig. 2, hs) and hyposternal {ps) elements of the plastron, most resembles that of the Chelone longiceps in the form of the carapace, and especially in the great transverse extent of the above-named parts of the plastron : it diff"ers, however, from the Chel. longiceps, and the other known fossil Chelonites, in the greater relative breadth of the vertebral scutes {v% ws), whicii are nearly twice as broad as they are long. The central vacuity of the plastron is subcircular ; and, as might be expected, from the apparent nonage of the specimen, is wider than in the Chel. longiceps ; but the toothed processes given off from the inner margin of both hyosternals and hyposternals are small, sub-equal, regular in their direction, and thus resemble those of the Chel. longiceps ; the slender point of the episternal is) is preserved in the interspace between CHELONIA. 21 the hyosternals. Both hyostemals {//s) and hyposternals (ps) are slightly bent upon a median longitudinal prominence of their under surfaces. The length of the third costal plate (jjIs) is one inch seven lines ; its antero- posterior diameter or breadth, six lines : in the form of the vertebral extremities of the costal plates, and of the neural plates to which they are articulated, the present fossil resembles the C/iel. longiceps ; but the fifth neural plate is more convex, and is crossed by the impression dividing the third vertebral scute (I's) from the fourth, which impression crosses the suture between the fifth and sixth neural plates in both Chelone longiceps and Chelone breviceps. Whether, in the progressive change of form, which the vertebral scutes may have undergone in the growth of this young turtle, as during the growth of the young loggerhead turtle {Chelone caouanna), hy an increase of length, without corresponding increase of breadth, the impression between the third and forth vertebral scute, might also retrograde to the interval between the fifth and sixth neural plates, I am uncertain, having only had the opportunity of comparing the scutes of the young and old loggerhead turtles, not the skeletons. The change in the lateral angles of the vertebral scutes, resulting from the elongation of the scutes themselves, in the loggerhead turtle, would be similar to that in the Chelone loiifficejjs, as compared with the Chel. lafiscutafa, on the hypothesis that the latter is the young of the former ; but in my present uncertainty I prefer to indicate the specimen in question, by the definite name proposed in my original Memoir ; its description as a distinct species being more likely to attract the attention of Collectors to similar specimens, and to enable them to identify such. Figure 3 gives the degree of convexity of the carapace, and the double curve of the plastron produced by the prominence of the principal hsemapophyses hs ?iXi(\. ps. The left scapular arch (51) is exposed in this view. Chelone convexa. Oioen. Plate 14 and Plate 24, fig. 4. Proceedings of the Geological Society of Loudon, December 1, 1841, p. .575. Report on British Fossil Reptiles, Trans. British Association, 1841, p. 178. The fourth species of Chelone, indicated by a nearly complete cuirass, from Sheppey, holds a somewhat intermediate position between the Chelone breviceps and the Chelone longicejis ; the carapace being narrower, and more convex than that of Chel. longiceps ; broader and with a more regular transverse curvature than in the Chelone bre'oiceps. Although the specimen is equal in size to either of the two with which it is here compared, the costal plates hold an intermediate length, which shows that this character is not due to a difference depending upon age. The fossil in question includes the first to the eighth neural plate inclusive ; the first plate (2) expands behind, and both posterior angles are truncated to articulate with the second costal plates {pli). The second neural plate (3) is quadrate, half as long again as broad, and the second pair of costal plates articulate with this, as well 22 BRITISH FOSSIL REPTILES. as with the first and third plates, as in the specimen of Chel. lonpceps noticed at p. 1 9. The tooth-like extremity of the connate rib is preserved on the right side. The fomth costal plate {ph) is two inches four lines in length, nine lines in breadth ; the angle at which the expanded part contracts to the extremity of the connate rib is well shown on the right side. The third to the eighth neural plates expand anteriorly, and have the anterior angles cut off to articulate with the costal plates in advance ; they diminish in size very gradually, and the antero-lateral borders, formed by the above-named truncated angles, do not increase in length as in the corresponding plates in the Chelone lonyiceps. The vertebral scutes (u2, vz, va) resemble more in form those of the Chel. lonyiceps than of CJicl. hreviceps ; but, notwithstanding that the whole carapace is narrower than in Chel. lonyiceps, the vertebral scutes are broader ; and the lines which converge to the lateral angle have a more marked sigmoid curvature. Chel. convexa. Chel. longiceps. Inclies. Lines Inches. Lines. The length of the second vertebral scute is 1 8 1 8 Breadth 2 (J 2 2 The two succeeding scutes (i'3 and va) more rapidly diminish in size than in either the Chel. breviceps or lonyiceps, and the transverse impression between the third and fourth vertebral scute crosses the lower third of the fifth neural plate, as in Chelone latiscutata. All the scutes have left deeper and rather wider impressions than in the preceding species. The second to the fifth costal plates inclusive, are more equal in length than in the existing Chelone mjdas or Chel. caouanna, and in this character the present species more resembles the Cliel. hnhricata. The distinction of the present from the previously described fossils, already manifested in the structure of the carapace and the form of the vertebral scutes, is more strikingly established in that of the plastron (PI. 14, fig. 2), which, in its defective ossification, resembles the same part in the existing species of Chelone. All the bones, but especially the xiphisternals [xs), are more convex on their outer surface than in other turtles, recent or fossil. The central vacuity is greater than in any of the above-described fossil species. The internal rays of the hyosternals come off from the anterior half of their inner border, and are divided into two groups : the lower consisting of two short and strong teeth, projecting inwards towards the extremity of the entostei:aial {s) ; while the rest extend forwards along the inner side of cpisternals [e.^). The same character may be observed in the corresponding processes of the hj/posternals {ps), which are limited to the posterior half of their inner border. The external radiated process of the hyosternals (/<*) arises from a larger proportion of the outer margin, than in tlie Chel. mydas ; but from a somewhat less proportion than in Cliel. breviceps. CHELONIA. 23 The external process of the hyposternal {ps) is relatively much narrower than in the Chel. hreviceps (PI. 16, fig. 2), and, a fortiori, than in C'/«?/. lonfficeps (PI .13, fig. 2). The straight transverse suture by which the hyosternals and hyposternals of the same side are joined together, is much shorter than in the other fossil Chelones ; and is similar in extent to that in CM. mi/das ; but the following differences present themselves in the plastron of the Chelone convexa, as compared with that of the Chelone mi/das. The median margin of the hyosternals forms a gentle curve, not an angle : that of the hyposternals is likewise curved, but with a sliglit notch. The longitudinal ridge on the external surface is nearer the median margin of the hi/osteriiah and huposternah and is less marked than in the Chelone longiceps ; especially in the hyposternals, which are characterised by a smooth concavity in the middle of their outer surface. Tlie suture between the liyosternals and hi/posterHals is nearer to the external, transverse, radiated process of the hyposternals. The median vacuity of the sternal apparatus is elliptical in the Chel. convexa, but square in the Chel. mydas. The characteristic lanceolate form of the episternal bone («) in the genus Chelone, is well seen in the present fossil. The cntosternal element of the plastron is sub- circular, or lozenge-shaped ; and generally broader than it is long in the Emydians. The true marine character of the present Sheppey Chelonite, so well given in the carapace and plastron, is likewise satisfactorily shown in the small relative size of the entire femur (65) which is preserved on the left side, attached by the matrix to the left xiphisternal. It presents the usual form, and slight sigmoid flexure, characteristic of the Chelones ; it measures one inch in length. In an Emys of the same size, the femur, besides its greater bend, is one inch and a half in length. A Chelonian cranium from Sheppey, two inches five lines in length, in the museum of Professor Bell (PI. 24, fig. 4), and a second of the same species from the same locality, two inches nine lines in length (PI. 25, figs. 1, 2, and 3), in the museum of Fred. Dixon, Esq., F.G.S., belong to the same species, and differ from the cranium of the Chelone breviceps, in the more pointed form of the muzzle, and the less rugose character of the outer surface of the bones ; they equally differ from the Chelone longiceps in the less produced, and less acute muzzle, and the more rugose surface of the bones. The parietals (7) are bounded anteriorly by a semicircular line, not by a semioval one, as in Chel. longiceps, or by an angular one, as in Chel. breviceps. The frontals (11) enter into the formation of the orbits, as in both the foregoing species. The orbits are subcircular, as in Chel. longiceps, not subrhomlwidal with the angle rounded off, as m Chel. breviceps. The postfrontals (12) are large, and forma slight projection at the back part of the supraorbital ridge. The tympanic cavity is larger in proportion than in the Chelone longiceps. The palate is traversed by a deep median, longitudinal groove, between which and the shallower grooves on the inner sides of the alveolar borders, are two well-marked, diverging, longitudinal prominences. The bony palate is longer than in Chelone breviceps, shorter than in Chel. longiceps. 24 BRITISH FOSSIL REPTILES. The symphysis of the lower jaw (PI. 14, fig. 3) is longer or deeper than 'in the Ch clone breviceps, but is convex below from side to side, and not flattened as in the Chelone planimentum. All the specimens of Chelone conv.exa, which I have been able to determine, are from the London clay of Sheppey. Chelone subcristata. Owen. Plate 15. Proceedings of the Geological Society of London, December 1, 1841, p. 5/6. Report ou British Fossil Reptiles, Trans. British Association, 1841, p. 179. The fifth species of Chelone from Sheppey, distinguishable by the characters of its carapace, approaches more nearly to the Chelone caouanna in the form of the vertebral scutes {v\ — va), which are narrower in proportion to their length, than in any of the previously described species ; but the Chelone subcristata is more conspicuously distinct by the form of the fifth and seventh neural plates (6, 8), each of which supports a short, sharp, longitudinal crest ; a similar crest is developed from the contiguous ends of the second and third neural plates (3, 4) ; the middle and posterior part of the nuchal plate (1) is raised into a convexity, as in the Chel. loiifficeps ; but not into a crest. The keeled structure of the above-cited neural plates is more marked than in the third and fifth neural plates of Chelone mydas, which are raised into a longitudinal ridge. The neural plates in the present carapace have the ordinary, narrow, elongated form of those in the true Chelones. The nuchal plate (1) has the middle of its hinder border produced backwards, instead of being emarginate, as in the Chel. brevicejjs (PL 16, fig. 1, ch). The first neural plate in the Chelone subcristata (PI. 15, 2j resembles that in the Chelone conveo:a, but is narrower in proportion to its length ; the second (3) is also quadrangular, as in Chel. convexa, but is narrower ; the third to the seventh likewise differ from those in Chel. convexa only by being narrower ; but the eighth and ninth neural plates are relatively smaller than in any of the befoi'e-described fossils, and resemble those of existing Chelones. The expanded plate is more elevated, and is bent down on each side, with the middle pai't forming an obtuse longitudinal ridge. A part of the contiguous portion of the first (jW/l) and the second {pli) costal plates are raised into a slight convex eminence on each side ; the surface of the remaining pairs of ribs is flat in the axis of the body, but they are more convex transversely to that axis, and in the direction of their own length, than in the other Chelonites. The whole outer surface of the bones of the carapace is as smooth as in the Chel. lonc/icejys and Chel. convexa. Subjoined are comparative lengths of the carapace from the first to the eighth neural plate inclusive : Ch. subcristata. Ch. breviceps. Ch. loiiyiceps. Ch. convexa. Inches Lines. Inches Lines. Inches. Lines. Inches. Lines. 74 56 59 58 CHELONIA. 25 The length of the present fossil carapace, to the tenth neural plate, inclusive, is nine inches. The breadth between the ends of the third costal plates, in a straight line, is six inches six lines. The succeeding costal plates more gradually decrease in breadth, than in the Chel. longiceps and Cliel. corwexa ; and the entire carapace more resembles in form that of the Chel. mi/das, and Chel. caouanna. The epidermal scutes are defined by deep impressions, and as wide, relatively, as in the Cltel. mydas and Chel. convcxa. The length of the second vertebral scute is two inches one line ; its breadth is two inches two lines ; the length of the fourth vertebral scute is two inches three lines ; and its breadth one inch eleven lines, and, at its posterior margin, only nine lines. This scute is narrower than in Chel. caouanna, or any of the previously described fossil species ; the outer angles are less produced than in the Chelone caouanna. Sufficient of the plastron is exposed in the present fossil to show by its narrow elongated xiphisternals (a's), and by the wide and deep notch in the outer margin of the conjoined hyosternals and hyposternals {hs andjo**), that it belongs to the marine Chelones. The xiphisternals are articulated to the hyposternals by the usual notch or gomphosis ; they are straighter and more approximated than in the Chel. mydas and Chel. caouanna. The external emargination of the plastron between the hyosternals and hyposternals, differs from that of the recent turtles in being semicircular, instead of angular ; the Chel. subcristata approaching, in this respect, to the Chel. breviceps. The shortest antero-posterior diameter of the conjoined hyosternals and hyposternals is two inches seven lines. The length of the xiphisternal is two inches six lines ; the breadth of both, across their middle part, is one inch three lines. The name proposed for this species indicates its chief distinguishing character, viz., the median interrupted carina of the carapace, which may be presumed to have been more conspicuous in the horny plates of the recent animal, than in the supporting bones of the petrified carapace. Chelone planimentum. Otven. Plates 18, 19, and 19^. Proceedings of the Geological Society of London, December, 1841, p. 5/6. Report on British Fossil Reptiles, Trans. British Association, 18-41, p. 1/8. Syn. Chelone Hakvicensis, Woodward (^l). The skull of a large Chelone (PI. 18) from the Eocene clay near Harwich, in Professor Sedgwick's collection at Cambridge, resembles, in the pointed form of the muzzle, the Chel. lonyicejjs of Sheppey ; but difi'ers in the greater convexity and breadth of the cranium (fig. 2) ; and the more abrupt declivity of its anterior contour (fig. 1), and from other Chelones by the broad expanse of the inferiorly-flattened symphysis menti (fig. 3). * Refer to fig. 3, p. 4, for these letter?. E 26 BRITISH rOSSIL REPTILES. The osseous roof of the temporal fossae, and the share contributed to that roof by the postfrontals (PI. 18, figs. 1 and 2, 12), distinguish the present, equally with the foregoing Chelonites, from the Emys {Podocnemys) eccpansa, and, a fortiori, from other genera and species of the fresh-water families {Emydidce and TrionicidcB) . In the oblique position of the orbits (fig. 2), and the diminished breadth of the interorbital space (fig. 1), the present Chelonite, however, approaches nearer to Trionyx and Emys than do the previously-described species. But the sides of the face converge more rapidly towards the muzzle. Its most marked and characteristic difference from all existing Chelones is shown by the greater antero-posterior extent, breadth, and flatness of the under part of the symphysis of the lower jaw (fig. 3), whence the specific name here given to the species. The posterior border of the symphysis is defined by a regular semicircular curve, and the rami of the jaw have completely coalesced. Since at present there is no means of identifying the well-marked species, of which the skull is here described, with the Chelonite figured in the frontispiece to Woodward's ' Synoptical Table of British Organic Remains,' and alluded to, without additional description or characters, as the Chelonia ITarvicensis, in the additions to Mr. Gray's ' Synopsis Reptihum' (p. 78, 1831); and since the extensive deposit of Eocene clay along the coast of Essex, like that at the mouth of the Thames, contains the relics of more than one species of ancient British turtles,* I prefer indicating the one here established by a name having reference to its peculiarly distinguishing character, rather than to associate arbitrarily the skull, which gives the true specific distinction, with the ill-defined carapace to which the vague name of Harvicensis has been applied; more especially as the fossil carapace to which the present skull more probably belongs, from the circumstance under which it was discovered, also presents well- marked, and readily-recognisable specific characters. This carapace (PI. 19) is also contained in the museum of Professor Sedgwick, and is understood to have formed part of the same individual turtle as the skull (PI. 1 8) on which the species, Chel. planimentum, was founded. In general form this carapace differs from that of the existing Chelones, in being less contracted and pointed posteriorly than in the Chelone mydas and CJiel caouanna, and more contracted posteriorly than in the Chel. iinhricata. In the proportion which the pleurapophyses (true ribs), bear to the superimposed costal plates, (yV4 — 8) it resembles Chelone mydas, and Chelone caouanna, more than it does the Chel. imbricata. But the pleurapophyses are more prominent and distinct from the costal plates throughout their entire length, than in the Chel. viydas or Chel. caouanna, and present an obtuse angular ridge towards the cavity of the abdomen. The five posterior pairs of ribs of the carapace {pl\ — jih) are preserved, with part * Sir C. Lyell alludes to the Chelonites of Harwich in his ' Elements of Geology :' " This formation is well seen in the neighbouring clifls of Harwich, where the nodules contain many marine shells, and sometimes the bones of Turtles." (Vol. ii, p. 337.) CHELONIA. 27 of the first three on the left side, and one of the coracoids showing the rather sudden and considerable expansion of its sternal or mesial half. The interval between the free extremities of most of the ribs, is about equal to twice and a half the breadth of each extremity ; but the interval between the seventh (jo//) and eighth (jo/s) rib, measured, like the others, at the terminal border of the costal plates, is equal to thrice the breadth of the free part of the seventh rib. In this respect the Chelone planimenttm resembles the Cliel. mydas more than it does the Chelone caoucmna, in which the interval between the free extremities of the seventh and eighth ribs is less than that between the sixth and seventh. The leno-th of the costal plate of the fourth rib is twice that of the eighth rib, as in the Chelone caouanna ; in Chel. mydas it is more than twice as long ; in Chel. imbricata it is only one third longer. The marginal pieces in the Chelone planimentum seem to have been narrow or slender in proportion to their length. The following admeasurements show that, in the large proportionate size of the head, the Chelone planimentum corresponds with the existing turtles : Inches. Lines. Length of the cranium ........ 5 6 Depth of ditto 4 0 Breadth of ditto 5 0 Length of the carapace ........ 15 6 Greatest breadth of ditto . . , . . . .13 0 Plates 18 and 19 satisfactorily illustrate the characteristic forms and proportions of the unique specimen in the Cambridge Museum ; the carapace is figured of its natural size, and shows its inner surface. Chelone crassicostata. Owen. Plates 20, 21, 22, 22^i, and 22-S. Testudo Plana. EOnig. ' Icones Sectiles,' PI. XVI, fig. 192? That the extinct species of Eocene turtles attained larger dimensions than those given above, is proved by a fossil skull from the Harwich clay, in the collection of Professor Bell, which gives the following dimensions : iches. Lines, 8 0 6 0 3 0 1 9 0 9 Total length of the cranium ....... Its greatest breadth ........ The antero-posterior extent of the symphysis menti . The vertical diameter of the orbit ...... do. do. of the nostril ..... This skull differs from that of the Chelone 'planimentum, in tlie minor depth of the ma.xillary bone below the orbit (compare PI. 18, fig. 1, with PI. 20, fig. 2), in the more acute and attenuated muzzle ; but especially in the minor breadth and the difi"erent configuration of the posterior margin of the synqyhysis of the lower jaw (compare PI. 18, 28 BRITISH FOSSIL REPTILES. fio-. 3, with PI. 20, fig. 3). With regard to the comparative anatomy of the bones of the skull, and the pattern of the scutation of the upper surface of the cranium, I regret that the state of the specimen in Professor Bell's collection does not permit the deduction of other distinctive characters which such parts of the cranial organization so satisfactorily afford. A great proportion of the osseous parietes is wanting ; but the cast in the hard matrix of the wide lateral cavities (12, 12), which were over-arched by the expanded postfrontal and parietal bones, indicates the prominence of the postfrontals at the upper and outer angle of the orbits. The orbits {or) appear to have been more ovate and less circular than in the Chelone planimentum ; and the sides of the orbital part of the skull do not converge so rapidly towards the muzzle, but meet at a more acute angle. That a second species of turtle, distinct from the Chelone planimentum,, has left its remains in the Harwich clay, is very decisively demonstrated by the almost complete carapace in the British Museum, the inner surface of which is represented, on the scale of six inches to a foot, in PI. 21. This carapace, both by its general contour, by the relative length of the costal plates to one another, and by their relative breadth to the adherent pleurapophyses beneath, more resembles the carapace of the Chelone imbricata than that of the other known existing species of turtle ; and, as the peculiar characters of the Chelone imhricata are exaggerated, it differs in a proportional degree from the Chelone planimentum. These characters are seen in the great breadth of the pro- minent inferior part of the ribs, and of the free extremity of the rib (/j/i— jyfe), as compared with the total breadth of the costal plate. The intervals between the free extremities, where the expanded plate terminates, are not equal to the breadth of the proper ribs ; in the Chelone imhricata they very slightly exceed the breadth of the free ends of the ribs. This character in the fossil, by which it is so markedly distinguished from the Chelone planimentum, and most other species, has suggested the name Chelone crassi- costata, or thick-ribbed turtle, which is proposed for the present species. The last pair of ribs of the carapace (PI. 21, ph) are remarkably short and thick, and are curved backwards on each side the broad terminal neural plates which they almost touch. In this character the Chel. crassicostata resembles the Chel. imbricata, and differs from the Chel. caouanna (fig. 2, p. 3), and from Chel. mydas. The subequality of length of the costal plates is another character by which the Chel. crassicostata resembles the Chel. imbricata, and differs from the Chel. mi/clas, the Chel. caouanna, as well as from the Chel. planimentum. In PI. 21, as in the other figures, ch is the nuchal plate, ph the first rib of the carapace (the second free pleurapoph)^sis or vertebral rib), ph to j'Vs the remaining ribs of the carapace and costal plates ; sg, siO, and pi/ are the terminal neural plates and pygal plate, which, like the nuchal plate, are developed in the substance of the integument, without becoming attached to the subjacent spinous processes of the vertebrae. The debris of the neural arches of the intermediate eight vertebrse of the CHELONIA. 29 carapace are preserved in the interspaces of the beginnings of the ribs and costal plates in this beautiful Chelonite. It forms part of the Fossil Collection in the British Museum. A carapace of a smaller individual of Chehne crassicostata, from the Harwich coast, vi'ith the character of the broad and inwardly-prominent ribs strongly marked, is likewise preserv^ed in the choice collection of my esteemed friend Professor Bell. One of the hyosternal bones, inclosed in the same nodule of clay, testifies to the partial ossification of the plastron in this species by its coarsely-dentated border ; and, at the same time, shows a specific peculiarity by the convexity of that surface which was turned towards the cavity of the thoracic-abdominal case. On the moiety of the nodule containing the carapace and exposing its under surface, the slender rudimental rib of the proper first dorsal vertebrae is preserved, in connexion with the first expanded rib of the carapace. Besides the specimen of Chehne crassicostata from Harwich, figured in PL 21, there is a mutilated carapace of a young Chehne, from the same locality, in the British Museum. This specimen exhibits the inner side of the carapace, with the heads, and part of the expanded bodies, of four pairs of ribs, which indicate its specific agreement with the foregoing specimen, and demonstrate unequivocally its title to rank with the marine turtles. It is figured in Mr. Koenig's ' Icoues Sectiles'' (pi. xvi, fig. 192), under the name of Testudo plana. A rare Chelonite from the hard Eocene clay apparently of Harwich, in the collection of my friend Frederick Dixon, Esq., F.G.S., of Worthing, shows the impressions from the under surface of the carapace, and also an instructive part of the under surface of the plastron itself. (PI. 22.) The proportions and degree of convexity of the under surface of the costal plates of the carapace (yV, pi) correspond with those parts in the Chehne crassicostata. The remains of the plastron include a great portion of the left hyosternal {hs), left hyposternal {ps), and left xiphisternal {xs) ; the latter is articulated to the hyposternal by a notch, receiving a toothed process, and, reciprocally, near the upper part of a long oblique harmonia, between the outer border of the hinder angle of the h3iiosternal and the inner border of the upper half of the xiphisternal. The hyosternal is concave lengthwise, and is convex across on its under surface ; the transverse linear impression, dividing the pectoral and abdominal scutes, crosses near its posterior border. The degree of concavity of the outer surface of this bone corresponds with the convexity of the upper and inner surface of the same bone in the specimen of the Chehne crassicostata from Harwich, in the Museum of Professor Bell ; and it concurs with the characters of the costal plates in proving the present Chelonite to be of the same species. Impressions of the toothed mesial margin of the right hyosternal remain, and part of the toothed margin of the left hyposternal. 30 BRITISH FOSSIL REPTILES. The right coracoid (52) is exposed by the removal of the right hyosternal ; it differs in form from that preserved in the large specimen of Chelone planimentum, in Professor Sedgwick's Museum, in expanding less suddenly at its sternal end, as compared with the coracoid of the Chelone mydas, or with that of the Chelone caouanna, which is somewhat broader than in the CIlcI. mydas ; the coracoid of the Chel. crassicostafa agrees with that of the Chel. planimentum in the greater degree of its expansion. At the anterior fractured surface of Mr. DLxon's Chelonite, the long and slender columnar or rib-like scapula, is shown, extending from the under part of the head of the second costal rib downwards and outwards, for an extent of two inches, and then sending its acromial or clavicular prolongation at the usual open angle downwards and inwards to rest upon the episternal. The proportions of these parts of the scapular arch are quite those which characterise the genus Chelone, but they do not supply such marks of specific distinction as the coracoid element does. Chelone declivis. Owen. Plate 23. The extinct turtle represented by this specimen, and indicated by the above terra, bears the same relation to the Chelone convexa, which the Chelone lonyleeps* does to the Chelone latiscutata ;t that is, it has the same general characters of the petrified parts of the carapace, but diff"ers in the narrower proportions of the vertebral scutes {v\ — v\), and the more open angle at which their two lateral borders meet ; the vertebral angles of the costal scutes being correspondingly less acute. The specimen is from the Eocene deposits of Bognor, Sussex, and is preserv^ed in the collection of Frederick DLxon, Esq. It consists of the seven anterior neural plates, and the corresponding seven pairs of costal plates (PI. 23, fig. 1), those of the right side having been broken away from their attachments to the neural plates, and bent upon the rest of the carapace at an acute angle with some slight separation of the sutures of the costal plates (fig. 2). The neural plates correspond in general form with those of the Chelone convexa, the hind ones being rather broader ; the first (.si) is crossed at its middle part by the impression dividing the first (^m) from the second (vi) vertebral scute ; the second neural plate (s'l) is an oblong four-sided one, with both ends of equal breadth. The third neural plate, S3, resumes the hexagonal figure with the broadest end, and two shortest sides at the fore part ; and is crossed in its lower half by the impression dividing the second, VI, from the third vertebral scute, t'3. The fifth neural plate (,s^5) is crossed by the next transverse impression nearer its lower border. The sixth and seventh neural j^lates retain the same form and proportions as in the Chelone convexa, except a somewhat * Proceedings of tlie Geological Society of London, December 1, 1841, p. 572. t Ibid., p. 574. CHELONIA. 31 greater breadth, and have not their antero-lateral borders increased in length, as in the Chelone longiceps. The dechnation of the ribs from the neural plates, gives a greater degree of steepness to the sides of the carapace than in the Chelone convexa, and the impressions of the scutes have equal depth and breadth. The chief difference indicative of specific distinctions, lies in the form of those impressions ; and the question is, whether, in the progress of growth which makes the longitudinal extent of two of the vertebral scutes in one specimen nearly equal to three, in another, so great a change could be effected in their shape as is shown in the specimen of Chelone convexa ; in which it will be seen that the second vertebral scute (PI. 14, fig. 1), though one third shorter than in Chel. declivis (PI. 23, V2), is of the same breadth as that in the larger specimen, and that the rest differ in the same remarkable degree. Fig. 3 shows the characteristic declivity of the sides of the carapace in the present species. Chelone trigoniceps. Oicen. Plate 25, figs. 4, 5, and 6. More than one of the old tertiary turtles {Chelone) are remarkable for the longitudinal extent or depth of the symphysis of the lower jaw. The turtles from the Eocene clay at Harwich have this character so strongly developed and the under surface of the symphysis so flattened, especially in one of the species (PI. 18), as to have suggested the " nomen triv'mle" planmentmn for it. The Chelone longiceps (PI. 12), if we may judge by the length of the upper jaw and bony palate, must have had a corresponding extent of the symphysis of the under jaw ; and we may infer the same peculiarity from the straight alveolar borders of the maxillaries and their acute convergence towards the premaxillary bones in an allied species, Chelone trigoniceps, which I have described and figured in the Appendix to Mr. Dixon's work on the 'Fossils of Sussex,' from a specimen which is in the collection of G. A. Coombe, Esq., and which was obtained from the Eocene clay at Bracklesham. Amongst the Chelonites which Mr. Dixon has obtained from the same formation and locality, ai'e portions of the fore part of the lower jaw of four individuals of the genus Chelone, all exhibiting the characters of the pointed form and great depth of the symphysis. One of these specimens (PI. 18, figs. 5 and 6) agrees so closely in size and shape with the fore part of the upper jaw of the Chelone trif/oniceps (fig. 4) — fits, in fact, so exactly within the alveolar border, and so closely resembles that specimen in texture and colour, that, coming from the same formation and locality, and being obtained by the same collectors, I strongly suspect it to belong to the same species of Chelone, if not to the same individual. The known recent Chelones differ among themselves in the shape and extent of the bony symphysis of the lower jaw. Both the Chelone imbricafa, and Chelone caouanna 32 BRITISH FOSSIL REPTILES. have this part deeper and more pointed than the Chcl. mydas, but neither species has the symphysis so depressed or so slightly convex below as it is in the Bracklesham CJielones. These also differ amongst themselves in this respect. The symphysis (figs. 5, 6, 11) which I have referred to the Chelone iriyomcep><, is the broadest and flattest ; at its back part (fig. 7) it shows a deep and broad genio-hyoid groove ; this is reduced to a transversely oblong foramen in Chelone mydas. The second species from Bracklesham, is indicated by the maxillary symphysis (fig. 9), the sides of which meet at a more acute angle, and it is narrower in proportion to its length, is more convex below, and more concave above, with the alveolar borders a little more raised, and the middle line less raised than in Chelone trigoniceps. In this respect it is intermediate between the Chelone imbricata, -where the upper surface of the symphysis is more concave, and the Chelone caouanna, where it is flatter than in the Chelone triyoniceps. The fossil symphysis under notice, has also a smooth, transverse, genio-hyoid groove at its back part. It accords so closely in form with the end of the upper jaw of the Chelone lonyiceps, from Sheppey, that I refer it provisionally to that species. Two other specimens of the symphysis of the lower jaw (figs. 8, 10), of rather larger size, appear to belong to the same species as that referred to the Chel. lonyiceps, by the characters of the concavity of the upper surface, the convexity of the lower surface, and the degree of convergence of the sides or borders of the symphysis. The larger of the two shows the genio-hyoid groove, and the nearly vertical outer side of the jaw, opposite the back part of the symphysis, and this shows no impression of the smooth fossa receiving the insertion of the biting muscles, whereas, in the Chelone trigoniceps, fig. 11, that fossa extends to the same transverse line or parallel with the back part of the symphysis. The very rare and interesting Chelonite in Mr. Coombe's museum (fig. 4) was the first portion of the cranium of a reptile of this order that I had seen from the Eocene deposits at Bracklesham. It includes the bones forming the roof of the mouth, with portions of the bony nostrils and orbits, and the tympanic pedicles. The extremity of the upper jaw is broken off, but the straight converging alveolar borders clearly indicate the muzzle to have been pointed, as in the Chelone longiceps of Sheppey; and the muzzle being shorter, the form of the skull has more nearly approached that of a right-angled triangle. The whole cranium is broader and shorter, and the tympanic pedicles wider apart. The middle line of the palate developes a somewhat stronger ridge ; the orbits were relatively larger and advanced near to the muzzle : the malar bones are more protuberant behind the orbits, and their external surface inclines inwards as it descends from behind and below the orbit, to form the lower border of the zygoma, which it does not do in the Chelone longicejis. The upper surface of the fossil shows the palatines rising to form the vomer at the middle line, and the two small subcircular vacuities (occupied by membrane in the CHELONIA. ,. 33 recent skull) between the palatines, prefrontals, and niaxillaries ; the anterior border of the temporal fossa, formed by the malar and pterygoid, is entire on one side, and shows that that vacuity was as broad as it is long. The olfactory excavations in the maxillaries are deep. The articular surface of the tympanic pedicles closely accords with those of recent Chelones. The very regular triangular form of the skull indicated by this fragment, has induced me to propose the name of Chelone trigoniccjis for the species. Chelone cuneiceps. Owen. Plate 11. One of the most complete and instructive crania of the fossil turtles of our Eocene deposits is the subject of PI. 1 1, the opportunity of describing and figuring which has been kindly afforded me by J. Toulmin Smith, Esq., F.G.S., of whose cabinet it forms part, and by whose skilful manipulation its variously configurated exterior has been disencumbered of the hard adherent clay. From the Chelone breviceps this specimen differs by its more prolonged and pointed muzzle ; by the more sudden and sloping declivity of the prefrontal part of the cranium (fig. I, 14) ; by the minor degree of rugosity of the surface of the bones ; and by the different disposition of the superincumbent horny scutella, which is indicated by their impressions. In the general arrangement of these impressions it accords better with the cranium of the Chelone lonpcejjs ; but differs in the greater breadth of the skull as compared with its length ; in the minor extent of the bony palate (fig. 3, 20, 21), the more advanced position of the posterior nostrils, and the greater length of the pterygoids (24). From the Chelone convexa it differs, in the greater relative breadth and flatness of the frontal bones, and of the whole intcrorbital platform (fig. 2, ii), in the downward slope of that part of the cranial profile, and in the more prominent convexities of the palatal pi'ocesses of the maxillaries. From the Chelone planivienfum it differs also, by the broader prefrontal part of the intcrorbital space, as compared with the transverse diameter of the back part of the skull ; by the minor degree in which the frontal enters into the formation of the upper rim of the orbits ; by the minor depth of the suborbital part of the maxillary and malar bones, and by a very different arrangement of the supracranial horny scutella. The basi-occipital (PI. 11, figs. 3 and 4) is remarkable for the strong development of the tubercles for the insertion of the strong " recti capitis antici," and for the depth of the median groove between them ; the semicircular fossa in front of these processes is bounded by a well-developed basi-sphenoidal ridge (5), the curve of which is deejjer than in Chcl. longiceps, but shallower than in Chel. breviceps. In the Chel. caoiianna, in which the basi-occipital tuberosities are better developed than in the Chel. hnhricata or Chel. mi/das, they are bounded anteriorly by an angular or chevron-shaped ridge of the basi-sphenoid. The exoccipitals (2) form the usual share of the trilobate occipital F 34 BRITISH FOSSIL REPTILES. condyle characteristic of the Chelonia. The paroccipitals (4) project backwards to a little beyond the posterior plane of the condyle, indicating an affinity to the Trionycidce. The inferior surface of the part of the tympanic to which they unite is concave. The parietals (fig. 2, 7) form together a large semielliptic, almost flattened, platform, relatively broader than in Chel. viydas, not convex, as in Chel. caouanna ; not in- dented by the mastoids, as in the Chel. hnpceps, and not forming an angle between the frontals and postfrontals, as in the Chel. breviceps. The frontals (11) together form a pentagon, with the longest margin joining the parietals, the next in length con- verging to a point between the prefrontals, and the shortest borders joining the post- frontals. The postfrontals (12) and prefrontals (14) almost meet above the orbits, and exclude the frontals from entering into the formation of its superior border. The Chel. mi/das comes nearest to the Chel. cuneiceps in this particular ; whilst in the Chel. imbricata the frontals enter as largely into the formation of the upper border of the orbit as they do in the Chel. breviceps, Chel. longicepts, and Chel. coiwexa. The precise form of the termination of the prefrontonasals, the maxillaries, and premaxillaries cannot be determined in the present specimen ; fortunately, the fracture of the anterior extremity of the skull has not extended to that of the bony palate. If this be bounded by a transverse line behind, drawn across the anterior border of the temporal fossse, the space included forms a right-angled triangle, and includes the whole of the posterior nostrils. In the Chel. longiceps the similarly defined space has the base shorter than the converging sides, and the posterior nasal aperture is behind the transverse line. The bony palate, also, of Chel. cuneiceps, instead of being pretty uniformly concave and even, as in Chel. longicep)s and Chel. caouanna, is raised on each side between the middle line and the marginal alveolar plate into two convexities, as in Chel. mydas and Chel. imbricata ; but the most prominent part of the palatal convexities (figs. 3 and 4, 21) is obtuse in Chel. cuneiceps, not sharp or angular, as in Chel. wydas and Chel. imbricata. The palatal part of the vomer (13) forms the median longitudinal groove dividing the convexities, which arc formed by the palatal processes of the maxillary bones. The small part of the alveolar border of the maxillary which is entire terminates in a sharp edge, extending about four and a half lines below the level of the palate. The ridge of the palatines, which forms the anterior boundary of the posterior nostril, is not produced or bent below the level of the bony palate, as in Chel. caouanna, and as it is, although in a minor degree, in Chel. mydas ; and there is not that concavity between it and the oblique palatal tuberosity which exists in the Chel. mydas and Chel. imbricata. The pterygoids are more deeply (semicircularly) emarginate laterally than in any of the existing species of Chelones, and they are shorter in proportion to their breadth ; they bound internally the lower apertures of the temporal fossse, which are broader than they are long ; in all the existing Chelones the opposite proportions prevail, CHELONIA. 35 and in Clicl. wibricata especially the homologous apertures are twice as long as they are broad. Tlic pterygoids, in the CJteL cunekqjs, develope a sharp ridge along their median suture ; and short but well-defined processes at their anterior and outer angles. The channel or concavity upon the under part of the diverging portion of the pterygoid conducts obliquely into the temporal fossae in the Chd. my das ; in Chel. cuneiceps it leads directly forwards upon the under surface of the anterior part of the pterygoids exclusively, as in the Chel. imhricata and Chd. caouanna. In the Cliel. mydas the malar approaches the mastoid very closely, and sometimes touches it by the posterior angle, thus separating the squamosal from the postfrontal ; the extent of the unioiv between the squamosal and postfrontal is also shorter in the Chel. caouanna than in the Chel. imhricata. In the extent of that union (between 12 and 27) the Chel. cuneiceps resembles the Chel. imhricata, as do likewise the Chel. hreviceps and Chel. loiiyiceps. But the Chel. cuneiceps diflFers from all the recent species in the form of the squamosal (27), which is bent upon itself, forming a slightly curved linear eminence, where the lower and smoother part of the bone is bent, and, as it were, pressed inwards towards the tympanic (28), against which it abuts. This modification is natural, not the effect of accidental pressure upon the fossil. The lower border of the malar (2G), which intervenes between the maxillary and squamosal, is sharp but convex, as in Chel. caouanna, not concave as in Chel. mydas, nor nearly straight, as in Chel. imhricata. But the concave curve of the inferior margin of the squamosal (27) most resembles that in Chel. imhricata. The antero-posterior extent of the mastoid (s) is less proportionally than in any of the recent Chelones, and it forms a smaller share of the upper border of the large meatus auditorius. The articular part of the tympanic descends below the squamosal further than in the i-ecent turtles ; and its articular surface is more convex at its outer half, and more concave at its inner half; Chel. imhricata makes the nearest approach to the fossil in this respect. In the Chel. mydas and Chel. caouanna the articular surface is nearly flat. As the supracranial scutella have left imusually deep and well-marked impressions on this fossil skull, I have reserved their description, and the comparison of their different forms and proportions in the sevei'al fossil species, to this place. Three scutella occupy the median line of the upper surface of the cranium in the present species of Chelone, which, from the absence of any impression along the frontal and sagittal sutures, appear to have been single and symmetrical. The anterior and smallest answers to the " frontal" scute (fig. 2, //•) ; the next in size and position to the " sincipital" scute {sy) ; the hindmost and largest answers to the " occipital" scute {oc), which is usually divided, and forms a pair in existing Chelones. The frontal scute is long, narrow, hexagonal, broadest across the antero-lateral angles, from which the impressions extend outwards to the supraorbital margin, which divide the " fronto-nasal" scute from the " supraorbital" scute {oh). The sincipital scute is bounded on each side by a sigmoid curve, and both before 36 BRITISH FOSSIL REPTILES. and behind by an entering angle ; it is broadest behind, and from the middle of the lateral border proceeds the transverse impression towards the back part of the orbit, which divides the " supraorbital" scute {ob) from the " parietal" scute {pa). The occipital scute is bounded laterally by straight lines, which slightly diverge as they extend back- wards : there is no trace of an interoccipital scute. The parietal {pa) scute is the largest ; impressions of five of its borders are preserved in the present fossil : the two exterior ones meet at an obtuse angle, a little above the middle of the meatus auditorius externus ; the antero-external border uniting with the postorbital scute {jjo) ; the postero-external border with the external occipital scute {eo). In the Clielone brevicejys (PL 1 7 A, fig. 2) the frontal scute is relatively larger than in the Clielone cimciceps, and is nearly as broad as long. The sincipital scute is bounded laterally by two straight lines meeting at a very open angle, from which the transverse impression extends outwards between the supraorbital and parietal scutes. The straight lines bounding the sides of the occipital scute diverge from each other as they extend backwards more than they do in the C/ielone cimcicejjs. In the Clielone lonc/iceps (PI. 1 2) a still more different pattern of the supracranial scuta- tion is presented. The occipital scutes {oc) are separated by an intervening interoccipital scute {io). The lateral borders of the sincipital scute are each bounded by three lines and two angles ; the antero-lateral and postero-lateral angles being curved with the concavity outwards ; and the transverse impression dividing the supraorbital scute {oh) from the parietal scute {pa), proceeds from the middle of the intervening straight border of the parietal. The frontal scute {fr) is long and narrow, broadest behind, with its lateral borders gradually converging to a point anteriorly ; the impression dividing the supraorbital {oh) from the frontonasal scute {fn) proceeds from the middle of that lateral border. Neither the division between the frontal and sincipital, nor that between the sincipital and interoccipital scutes are well marked. The Clielone convexa (PI. 24, fig. 4), like the Clielone lonpceps, has an interoccipital scute {io), and the sincipital scute {sif) has its sides bounded by three lines, of which the posterior one is curved with its concavity towards the occipital scute (oe), and so directed as to appear to form part of the posterior rather than the lateral border ; the other two lines completing the lateral border and converging forwards, are divided or defined by a slight angle, from which the transverse impression proceeds outwards, which divides the supraorbital {oh) from the parietal {pa) scutes. The frontal scute (//•) is a small hexagon, relatively \\\A.ev than in Cliel. longiceps or Cliel. cuneiceps. The impression dividing the supraorbital {oh) from the frontonasal {fn) scutes proceeds from the angle between the lateral and anterior sides of the frontal scute. The Clielone planimentum (PI. 18) is peculiar, and differs fi-om all the foregoing species by the forward extension of the occipital scutes which join the supraorbital scutes, and thus divide the sincipital scute {si/) from the parietal scute {pa) ; the sincipital scute CHELONIA. 37 is correspondingly encroached upon, as it were, and narrowed, its broadest part being nearer the anterior end, at the angle between its two straight lateral borders, from which angle the impression extends outwards that divides the occipital from the supra- orbital scute. The frontal scute (/;•) is small and narrow, and the large supraoi-bital scutes meet in front of it at the middle line. They appear to be divided from the orbits by the encroachment of palpebral scutes (/;/) upon the supraorbitary border. There appears to have been an interoccipital scute in the Chel. jjlanimentum, as in the Chel. lon^icejjs and Chel. convexa. Amongst existing Chelones the interoccipital scute is constant only in the Cliel. caouanna — the loggerhead of Catesby and Brown ; but the sincipital scute in this species is vastly larger in proportion than in any of the fossils above described ; and it is further distinguished by the peculiar division of the supraorbital and parietal scutes. In the hawks-bill turtle {Chel. imhricata), the supracranial scutes leave as well- marked indentations upon the bones of the cranium as are seen in most of the fossil turtles, but the supraorbital scute is proportionably larger than in any of these, and the proportions and forms of all the other scutes are different. There are, also, two nasal scutes divided by a transverse groove from the frontonasals, which groove I have not yet met with in the corresponding part of any of the fossil Chelonian crania. The skull of the Chelone cimeiceps, here described, is from the London clay of Sheppy. Chelone subcarinata. Bell. Plate 10. The resemblance of this species to Chelone subcristata (p. 24, PL 15) is so con- siderable, that it has not been without some hesitation that I have ventui'ed to describe it as distinct. There are, however, certain characters by which it may be distinguished, and those of sufficient importance to be considered as specific. On comparing it with recent species, and even with most of the fossil ones from the same locality, there is a remarkable evenness in the arch of the carapace, which, with the exception of a slight carina on some of the posterior neural plates, to be hereafter mentioned, forms nearly a perfect arc of a circle, from the extremity of the costal plate of the one side to that of the other, without that flattening of the side which is seen in most other species. The nuchal plate (PI. 10, fig. 1, ch) has the posterior margin arched, and there is a short median process which goes to join the first neural plate (*l), in which respect it agrees with Chel. lo)i(/ice2)s and with Chel. subcristata. This process is emarginate, to receive a slight triangular projection of the anterior margin of that plate. The first neural plate {s\) forms a parallelogram, the sides not being interrupted by any costal suture ; the posterior suture of the first costal plate (jo/l) extending to the second neural plate (6'2). In this circumstance it differs from Chel. subcristata, lofipcejjs, and convexa, and agrees with Chel. breviceps. This, however, may possibly be a variable character here, as 38 BRITISH FOSSIL REPTILES. it is in Chel. loncjiceps ; in one specimen of which, now before us, the articulation of the first costal plate was with the anterior part of the second, instead of the posterior part of the first, neural plate ; in other words, the first neural plate was the isolated one instead of the second. The remaining neural plates are hexagonal, becoming almost regularly shorter to the eighth ; the lateral angles meeting the costal sutures being nearly at the same distance from the anterior margin in each, and in no one at all approaching a regular equilateral hexagon, as in many of the neural plates in C/iel. breviceps. The first three, and the anterior half of the fourth neural plates are flat; but on the posterior half of the fourth commences a low carina, which becomes highest on the posterior half of the sixth (*g), and anterior half of the seventh {&-). It thus differs from Chel. subcristata, in which there is a distinct, short, sharp, longi- tudinal crest (.si) on the fifth and seventh neural plates, " and a similar crest is developed on the contiguous ends of the second and third neural plates." The ninth and tenth neural plates are wanting in the only specimen I have seen of the Chel. subcarinata. The first costal plate is flat [ph), but the remaining ones, to the seventh inclusive, are slightly hollowed along the middle, being raised towards the anterior and posterior margins, where they are articulated to the contiguous ones. The w'hole surface of the bones of the carapace is less smooth than in most other fossil species, and conspicuously less so than in Chel. subcristata. In describing the forms of the vertebral scutes, (n — va), and of the costal ones as depending upon them, it is necessary, in order to arrive at any satisfactory comparison between these parts in difl'erent species, to bear in mind that a great change takes place in their outline during the growth of the animal ; and that a vertebral scute, w^hich, in a younger individual, has the middle of its outer margin exceedingly extended, so as to form a very acute angle, where the lateral margin of the costal scute joins it, and thus rendering it twice as broad as it is long, may in more advanced age have that angle verv open, and having increased greatly in length, and scarcely at all in breadth from angle to angle, the length becomes greater than the breadth. Allowing, however, for this fact, there are doubtless considerable variations in this respect according to the difl'erent species, which are permanent and well marked. The first vertebral scute {v\) in the present species is quadrilateral, broader anteriorly ; the second and third {v2, V3) hexagonal, with the outer margins slightly waved, somewhat broader in the middle at the angles than at the anterior and posterior margins, the comparative breadth at that part being rather greater than in the corresponding scutes of Chel. svbcrisfata, and much less so than in Chel. convexa, Chel. brevicejis, or Chel. longiceps. The fourth vertebral scute (r4) is also hexagonal, but the portion posterior to the lateral angles is narrowed and produced backwards. The last of the series is fan-shaped. The outline of the costal scutes follows of course that of the vertebral ones. The plastron, in the specimen from which this description is taken (PI. 10, fig. 2), is more perfect than in that of almost any other fossil Chelonian I have seen. It CHELONIA. 39 agrees in its general form with that of Chel. subcristata, but is less extensive, as regards its bony surface, than in Chel. loiifflceps or even than in Chd. breoiceps. The entosternal bone (s) is somewhat wedge-shaped, with the anterior margin triangular, and a short winged process on each side of the anterior third of the bone extending outwards and backwards. The posterior extremity of the bone, and the winged processes are dentate. The episternals {es) are aliform, tending backwards and outwards, and inclosing between them the head of the entosternal (*), and the anterior processes of the hyosternal bones [Its). The latter have the anterior processes extending forwards on each side of the entosternal, approximating at their extremity the aliform processes of that bone. The median or internal processes nearly meet on the median line, and the den- tations are deep but slender ; each hyposternal {ps) unites similarly with its fellow, and the posterior process extends backwards, in a long, narrow, triangular piece, uniting with the xiphisternal {xs), which latter forms a very elongated rhomb, the breadth of which is scarcely one fourth of its length, which in the present specimen is no less than two inches six lines. This form, with the elongation and narrowness of the posterior process of the hyposternal, gives to the hinder portion of the plastron in this species a narrower and more elongated outline than we find in almost any other; an approach to which is, however, indicated in the imperfect specimen of Chel. subcristata figured in Plate 15. The external notch, between the external process of the hyosternal and hyposternal, is deep and rounded. The central interspace is nearly quadrate, and about half as long again as it is broad. Inches. Liues. Lengtli of the carapace as far as it is preserved ... 9 5 Breadth of ditto from the extremity of the third costal plate on one side to that on the other ...... 7 4 Ditto, following the convexity of the carapace ....!) 3 Length of plastron from the anterior margin of the episternal to the extremity of the xiphisternal .... 8 4 Breadth of ditto across the hyosternals ..... 7 0 The only specimen of this species which I have seen is from Sheppy, and is in the fine collection of J. S. Bowerbank, Esq., F.R.S. T. B. SUPPLEMENTAL REMARKS ON THE TURTLES FROM THE LONDON CLAY AT HARWICH. In the progress of the works now carried on in a part of the Harwich cUfFs, with a view to the acquisition of the remains of the animal tissues and bone-eartli which form the nodules that are ground up and used as manure, many remains of the Chelonian reptiles which formerly frequented the seas from which those Eocene tertiary strata have been deposited have been discovered. Mr. Colchester, of Little Oakley, Essex, who carries on large works of this kind for the " Fossil Guano," as it is termed, has transmitted to me a number of the nodules in question. The most intelligible and instructive of these I have marked from 1 to 10 consecutively, and shall notice them here in the same order. No. I. CJtelone planimentum. This is the half of an oval nodule of petrified clay, 20 inches in length, by 17 inches in breadth, exposing an in-egular group of disarticulated bones of the carapace and other parts of the skeleton. The species is determined by a fragment of one of the costal plates with the connate rib. The plate measures 2\ inches in breadth, the rib 8 lines, and forms the usual partial prominence from the even surface of the under part of the costal plate. Almost the whole of the very broad but short nuchal plate is recognisable : it measures 6 inches in transverse diameter, and only I5 inch in antero-posterior diameter. Part of the hyosternal bones, and the impression of the humerus are recognisable. No. 2 is the half of a nodule, 20 inches in length and 17 inches in breadth, exposing part of the plastron, and some other bones of the skeleton of the CIicJ. j^Iani- mentum. It shows well the natural form of the under and outer part of the hyposternal bone, which is much more deeply excavated than in the Chel. crassicosfafa ; the lower portion of the bone is narrower in proportion to its length, and the xiphisternals are also in proportion longer and narrower than in that species. No. 3. Clidone 2ilanimenhm . The half of an oval nodule, 17 inches in length and 13 inches in breadth. The fractured side exposing a cast of the inner surface of the carapace, which measures in length from the nuchal to the tenth neural plate inclusive 13^ inches ; and in breadth, across the third pair of costal plates from one end of the projecting rib to that of the opposite side, 1 1 inches. The anterior contour of the CHELONIA. 41 carapace is well shown in this nodule, the marginal plates which join the nuchal plate being preserved. The free extremity of the rib attached to the third costal plate projects 1 inch 9 lines from that plate, and measures 7 lines in breadth, where it becomes free ; the breadth of the plate being nearly 2 inches. The transverse curve of the carapace is shown by this specimen to be much less than in the Chel. crassicostata. No. 4. Cliel. 2^lcinhnentum. The nodule shows partly a cast of the outer surface of the carapace, with part of the carapace itself. The outer angles of the third and fourth vertebral scutes are here seen with the inner angle of the third costal scute. The outer angles of the vertebral scutes are more prominent than in Chel. declivis, Chel. subcristata, Chel. subcarinata, Chel. convexa, or Chel. longiceps ; they resemble most those in Chel. breviceps. The breadth of the third costal scute is 4 inches. The characteristic angular ridge, formed by the narrow connate rib, where it projects from the lower surface of the costal plate, is well shown in this specimen. No. 5. A nodule showing a cast of the under surface of the carapace seen from above, apparently of the Chel. planivientum. No. 6. A nodule, 10 inches long by 9 inches broad, showing a still more imperfect cast of the under surface of the carapace, of apparently a younger specimen of the Chel. planimentum. No. 7. A fragment of a nodule showing the outer dentated extremity of the left hyosternal of the Chel. pilunimentum. No. 8. A portion of a nodule, with part of the carapace of the Chel. plani- mentum, showing the second to the seventh neural plates inclusive, and portions of the second to the seventh costal plates of the right side, with more or less of their bony substance broken away, exposing their coarse fibrous character, the fibres diverging on each side from the subjacent rib, as they extend obliquely towards the periphery of the carapace. The third neural plate is 2 inches 3 lines in length and 1 inch in breadth ; it is crossed at its middle part by a moderately broad and deep channel, indicating the junction of the second with the third vertebral scute. The third neural plate is hexagonal ; the two shortest sides being formed by the truncation of the contiguous angles of the second costal plates bending down a little to articulate with them. The fourth neural plate is 2 inches 6 lines in length, and 1 inch 4 lines across the broadest part. The anterior surface is concave, the posterior convex ; the two longest sides converge towards the posterior surface, and are straight. The fifth and sixth neural plates progressively decrease in length, without a proportionate decrease in breadth. The breadth of the fourth costal plate is 2 inches 3 lines at its peripheral extremity ; its length is 6 inches ; the rib projects 2 inches beyond it. The upper 42 BRITISH FOSSIL REPTILES. surface of the neural and costal plates is so minutely fibrous or striated as to seem at first sight almost smooth. The upper surface of the costal plate seems naturally to be slightly concave in the direction of the axis of the carapace, but not so much as in Chel. crassicostata, and the rib is much bent lengthwise. No. 9. Chelone crassicontata (PI. 22 A). This instructive specimen is contained in a subspherical nodule, 13 inches long by 12 inches broad, exposing a large proportion of the outer surface of tlie carapace, with more than one half of the circle formed by the marginal plates {mi—jiij). The carapace has been fractured, and the ribs of the left side dislocated and pressed down below those of the right. The third {ph) to the eighth {ph) costal plates inclusive are present on the left side; the fifth to the eighth on the right side, and the neural plates from the fourtli to the pygal plate {py) inclusive. The fourth, fifth, and sixth neural plates are hexagonal, with the anterolateral sides shortest, and chiefly remarkable for their great breadth in proportion to their length. The seventh and eighth are small, and more regularly hexagonal. The ninth is a broad sub- crescentic plate, with the broad concave side backwards, and the space between this and the pygal plate is filled up by an equally broad but pentagonal neural plate. The length of the ninth and tenth neural plates, with the pygal plate inclusive, is 2 inches 9 lines. The pygal plate is subquadrangular and broadest behind, where it is slightly emarginate. The length of the fourth to the eighth neural plate inclusive is 3 inches 8 lines. The upper surface of the bones of the carapace is almost smooth. That of the costal plates is chiefly remarkable for its concavity transversely, or in the direction of the axis of the carapace, which is to a greater degree than in the Clieh suhcristata or CheL longiceps ; the lines of the sutural union of these plates with each other forming so many ridges across the sides of the carapace. The degree of curvature or convexity in the direction of the length of the costal plate is much greater than in the Cliel planimentum. The length of the third costal plate is 3^ inches, its breadth at the outer extremity, 1 inch 4 lines ; the breadth of the rib where it projects beyond it is 9 lines. The margin of the plate attached to that rib is 1 inch 4 lines in length, and 8 inches in breadth. The margin of the plates gradually increases in breadth towards the posterior part of the carapace, the one joining the pygal plate being 1 inch 2 lines in breadth. The general form of the carapace of the Ckel. crassicostata is shown by the present specimen to have been that of a full oval, with a gently festooned border, not pointed behind. No. 10. Chelone crassicostata (PI. 22B.) A still more remarkable example of this species was kindly transmitted to me by the Rev. S. N. Bull, M.A., of Harwich, of which a figure is given in PI. 22B. When it first came into my hands it was an unpromising semioval nodule, 10 inches in length by 7 inches in breadth, presenting on its convex surface portions of the posterior neural and costal plates, with their external surface entire ; but no trace of plastron on the flattened side. The degree of convexity formed by the costal plates equalled that of the CHELONIA. 43 most dome-shaped tortoise. The flatter surface of the nodule was shghtly convex, which I thought might arise from a layer of petrified clay adhering to the plastron. A portion of the cranium was indicated at the produced angle of the nodule. To ascertain whether this remarkable degree of convexity of the carapace, both length'wise and transversely, was natural, I had the matrix carefully removed, with the permission of the owner of the specimen, and the same was done on the opposite side, with a view to expose the plastron. Instead of finding a plane plastron where it was expected, in its natural horizontal position, it was found to have been crushed inwards, as repre- sented in fig. 2, by the pressure of a hard petrified mass as big as a paving-stone, which had been forced in upon this part of the body of the turtle whilst in a decom- posing state ; and when finally lodged in the clay, the carapace and plastron, as they became dislocated, had become more or less moulded upon it ; and thus was produced the convexity which originally attracted my attention. In the breadth of the connate rib, as compared with that of the costal plate, in the extent of the free extremity of the rib, in the degree of concavity of the upper surface of the costal plate and the curvature lengthwise, the distinctive characters of the Chel. crassicostata are well show'n. The same characters are likewise presented by the parts of the plastron, as in the breadth of the xiphisternals (MJoES>-i''™"p<'p''y=>s- artery.' The names of the vertebral elements parapcphys,s.----'' ^\^V^ ^^"'^^' ^^^^^ usually dcveloped from distinct XV/y ■■•--ha^inapophyB.s. ceutrcs, are called ' autogenous,' are printed in zvgapopi.piu.--''' W '^ Roman type ; the italics denote the ' exogenous' W"'--- hiemai spine. parts, uiore properly called 'processes,' which Ideal typical Tcvtcbra. shoot out from the preceding elements. On comparing this form of the primary segment with that figured in Cut 4, p. 5, it will be seen that they differ by altered proportions with some change of position of certain elements ; but every modification resulting in the various forms of the parts of the skeleton figured in PI. 1, has its seat in one or other of the segmental or ' vertebral' elements above defined ; and the same principle I believe that I have established with regard to the internal skeleton in all vertebrate animals. With this preliminary explanation, the nature and relations to the typical vertebra of the parts of the Crocodilian vertebrae, figured in Plates 1 D, 3, will be, it is hoped, readily appi'eciated. In Plate 1 D, in which are figured some of the most perfectly- preserved fossil reptilian vertebrae which have hitherto been discovered, the elements and processes are indicated by the initial letter of their names. Figs. 1 and 2 give a side view and a back view of a cervical vertebra, apparently the fourth, of the CrocodUits Ilasdiif/nia:, from the Eocene deposits at Hordwell ; c is the centrum, n the neural canal formed by the neurapophyses, which have coalesced superiorly with each other, and with the neural spine {ns). Inferiorly they articulate by a suture (which is shown by the wavy line on each side of the process d in fig. 1 ) vdt\\ the centrum ; pi is the pleurapophysis, which articulates by two parts, the lower one called the ' head' to the process from the centrum, the upper one called the ' tubercle' to the process from the neurapophysis ; beyond the union of the head and tubercle, the pleurapophysis projects freely outwards and downwards, but instead of being elongated in that direction, it becomes expanded in the direction of the axis of the body, i. e. forwards and backwards, and so acquires a shape which has given rise to the name ' hatchet bone' or ' hatchet-shaped process,' * applied to this element in the Plesiosaurus. * " To compensate for the weakness that would have attended this great elongation of the neck, the Plesiosaurus had an addition of a series of hatchet-shaped processes on each side of the lower part of the cervical vertehra." (Buckland, Bridgcwatcr Treatise, vol. i, p. 206, and vol. ii, p. 30, 1836.) Cuvier recognised in these lateral bones, " cu forme de liache," the homologues of the " petites cotes cervicales" of the Crocodile. (Ossemens Fossiles, 4to, torn, v, pt. ii, p. 479, 1824.) And Conybeare had CROCODILIA. 85 The purport of this modification is the same in the Crocodilia as that which seems to be more called for in the Plesiosaurus, viz. to augment the strength of the cervical region of the skeleton ; and this is so effectually done by the overlapping of the hatchet- shaped ribs of this region in the Crocodilia, as shown in Plate 1 , that the flexibility of the neck is much restricted, although the joint of the head allows that part to be bent from side to side at nearly right angles with the neck. When, however, the head is held firmly forwards by its powerful muscles, the imbricated vertebrse of the neck transmit with great effect the impulse which the strong and long tail gives to the rest of the body in the act of swimming. In fig. 3 the cervical vertebra is represented minus its pleurapophyses, and it answers accordingly to that portion of the natural segment to which the term ' vertebra' is usually restricted in the dorsal region of the trunk. The exogenous processes shown in this view of the vertebra are, ^j, the ' parapophysis' or inferior transverse process, developed from the centrum ; d, the ' diapophysis' or upper transverse process de- veloped, as in most cases it is, from the neurapophysis ; z, z, are the ' zygapophyses' or ' oblique processes,' which, from their function in articulating together contiguous vertebrae, are also called ' articular processes.' In most of the cervical, and in some of the dorsal, vertebrae of the Crocodile, an exogenous process is developed from the under surface of the centrum, called ' hypapophysis ;' it is indicated by the letters hy in fig. 2. In some species it is double,* and beneath the atlas it becomes ' autogenous' or is developed as a separate element, ca, ex, fig. 8, in which condition the part is found beneath the centrums of two or three of the anterior cervical vertebras in the Ichthyosaurus. f The first and second vertebrae of the neck are peculiarly modified in most air- breathing Vertebrata, and have accordingly received the special names, the one of ' atlas,' the other of ' axis.' In Comparative Anatomy these become arbitrary terms, the properties being soon lost which suggested those names to the human anatomist ; the ' atlas' e. g. has no power of rotation upon the ' axis' in the Crocodile, and it is only in the upright skeleton of man that the large globular head is sustained upon the shoulder- hke processes of the ' atlas.' In the Crocodile, these vertebrae are concealed by the pecvdiarly prolonged angle of the lower jaw in the side view of the skeleton in Plate 1 , and a woodcut of the , ,, , , • , , ' Atlas and Axis vertebrie two vertebrae is therefore subjoined. The pleurapophyses are of the Crocodile. previously extended the same homology to the "particularly prominent wing-like appendages to the transverse processes in many of the long-necked quadrupeds, and the long styloid processes of the cervical vertebra of birds." (See his admirable Memoir of June 1 Ith, 1822, in the Geol. Trans., 2d series, vol. i, p. 384.) * In Crocodilus basifissus, e. g., see the Quarterly Journal of the Geological Society, November 1849, p.381,pl. X, fig. 2. t This interesting discovery was communicated by its author, Sir Phihp de M. Grey Egerton, Bart., to the Geological Society of London, in 18.36, and is published in the fifth volume of the second series of their Transactions, p. 187, pi. 14. N 86 BRITISH FOSSIL REPTILES. retained in both segments, as in all the other vertebrte of tlie trunk. That of the atlas, fig. 8, pi. a, is a simple slender style, articulated by the head only, to the independently developed inferior part of the centrum, or ' hypapopliysis' (ra, ex). The neurapophyses {no) of the atlas retain their primitive distinctness ; each rests in part upon the proper body of the atlas (ca), in part upon the hypapophysis. The neural spine {ns, a) is also here an independent part, and rests upon the upper extremities of the neurapophyses. It is broad and flat, and prepares us for the farther metamorphosis of the corresponding element in the cranial vertebrae. The centrum of the atlas {ca), called the odontoid process of the axis in Human Anatomy, here supports the abnormally-advanced rib of the axis vertebra, which in some Crocodilia is articulated by a bifurcate extremity, like the ribs of the succeeding cervical vertebrae ; but it is not expanded or hatchet-shaped at the free extremity. The proper centrum of the axis vertebra {c,r) is the only one in the cervical series which does not support a rib ; it articulates by suture with its neurapophyses {nx), and is characterised by having its anterior surface flat, and its posterior one convex. With the exception of the two sacral vertebrae, the bodies of which have one articular surface flat and the otlier concave, and of the first caudal vertebra, the body of which has both articular surfaces convex, the bodies of all the vertebrse beyond the axis have the anterior articular surface concave, and the posterior one convex, and articulate with one another by ball-and-socket joints. This type of vertebra, which I have termed ' procoe- lian,'* characterises all the existing genera and species of the family Crocodilia, with all the extinct species of the tertiary periods, and also two extinct species of the Greensand formation in New Jersey. f Here, so far as our present knowledge extends, the type was lost, and other dispositions of the articular surfaces of the centrum occur in the vertebrae of the Crocodilia of the older secondary formations. The only known Crocodihan genus of the periods antecedent to the Chalk and Greensand deposits with vertebrae articulated together by ball-and-socket joints, have the position of the cup and the ball the reverse of that in the modern Crocodiles, and the genus, thus cha- racterised by vertebrae of the ' opisthococlian' type, has accordingly been termed Streptospotidi/hi.s, signifying ' vertebrae reversed.' The aspects of the zygapophyses are, however, more constant ; the anterior ones, PI. 1 D, fig. 3 ~, look obliquely inwards ; the posterior ones, ib. ~', obliquely outwards. In a vertical section, therefore, of a Crocodilian vertebra, such as is figured in PI. 4, fig. 3, the smooth, flattened inner surface of the anterior zygapophysis is turned towards the observer, and the convex outer surface of the posterior zygapophysis. Thus the anterior and posterior extremity of the vei'tebra being determined by observation of the aspect and direction of the zygapophyses, it is at once seen whether the body has the procoelian structure, as in PI. 4, fig. 3, or the opisthococlian structure, as in fig. 4. But the most prevalent type * npos, before ; koiXos, concave. f . Quarterly Journal of the Geological Society, November 1849. CROCODILIA. 87 of vertebra amongst the Crocodilia of the secondary periods was that in which both articular surfaces of the centrum were concave, but in a less degree than in the single concave surface of the vertebrae united by ball and socket. A section of a vertebra of this ' amphicoelian' type, such as existed in the Teleosaurus and Steneoscmrus, is figured in PI. 4, fig. 6. In the Ichtlnjosaurm, the concave surfaces are usually deepened to the extent and in the form shown in fig. 7. Some of the most gigantic of the Crocodilia of the secondary strata had one end of the vertebral centrum flattened, and the other (hinder) end concave ; this ' platycoehan' type we find in the dorsal and caudal vertebrae of the gigantic Cetiosaums (PI. 4, fig. 5). With a few exceptions, all the modern Reptiles of the order Lacertilia have the same procoelian type of vertebrae as the modern Crocodilia, and the same structure prevailed as far back as the period of the Mosasaurus, and in some smaller members of the Lacertilian order in the Cretaceous and Weal den epochs. Resuming the special description of the osteology of the modern Crocodilia, we find the procoelian type of centrum established in the third cervical, which is shorter but broader than the second ; a parapophysis is developed from the side of the centrum, and a diapophysis from the base of the neural arch ; the pleurapophysis is shorter, its fixed extremity is bifid, articulating to the two above-named processes ; its free ex- tremity expands, and its anterior angle is directed forwards to abut against the inner surface of the extremity of the rib of both the axis and atlas, whilst its posterior pro- longation overlaps the rib of the fourth vertebra. The same general characters and imbricated coadaptation of the ribs characterise the succeeding cervical vertebrae to the seventh inclusive, the hypapophysis {/i!/, fig. 2, PL 1 B) progressively though slightly increasing in size. In the eighth cervical the rib becomes elongated and slender ; the anterior angle is almost or quite suppressed, and the posterior one more developed and produced more downwards, so as to form the body of the rib, which terminates, however, in a free point. In the ninth cervical the rib is increased in length, but is still what would be termed a 'false' or ' floating rib' in anthropotomy. In the succeeding vertebra the pleurapophysis articulates with a haemapophysis, and the haemal arch is completed by a haemal spine ; and by this completion of the typical segment we distinguish the commencement of the series of dorsal vertebrae. With regard to the so-called ' perforation of the transverse process,' this equally exists in the present vertebra, as in the cervicals, as may be seen by comparing fig. 6, p. 5, with fig. 2, PI. 1 D; in both, the foramen is the vacuity intercepted between the bifurcate extremity of the rib and the rest of the vertebra with which that rib articulates ; and, on the other hand, the cervical vertebrae equally show surfaces for the articulation of ribs. Cuvier, in including the proximal portions of the ribs with the rest of the vertebra, in his figure of a dorsal vertebra of a Crocodile, * so far follows nature, and produces a parallel to * Ossemens Fossiles, -Ito, torn, v, pt. ii, pi. iv, fig. 4. 88 BRITISH FOSSIL REPTILES. his figure of a cervical vertebra ; but the entire natural vertebra or segment includes the parts delineated in outline in Cut G, p. 5. In that figure is shown the semiossified bar // which is interposed between the pleurapophysisj?^/ and hfemapopliysis // in the Crocodilia and some existing Lizards. The typical characters of the segment due to the completion of both neural and litcmal arches, is continued in some species of Crocodilia to the sixteenth, in some {Crocodilus acutns) to the eighteenth vertebra. In the Crocodilus acutns and the AUiyafor lucius, the hsemapophysis of the eighth dorsal rib (seventeenth segment from the head) joins that of the antecedent vertebra. The pleurapophyses project freely outwards, and become 'floating ribs' in the eighteenth, nineteenth, and twentieth vertebrae, in which they become rapidly shorter, and in the last appear as mere appendages to the end of the long and broad diapophyscs : but the hgemapophyses by no means disappear after the solution of their union with their pleurapophyses ; they are essentially independent elements of the segment, and they are continued, therefore, in pairs along the ventral surface of the abdomen of the Crocodilia, as far as their modified homotypes the pubic bones. They are more or less ossified, and are generally divided into two or three pieces. Another character afi'orded by the haemal arch is the more important in reference to palaeontology, as it affects the centrum and neural arch of the vertebra as well as the pleurapophysis ; and thus aids in the determination of the vertebra. The parapophysis progressively ascends upon the side of the centrum in the two anterior dorsal vertebrae, and disappears in the third, or, passing upon its neurapophysis, blends with the base of the diapophysis. In this segment, therefore, the proximal end of the rib ceases to be bifurcate, but is simply notched, the curtailed head being applied to the end of the thickened anterior part of the transverse process, and the tubercle abutting against its extremity ; in the five following dorsals the head and tubercle of the rib progressively approximate and blend together, or the head disappears in the tenth dorsal, in which the rib is simply attached to the end of the diapophysis. The hypapophysis ceases to be developed after the third or fourth dorsal vertebrae. The zygapophyses become gradually more horizontal, the anterior ones looking more directly upwards, the posterior ones downwards. The ' lumbar vertebrae' are those in which the diapophyses cease to support moveable pleurapophyses, although they are elongated by the coalesced rudiments of such which are distinct in the young Crocodilia. The development and persistent individuality of more or fewer of these rudimental ribs determines the number of the dorsal and lumbar vertebrae respectively, and exemplifies the purely artificial character of the distinction. The number of vertebrae or segments between the skull and the sacrum, in all the Crocodilia I have yet examined, is twenty-four. In the skeleton of a Gavial I have seen thirteen dorsal and two lumbar ; in that of a Crocodilus cafa- phractus twelve dorsal and three lumbar ; in those of a Crocodilus acutus, and Allir/afor lucius, eleven dorsal and four lumbar, and this is the most common number ; but in CROCODILIA. 89 tlic skeleton of tlie Crocodile, I believe of the species called Croc, biporcatus, described by Cuvier,* he gives five as the number of the lumbar vertebree. But these varieties in the development or coalescence of the stunted pleurapophysis are of little essential moment; and only serve to show the artificial character of the 'dorsal' and 'lumbar' vertebrae. The coalescence of the rib with the diapophysis obliterates of course the character of the ' costal articular surfaces ;' which we have seen to be common to both dorsal and cervical vertebrae. The lumbar zygapophyses have their articular surfaces almost horizontal, and the diapophyses, if not longer, have their antero-posterior extent somewhat increased ; they are much depressed, or flattened horizontally. The sacral vertebrae are very distinctly marked by the flatness of the coadapted ends of their centrums ; there are never more than two such vertebrae inthQ Cwcodilia recent or extinct : in the first the anterior surface of the centrum is concave ; in the second it is the posterior surface ; the zygapophyses are not obliterated in either of these sacral vertebrae, so that the aspects of their articular surface — upwards in the anterior pair, downwards in the posterior pair — determines at once the corresponding extremity of a detached sacral vertebra. The thick and strong transverse processes form another characteristic of these vertebrae ; for a long period the suture near their base remains to show how large a proportion is formed by the pleurapophysis. This element articulates more with the centrum than with the diapophysis developed from the neural arch : f it terminates by a rough, truncate, expanded extremity, which almost or quite joins that of the similarly but more expanded rib of the other sacral vertebrae. Against these extremities is applied a supplementary costal piece, serially homologous with the appendage to the proper pleurapophysis in the dorsal vertebrae, but here interposing itself between the pleurapophyses and haemapophyses of both sacral vertebras, not of one only. This intermediate pleurapophysial appendage is called the ' ilium ;' it is short, thick, very broad, and subtriangular, the lower truncated apex forming with the connected extremities of the haemapophysis an articular cavity for the diverging appendage, called the ' hind leg.' The haemapoph)^sis of the anterior sacral vertebra is called ' pubis ;' it is moderately long and slender, but expanded and flattened at its lower extremity, which is directed forwards towards that of its fellow, and joined to it through the intermedium of a broad, cartilaginous, haemal spine, completing the haemal canal. The posterior haemapophysis is broader, subdepressed, and subtriangular, expanding as it approaches its fellow to complete the second haemal arch ; it is termed ' ischium.' The great development of all the elements of these luemal arches, and the peculiar and distinctive forms of those that have thereby acquired, from the earliest dawn of anatomical science, special names, relates phy- * Tom. cit., p. 95. It is to be observed that Cuvier begins to couut the dorsal vertebra when the rib has changed its hatchet-shape for a styloid shape. f Cuvier, who well describes this structure, remarks, "aussi raeritent-elles plutot le nom des cotes que celiii d'apophyses transverses." (Tom. cit., p. 98.) 90 BRITISH FOSSIL REPTILES. siologically to tlie functions of the diverging appendage which is developed into a potent locomotive member. This hmb appertains properly, as the pi-oportion contri- buted by the ischium to the articular socket and the greater breadth of the pleura- pophysis show, to the second sacral vertebra ; to which the ilium chiefly belongs. The first caudal vertebra, which presents a ball for articulating with a cup on the back part of the last sacral, retains, nevertheless, the typical position of the ball on the back part of the centrum ; it is thus biconvex, and the only vertebra of the series which presents that structure. I have had this vertebra in three different species of extinct Eocene Crocodilia. In the Crocodilus toliapicus, PI. 5, fig. 7 ; in the Croc, champso'ides, PL 3v^, fig. 10; and in the Crocodilus Ilastinf/sia;, PL 1 D, fig. 7. The advantage of possessing such definite characters for a particular vertebra is, that the homologous vertebra may be compared in different species, and may yield such distinctive characters as will be hereafter pointed out in those of the three species above cited. The first caudal vertebra, moreover, is distinguished from the rest by ha\'ing no articular surfaces for the hfemapopliyses, which in the succeeding caudals form a haemal arch, like the neurapophyses above, by articulating directly with the centrum. The arch so formed has its base not applied over the middle of a single centrum, but like the neural arch in tlie back of the tortoise and sacrum of the bird, across the interspace between two centrums. The first hsemal arch of the tail belongs, however, to the second caudal vertebra, but it is displaced a little backwards from its typical position. The detached centrum of a caudal vertebra, besides being more slender and com- pressed, is distinguished from those of the before-described vertebrae by the two articular surfaces at the posterior border of their under surface. The zygapophyses become vertical as far as the sixteenth or seventeenth, beyond which the two posterior zygapophyses coalesce in an oblique plane notched in the middle, which is received into a wider notch at the fore pai't of the neural arch of the succeeding vertebra. The sutures between the pleurapophyses and diapophyses are maintained during a long period of the animal's growth, and demonstrate the share which these two elements respectively take in the formation of the transverse process. So constituted, these processes progressively decrease in length to the fifteenth or sixteenth caudal vertebra, and then disappear. The neural spines progressively decrease in every dimension, save length, which is rather increased as far as the twenty-second or twenty-third vertebra, beyond which they begin again to shorten, and finally subside in the tei'minal vertebrae of the tail. The caudal hcemapophyses coalesce at their lower or distal ends, from which a spinous process is prolonged downwards and backwards ; this grows shorter towards the end of the tail, but is compressed and somewhat expanded antero-posteriorly. The hsemal arch so constituted has received the name of ' chevron bone.' A side view of the body of a middle caudal vertebra of the Crocodilus toUapicus is CROCODILIA, 91 given in PI. 3, fig. 8, and an under view of the same in fig. 9, showing the two hyp- apophysial ridges extending from tlie articular facets for the hsemapophyses atone end to the other end of the centrum. The segments of the endo-skelcton composing the skull are more modified than those of the pelvis ; but just as the vertebral pattern is best preserved in the neural arches of the pelvis, which are called collectively ' sacrum,' so, also, is it in the same arches of the skull, which are called collectively ' cranium.' The elements of which these cranial arches are composed preserve, moreover, their primitive or normal individuality more completely than in any of the vertebrre of the trunk, except the atlas, and consecpiently the archetypal character can be more completely demonstrated. In fossil Crocodilia, and many other reptiles, the bones of the head are very liable from this cause to a greater extent of dislocation and separation than happens to the skull of the warm-blooded animal, in which a greater proportion of those primitive bones coalesce with age. It not unfrequently happens that detached bones of the skull of a reptile are found fossil, and the usually much modified form of these vertebral elements renders their determination difficult. In order to diminish this difiiculty, I subjoin some figures of the individual bones from my work on the ' Archetype of the Vertebrate Skeleton,' with such indication of their natural connexions, as is compatible with a clear outline. A profile or side view of all the bones is offered in fig. 13, and as those of the cranium are least familiar to the pateontologist in their detached state, I have added a direct view of them nearly as they are arranged in the formation of the successive neural arches of the skull. Such figures are the more necessary in the present state of anatomy and palaeontology, since the illustrations of the osteology of the crocodile which have hitherto been prefixed to the descriptions of the fossil remains of the Reptilian class, as, e. g., in the great work of Cuvier, include only figures of the bones in question as they are naturally combined together in the entire skull. If, after separating the atlas from the occiput, we proceed to detach the occipital segment of the cranium from the next segment in Pi„. g. advance, we find the detached segment presenting the form of the neural arch, and it is easily and naturally divisible into the four bones figured in Cut 9. The dotted circle crosses the mars-ins at which the bones were joined v together, in order to encompass the hindmost segment of the brain, called ' epencephalon,' whence this neural arch of the occiput is termed ' epencephalic arch.' No. 1 is the base of the arch, and is the 'centrum' or Bonesoftliedisarticulatedepencephalic body of the whole occipital vertebra : it presents, like arch, viewed from behind (Crocodae). those of the trunk, a convexity or ball at its posterior articular surface, but its anterior one, like the hindmost centrum of the sacrum, unites with the next centrum in advance by a flat rough ' sutural' or ' symphysial' surface. Like most of the centrums in the 92 BRITISH FOSSIL REPTILES. neck and beginning of the back, that of the occiput developes a ' hypapophysis,' but this descending process is longer and larger, its base extending over the whole of the under surface of the centrum. It is a character whereby the occipital centrum of a Crocodilian reptile may be distinguished from that of a Lacertian one; for in the latter a pair of diverging hypapophyses project from the under surface, as is shown in most recent lizards and in the great extinct Mosasaurus* The upper and lateral parts of no. i present rough sutural surfaces, like those in the centrums of the trunk, for articulating with the ' neurapophyses,' nos 2, 2, which developc short, thick, obtuse, transverse processes (4, 4). The modified or specialized character of the elements of the cranial vertebne has gained for them special names. The centrum (1) is called the ' basioccipital ;' the neurapophyses (2,2) are the ' ex- occipitals ;' the neural spine (3) is the ' superoccipital.' The transverse processes (4, 4), which may combine both diapophyses and parapophyses, but which, from the modifications of the transverse processes of the atlas, and the autogenous character of the parapophyses in some fishes, and of the processes in question in the Chelonian Reptiles, I believe to be best entitled to be regarded as the parapophyses, are called the ' paroccipitals ;' they are never detached bones in the Crocodilia, as they are in the Chelonia and in most fishes. The exoccipitals perform the usual functions of neurapophyses, and, like those of the atlas, meet above the neural canal ; they are perforated to give exit to the vagal and hypoglossal nerves, and protect the sides of the medulla oblongata and cerebellum — the two divisions of the epencephalon. The superoccipital (3) is broad and flat, like the similarly detached neural spine of the atlas ; it advances a little forwards, beyond its sustaining neurapophyses, to protect the upper surface of the cerebellum : it is traversed by tympanic air-cells, and assists with the exoccipitals (2, 2) in the formation of the chamber for the internal ear. The chief modification of the occipital segment of the skull, as compared with that of the osseous fish, or with the typical vertebra, is the absence of an attached htemal arch. We shall afterwards see that this arch is present in the Crocodile, although displaced ; a profile of it is given, as restored to its typical position, in the side view of the bones of the skull, fig. 13. Proceeding with the neural arches of the Crocodile's skull, if we dislocate the segment in advance of the occiput, we bring away in connexion with the long base-bone, 5 and 9, fig. 13, the bones which, in the same figure, are tied together by the double lines, N 11, N in, and by the curved arrows, H 11 and H in. In fact, the centrums of two vertebrae have here coalesced, as we find to happen in the neck of the Siluroid fishes, and in the sacrum of birds and mammals. The two connate cranial centrums must be artificially divided, in order to obtain the segments distinct to which they belong. Fig. 10 gives a back view of the disarticulated bones of the neural * See Quarterly Journal of the Geological Society, Nov. 1, )S49, p. 382, pi. x, figs. 5, 6. CROCODILIA. 93 arch of the ' parietal vertebra,' as the segment is termed which is in advance of the occipital one. The hinder portion (5) of the great base-bone, which is the centrum of the parietal vertebra, is called 'basisphenoid.' Fig. 10. It supports that part of the ' mesencephalon,' which is formed by the lobe of the third ventricle, and its upper surface is excavated for the pituitary prolongation of that cavity. The basisphenoid developes from its under surface a ' hypapophysis,' which is suturally united with the fore part of that of the basioccipital, but extends further down, and is similarly united in front to the ' pterygoids' (24). These rough sutural surfaces of the long descending process of the basisphenoid are very Disarticulated mesencephalic arch, viewed characteristic of that centrum, when detached in fto"i bcliind (Crocodile). a fossil state. The neurapophyses of the parietal vertebra (G, 6) are called the ' ali- sphenoids ;'* they protect the sides of the mesencephalon, and are notched at their anterior margin, for a conjugational foramen transmitting the trigeminal nerve. As accessory functions they contribute, like the corresponding bones in fishes, to the formation of the ear-chamber. They have, however, a little retrograded in position (see fig. 14, 6), resting below, in part upon the occipital centrum, and supporting more of the spine of that segment (3) than of their own (7)- The spine of the parietal vertebra (fig. 10, 7) is a permanently distinct, single, depressed bone, like that of the occipital vertebra ; it is called the ' parietal,' and completes the neural arch, as its crown or key-bone ; it is partially excavated by the tympanic air-cells. The bones 8, 8 wedged between 6 and 7, manifest more of their parapophysial character than their homotypes (4, 4) do in the occipital segment, since they support modified ribs, are developed from independent centres, and preserve their individuality. They form no part of the inner walls of the cranium, but send outwards and backwards a strong transverse process for muscular attachment. They afford a ligamentous attachment to the haemal arch (fig. 13, H 11) of their own segment, and articulate largely with the pleurapophysis (28) of the antecedent haemal arch (H iii), whose more backward dis- placement, in comparison with its position in the fish's skull, is well illustrated in the metamorphosis of the toad and frog. On removing the neural arch of the parietal vertebra, after the section of its confluent centrum, the elements of the corresponding arch of the frontal vertebra, slightly disarticulated, present the arrangement shown in fig. 11. The compressed produced centrum (9) shown in natural connexion with the parietal centrum 5 in fig. 13, * This bone is the ' rocher' or petrous portion of the temporal bone, according to Cuvier, in the Reptiles (Ossemens Fossiles, v, pt. ii, 1824) ; but is the 'aile temporalc du spheuoide' in fishes (Histoire Naturellc des Poissons, torn, i, 1828), birds, and mammals. O 94 BRITISH FOSSIL REPTILES. Disarticulated proaenceplialic arch, viewed from behind (Crocodile). and with the bone lo in fig. 14, has its form modified like that of the vertebral centrums at the opposite extreme of the body in many birds ; it is called the ' presphenoid.' Eig. 11. Theneurapophyses 10, lO, articulate with the upper part of 9 ; they are expanded and smoothly excavated on their inner surface to support the sides of the large prosencephalon ; they dismiss the great optic nerves by the notch marked op in fig. 14, and the motor nerves of the eyeball by the notch s. They show the same tendency to a retrograde change of position, as the neighbouring neurapophyses {(t) ; for though they support a greater proportion of their proper spine (ii), they also support part of the parietal spine (7), and rest, in part, below upon the parietal centrum (.')) : the neurapophyses (10, lO) are called ' orbitosphenoids.'* The neural spine (11) of the frontal vertebra retains its normal character as a single symmetrical bone, like the parietal spine which it partly overlaps ; it also completes the neural arch of its own segment, but is remarkably extended longitudinally forwards, as is shown in figs. 13 and 14, 11, where it is much thickened, and assists in forming the ca^^ties for the eyeballs {or, fig. 14) : it is called the (frontal) bone. In contemplating in the skull itself, or in such side views as are given in figs. 13 and 14, the relative position of the frontal (11), to the parietal (7), and of this to the superoccipital (3), which is overlapped by the parietal, just as itself overlaps the flattened spine of the atlas, we gain a conviction which cannot be shaken by any difi"erence in their mode of ossification, by their median bipartition, or by their extreme expansion in other animals, that the above-named single, median, imbricated bones, each completing its neural arch, and permanently distinct from the piers of such arch, must repeat the same element in those successive arches, in other words, must be ' homotypes,' or serially homologous.! In like manner the serial homology of those piers, called ' neur- apophyses,' viz. the laminse of the atlas (fig. 8 na), the exoccipitals (figs. 13 and 14, 2), the alisphenoids (e), and the orbitosphenoids (10), is equally unmistakable. Nor can we shut out of view the same serial relationship of the paroccipitals (4), as coalesced parapophyses of the occipital vertebra, with the mastoids (s), and the postfrontals (12), as permanently detached parapophyses of their respective vertebrse. All stand out from the sides of the cranium, as transverse processes for muscular attachment, all are alike autogenous in the Chelonians, and all of them, in fishes, ofifer articular surfaces * According to Cuvier, this bone is the ' aile temporale Ju sphenoide et une grande partie de I'aile orbitaire' in Crocodiles. (Ossemens Fossiles, torn, v, pt. ii.) t See my work 'Ou the Archetype of the Vertebrate Skeleton,' pp. 5-8, 8vo, Van Voorst, for the expla- nation of these terms. CHOCODILIA. 95 Fig. 12. for the ribs or haemal arches of their respective vertebrae ; and these characters are retained in the postfrontals as well as in the mastoids of the Crocodiles. The frontal parapophysis ( 12, fig. U) is wedged between the back part of the spine (ll) and the neurapophysis (lo) ; its outwardly projecting process extends also back- wards and joins that of the succeeding parapophysis (s) ; but, notwithstanding the retrogradation of the inferior arch (fig. 13, H iii), it still articulates with part of its own pleurapophysial element (28), which forms the proximal element of that arch. There finally remain in the cranium* of the Crocodile, after the successive detach- ment of the foregoing arches, the bones intersected by the double line N iv, in fig. 13, which, as in fig. 14, are numbered 13, U, and 15, and of which a foreshortened back view is represented in Cut 12 ; but, notwithstanding the extreme degree of modification to which their extreme position subjects them, we can still trace in their arrangement a correspondence with the vertebrate type. A long and slender symmetrical grooved bone (i3, between 24, 24), like the ossified inferior half of the capsule of the notochord, is con- tinued forwards from the inferior part of the cen- trum (y) of the frontal vertebra, and stands in the relation of a centrum to the vertical plates of bone (14), fig. 12, and fig. 14, which expand as they rise into a broad, thick, triangular plate, with an exposed hori- zontal superior surface. These bones, which are called ' prefrontals,' stand in the relation of ' neurapophyses' to the rhinencephalic prolongations of the brain, com- monly but erroneously called ' olfactory nerves ;' and they form the piers or haunches of a neural arch, which is completed above by a pair of symmetrical bones (15) called ' nasals,' which I regard as a divided or bifid neural spme. Disarticulated rhinencephalic arch, with The centrum of this arch is established by ossifi- the anchylosed pterygoids (24) in dotted cation in the expanded anterior prolongation of the "'^^^'^^ (Crocodne). fibrous capsule of the notochord, beyond the termination of its gelatinous axis. The * The part called cranium in human anatomy is a quite artificial division of the skull ; it includes the neurapophyses of the nasal vertebrae, coalesced with the capsules of the sense of smell, and excludes the centrum and neural arch of the same natural segment ; it also includes one portion of the diverging appendage (27) of the maxillary arch, because it enters largely into the formation of the capacious cranial cavity of man, and another portion of the diverging appendage of the same arch (24), because it happens to coalesce with the basisphenoid. The capsule of the organ of hearing is included together with part of that of the olfactory organ, whilst the capsule of the organ of sight, and part of that of the organ of smell are excluded. None of these sense-capsules properly form any part of the cranium, but they are lodged in interspaces of its constituent arches. The cranial portion of the skuU, as a natural division of that part of the endoskeleton, ought to consist exclusively of the neural arches and centrums of the cranial vertebrae. 96 BRITISH FOSSIL REPTILES. median portion above specified retains most of tlie formal characters of the centrum, but there is a pair of long, slender, symmetrical ossicles, which, from the seat of their original development, and their relative position to the neural arch, must be regarded as also parts of its centrum. And this ossification of the element in question from different centres will be no new or strange character to those who recollect that the vertebral body in man and mammalia is developed from three centres. The term 'vomer' is applied to the pair of bones 13, in fig. 12, because their special homology with the single median bone, so called in fishes and mammals, is indisputable; but a portion of the same element of the skull retains its single symmetrical character in the Crocodile, and is connate with the enormous pterygoids (24), between which it is wedged. In some Alligators {All. niger) the divided anterior vomer extends far forwards, expands anteriorly, and appears upon the bony palate. Almost all the other bones of the head of the Crocodile are adjusted so as to constitute four inverted arches, respectively completed or closed below at the points marked H iv, H iii, H ii, and H i, in fig. 13. These are the haemal arches of the four segments or vertebrae, of which the neural arches have been just described. But they have been the seat of much greater modifications, by which they are made sub- servient to a variety of functions unknown in the haemal arches of the rest of the body. Thus the two anterior haemal arches of the head perform the office of seizing and bruising the food ; are armed for that purpose with teeth : and, whilst one arch is firmly fixed, the other works upon it like the hammer upon the anvil. The elements of the fixed arch (H iv), called ' maxillary arch,' have accordingly undergone the greatest amount of morphological change in order to adapt that arch to its share in mastication, as well as for forming part of the passage for the respiratory medium, which is perpetually traversing this haemal canal in its way to purify the blood. Almost the whole of the upper surface of the maxillary arch is firmly united to contiguous parts of the skuU by rough or sutural surfaces, and its strength is increased by bony appendages, which diverge from it to abut against other parts of the skull. Comparative anatomy teaches that, of the numerous places of attachment, the one which connects the maxillary arch by its element (20) with the centrum (13) and the descending plates of the neurapophyses (14) of the nasal segment, is the normal or the most constant point of its suspension, the bone (20) being the pleurapophysial element of the maxillary arch : it is called the 'palatine,' because the under surface, shown in PI. A, 2, and PI. 1 B, at 20, forms a portion of the bony roof of the mouth called the ' palate.' It is articulated at its fore part with the bone (21) in the same plates, which bone is the haemapophysial element of the maxillary arch. It is called the ' maxillary,' and is greatly developed both in length and breadth ; it is connected not only with 20 behind, and 22 in front, which are pai'ts of the same arch (see fig. 13), and with the diverging appendages of the arch, viz. (26) the malar bone, and (24) the pterygoid, but also with the nasals (15) and the lachrymal (ic), as well as with its fellow of the CROCODILIA. 97 opposite side of the arch. The smooth expanded horizontal plate which efifects the latter junction, shown in PI. 1 B, and PI. A % at 21, is called the palatal plate of the maxillary ; the thickened external border, where this plate meets the external rough surface of the bone, and which is perforated for the lodgement of the teeth, is the ' alveolar border' or ' process' of the maxillary. The haemal spine or key-bone of the arch (22) is bifid, and the arch is completed by the symphysial junction of the two symmetrical halves at H iv, fig. 13 ; these halves are called ' premaxillary bones ;' Ym. 13. Disarticulated bones of tlie Skull of an Alligator, N i to iv tlie neui-al arches ; H I to iv the hajmal arches and appendages. these bones, like the maxillaries, have a rough facial plate, PI. 1 A, 22 and a smooth palatal plate PI. 1 B, 22, with the connecting alveolar border. The median symphysis is perforated vertically through both plates ; the outer or upper hole being the external nostril, the under or palatal one being the prepalatal or naso-palatal aperture ; this is completely inclosed by the premaxillary bone, as shown in PI. 1 B, fig. 2, 22, and PI. 1 C, 22, np ; whilst, in all known existing Crocodiles and Alligators, the tips of tlic nasal bones, as at 15, fig. 1, PI- A 2, enter into the back part of the circumference of the nasal aperture. In the Gavials, as may be seen in PI. 1, fig. 1 a, the nasal aperture is wholly surrounded by the premaxillaries, i ; and one of the fossil Eocene Crocodiles, 98 BRITISH FOSSIL REPTILES. presently to be described, PI. 1 A, fig. 1, differs from all the modern species, in the exclusion of the nasal bones (i.i) from the nasal aperture. Both the palatine (fig. 13, 20) and the maxillary (ib. 21) send outwards and back- wards, parts or processes which diverge from the line of the haemal arch of which they are the chief elements ; and these parts give attachment to distinct bones which form the ' diverging appendages' of the arch, and serve to attach it, as do the diverging appendages of the thoracic haemal arches in the bird, to the succeeding arch. The appendage (24) called ' pterygoid' effects a more extensive attachment, and is peculiarly developed in the CrocodiUa. As it extends backwards it expands, unites with its fellow, below the nasal canal, and encompassing that canal, coalesces above it with the vomer, and is firmly attached by suture to the presphenoid and basisphenoid : it surrounds the hinder or palatal nostril, and, extending outwards, as shown in PI. 1 A, fig. 3 (24), it gives attachment to a second bone (25), called ' ectopter}'goid,' which is firmly connected with the maxillary (25), the malar (26), and the post-frontal (12). The second diverging ray is of great strength ; it extends from the maxillary (21) (' haema- pophysis' of the maxillary arch) to the tympanic (28) ('pleurapophyses' of the mandibular arch), and is divided into two pieces, the malar (26), and the squamosal (27). Such are the chief Crocodilian modifications of the haemal arch and appendages of the anterior or nasal vertebra of the skull. The haemal arch of the frontal vertebra is somewhat less metamorphosed, and has no diverging appendage. It is slightly displaced backwards, and is articulated by only a small proportion of its pleurapophysis (28), to the parapophysis (12) of its own segpient ; the major part of that short and strong rib articulating with the para- pophysis (8) of the succeeding segment. The bone (28) called ' tympanic,' because it serves to support the ' drum of the ear,' in air-breathing vertebrates, is short, strong, and imraoveably wedged, in the CrocodiUa, between the paroccipital (4), mastoid (s), post-frontal (12), and squamosal (27); and the conditions of this fixation of the pleura- pophysis are exemplified in the great development of the haemapophysis (mandible), which is here unusually long, supports numerous teeth, and requires, therefore, a firm point of suspension, in the violent actions to which the jaws are put in retaining and overcoming the struggles of a powerful living prey. The moveable articulation between the pleurapophysis (28) and the rest of the haemal arch is analogous to that which we find between the thoracic pleurapophysis and haemapophysis in the Ostrich and many other birds. But the haemapophysis of the mandibular arch in the Crocodiles is subdivided into several pieces, in order to combine the greatest elasticity and strength with a not excessive weight of bone. The different pieces of this purposely sub- divided element have received definite names. That numbered 29, which offers the articular concavity to the convex condyle of the tympanic (28), is called the ' articular' piece ; that beneath it (30), which dcvelopes the angle of the jaw, when this projects, is the ' angular' piece ; the piece above (29') is the ' surangular ;' the thin, broad, flat CROCODILIA. 99 piece (3i)j applied, like a splint, to the inner side of the other parts of the mandible, is the 'splenial;' the small accessory ossicle (31') is the ' coronoid,' because it developes the process so called, in lizards ; the anterior piece (32), which supports the teeth, is called the ' dentary.' This latter is the homotype of the preraaxillary, or it represents that bone in the mandibular arch, of which it may be regarded as the haemal spine ; the other pieces are subdivisions of the hBemapophysial element. The purport of this subdivision of the lower jaw-bone has been well explained by Conybeare* and Buckland,t by the analogy of its structure to that adopted in binding together several parallel plates of elastic wood or steel to make a crossbow, and also in setting together thin plates of steel in the springs of carriages. Dr. Buckland adds, "those who have witnessed the shock given to the head of a Crocodile by the act of snappino- together its thin long jaws, must have seen how liable to fracture the lower jaw would be, were it composed of one bone only on each side." The same reasoning applies to the composite structure of the long tympanic pedicle in fishes. In each case the spHcing and bracing together of thin flat bones of unequal length and of varyino- thickness, affords compensation for the weakness and risk of fracture that would other- wise have attended the elongation of the parts. In the abdomen of the Crocodile the analogous subdivision of the hsemapophyses, there called abdominal ribs, allows of a slight change of their length, in the expansion and contraction of the walls of that cavity ; and since amphibious reptiles, when on land, rest the whole weight of the abdomen directly upon the ground, the necessity of the modification for diminished liability to fracture further appears. These analogies are important, as demonstratino- that the general homology of the elements of a natural segment of the skeleton is not affected or obscured by their subdivision for a special end. Now this purposive modification of the hsemapophyscs of the frontal vertebra is but a repetition of that which affects the same elements in the abdominal vertebrae. Passing next to the haemal arch of the parietal vertebra (fig. 13, H iir), we are first struck by its small relative size ; its restricted functions have not required it to ^row in proportion with the other arches, and it consequently retains much of its embryonic dimensions. It consists of a ligamentous ' stylohyal' — its pleurapophysis, retaining the same primitive histological condition which obstructs the ordinary recognition of the same elements of the lumbar haemal arches. A cartilaginous ' epihyal' (39) intervenes between this and the ossified ' haemapophysis' (40), which bears the special name of ceratohyal. The haemal spine (41) retains its cartilaginous state, like its horaotypes in the abdomen : there they get the special name of ' abdominal sternum,' here of ' basi- hyal.' The basihyal has, however, coalesced with the thyrohyals, to form a broad cartilaginous plate, the anterior border rising like a valve to close the fauces, and the posterior angles extending beyond and sustaining the thyroid and other parts of the * Geol. Trans., 1821, p. 565. t Bridgewater Treatise, 1836, vol. i, p. 176. 100 BRITISH FOSSIL REPTILES. larynx. The long bony ' ccratohyal' (fig. 13, 40), and the commonly cartilaginous 'cpihyal' (ib. 39), are suspended by the hgamentous ' stylohyal' to the paroccipital process ; the whole arch having, like the mandibular one, retrograded from the con- nexion it presents in fishes. This retrogradation is still more considerable in the succeeding hsemal arch. In comparing the occipital segment of the crocodile's skeleton with that of the fish, the chief modification that distinguishes that segment in the crocodile is the apparent absence of its hsemal arch. We recognise, however, the special homologues of the constituents of that arch of the fishes' skeleton in the bones 51 and 52 of the crocodile's skeleton (fig. 13) ; but the upper or suprascapular piece (50) retains, in connexion with the loss of its proximal or cranial articvilations, its cartilaginous state : the scapula (51) is ossified, as is likewise the coracoid (52), the lower end of which is separated from its fellow by the interposition of a median, symmetrical, partially ossified piece called ' epistefnum' (Hi). The power of recognising the special homologies of 50, 51, and 52 in the crocodile, with the similarly numbered constituents of the same arch in fishes*, though masked, not only by modifications of form and proportion, but even of very substance, as in the case of 50, depends upon the circumstance of these bones constituting the same essential element of the archetypal skeleton; for although in the present instance there is superadded to the adaptive modifications above cited, the rarer one of altered connexions, Cuvier does not hesitate to give the same names, ' suprascapulaire ' to 50 and 'scapulaire' to 51, in both fish and crocodile: but he did not perceive or admit that the narrower relations of special homology were a result of, and necessarily included in, the wider law of general homology. According to the latter, we discern in 50 and 51 a teleologically compound ' pleurapophysis,' in 52 a ' hsemapophysis,' and in hs the ' haemal spine,' completing the haemal arch. The general relations of the scapulo-coracoid arch to a haemal or costal one was early recognised by Oken. This philosopher, having observed the free cervical ribs in a specimen of the Lacerfa apoda, Pallas {Fseudojjus), deemed them representatives of the scapula, and this bone to be, in other animals, the coalesced homologues of the cervical pleurapophyses.f In no animal are the conditions for testing this question so favor- able and obvious as in the crocodiles and ga vials (PI. 1) ; not only do cervical ribs coexist with the scapulo-coracoid arch, but they are of unusual length, and are developed from the atlas as well as from each succeeding cervical vertebra : we can also trace them beyond the thorax to the sacrum, and throughout a great part of the caudal region, as the sutures of the apparently long transverse processes of the * See fig. 5, p. 18, and pi. ii, fig. 2, in ' The Arclietype and Homologies of the Vertebrate Skeleton.' t " Auch die Scapula nicht ein Kuoehen, soudern wenigstens eine aus fiinf Halsrippen zusaminengeflossene Platte iii"— Programmiiher die Bedeutuny der Schiidelhwchen, Aio, 180", p. 16. He reproduces the same idea of the general homology of the scapula in the ' Lehrbuch der Natiir-philosophie,^ 1843, p. 331, ^2381. Cams also regards the scapulo-coracoid arch as the reunion of several (at least three) proto- vertebral arches of the trunk-segments. {Urtheilen des Knochen wid Schalen r/enistes, fol., 1828.) CROCODILIA. 101 coccygeal vertebrae demonstrate in the young animal ; the lumbar pleurapophyses being manifested at the same period as cartilaginous appendages to the ends of the long diapophyses. The scapulo-coracoid arch, both elements (51, 52) of which retain the form of strong and thick vertebral and sternal ribs in the crocodile, is applied in the skeleton of that animal over the anterior thoracic htemal arches. Viewed as a more robust haemal arch, it is obviously out of place in reference to the rest of its vertebral segment. If we seek to determine that segment by the mode in which we restore to their centrums the less displaced neural arches of the antecedent vertebrae of the cranium or in the sacrum of the bird,* we proceed to examine the vertebras before and behind the dis- placed ai'ch, with the view to discover the one which needs it, in order to be made typically complete. Finding no centrum and neural arch without its pleurapophyses from the scapula to the pelvis, we give up our search in that direction ; and in the opposite direction we find no vertebra without its ribs until we reach the occiput : there we have centrum and neural arch, with coalesced parapophyses — the elements answering to those included in the arch N i, fig. 13 — but without the arch H i; which arch can only be supplied, without destroying the typical completeness of antecedent cranial segments, by a restoration of the bones 50 — 52, to the place which they naturally occupy in the skeleton of the fish. And since anatomists are generally agreed to regard the bones 50 — 52 in the crocodile (fig. 13) as specially homologous with those so numbered in the fish,t we must conclude that they are likewise homo- logous in a higher sense ; that in the fish, the scapulo-coracoid arch is in its natural or typical position, whereas in the crocodile it has been displaced for a special purpose. Thus, agreeably with a general principle, we perceive that, as the lower vertebrate animal illustrates the closer adhesion to the archetype by the natural articulation of the scapulo-coracoid arch to the occiput, so the higher vertebrate manifests the superior influence of the antagonising power of adaptive modification by the removal of that arch from its proper segment. The anthropotomist, by his mode of counting and defining the dorsal vertebrae and ribs, admits, unconsciously perhaps, the important principle in general homology which is here exemplified, and which, pursued to its legitimate consequences and further applied, demonstrates that the scapula is the modified rib of that centrum and neural arch which he calls the ' occipital bone,' and that the change of place which chiefly masks that relation (for a very elementary acquaintance with comparative anatomy shows how little mere form and proportion afi"ect the homological characters of bones) differs only in extent and not in kind from the modification which makes a minor amount of comparative observation requisite, in order to determine the relation of the shifted dorsal rib to its proper centrum in the human skeleton. * See 'On the Archetype and Homologies of the Vertebrate Skeleton,' p. 11", p. 159. t Op. cit., fig. 5, p. 17. P 102 BRITISH FOSSIL REPTILES. With reference, therefore, to the occipital vertebra of the crocodile, if the com- paratively well-developed and permanently distinct ribs of all the cen'ical vertebrae prove the scapular arch to belong to none of those segments, and, if that hjemal arch l^e required to complete the occipital segment, which it actually does complete in fishes, then the same conclusion must apply to the same arch in other animals, and we must regard the occipital vertebra of the tortoise as completed below by its scapulo-coracoid arch and not, as Bojanus supposed, by its hyoidean arch.* Having thus endeavoured to show what the scapular arch of the crocodile is, I proceed to point out the characteristic form of its chief elements. The upper and principal part of the scapula (.51, fig. 13) is flattened, and gradually becomes narrower to the part called its neck, which is rounded, bent inwards, and then suddenly expanded to form a rough articular surface for the coracoid, and a portion of a smoother surface for the shoulder-joint. The contiguous end of the coracoid (52) presents a similar form, having not only the rough sui'face for its junction with the scapula, but contributing, also, one half of the cavity for the head of the humerus. It is perforated near the interspace between these two surfaces. As it recedes from them, it contracts, then expands and becomes flattened, terminating in a somewhat broader margin than the base of the scapula, which margin is morticed into a groove at the anterior border of the broad rhomlwidal cartilage continued beyond the ossified part of the manubrium, which forms the key-bone of the scapular arch. The anterior locomotive extremity is the diverging appendage of the arch, under one of its numerous modes and grades of development.f The proximal element of this appendage or that nearest the arch, is called the ' humerus' (53, fig. 13) : its head is subcompressed and convex; its shaft bent in two directions, with a deltoid crest developed from its upper and fore part ; its distal end is transversely extended, and divided anteriorly into two condyles. The shaft of this bone has a medullary cavity, but relatively smaller than in the mammalian humerus. The second segment of the limb consists of two bones : the larger one (54) is called the ' ulna :' it articulates with the outer condyle of the humerus by an oval facet, the * Anatome Testudinis Europpea, fol., 1S19, p. 44. GeofFroy St. Hilaii-e selected the opercular audsub- opercular bones to form the inverted arch of his seventh (occipital) cranial vertebra, and took no account of the instructive natural connexions and relative position of the hyoidean and scapular arches in fishes. With regard to the scapular arch, he alludes to its articulation with the skull in the lowest of the vertebrate classes as an ' amalgame inattendue' {Anatomie Philosophique, p. 481) : and elsewhere describes it as a " disposition veritablement trfes singuliere, et que le manque absolu du cou et une combinaison des pieces du sternum avec celles de la tete pouvoicut seules rendre possible." — Annalesdu Museum, i,\, p. 3()1. A due appreciation of the law of vegetative uniformity or repetition, and of the ratio of its prevalence and power to the grade of organization of the species, was, perhaps, essential in order to discern the true signification of the connexion of the scapular arch in fishes. f See my Discourse ' On the Nature of Limbs,' 8vo, Van Voorst, 1849, pp. 64-/0. CROCODILIA. 103 thick convex border of which swells a Httie out behind, and forms a kind of rudimental ' olecranon ;' the shaft of the ulna is compressed transversely, and curves slightly out- wards ; the distal end is much less than the proximal one, and is most produced at the radial side. The radius (55) has an oval head ; its shaft is cylindrical; its distal end oblong and subcompressed. The small bones (sG) which intervene between these and the row of five longer bones, are called ' carpals :' they are four in number in the Crocodilia. One seems to be a continuation of the radius, another of the ulna ; these two are the principal carpals ; they are compressed in the middle and expanded at their two extremities ; that on the radial side of the wrist is the largest. A third small ossicle projects slightly backwards from the proximal end of the ulnar metacarpal : it answers to the bone called ' pisiforme' in the human wrist. The fourth ossicle is interposed between the ulnar carpal and the metacarpals of the three ulnar digits. These five terminal jointed rays of the appendage are counted from the radial to the ulnar side, and have received special names : the first is called ' poUex,' the second ' index,' the third ' medius,' the fourth ' annularis,' and the fifth ' minimus.' The first joint of each digit is called ' metacarpal ;' the others are termed ' phalanx.' In the Crocodilia the poUex has two phalanges, the index three, the medius four, the annularis four, and the minimus three. The terminal phalanges, which are modified to support claws, are called ' ungual' phalanges. As the above-described bones of the scapular extremity are developments of the appendage of the scapular arch, which is the haemal arch of the occipital vertebra, it follows, that, like the branchiostegal rays and opercular bones in fishes, they are essentially bones of the head. But the enumeration of the bones of the crocodile's skull is not completed by these: there is a bone anterior to the orbit, marked 73 in fig. 13, and in PI. 1 A and J2 ; it is perforated at its orbital border by the duct of the lachrymal gland, whence it is termed the 'lachrymal bone,' and its facial part extends forwards between the bones marked 14, 15, 21, and 26. In many Crocodilia there is a bone at the upper border of the orbit, which extends into the substance of the upper eyelid ; it is called ' superorbital.' In the Crocodllm palpehrosus there are two of these ossicles. Both the lachrymal and superorbital bones answer to a series of bones found com- monly in fishes, and called ' suborbitals' and ' superorbitals.' The lachrymal is the most anterior of the suborbital series, and is the largest in fishes ; it is also the most constant in the vertebrate series, and is grooved or perforated by a mucous duct. These ossicles appertain to the dermal or muco-dermal system or ' exoskeleton ;' not to the vertebral system or ' endoskeleton.' The little slender bone, marked Hi' in fig. 13, has one of its extremities in the form of a long, narrow, elliptic plate, which is applied to the ' fenestra ovalis' of the internal 104 BRITISH FOSSIL REPTILES. Fig. 14. Vertical longitudinal section of the cranium of a Crocodile {Crocodilus acutus). ear ; from this plate extends a long and slender bony stem, which grows somewhat cartilaginous, expands and bends down, as it approaches the tympanum or ear-drum, to which it is attached. The cartilaginous capsule of the labyrinth or internal ear is partially ossified by sinuous plates of bone connate with the neurapophyses (2 and 6), between which that organ is lodged ; I apply the term ' petrosal' to the principal and most independent of those ossifications of the ear-capsule, to that, e. g., which retains some mobility after it has con- tracted a partial anchylosis to the exoccipital (2), and which appears upon the inner surface of the cranial walls at the part marked 16 in the subjoined Cut 14, between 2 and 6. It is the only independent bone on that surface of the cranium which, in my opinion, answers to the ' petrous portion of the temporal' in human anatomy, and to which the term ' roclier' can be properly applied, in the language of the French comparative anatomists. Cuvier, however, restricts that name to the 'ahsphenoid' (6, figs. 13, 14) in the Crocodiles. The ossicles, (16 and 16'), together with the partial ossifications in the sclerotic capsule of the organ of sight, (17, fig. 13) — always more distinct in Chelonia than in Crocodilia — belong to that category of visceral bones to which the term ' splanchno- skeleton' has been given ; they also are foreign to the true vertebrate system of the skeleton. Thus the classification of the bones of the head of the Crocodiles, as of all other vertebrate animals, is primarily into those of The Endo-skeleton, The Splanchno-skeleton, and The EXO-SKELETON. The bones of the endo-skeleton of the head form naturally four segments, called Occipital vertebra, N i, H i ; Parietal vertebra. Nil, H 11 ; Frontal vertebra, N iii, H iii ; Nasal vertebra, N iv, H iv. These segments are subdivided into the neural arches, called Epencephahc arch (1 basioccipital, 2 exoccipital, 3 superoccipital, 4 connate paroccipital) ; Mesencephalic arch (5 basisphenoid, 6 alisphenoid, 7 parietal, 8 mastoid) ; Fig. 13. CROCODILIA. 10.5 Prosencephalic arch (9 presphenoid, 10 orbitosphenoid, 11 frontal, 12 post- frontal) ; Rhinencephalic arch (13 vomer, 14 prefrontal, 15 nasal) : and into the heemal arches and their appendages, called Maxillary arch (20 palatine, 21 maxillary, 22 premaxillary) and appendages (24 pterygoid, 24' ectopterygoid, 26 malar, 27 squamosal) ; Mandibular arch (28 tympanic, 29—32 mandible) ; Hyoidean arch (39 epihyal, 40 ceratohyal, 41 basihyal) ; Scapular arch (50 suprascapula, 51 scapula, 52 coracoid) and appendages (53—58 bones of fore-limb). The bones of the splanchno-skeleton, are The petrosal (16) and otosteals (le') ; The sclerotals (17) which in most retain their primitive histological condition as fibrous membrane. The turbinals (18 and 19) and teeth. The bones of the exo-skeleton, are The lacrymals (73). The superorbitals (present in Alligator sclerqps). There remains to complete this preliminary sketch of the osteology of the Crocodile a brief notice of the bones composing the diverging appendage of the pelvic arch : these being a repetition of the same element as the appendage of the scapular arch modified and developed for a similar office, manifest a very close resemblance to it. The first bone, called the ' femur,' is longer than the humerus, and, like it, presents an enlargement of both extremities, with a double curvature of the intervening shaft, but the directions are the reverse of those of the humerus, as may be seen in PI. 1, where the upper or proximal half of the femur is concave, and the distal half convex, anteriorly. The head of the femur is compressed from side to side, not from before backwards as in the humerus ; a pyramidal protuberance from the inner surface of its upper fourth represents a ' trochanter ;' the distal end is expanded transversely, and divided at its back part into two condyles. The next segment of the hind-limb or ' leg,' includes, like the corresponding segment of the fore-limb called ' fore-arm,' two bones. The largest of these is the ' tibia,' and answers to the radius. It presents a large, triangular head to the femur ; it terminates below by an oblique crescent with a convex surface. The ' fibula' is much compressed above ; its shaft is slender and cylindrical, its lower end is enlarged and triangular. All these long bones have a narrow medullary cavity. The group of small bones which succeed those of the leg, are the tarsals ; they are four in number, and have each a special name. The ' astragalus' articulates with the tibia, and supports the first and part of the second toe. It is figured in Cuvier's 106 BRITISH FOSSIL REPTILES. 'Osscmen's Fossiles,' torn, v, pt. ii, pi. iv, figs. 19 J, B, C, D. The 'calcaneum' inter- venes between the fibula and the ossicle supporting the two outer toes ; it has a short but strong posterior tuberosity. The ossicle referred to represents the bone called ' cuboid' in the human tarsus. A smaller ossicle, wedged between the astralagus and the metatarsals of the second and third toes is the ' ectocuneiform.' Four toes only are normally developed in the hind-foot of the CrocodiUa ; the fifth is represented by a stunted rudiment of its metatarsal, which is articulated to the cuboid and to the base of the fourth metatarsal. The four normal metatarsals are much longer than the corresponding metacarpals. That of the first or innermost toe is the shortest and strongest ; it supports two phalanges. The other three metatarsals are of nearly equal length, but progressively diminish in thickness from the second to the fourth. The second metatarsal supports three phalanges ; the third four ; and the fourth also has four phalanges, but does not support a claw. The fifth digit is represented by a rudiment of its metatarsal in the form of a flattened triangular plate of bone, attached to the outer side of the cuboid, and slightly curved at its pointed and prominent end. The teeth. — The most readily recognisable character by which the existing Crocodilians are classified and grouped in appropriate genera, are derived from modifications of the dental system. IQ lo OO OO In the Caimans (genus AUifjatof) the teeth vary in number from -^ — i-^ to ^^^r — - : the fourth tooth of the lower jaw is received into a cavity of the alveolar surface of the upper jaw, where it is concealed when the mouth is shut. In PI. 1 C, fig. 2, these pits are shown behind the last premaxillary tooth e, in an eocene Alligator from Hordwell. In old individuals of the existing species of Alligator, the upper jaw is perforated by the large inferior teeth in question, and the fossae are converted into foramina. In the Crocodiles (genus Crocodilus) the fourth tooth in the lower jaw is received into a notch excavated in the side of the alveolar border of the upper jaw, as in fig. 1, PI. 1 C, behind the tooth e, and is visible externally when the mouth is closed, as in PI. ] B, fig. 1. In most Crocodiles, also, the first tooth in the lower jaw perforates the premaxillary bone when the mouth is closed, as in PI. A 2, between the teeth marked a and h. In the two preceding genera the alveolar borders of the jaw have an uneven or wavy contour, and the teeth are of an unequal size. In the Gavials, (genus Gavialis) the teeth are nearly equal in size and similar in form in both jaws, and the first as well as the fourth tooth in the lower jaw, passes into a groove in the margin of the upper jaw when the mouth is closed, PI. 1. In the Alligators and Crocodiles the teeth are more unequal in size, and less regular CROCODILIA. 107 in arrangement, and more diversified in form than in the Gavials : witness the strong thick conical laniary teeth at the fore part of the jaw, as shown in PI. 2 A, figs. 3 and 6, as contrasted with the blunt mammillate summits of the posterior teeth, as shown in Pi. 3 A, fig. 12. The teeth of the Gavial are subequal, most of them are long, slender, pointed, subcompressed from before backwards, with a trenchant edge on the right and left sides, between which a few faint longitudinal ridges traverse the basal part of the enamelled crown. The teeth of both the existing and extinct Crocodilian reptiles consist of a body of compact dentine forming a crown covered by a coat of enamel, and a root invested by a moderately thick layer of cement. The root slightly enlarges, or maintains the same breadth to its base, which is deeply excavated by a conical pulp-cavity extending into the crown, and is commonly either perforated or notched at its concave or inner side. The dentinal tubes in the crown of a fully-developed tooth form short curvatures at their commencement at the surface of the pulp-cavity, and then proceed nearly straight to the periphery of the crown ; they very soon bifurcate, the divisions slightly diverging ; then continuing their course with gentle parallel undulations, they subdivide near the enamel, and terminate in fine and irregular branches, which anastomose generally by the medium of cells. The dentinal tubes send ofl" from both sides, throughout their progress, minute branches into the intervening substance, and terminate in the dentinal cells. These cells are subhexagonal, about -^^ of an inch in diameter, and are traversed by from ten to fourteen of the dentinal tubes ; they are usually arranged in planes parallel with the periphery of the crown, near which they are most conspicuous, and towards which their best defined outline is directed : they combine with the parallel curvatures of the dentinal tubes to form the striae, visible in sections of the teeth by the naked eye, which cause the stratified appearance of the dentine as if it were composed of a succession of superimposed cones. The diameter of the dentinal tube before the first bifurcation is T^Tnrth of an inch, both the trunks and bifurcations of the tubes have interspaces equal to four of their respective diameters. The enamel viewed in a transverse section of the crown presents some delicate striae parallel with its surface, whilst the appearance of fibres vertical to that surface is only to be detected, and these faintly, on the fractured edge. It is a very compact and dense substance ; the dark brownish tint is strongly marked in the middle of the enamel when viewed by transmitted light. The cells with which the fine tubes of the basal cement communicate, are oblong, about -yijVirth of an inch across their long axis, which is transverse to that of the tooth ; the inter-communicating tubes, which radiate from the cells, giving them a stellate figure. I have entered into these particulars of the microscopic texture of the teeth of the Crocodile because it will be seen in the sequel that important modifications of the dental tissues characterise some of the extinct RejMlia. 108 BRITISH FOSSIL REPTILES. In the black Alligator of Guiana the first fourteen teeth of the lower jaw are implanted in distinct sockets, the remaining posterior teeth are lodged close together in a continuous groove, in which the divisions for sockets are faintly indicated by vertical ridges, as in the jaws of the Ichthyosaurs. A thin compact floor of bone separates this groove, and the sockets anterior to it, from the large cavity of the ramus of the jaw ; it is pierced by blood-vessels for the supply of the pulps of the growing teeth and the vascular dentiparous membrane which lines the alveolar cavities. The tooth-germ is developed from the membrane covering the angle between the floor and the inner wall of the socket. It becomes in this situation completely en- veloped by its capsule, and an enamel-organ is formed at the inner surface of the capsule before the young tooth penetrates the interior of the pulp-cavity of its predecessor. The matrix of the young growing tooth affects, by its pressure, the inner wall of the socket, and forms for itself a shallow recess ; at the same time it attacks the side of the base of the contained tooth ; then, gaining a more extensive attachment by its basis and increased size, it penetrates the large pulp-cavity of the previously formed tooth, either by a circular or semicircular perforation. The size of the calcified part of the tooth matrix which has produced the corresponding absorption of the previously formed tooth on the one side, and of the alveolar process on the other, is represented in the second exposed alveolus of the portion of jaw figured in PI. 7.5, fig. 4, of my ' Odontography,' the tooth marked a in that figure, having been displaced and turned round to show the effects of the stimulus of the pressure. The size of the perforation in the tooth, and of the depression in the jaw, proves them to have been, in great partj caused by the soft matrix, exciting dissolution and absorbent action, and not by mere mechanical force. The resistance of the wall of the pulp-cavity having been thus overcome, the growing tooth and its matrix recede from the temporary alveolar depression, and sink into the substance of the pulp contained in the cavity of the fully- formed tooth. As the new tooth grows, the pulp of the old one is removed ; the old tooth itself is next attacked, and the crown being undermined by the absorption of the inner surface of its base, may be broken off by a slight external force, when the point of the new tooth is exposed. The new tooth disembarrasses itself of the cylindrical base of its predecessor, with which it is sheathed, by maintaining the excitement of the absorbent process so long as the cement of the old fang retains any vital connexion with the periosteum of the socket ; but the frail remains of the old cylinder, thus reduced, are sometimes lifted off the socket upon the crown of the new tooth, when they are speedily removed by the action of the jaws. This is, however, the only part of the process which is immediately produced by mechanical force : an attentive observation of the more important pre- vious stages of growth, teaches that the pressure of the growing tooth operates upon the one to be displaced only through the medium of the vital dissolvent and absorbent action which it has excited. CROCODILIA. 109 Most of the stages in the development and succession of the teeth of the Crocodiles are described by Cuvier* with his wonted clearness and accuracy; but the mechanical explanation of the expulsion of the old tooth, which Cuvier adopts from M. Tenon, is opposed by the disproportion of the hard part of the new tooth to the vacuity in the walls of the old one, and by the fact that the matter impressing — viz. the uncalcified part of the tooth-matrix — is less dense than the part impressed. No sooner has the young tooth penetrated the interior of the old one, than another germ begins to be developed from the angle between the base of the young tooth and the inner alveolar process, or in the same relative position as that in which its imme- diate predecessor began to rise, and the processes of succession and displacement are carried on, uninterruptedly, throughout the long life of these cold-blooded carnivorous reptiles. From the period of exclusion from the egg, the teeth of the crocodile succeed each other in the vertical direction ; none are added from behind forwards, like the true molars in Mammalia. It follows, therefore, that the number of the teeth of the cro- codile is as great when it first sees the light as when it has acquired its full size ; and, owing to the rapidity of the succession, the cavity at the base of the fully-formed tooth is never consolidated. The fossil jaws of the extinct Crocodilians demonstrate that the same law regulated the succession of the teeth, at the ancient epochs when those highly organized reptiles prevailed in greatest numbers, and under the most varied generic and specific modi- fications, as at the present period, when they are reduced to a single family, composed of so few and slightly varied species, as to have constituted in the Systema Naturce of Linnaeus, a small fraction of the genus Lacerta. Having completed the analysis of the constituent parts of the framework of the? Crocodilia, which are petrifiable or conservable in a fossil state, and from the study and comparison of which we have to gain our insight into the nature and affinities of the extinct Reptiles, there remains only to be made a few observations on the charac- teristic mode in which the bones are associated together in certain parts of the skeleton in the present order, and especially in the skull. With regard to the trunk, the Crocodilia are distinguished from the Lacertilia and from all other existing orders of Reptiles, by the articulation of the vertebral ribs (pleurapophyses) in the cervical and anterior part of the dorsal segments by a head and tubercle to a parapophysis and diapophysis. As this double joint is associated with a double ventricle of the heart, and as the single articulation of every rib in other Reptiles is associated with a single ventricle of the heart, we may infer a like difference in the structure of the central organ of circulation in the extinct reptiles, manifesting the above-defined modifications in the proximal joints of the ribs. * Op. cit.,pp. 90-3. Q no BRITISH FOSSIL llEPTILES. The sacrum consists of two vertebrae onl}^ in Crocodilia as in Lacertilia : they are modified in the present order, as before described, jj. 89. The skull consists, as we have also seen, of four segments. The hinder or occi- pital surface of the skull presents, in the Crocodilia as in the Lacertilia, a single convex occipital condyle, formed principally by the basioccipital, and not showing the trefoil character which it bears in the Chelonia (PI. 11, fig. 4), in which the exoccipitals con- tribute equal shares to its formation. In the Batrackia, the exoccipitals exclusively form the joint with the atlas, and there are accordingly two condyles. The occipital region of the crocodilian skull is remarkable for its solidity and complete ossification, and for the great extent of the surface which descends below the condyle. (PI. 1 A, fig. 2.) In the Lacertilia, a wide vacuity is left between the mastoid, exoccipital, and par- occipital ; but in the Crocodilia this is reduced to the small depressions or foramina near 3, fig. 2, PL 1 A. The tympanic pedicles (28) extend outwards and downwards, firmly wedged between the paroccipital, mastoid, and squamosal ; in the Lacertians these pedicles are suspended vertically from the point of union of the mastoid and paroccipital. The chief foramen in the occipital region is that called 'foramen magnum' (between 2 and 2, in fig. 2), through which the nervous axis is continued from the skull. On each side of the foramen magnum is a small hole, called ' precondyloid foramen,' for the exit of the hypoglossal nerve. External to this is a larger foramen, marked n in fig. 2, for the transmission of the nervus vagus and a vein. Below this is the ' carotid foramen' c. All these are perforated in the exoccipital. Below the condyle there is usually a foramen, and sometimes two, for the transmission of blood-vessels. Lower down, at the suture between the basioccipital and basisphenoid, is a larger and more constant median foramen, indicated by the dotted line from e t ; it is the bony outlet of a median system of eustachian tubes, peculiar to the Crocodilia. On each side of the median eustachian foramen, and in the same suture, is a smaller foramen, which is the bony orifice of the ordinary lateral eustachian tube. The membranous continuations of the lateral eustachian tubes unite with the shorter continuation from the median tube, and all three terminate by a common valvular aperture, upon the middle line of the faucial palate, behind the posterior or palatal nostril. The large, bony aperture of this nostril is formed by the pterygoids (24 in fig. 2). The carotid canal, c, opens by a short bony tube into the tympanic cavity, and is described as the ' eustachian canal' in the ' Legons d' Anatomic comparce' of Cuvier. The artery crosses the tympanic cavity, and enters a bony canal at its fore part, which conducts to the ' sella turcica' in the interior of the cranium. The median eustachian foramen is described by Cuvier as the ' arterial foramen,'* the canal from which divides and terminates in the ' sella turcica.'! By MM. Bronn, * Ossemens Fossiles, torn, v, pt. ii, p. 133. t lb. p. 78. CROCODILTA. Ill Kaup, and De Blainville, the median Eustachian foramen is contended to be the bony aperture of the posterior nostrils.* The results of the dissections and injections of recent Crocodiles and Alligators, by which I have been able to rectify the discrepant opinions regarding the carotid, eustachian, and naso-palatal foramina, and which have led to the discovery of a third median eustachian canal, or rather system of canals, between the tympanic cavities and fauces, peculiar to the Crocodilian Reptiles, are given In detail in the ' Philosophical Transactions' for 1850. The complexity of the superadded system has doubtless chiefly contributed to mislead the justly-esteemed authorities who have believed that they saw in it characters of the carotid canals or of the posterior nasal passages. The eustachian apparatus in the Crocodilia may be briefly described as follows : From the floor of each tympanic cavity two air-passages are continued ; the canal from the fore part of the cavity extends downwards, backwards, and inwards, in the basisphenoid, which unites with its fellow from the opposite tympanum, to form a short median canal, which descends backwards to the suture between the basisphenoid and the basioccipital, where it joins the median canal formed by the union of the two air-passages from the back part of the floor of the tympanum, which traverse the basioccipital. The common canal formed by the junction of the two median canals descends along the suture to the median foramen e t, fig. 2, PI. 1 A. The air-passage from the back part of the tym- panum, which traverses the basioccipital, swells out into a rhomboidal sinus in its convergent course towards its fellow, and from this sinus is continued the normal lateral eustachian canal, which, on each side, terminates below in the small aperture, external to the median eustachian foramen. That part of the outer surface of the skull which is covered by the common integument is more or less sculptured with wrinkles and pits in the Crocodilia .• the modifications of this pattern are shown in PI. A 2, fig. 1, in the nilotic Crocodile, and in PI. 1 A, in the eocene Crocodile from Hordwell. The flat platform of the upper surface of the cranium is perforated by two large apertures, surrounded by the bones numbered 7, 8, 11, 12; these apertures are the upper outlets of the temporal fossae, divided from the lower and lateral outlets by the conjoined prolongations of the mastoid 8 and postfrontal 12: if ossification were continued thence to the parietal 7, the temporal fossae would be roofed over by bone, as in the Chelones. In old Crocodiles and Alligators there is an approximation to this structure, and the upper temporal apertures are much diminished in size. In the Gavials (PI. 1, fig. 1 a) they remain more widely open, and, in the fossil Gavials of the secondary strata, they are still wider, as seen in fig. 2 « ; by which the structure of the cranium approaches more nearly to that of the Lacertian reptiles, where the temporal fossa is either not divided into an upper and lateral outlet, or is bridged over by a very slender longitudinal bar from the postfrontal to the mastoid. The lateral outlets of the temporal fossae (PI. 1 J, * Abhandlungen iiber die Gavialiirtigen Reptilien der Lias-formation, folio, 1841, pp. 12, 16, 41. 112 BRITISH FOSSIL REPTILES. fig. 1) are divided from the orbits by a bar of bone developed from the postfrontal (12) and malar (26), and against the inner side of the base of whicli the ectopteiygoid abuts ; the posterior boundary of the fossa is made by the tympanic (28) and squamosal (27). The orbits, having the postfronto-malar bar (12, 26) behind, are surrounded in the rest of their circumference by the frontal (11), the prefrontal (14), the lachrymal (73), and the malar (26). The supraorbital or palpebral ossicle is rarely preserved in fossil specimens. The facial or rostral part of the skull anterior to the orbit, is of great extent, broad and flat in the AUigators and some Crocodiles, narrower, rounder, and longer in other Crocodiles, always most narrow, cylindrical, and elongated in the Gavials. The anterior or external nostril is single, and is perforated in the middle of the anterior terminal expansion of the upper jaw. This expansion is least marked in the broad- headed species (compare PL 1 A, fig. 1, with PI. 1 A, fig. 1); in existing Crocodiles and Alligators the points of the nasal bones penetrate its hind border, as at 15, fig. 1, PI. A 2. In the Gavials (PI. 1, fig. 1 a) the nasals («) terminate a long way from the nostril. The Crocodilia resemble the Chelonia in the single median nostril.* In the Lacertilia there is a pair of nostrils, one on each side the median plane, which is occupied by a bridge of bone extending from the usually single premaxillary to the nasals. The plane of the single nostril is almost horizontal in all existing and tertiary Crocodilia. On the inferior or palatal surface of the skull (PL 1 B, fig. 2), the most anterior aperture is the circular prepalatal foramen surrounded by the premaxillaries 22 ; then follows an extensive smooth, horizontal, bony plate, formed by the premaxillaries (22), the maxillaries (21), and the palatines (20). The postpalatal apertures are always large in the Crocodilia, and are bounded by the palatines (20), maxillaries (21), pterygoids (24), and ectopterygoids (25). The posterior aperture of the nostril is formed wholly by the pterygoids ; it is shown in PL 1 a, fig. 3, between the bones marked 24. Behind it is the median and lateral eustachian foramen already described, as belonging rather to the posterior region of the head. Crocodilus TOLiAPicus, Owe7i. PL 2, 2, B, fig. 1. Syn. Crocodile de Sheppy (?), Cuvier. Ossemens Fossiles, 4to, torn, v, pt. ii, p. 165. Crocodilus Spenceui, i?i A, figs. 1, 2, 3, 5, 6. The vertebra, figs. 1, 2, PI. 3 A, is the fourth cervical ; it differs from that of the Crocodilus acufus. Croc. Suchus, and Croc, biporcaius, in the greater breadth and squareness of the base of the hj^papophysis (fig. 2 h), which extends almost to the bases of the parapophyses J9 ; the vertical diameter of the parapophyses is greater in comparison with their antero-posterior extent in the fossil than in tlie above-cited recent Crocodiles ; the neurapophyses are thicker, and terminate in a more rounded border both before and behind ; their bases extend inwards, and meet above the centrum, whilst a narrow groove divides them in the recent Crocodiles above cited ; the length of the centrum is greater in proportion to the height and breadth in the fossil vertebra. In other respects the correspondence is very close, and the modem crocodilian characters are closely repeated. Traces of the suture between the centrum and neurapophysis remain, as shown at n, n, fig. 1 . The diapophysis d, and the upper portion of the neural arch, with the zygapophyses and neural spine, have been broken away ; the borders of the articular ends of the centrum have been worn away. The vertebra (fig. 3, PI. 3 A) is the sixth cervical : in this specimen the base of the hyi^apophysis is contracted laterally and extended antero-posteriorly ; the side of the centrum above the parapophysis {p) has become less concave ; the vertebra has increased R 118 BRITISH FOSSIL REPTILES. more in thickness than in length ; in these changes it corresponds with the modern Crocodiles ; it has been mutilated and worn in almost the same manner and degree as the fourth cervical. The vertebra (figs. 1, 2, PI. 3) is a seventh cervical of a smaller individual of the Crocodilm toUapicus. The hypapophysis has become more compressed and more extended antero-posteriorly ; the parapophysis has become shortened antero-posteriorly, and increased in vertical diameter. The anterior concave surface of the centrum (fig. 1) is more circular, less extended transversely, than in the corresponding vertebra of the recent Crocodiles compared with the fossil. Figures 3, 4, PI. 3, are two views of the eighth cervical of an individual of about the same size as that to which the fourth and sixth cervicals in PL 3 A belong. Fig. 4, exemplifies the same difi'erence which fig. 1 presents in regard to the more circular contour of the anterior concave surface of the centrum as compared with recent Crocodiles ; the bases of the neurapophyses are thicker and more rounded anteriorly ; the neural canal is rather more contracted ; the base of the hypapophysis more extended in the axis of the vertebra (see fig. 3) than in the recent Crocodiles compared. Tlie parapophyses have now risen, as in those Crocodiles, to the suture of the neurapophysis, and the diapophysis springs out at some distance above that suture. Fig. 6, PI. 3, shows the under surface of a dorsal vertebra, in which the hypapophysis ceases to be developed (probably the fourth or fifth). Fig. 5, PI. 30, gives the same view of one of the lumbar vertebras, showing the elongation of the centrum, and the broad bases of the depressed diapophyses ; there is an indication of two longitudinal risings towards the back part of the under surface of the centrum. Figs. 5 and 6, PI. 3 A, give two views of the anterior sacral vertebra of the Crocodilus toUapicus ; it is concave and much expanded transversely at its fore part (fig. 5), flattened and contracted behind. Traces of the suture remain to show the proportion of the anterior articular surface which is formed by the base of the pleurapophysis jo ; and fig. 6 shows the extension of that base from the side of the centrum upon the diapophysis or overhanging base of the neurapophysis ; the under surface of the centrum of this vertebra has a slight median longitudinal rising. Fig. 7, PI. 3, gives a side view of the characteristic, biconvex, anterior caudal vertebra of the Crocodilus toUapicus. Figs. 8, 9, PL 3, give two views of a middle caudal vertebra : in fig. 9 are shown the characteristic hypapophysial ridges extending from the articular surfaces for the hsemapophyses at the hind part of that aspect of the centrum : in fig. 8 the processes of the neural arch are restored in outline ; a thick and low ridge extends from the middle of the side of the centrum to the base of the transverse process which it strengthens, like an underjjropping buttress. CROCODILIA. 119 Vertebrae of the Crocodilus champsoides. Figui'es 7 and 8, PI. 3 A, give two views of the third cervical vertebra of the above- named gavial-hke Crocodile, which vertebra, besides its longer and more slender propor- tions, differs in the smaller size of its hy|}apophysis from the corresponding vertebra in any existing species of Crocodile or Gavial : the process in question being in the form of alow crescentic ridge, as shown at figure 8, between the bases of the parapophyses {p). Both parapophyses terminate by a convex surface, which appears to have been a natural one. Between the parapophysis {p) and diapophysis [d), fig. 7, the side of the centrum is more deeply excavated than in the Crocodilus toliapiciis. The centrum contributes a small part to the base of the diapophysis, as in the third cervical vertebra of modern Crocodiles. The neurapophysis are thinner than in the Croc, toliapiciis, and their bases do not join one another above the centrum. The longitudinal ridge extending from the anterior to the posterior zygapophysis is sharply defined. Figure 4, PI. 3 A, is the first dorsal vertebra of the Crocodilus champsoides, in which, as in existing Crocodiles, the parapophysis {p) has passed almost wholly from the centrum upon the neurapophysis, the diapophysis {d) having been subject to a corresponding ascent. The base of the compressed hypapophysis extends over the anterior third of the middle line of the under surface of the centrum. There is a remarkable transverse constriction at the base of the posterior ball of the centrum, as if a string had been tied round that part when it was soft, and there is no appearance of this groove having been produced by any erosion of the fossil, or being otherwise than natural. The same character is repeated, though with less force, in the posterior dorsal vertebra, fig. 9, PI. 3 A, and, together with the general proportions of the specimen, supports the reference of that vertebra to the Crocodilus champ)soides. There is a slight longitudinal depression at the middle of the side of the centrum near the suture with the neurapophysis («, n). Figure 10 is a side view of the first caudal vertebra of the Crocodilus champsoides : besides being longer and more slender than that vertebra is in the Croc, toliapicus, the inferior surface of the centrum is less concave from before backwards. Tlie evidences of Crocodilian reptiles from the deposits at Sheppy less characteristic of particular species than those above described, are abundant. Mr. Bowerbank possesses numerous rolled and fractured vertebrae, condyloid extremities, and other portions of long bones ; with fragments of jaws and teeth. Mr. J. Whickham Flower, F.G.S., has transmitted to me some fragments of the skull of a Crocodile from Sheppy, including the articular end of the tympanic bone, equalling in size that of a Crocodilus hiporcatas the skull of which measures two feet eight inches in length. Mr. Leifchild, C.E., possesses a considerable portion of the lower jaw of a Crocodile 120 BRITISH FOSSIL REPTILES. of at least equal dimensions, also from Shcppy, showing the angle of union of the rami of tlie lower jaw which corresponds with that in the Crocodllus iolicqncus, PI. 2. In the museum of my esteemed and lamented friend, the late Frederic Dixon, Esq., F.G.S., at Worthing, is preserved a portion of the fossilized skeleton of a Crocodile, from the Eocene clay at Bognor, in Sussex ; it consists of a chain of eight vertebrae, including the lumbar, sacral, and the biconvex first caudal, which are represented of their natural size in tab. xv, of Mr. Dixon's beautiful and valuable work on the ' Geology of Sussex.' A dorso-lateral bony scute adheres to the same mass of clay close to the vertebrae, and doubtless belonged to the same individual. The proportions of the vertebrae agree with those of the Crocodilus toliapicics. This fine specimen was dis- covered, and presented to Mr. Dixon, by the Rev. John Austin, M.A., Rector of Pulbrough, Sussex. Mr. Dixon had also obtained from the same locality a posterior cervical vertebra of a Crocodile, similar in its general characters to those above mentioned, but belonging to a larger individual. The length of the body of this vertebra is two inches and a half. I have examined some remains of Crocodilia from the London Clay at Hackney; but as these also are not sufficiently perfect or characteristic for decided specific determination, no adequate advantage would be obtained by a particular description, or by figures of them. The chief conclusion arrived at from the study of the Crocodilian fossils from the Island of Sheppy has been the proof, by the specimens selected for depiction in the present work, that at least two species of true Crocodile have left their remains in that locality ; that neither of these had a short and broad snout like the Caimans, but that one of them — the Croc, champso'ides — much more nearly resembled the Gavial of the Ganges in the proportion of that part of the skull ; although, in its composition, especially as regards the length and connexions of the nasal bones, it is a true Crocodile. Amongst the existing species of Crocodile the Croc, aciitus of the West Indies offers the nearest approach to the Croc, toliapicus, and the Croc. ScJilc(jeUi of Borneo, most resembles the Croc, champsoides. But there are well-marked characters in both the skull and the vertebrae which specifically distinguish the two fossil Crocodiles of Sheppy from their above-cited nearest existing congeners. Crocodilus Hastings:^, Owen. Plates 1 ^ 1 -8, 1 C,fig. 1 and PI. 1 ^, figs. 2 and 5- ReporU of the British Association, 1847, p. 65. That Crocodiles with proportions of the jaws assigned to the Eocene species noticed in Dr. Buckland's ' Bridgewater Treatise' and especially adapted for grappling wdth strong mammiferous animals, actually existed at that ancient tertiary epoch, and have left their remains in this island, is shown by the singularly perfect fossil skull figured in the above-cited plates. This specimen was discovered by the Marchioness of Hastings, in the Eocene fresh-water deposits of the Hordle Cliffs in Hampshire, which her CROCODILIA. 121 Ladyship has described m the volume of ' Reports of the British Association' above cited, (p. 63). When the specimen was originally exposed, it was in the same extremely fragile and crumbling state as the beautiful carapaces of Trionyx obtained by Lady Hastings from the same locality, and described and figured in the chapter Chelonia ; but thanks to the skill and care with which the noble and accomplished discoverer readjusted and cemented the numerous detached fragments of those specimens, the present unique fossil has been in like manner restored as nearly to its original state as is represented in the plates ; and all the requisite characters for determining the nature and affinities of the species, can now be studied wdth the same facility as in the skulls of existing Crocodiles. If the reader will compare the plates above cited with the section of Cuvier's ' Ossemens Fossiles,' in which the distinctions between the Alligators and Crocodiles are specified,* he will see, (in fig. 1, PI. 1 S) for example, that the fourth tooth or canine of the lower jaw is not received into a circumscribed cavity of the upper jaw, but is applied to a groove upon the side of the upper jaw, and is exposed. Fig. 1, PI. 1 A, shows that the prefrontal (i4) and lachrymal (73) bones, instead' of descending much less upon the facial part of the skull, extend much more, and advance nearer to the end of the muzzle than in any Alligator, or even than in any actual species of broad- nosed Crocodile. The vacuities left between the postfrontal (12), the parietal (7), and the mastoid (s) (PI. 1 A, fig. 1, and PI. 2 B, fig. 3), are as wide as in the skull of a Crocodiiiis biporcatus of equal size, and are larger than in the Alli(/ator Indus or All. sclerops. Fig. 2, PI. 1 B, shows that no part of the vomer is visible between the premaxillaries (22) and maxillaries (21), or elsewhere on the palate. But the palatine expansion of the vomer is not a constant character ; it is wanting, for example, in the Alligator liicius of North America. The palatines (20) are not more advanced in the fossil in question than they are in the true Crocodiles, and their anterior portion does not expand to its anterior truncated termination. The posterior nostril, the entire contour of which is shown in the portion of the skull of the same species figured in PI. 1 A, fig. 3, is longer than it is broad. There is but one character in which the fossil skuU in question differs from the true Crocodile, and agrees with most species of Alligator ; it is in the reception of the two anterior teeth of the lower jaw into cavities of the premaxillaries, shown in * " Les tetes des caimans, outre le nombre des dents, et surtout la manifere dont la quatrieme d'en bas est recue, outre les differences qui dependent de la circonscriptiou totale, se distinguent de celles des Crocodiles proprement dits, 1°, parce que le frontal anterieur et le lacrynial desceudent bcaucoup moins sur le museau ; 2°, en ce que les trous perces a la face superieure du crane, entrele frontal posterieur, le parietal et le mastoidien, y sont beaucoup plus petits, souvent meme y disparaissent tout-i-fait, comme dans le caiman a paupieres osseuses ; 3°, en ce que Ton aper^oit uue partie du vomer dans le palais, entre les interma.iillaires et les maxillaires ; 4°, en ce que les palatins avancent plus dans ce meme palais, et s'y elargissent en avant; 5°, en ce que les narines posterieures y sont plus larges que lougues, etc." (torn, v, pt. ii, p. 105.) 122 BRITISH FOSSIL REPTILES. fig. 2, PI. 1 B, which are not perforated ; so that there are no foramina anterior to the bony nostril, as in PI. A 2, in the bone marked 22. These foramina are not, however, absent in all Alligators ; the skull of the Allic/ator sderops, figured by Cuvier (tom. cit., pi. i, fig. 7), shows them, as do all the species of true Crocodile the skulls of which are figured in the same plate. There is one character by which the Crocodilus Hastingsia differs from all known species of both Crocodile and Alligator : it is that afforded by the broad and short nasal bones (i.'5, fig. I, PI. 1 A), which do not reach the external nostril ; this being formed, as in the Gavials, exclusively by the premaxillaries 22. In the general proportions, however, of the skull in question, especially the great breadth, shortness, and flatness of the obtusely-rounded snout, it resembles that of the Alligators more than that of any known species of true Crocodile, the length from the tympanic condyle to the end of the snout being to the breadth taken at the condyles as 16 to 9. The following are dimensions of the fossil in question : Feet. Inches. Lines. Length of skull from the angle of the lower jaw to the end of the snout Do. from the tympanic condyle to ditto. Do. do. to the orbit Do. from the orbit to the external nostril . Breadth of the skull across the tympauic condyles Do. the orbits Do. the external nostril . Longest diameter of upper temporal aperture Do. the post-palatal vacuities Depth of the lower jaw at the posterior vacuity . Depth of the occipital region ..... The occipital region of the skull (PI. I A, fig. 2), in the proportion of its breadth to the depth of the lateral parts formed by the conjoined paroccipitals (4) and mastoids (s), resembles that of the true Crocodiles rather than that of the Alligators, in which that region is proportionally deeper than in the Crocodiles ; the vertical extent of the supraoccipital is less, and that of the conjoined parts of the exoccipitals above the foramen magnum is greater ; the vertical extent of the descending part of the basioccipital is also greater in proportion to its breadth than in the Alligators. The proportion of the basisphenoid (.5) and of the conjoined parts of the pterygoids (24) which appear in this view (fig. 2), is less than in the Alligators, but is greater than in most Crocodiles, thus presenting an intermediate character ; but the entire exclusion of any part of the posterior nostril from this view is a character of the Alligators, and is due to the horizontal plane of that aperture in them, and to its position in advance of the posterior border of the pterygoids, from which it is partitioned off usually by a bony ridge. The posterior nostril has the same position and aspect in the Crocodilus Hadingsice, and these characters of the posterior nostril are perhaps more distinctive between 1 6 6 1 4 6 0 5 4 0 7 0 0 9 3 0 7 0 0 4 0 0 1 9 0 4 9 0 3 0 0 4 3 CROCODILTA. 123 Alligator and Crocodile than the shape of the aperture, in which the present fossil differs from botli the Alhgators and most of the Crocodiles with which I have compared it. The backward extension of the exoccipitals and of the basioccipital condyle, is such as to bring both parts into view in looking directly upon the middle of the upper surface of the skull, as in PI. 1 J, fig. 1 . In this character the fossil resembles the Crocodiles more than the Alligators, but the projection is greater than in existing Crocodiles, and equals that in the Sheppy Crocodilus cliamjisoidcs. On the upper surface of the skull a distinctive character has been pointed out by Cuvier in the different proportions of the supra-temporal apertures in the Alligators and Crocodiles. The horizontal platform in which these apertures are perforated, is also square in the Alligators ; the mastoidal angles being less produced outwards and backwards, and the postfrontal angles less rounded off ; this difference is shown in the skulls figured in Cuvier's pi. i, tom. cit. The Croc. Hastuiffsice, both by the obtuseness of the postfrontal angles, and the acuteness and production of the mastoidal angles, resembles the Crocodiles, as well as by the size of the supra-temporal apertures ; these are ovate with the small end turned forwards and a little outwards. Another character may be noticed in the figures of the skulls of the three species of Alligators as compared with those of the three species of Crocodile in Cuvier's pi. i, viz. the larger proportional size of the orbits in the former, in which the orbit much exceeds in size the lateral temporal aperture. In the Alligator niffer, also, I find the orbits enormous, and it is the encroachment of the narrow anterior part of the orbital cavity upon the facial part of the prefrontal and lachrymal, that renders that part of those bones relatively shorter in the Alligators. In the Crocodilus Haslingsm the proportions of the lateral temporal apertures (PI. 1 A, fig. 1, 12, 2C) and orbital (11, u, 73) apertures, are like those in the species of Crocodile in which the orbits are smallest. The extent of the facial part of the prefrontal (14) and lachrymal (73) is greater in the Croc. Ilastinr/sia than in any existing species of true Crocodile. Another characteristic of the present fossil presented by the upper surface of the skull, is the shortness as well as breadth of the nasal bones, and their almost truncate anterior termination at nearly one inch from the external nostril. In all the Alligators' skulls that I have examined or seen figured, the nasal bones are broadest at their posterior third part, and converge to a point anteriorly, where in the Alligator lucius, e. g., they extend across the nasal aperture. The interorbital space is slightly concave in the Crocodilus Hastingsice ; two broad and slightly elevated longitudinal tracts are continued forwards upon the face from the fore part of the orbits ; but they are not developed into ridges, as in the Croc, biporcatus. The maxillaries swell out a little in advance of the middle of the nasals, and then contract to the crocodihan constriction at the suture with the premaxillaries, where the tips of the lower canines appear in the upper view (fig. 1, PL 1 A), and their whole crown is exposed in the side view (fig. 1, PI. 1^. The conjoined parts of the premaxillaries send a short pointed projection into the back part of the exteraal nostril. 124 BRITISH FOSSIL REPTILES. On the under or palatal surface of the skull (PI. 1 B, fig. 2) the niaxillo-prcmaxillary suture runs almost transversely across, as in the Crocodilus rhomhifcr, figured by Cuvier in pi. iii, fig. 2, of the volume above cited. There is no appearance of the vomer upon the palate. The palatal bones (20), though somewhat broader anteriorly, and more abruptly truncate than in any existing Crocodile that I have seen, are more like those bones in the true Crocodiles than in the Alligators. The portion between the post- palatal vacuities is longer and narrower ; the posterior end of the palatines is nar- rower, and the part of the bone anterior to the notch receiving the posterior angle of the palatal plate of the maxillary does not expand in advancing forwards, as it does in the Alligators : in the Alligator niger this expansion is greater than in the All. liicius, and the posterior ends of the palatines are also remarkably expanded, and applied to the anterior borders of the pterj^goids almost as far as their articulation with the ectopterygoids, the postpalatal vacuities not at all encroaching on the pterygoids, as they are seen to do at 24, PI. 1 B, fig. 2, and also in the figure of the Crocodilus rhoinhifcr above cited, and in other true Crocodiles. The form of the pterygoids (24, PI. 1 B, fig. 2) is peculiar in the Crocodilus Hastivgsice -. they are contracted anteriorly, and send forwards a short truncated process to meet the narrow posterior ends of the palatines (20) ; and the same character being repeated in another skull of the same species, from Hordle, also in the collection of Lady Hastings, in which this part of the bony palate (PI. 1 A, fig. 3) is more perfect than in the subject of PI. 1 B, fig. 2, it may be regarded with some confidence as specific. In the Crocodilus chamjjsoides of Slieppy it will be seen, by fig. 2, PI. 2 B, that the pterygoids (24, 24) are not produced where they join the palatines (20). In the Alligators, the posterior border of the conjoined pterygoids is deeply notched behind the posterior nostrils, the angles of the notch being slightly extended backwards : in most Crocodiles, the sides of the notch are so developed that it does not sink deeper than the line of the posterior border of the pterygoids ; and this modification is exaggerated in the Crocodilus Hastingsice (PL 1 A, fig. 3) in which the notch in question is merely the interval between two slender diverging processes from the middle of the back part of the pterygoids, 24. The posterior aperture of the nasal passages is wholly surrounded in the Crocodilus TIastingsia by the horizontal plate of the pterygoids, and has the same position and aspect as in the Alligators ; but its form is heart-shaped, with the apex directed backwards, and the antcro-posterior diameter exceeding the transverse one. I have not met with this form of the posterior nostril in any other species of Crocodilian ; but it is repeated in two individuals of the Croc. liastingsicB, and may be regarded as a specific character. The ectopterygoid, 25, PI. 1 A, fig. 3, PI. 1 B, fig. 2 {d, fig. 2, pi. iii, 'Ossemens Fossiles,' t. V, pt. ii) articulates with a larger proportion of the outer surface of the pterygoids (24) in the Crocodiles than in the Alligators : it agrees with the Crocodiles in the extent of this articulation in the Croc. Ilastingsia. . 22 — 22 Q , The number of teeth in this species is .,^_., — o4. CROCODILIA. 125 In the upper jaw the fourth, ninth, and tenth are the largest ; and the fifteenth and sixteenth exceed in size those immediately before and behind them. The alveolar border of the jaw increases in depth to form the sockets requisite for firmly lodging these larger teeth, and gives rise to the festooned outline of the jaw, which is found in all Crocodiles and Alligators in proportion as the teeth are unequal in size. The lower jaw presents the same compound structure as that in the Crocodilia, with the general form characteristic of that in the Alligators and in most of the true Crocodiles : the symphysis, e. g. is as short as Crocodilus biporcatus and the Alligator niger, in which it extends as far back as the interval between the fourth and fifth socket. This is the relative position of the back end of the symphysis in a fine and perfect under jaw of the Crocodilus Hasfingsies in the collection of the Marchioness of Hastings. In a portion of the under jaw of apparently the same species of Crocodile, from the same locality, in the collection of Searles Wood, Esq., F. G. S., the symphysis terminates opposite the interval between the third and fourth tooth. The chief distinction observable between the modern Crocodiles and Alligators in the lower jaw is the greater relative size of the vacuity between the angular (30) and surangular (29) pieces, and the greater relative depth of the ramus at that part, in the Alligators. In these characters the lower jaw of the present species more resembles that of the true Crocodiles ; although, as the vacuity in question is somewhat larger, a slight affinity to the Alligator might be inferred from that circumstance. The comparative figures of the hinder third of the mandibular ramus in Plate 1 E, figs. 4, 5, 6, will exemplify the difference in question, and the degree of proximity to the crocodilian and alligatorial characters respectively. With regard to another character deducible from the relation of the backwardly- produced angle of the jaw to the articular surface, the Crocodilus Hasfuigsice more decidedly resembles the Alligator : I allude to the depth of the excavation between the articular cavity (29) and the end of the angle (30), and to the lower or higher level of the angle itself: the fossil jaw (fig. 5) resembles the Alligator (fig. 6) in this respect more than the Crocodile (fig. 4). The alveoli are twenty in number in each ramus of the Crocodilus Hastingsice : the third and fourth are large, of equal size, and close together ; behind these the eleventh, twelfth, and thirteenth are the largest, and the alveolar ridge is raised to support them ; after the seventeenth the summits of the crowns of the teeth become obtuse, and the crowns mammilloid, and divided by a constriction or neck from the fang ; they each, however, have a separate socket, as in the Crocodiles, the septa not being incomplete at the hinder termination of the dental series, as in the Alligator niger figured in my ' Odontography.'* Fig. 3, PI. 2 B, gives a representation, of the natural size, of the cranial platform of a young Crocodilus Hasliiigsice in the collection of Searles Wood, Esq. ; the hemi- spheric depressions in the surface of the bone are more regular, distinct, and relatively * Tom. ii, pi. Ixxv, fig. 3. 126 BRITISH FOSSIL REPTILES. larger, and the interorbital part of the frontal is narrower, concomitantly with the larger proportional eyeballs and orbits of the young animal. The relatively larger supratemporal apertures form another character of nonage ; but there is no ground for deducing a specific distinction from any of the differences observable between this part of the young crocodile's cranium and the corresponding part of that of the more mature specimen (PI. \ J). Alligator Hantoniensis, JFood. Plate 1 C, fig. 2. London Journal of Palseontology and Geology. On reviewing the characters of the skull of the Crocodilus HastingslcE we perceive that they combine to a certain extent those which have been attributed to the genus Crocodilus and the genus Alligator ; in general form it resembles most the latter, but agrees with the former in some of the particulars that have been regarded by Cuvier and other palaeontologists as characteristic of the true Crocodiles. I allude more particularly to the exposed position of the inferior canines when the mouth is shut. Respecting which, however, I am disposed to ask, whether this be truly a distinctive character of importance ? One sees that it needs but a slight extension of ossification from the outer border of the groove to convert it into a pit ; yet the character has never been found to fail as discriminative of the several species of existing Crocodiles and Alligators hitherto determined. It constitutes, however, the only difference between the skulls of the Crocodilus Hastmgsice in the collection of the Marchioness of Hastings and that fine portion of skull now, by the kindness of Mr. Searles Wood, before me, on which he has founded the species named at the head of the present section. So closely, in fact, do those specimens from the same rich locality correspond, that any other comparative view than that given in PI. 1 C appeared superfluous. In both the broad nasal bones terminate at the same distance from the extei'nal nostril, which is accordingly formed exclusively by the premaxillai'ies ; in both, the palate-bones present the same narrow, truncate posterior ends, and the same equal breadth of their anterior portions included between the maxillaries ; only these terminate rather more obliquely in Mr. Wood's specimen, their anterior ends forming together a very obtuse angle directed forwards. But this is comparatively an unimportant difference, and I regard as equally insignifi- cant the slight interruption of the transverse line of the maxillo-premaxillary suture, at the middle part, which will be seen by comparing fig. 2 with fig. 1, in PL 1 C. The teeth are the same in number, arrangement, and proportion in the Alligator Hantoniensis as in the Crocodilus Hastingsice, and the alveolar border of the jaws describes the same sinuous course. Had the complete fossil skull first submitted to my inspection at the meeting of the British Association at Oxford presented the same fossae for the reception of the lower canines which exist in fig. 2, PI. I C, I should have referred it to the Alligators, CROCODILIA. 127 notwithstanding the crocodilian characters of the small orbits, the long facial plates of the prefrontal and lachrymal, the wide supratemporal apertures, the non-expansion of the fore part of the palatines, and the non-appearance of the vomer on the palate, with other minor marks of the like affinity. For all these characters arise out of secondary modifications, and are presented in different degrees in the different species of Crocodile, and are rather of a specific than a generic value. They determine the judgment by the extent of their concurrence rather than by their individual intrinsic worth, and for that reason, therefore, the exposed position of the lower canine in the lateral groove of the upper jaw inclined the balance in favour of a reference of the previously-described fossil to the true Crocodiles. One cannot, indeed, attach any real generic importance to the modification of the upper jaw in relation to the lower canines. In three examples, however, in the collection of the Marchioness of Hastings, the crocodilian modification of this character is repeated, as it is shown in PI. 1 B, fig. 1 ; and we have to choose, therefore, between the conclusion that Mr. Wood's specimen (Pi. 1 C, fig. 2) presents an accidental variety in this respect, or to view the fossae in the upper jaw as indicative of not only a different species but a distinct genus from the Crocodilus Hastingsim. I should be glad to have more evidence on this point, and especially the opportunity of comparing the posterior nostrils, the orbits, the supra- temporal apertures, and the occipital part of the skull of a specimen from Hordle, repeating the alligatorial character of the fossse in the upper jaw for the lower canines. I am disposed to regard this character, notwithstanding its constancy in the living species of Alhgator, as a mere variety in the Hordle fossil ; but pending the acquisition of further evidence, it seems best to record this fossil under the title proposed for it by the able geologist by whom it was discovered. Crocodilus Hastingsi^. Plate 1 1). VertebrcB referable to the Crocodilus Hastingsi^. The fossil crocodilian vertebrae obtained from the Eocene sand at Hordle, notwith- standing the comparatively limited extent of the researches in that interesting formation, are at least as abundant as those which have been discovered at Sheppy, but they do not, as at that locality, indicate two distinct species ; all that have, hitherto, been found belong to one and the same kind of Crocodile, and from their robust proportions, would seem to have come from a species with a short and broad muzzle, like that of the Crocodile or Alligator, the fossil skulls of which have been described. Perhaps the most perfect fossil reptilian vertebra that has hitherto been discovered is the one figured, of the natural size, in PL 1 A figs. 1, 2, and 3. It is the fifth cervical vertebra. As compared with that of the Crocodilus toliapicus (PI. 3 A, figs. 1, 2), which it resembles in size, the hyjiapophysis, hy (fig. 2, PI. I B), is much more compressed, and the under part of the centrum is more extensively and deeply exca- 128 BRITISH FOSSIL REPTILES. vated between it and the parapophyses {p) ; it is also excavated on each side behind the base of the hypapophysis, from which a progressively widening smooth ridge is continued to near the posterior surface of the centrum. The interspace at the side of the vertebra, between the parapophysis and diapophysis, is smaller but deeper in the Crocodilus Hastingsi(B. The neurapophyses meet above the centrum in both ; but in the Crocodilus Hastinf/sice they are thicker anteriorly and thinner at their posterior border, and the neural canal (fig. 2, ti) is more contracted than in the Crocodilus toliapicus. As compared with the cervical vertebra of the Crocodilus champso'ides from Sheppy, the present vertebra differs in the form of the hypapophysis in a greater degree than from the Crocodilus tolicqncus. Fig. 8, PI. 3 A, shows as little as does fig. 2 in the same plate, the median ridge and lateral excavations of the under part of the centrum which charac- terise the present vertebra of the Crocodilus HastingsioE. The Crocodilus cJiampsoides resembles the Crocodilus Hastingsiai in the character of the proportion and depression of that part of the side of the centrum forming the interspace between the par- apophysis and diapophysis ; but the antero-posterior extent of the parapophysis is relatively less in that Sheppy species. The outer surfaces of the neurapophyses in the Crocodilus Hastinxjsice slope or converge towards each other from before backwards, in a much greater degree than in either of the Sheppy species. I have not observed in any recent Crocodile or Alligator the median ridge, continued backwards from the hypapophysis and the lateral depressions, so strongly developed, as in the Crocodilus Hastin(jsice. The fore part of the neurapophyses is relatively thicker in this than in the recent species. The pleurapophyses pi, (figs. 1, 2), are well developed both forwards and backwards, and the latter productions are expanded and excavated above for the reception of the fore part of the succeeding cervical rib. The zygapophyses [z) are thicker at their base, especially the hinder pair, where the base fills up the entire interval between the articular surface and the base of the spine (see fig. 2). There is the usual deep exca- vation at the fore and back part of the base of the spine {ns) for the insertion of the interspinal ligaments. The neural spine is compressed, moderately long, straight and truncate at its summit. Although the hypapophysis maintains its characteristic form with much constancy in the homologous vertebrae of the same species of Crocodile, it varies in different cervical vertebrae of the same individual in certain existing species. It is, for example, shorter and thicker in the third and fourth vertebrae than in the succeeding ones in the Crocodilus acufus ; whilst in the Crocodilus hiporcatus the hypapophysis of the third cervical is more compressed than that of the sixth. The greatest difference is, how- ever, presented, as far as I have yet made the comparison, by the cervical vertebrae of the Alliffcttor lucius, in respect of the hypapophysis, which is broad and short in the third and fourth cervicals, but becomes long and slender in the succeeding ccrvicals. The small vertebral centrum (fig. 4, PI, 1 D) i-esembles, in its broad and stunted CROCODILIA. 129 hypapophysis, that of the third cervical vertebra of the Alhgator, but with an indication of a median rising and lateral depressions, behind that process, Uke those which are more decisively shown in the fifth cervical vertebra of the larger individual of the Croco- dilus HastingsicB, to which species I believe the specimen fig. 4 to belong. It is the homologous vertebra with fig. 8, PI. 3 A, and well illustrates the different proportions of the bones in different species of Crocodile. Fig. 6 gives a view of the anterior surface of the first sacral vertebra of the Crocodilus Ilastingsia : the under surface of the centrum has ceased to develope the median ridge ; the short and thick ribs {-pi) have completely coalesced with both the centrum and neural arch. The anterior concavity has a fuller and more exact elliptical form than that of the Crocodilus toliapicus (fig. 5, PI. 3 A) ; the anterior zygapophyses do not project over the rim of that concavity ; but, like those of the Alligator and Crocodile, they are more transversely extended than in the Gavial. The general proportions of the first caudal vertebra (fig. 7, PI. 1 D) are intermediate between those of the Crocodilus toliapicus (fig. 7, PI. 3) and of the Crocodilus champsoides (fig. 10, PI. 2>A) : the under surface of the centrum is flat, not concave, lengthwise, as in both the Sheppy Crocodiles ; the side of the centrum is irregularly tuberculate, not smooth, and concave lengthwise; the broad and high neural spine is deeply grooved at its fore part : a smaller proportion of the hinder end of the centrum (fig. 5) is occupied by the articular ball than we find in the antecedent vertebrae. As none of the other numerous vertebrae and portions of vertebrae give any indi- cations of a different species from the Crocodilus Hastingsice, or add any material characters to those of that species which have been deduced from the parts of the skeleton already described, I refrain from trespassing on the reader's attention or occupying further space by their description or figures. Genus — Gavialis, Oppel. Gavialis Dixoni, Oiven. Plate 3 B. The characters of the genus Gavialis are much more strongly marked than are those which distinguish the Alligators from the Crocodiles, and leave no ambiguity in the conclusions that may be deduced from them. The present interesting addition to the catalogue of British Fossil Reptiles, is due to the discovery in the Eocene deposits at Bracklesham, by my lamented friend the late Frederic Dixon, Esq., F.G.S., of the remains figured in PI. 3 B. The portions of the lower jaw demonstrate, by the slender pro- portions of the mandibular rami (figs. 1, 5), the extent of the symphysis, the uniform level of the alveolar series, and the nearly equal distance of the sockets of the com- paratively small, slender, and equal-sized teeth, the former existence in England, during the early tertiary periods, of a Crocodilian with the maxillary and dental 130 BRITISH FOSSIL REPTILES. characters of the genus Gavialis. These characters are, however, participated in by some of the extinct Crocodihans of the secondary strata (see PI. 1, fig. 2') ; but in them they coexist with a different type of vertebra from that of the recent and known tertiary Crocodihan genera : it became necessary, therefore, to ascertain what form of vertebra might be so associated with the fossil Gavial-like jaws and teeth in the Bracklesham Eocene deposits, as to justify the conchision that such vertebrae had belonged to the same species as the jaws. Now, the only Crocodilian vertebrse that have yet been found at Bracklesham, so far as I can ascertain, present the procoelian type of articular surfaces of the body (PI. 3^), like that in Mr. Dixon's collection fig. 8. This vertebra answers to the fifth cervical vertebra in the existing Crocodihans, and accords in its proportions with that in the Gangetic Gavial. There are a few indications of specific distinction ; the parapophysis {p) or lower transverse process articulating with the head of the rib, is relatively shorter antero-posteriorly. The broad, rough, neurapophysial sutures {n) meet upon the middle of the upper part of the centrum ; the elsewhere intervening narrow neural tract sinks deeper into the centrum than in the modern Gavial, but is perforated, as in that species, by the two approximated vertical vascular fissures. The hypapophysis {hs) or process from the inferior surface of the centrum, has been broken oiF in the fossil, but it accords in its place and extent of origin with that in the fifth and follo\raig cervical vertebrse of the Gavial. Assuming the fossil procoelian vertebrae from Bracklesham, and the above- described vertebra in particular, to have belonged to the same individual or species as the portions of fossil jaw (figs. 1, 5), then these mandibular and dental fossils must be referred to the genus Gavialis, or to the long-, slender-, and subcylindrical-snouted Crocodilia with procoelian vertebrae. This genus is now represented by one or two species peculiar to the great rivers of India, more especially the Ganges ; and the fossil difi'ers from both the Gavialis ffaiiffeticus, Auct., and from the (perhaps nominal) Gavialis tcnuirostris, Cuv., in the form and relative size of the teeth. The crown (figs. 6, 7) is less slender in the fossil than in the existing Gavials, and less compressed, its transverse section being nearly circular. There are two opposite principal ridges, but they are less marked than in the existing Gavials ; and are placed more obliqviely to the axis of the jaw, i. e., the internal ridge is more forward, and the external one more backward, when the tooth is in its place in the jaw. In the modern Gavial, the opposite ridges, besides being more trenchant, are nearly in the same transverse line. The other longitudinal ridges on the enamel of the fossil teeth, are more numerous, more prominent, and better defined, than in the existing Gavials : the intermediate tracts of enamel present the same fine wrinkles in the fossil as in the existing Gavials' teeth. The two chief portions of jaw (fig. 1, and figs. 4, 5) belong to two individuals of different ages ; indicated by the difference in the breadth and depth of the ramus : both specimens being from the corresponding part of the jaw, viz. where it forms the CROCODILIA. 131 long symphysis characteristic of the Gavials. The specimen (figs. 4, 5) includes a larger proportion of the jaw than the fragment delineated in fig. 1. On comparing the latter fragment of the fossil lower jaw with a specimen of a lower jaw of the Gavialis gangeticm of the same breadth across the symphysial part, at the intervals of the sockets, which breadth is 3 centimeters (1 inch 3 lines), I find that the longitudinal extent of 10 centimeters (near 4 inches) of a ramus of the fossil jaw includes five sockets ; but in the recent Gavial the same extent of jaw includes seven sockets, showing that the teeth are fewer as well as larger in the fossil Gavial, in proportion to the breadth of the jaws. The second portion of the jaw (fig. 2) is from the part where the rami diverge posteriorly from the symphysis, and near the posterior termination of the dentary series. Here the teeth become shorter in proportion to their thickness, and somewhat closer placed together : there is a shallow depression (e) in each interspace of the teeth, for the reception of the crowns of the opposite teeth when the mouth is shut. These depressions are longer, deeper, and better defined in the fossil than in the recent Gavial of the same size. The fragments of jaw and teeth of the fossil Gavial of Bracklesham show examples of young teeth penetrating the base of the old ones, according to the law of succession and shedding of the teeth, which characterises the existing Crocodilia : fig. 2 shows the apex of one of the successional teeth at d ; and fig. 3 d the hollow base of the same incompletely formed tooth seen from below. Besides the fossil jaws, teeth, and vertebrae of the extinct Gavial, a nearly entire femur (fig. 9) of a Crocodilian has been discovered in the Eocene deposits at Bracklesham, which in its proportions, agrees with that bone in the Gavial of the Ganges. Cuvier, in his comparison of the bones of the Gavial with those of the Alligators and true Crocodiles, merely observes, "La forme des os du Gavial ressemble aussi prodigieusement a celle des os du Crocodile, seulement les apophyses epineuses des vertebres sont plus carrees."* With regard to the femur, this bone is more slender in proportion to its length in the Gangetic Gavial, than in the Crocodihis hvporcatus or the AUif, an awl; uavpos, a lizard. f Odontography, 4to, p. 182. X Transactions of the Geological Society, 2d Series, vol. vi, p. 412, 184). § lb. p. 413, pi. 39, fig. 3. CRETACEOUS LIZARDS. 175 Genus, Coniosaurus,* Owen. Species, Coniosaurus crassidens. (PI. 2, figs. 18, 19, \^ a, and 20.) Dixon's 'Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex,' 4to, p. 386. Two genera of Lizards of the Cretaceous period, with procoelian cup-and-ball vertebrae, similar in size and form to those of the series figured and described in the ' Geological Transactions,' vol. vi, 2d ser., pi. 39, fig. 3, are now no longer hypothetical, but have been satisfactorily established by the discovery of portions of jaws and teeth associated with such vertebrae. The first of these specimens, which discloses a small extinct Lacertian, distinct from Baphiosaurus, and characteristic of the chalk formation, was obtained from the Middle Chalk at Clayton, Sussex, and forms part of the choice and instructive collection of Henry Catt, Esq., of Brighton. It is figured in ' Lacertians,' PI. 2, figs. 19 and 20, and a group of vertebrae of apparently the same species is represented in fig. 19. These vertebrae are represented of the natural size. Like those first figured in the ' Geological Transactions,' torn, cit., pi. 39, they present an anterior concavity or cup, and a posterior ball upon the bodies for their reciprocal articulation ; and a tubercle is developed from each side of the vertebral body near its anterior end, for the articulation of the rib. The nop-articular surface of the vertebra is smooth ; its under part is concave in the axis of the body, convex transversely. On the very probable supposition, however, that the vertebra, v, fig. 19, belonged to the same animal as the jaw which is imbedded in the same portion of chalk, such vertebrae must be smaller in proportion to the head than in the extinct species of Lacertine Saurian, PL 8, fig. 1, likewise from the chalk, and to which there will be adduced reasons for believing that the fine specimen, in the collection of Sir P. de M. Grey Egerton, Bart. (PI. 9, fig. 4), belongs. The fossil jaw and teeth in PI. 2, fig. 19, determine the distinctness of the Coniosaurus from the above-named fossil, as well as from all known recent Lizards. The dentary bone contains from eighteen to twenty teeth ; the anterior five or six teeth are slender, slightly recurved, pointed, or laniariform ; the rest progressively increase in thickness as they are placed further back ; expanding above the neck, slightly compressed laterally, most convex inwardly, with an anterior border, which is more prominent and curved than the posterior one : the anterior margin is further characterised by a longitudinal groove on its outer side. Some of the posterior teeth show a slight longitudinal indent near the posterior obtuse border ; the last molar is smaller and more obtuse than the others. The enamel is very finely wrinkled. The teeth are closely and rather obliquely arranged ; the long simple roots are anchylosed to the bottom of the shallow alveolar groove, and to the inner side of the outer wall, * Kofis, los, chalk ; aavpos, lizard. 176 BRITISH FOSSIL REPTILES. and their excavations indicate the usual mode of succession and displacement : a few alternate teeth have been shed. The mode of attachment more resembles that which characterises the teeth in Lacerta proper and other " coelodont" genera of the Lacertian tribe ; but in the number, proportions, and general shape of the teeth, the present species more resembles some of the Iguanian tribe. The anterior coronal groove is continued to the anterior margin of the crown, which it slightly indents in the larger teeth ; but this is the only approach to that complex structure which characterises the teeth of the typical Iguanidce. PI. 2, fig. 19 a is a magnified view of the crown of one of the anterior teeth ; and fig. 1 9 a of one of the posterior teeth. There is no existing species of the Iguanian or other herbivorous family, nor of any of the ' pleurodont' Saurians, with which the present chalk-fossil is identical ; nor can I refer it to any of the established genera of LacertUia. The absence of the cranium and bones of the extremities, does not allow of any closer comparison with the Monitors, Iguanas, or Scinks ; but the characters of the teeth justify the consideration of the fossil as the type of a hitherto undescribed genus and species, which I therefore propose to call Coniosaums crassidens, or the thick-toothed Lizard of the Chalk formation. The specimens represented in figs. 18, 19, and 20, are from the Clayton chalk-pit near Brighton : a smaller portion of a lower jaw and a few teeth have been obtained bv Mr. Dixon from the Washington chalk-pit near Worthing : and vertebrae have been found by Mr. Catt in the upper chalk near Palmer, during the cutting of the railroad from Brighton to Lewes. These are the only specimens of the genus and species that have jeX been discovered. Genus, Dolichosaurus,* Owen. Dixon's ' Geology of Fossils of the Tertiary and Cretaceous Formations of Susse.x,' 4to, p. 388. Species, Dolichosaurus longicollis. (Plate 8, figs. 1 and 2.) My esteemed friend the late Frederic Dixon, Esq., F.G.S., in the course of his indefatigable inquiries respecting the fossils of the cretaceous period, obtained such information relative to the unique specimen of the mutilated head and anterior thirty six vertebrae of the fossil Lizard from the lower chalk of Kent, in the admirable collection of Mrs. Smith of Tunbridge Wells, figured in PI. 8, fig. 1, as left no doubt in his mind that it formed part of the same skeleton with the chain of posterior abdominal and sacral vertebrae in the collection of Sir P. de M. Grey Egerton, Bart., M.P., F.G.S., and which is figured in the ' Geological Transactions/ 2d Series, vol. vi, pi. 39 ; and in the present work at PI. 9, fig. 4. * AoXij^os, long, aavpos, lizard. CRETACEOUS LIZARDS. 177 Both specimens are from the same quarry or pit at Burham, in Kent, were found at the same time, and there is good reason to suppose in the same block of chalk. It appears, however, that they were disposed of by the quarrymen to different persons, and ultimately found their way to the two collections of which they are now respec- tively the ornaments. Assuming, then, the two groups of vertebrae to have belonged to the same skeleton, and the conformity in shape and size of the vertebrae and ribs favours the conclusion which Mr. Dixon had drawn from the historical evidence, we may then enumerate fifty- seven vertebrae between the skull and the pelvis, supposing that none have been lost between the end of the specimen in PL 8, fig. 1, and the beginning of that in PI. 9, fig. 4. Amongst existing Lizards this number of trunk (cervical, dorsal, and lumbar) vertebrae is equalled only by those snake-like species (Pseudopus, Bipes, OpJdsaurus) which seem to make the transition from the Lacertian to the Ophidian reptiles : but not any of such genera manifest so well-developed a humerus and scapular arch as are indicated in PI. 8, fig. 1, or so complete a sacrum and pelvic bones as are shown in PI. 9, fig. 4. Of those existing Lacertians which had the hinder extremities as well developed as in the extinct species under consideration, the greatest recorded number of vertebrae between the skull and the sacrum is forty-one.* Although the evidence relating to the discovery of the specimens (PI. 9, fig. 4, and PI. 8, fig. 1 ) is such as to lead me to deem it highly probable that they form the anterior and posterior moieties of the backbone of the same individual ; yet, as it does not amount to absolute demonstration, the characters of the Saurian in question must for the present be rigorously deduced from those parts which are unaffected by such uncertainty. In this fit condition for scientific comparison must be regarded the frag- ment of skull, and the chain of thirty-six vertebras imbedded in one block of chalk, and represented in PI. 8, fig. 1 . The most cautious and sceptical Palaeontologist must admit, after scrupulous examination of the sjDecimen, that the jaws and the portion of vertebral column, which are accurately figured in the plate, have belonged to one and the same animal, having been subject to no greater amount of dislocation than is represented at the twenty-fifth vertebra for example, and in the position of some of the ribs. Viewing the slight extent of displacement of any of these parts in the fossil, it is very improbable that the scapular arch should have been subjected to any considerably greater degree of displacement ; and taking, also, into consideration the gradual diminution of the vertebrae, as they extend forwards from the place of the scapular arch in the fossil, at the eighteenth or twentieth vertebrae, to the cranium, and the remarkable and striking difference in the shape and size of the pleurapophyses (vertebral ribs,^;., j^i.) in those anterior vertebrae, I am led to conclude that the position of the remains of the scapular arch in the fossil was, in relation to the vertebral * According to the table in Cuvier, Legons d'Anat. Comp. i (1836), p. 221, e.^. in the Sc««cm4 oeeZ/a. 186 BRITISH FOSSIL REPTILES. teeth, those of the upper jaw chiefly, of the Mosasaurus Hojfmanni, do not bear out the term " polygonal" which he applies to the crowns of the teeth of that species, as well as to those of his Mosasaurus Maximiliani ; still less can I find these angles so con- stant and regular as to divide the outer surface of the crown into five, and the inner surface into seven facets ; nor have I seen in any maxillary or mandibular tooth of Mosasaurus Iloffmanni that near equality of extent and convexity between the inner and outer surfaces of the crown, which Dr. A. Goldfuss describes (p. 178) and figures in Tab. IX, fig. 4, of the memoir above cited. If that figure accurately represents a maxillary tooth of the same species of Mosasaurus as the one described by Cuvier and recorded by V. Meyer and Pictet under the name of M. Camperi and Iloffmanni ; and if the outer surface of the crown is ever flat or level, the range of variety between the two extremes of flatness and convexity is greater than I have yet found in any of the equally well-marked forms of teeth in other fossil reptiles. The teeth in the specimens of upper and lower jaw of the species of Mosasaur from the chalk-pit at Offham, Sussex, now in the Museum of Henry Catt, Esq., of Brighton, and figured of the natural size in PI. 2, fig. 1 and Iff, equally difi"er from the typical form of tooth of the Mosasaurus Iloffmanni, and from those of the Mosasaurus Maxi- miliani, PI. 10, fig. 8: the outer surface of the crowns of the mandibular teeth of Mosasaurus gracilis are more convex than those of Mos. Iloffmanni, and are less convex than those of Mos. Maximiliani : not any of the teeth of Mosasaurus gracilis present that angular disposition of the enamel which gives the polygonal form to the pyramidal crowns of the teeth of the Mos. Maximiliani. The lower jaw, PL 2, fig. 1, is more slender, less deep in proportion to its length, than in the great Maestricht Mosasaur, and the hinder teeth are relatively smaller and closer together ; I have proposed, therefore, to indicate the species by the name of Mosasaurus gracilis. The general form of the crown of the teeth in Mos. gracilis is shown at a, b, and c, fig. 1 ; an exact contour of the crown a little above its base is given at PI. 10, fig. 9. The smooth and polished enamel ; the inequality of the outer and inner sides of the crown, such as it is ; the implanted fang of the tooth thickly coated by a coarse osseous cement ; the general anchylosis of the fang to the bony walls of the socket, which rise in a pyramidal form from alveolar border of the jaw ; all manifest the peculiar generic characters of the great acrodont marine lizard, Mosasaurus. The maturity of the individual from which the present specimen (PI. 2, fig. 1) has been derived, cannot be inferred from the solidifi- cation and complete development of the anchylosed fangs of the teeth in a class of animals in which those organs are repeatedly shed and renewed : the worn-out teeth, in course of displacement, of the young crocodile, with their alveoli, present in miniature all the senile characters of the corresponding teeth of the mature and aged animal. If, however, the specimen of Mosasaur in question should be adult, it would derive a well-marked specific character from its diminutive size as compared with the Mosasaurus Iloffmanni or Mos. Maximiliani ; being only one third the size of the latter, CRETACEOUS LIZARDS. 187 and one fourth that of the former species. But the characters of immaturity are not manifested by the cold-blooded animals in their osseous and dental systems as they are in the warm-blooded and higher organised mammalia.* In all the teeth of the Mosasaurus gracilis in which the crown is broken, the remains of the pulp-cavity are exposed in the centre of its base : but the immaturity of the specimen is not demonstrated by this character ; for, in the largest sized teeth of the Mosasaurus Hoffmanni, even in one with a completely developed fang, measuring with the crown nearly five inches in length, I have found a pulp-cavity extending from the base of the crown into the expanded fang, but becoming almost obliterated at the base of the fang. The cast of the crown of a still larger tooth of a Mosasaurus from the green-sand of New Jersey, U.S., also shows the remains of a pulp-cavity at its base. This cavity becomes filled in the fossil specimens with the matrix, which is usually chalk ; but sometimes the cavity, like the air-chambers of polythalamous shells, is filled with silex. The number of teeth in each ramus of the lower jaw o^ 3Iosasaurus gracilis seems not to have exceeded twelve. In Mosasaurus Maximiliani they are reckoned at eleven ;f in Mosasaurus Hoffmanni at fourteen ; and in this species they are placed closer together than in the Mas. gracilis, as may be seen by comparing figure 1 of PI. 2 with that of the lower jaw given by Camper in the ' Philosoi^hical Transactions ' for 1786, tab. xvi, which is copied by Faujas St. Fond, in pi. vi, of his ' Histoire de la Montagne de St. Pierre.' j The posterior teeth are rather smaller than the others in Mosasaurus gracilis. At the fore part of the jaw the implanted and anchylosed base of the teeth extends through about half the vertical diameter of the jaw ; at the posterior part of the series the fangs sink into one third or one fourth the depth of the jaw. The canal, which, as in the crocodile, extends below and along the inner side of the bases of the sockets and anchylosed fangs, is shown, filled by chalk, at d, fig. 1. Traces of the vascular foramina along the outer side of the jaw are visible in the right dentary piece, the outer side of which is exposed : the " splenial " (" opercular," Cuvier,) element is shown at x, fig. 1, on the left ramus. In the portion of the left superior maxillary bone (PI, 2, fig. 1 a) all the teetli are, unluckily, too much broken or abraded to give an idea of the precise form of their crowns ; they are rather more compressed at their base tlian in Mosasaurus Hoffmanni : the posterior ridge is much less developed, and the whole of the posterior longitudinally concave border is more transversely convex than in Mosasaurus Hoffnumm or 3Ios. Maximiliani. There is as little indication of the angular or polygonal * Dr. Goldfuss infers the maturity of his Mosasaurus Maxhniliaiii from the characters, of which the inadequacy is exphiined above. "Die vollstiindige Verlinocherung alter Tlieile, so wie die hiiufige bemerk- bare Aussfullung der Zahne beweisen, dass das Individuum seine vollstiindige Ausbildung und mit dieser nur die halbe liinge des Mosasaurus Hoffmanni erreicht hatte." (Ijoc. cit., p. 177.) t Goldfuss, loc. cit. p. 178. % Cuvier, loc. cit. p. 320. 188 BRITISH FOSSIL REPTILES. structure in these teeth as in those of the lower jaw ; but the enamel shows some longitudinal striations. All the vertebrae of the Mosasaurm, according to Cuvier, are concave at the fore part, convex at the hind part of their bodies ; the convexity and concavity being greatest on the anterior vertebrae. The foremost of these are characterised by an inferior process or " hypapophysis," developed from the middle of the lower surface of the centrum : they have two transverse and four articular processes, and a long com- pressed upper or neural spine. The centrum is longer than it is broad, and broader than it is high; the terminal articular surfaces are transversely oval or reniform. Such are the characters of the last cervical or first dorsal vertebrae. The middle dorsal vertebrae are like these, but have no hypapophysis. Then follow vertebrae which have no articular or oblique processes (zygapophyses), but have longer and flatter transverse processes (diapophyses), and terminal articular surfaces of a pen- tangular form, or of a triangidar form with the base downwards (see PI. 1, fig. 5). Next come vertebrae with diapophyses and a pair of inferior processes (hypapophyses) for the articidation of chevron-bones (haemapophyses) ; afterwards vertebras without transverse processes and with large anchylosed chevron-bones (haemapophyses) ; and finally vertebrae devoid of all processes whatever. The vertebrae discovered in the Kentish Chalk, with the jaws and teeth above described, and of corresponding proportions to those parts which we observe in the vertebrae of the Mosasaurus Hoffmanni, present all the generic vertebral characters of that Lacertian genus, and correspond with the third and sixth kind, or with the posterior dorsal and the anterior caudal vertebrae, as defined by Cuvier. But the terminal articu- lations of the centrum of the dorsal vertebrae of ISLosasanrus gracilis present a full oval (not elliptical) form, the long axis of which is vertical and the great end downwards (PL 2, fig. 4). The length of the centrum {j,b., fig. 3), which is three centimeters and a half, or one inch and five lines, exceeds the breadth ; but this is equalled by the height of the centrum. The diapophyses in fig. 2, d, are broken away ; in fig. 3 it is uncertain whether the surface be a fractured one, or whether it is a natural cavity for the rib ; the analogy of Blosasaurus Hoffmanni favours the former view of it. The neural arch (fig. 3, «) is anchylosed to the centrum, as in the larger species of Mosasaurus. I can perceive only a feeble indication of zygapophyses, which shows that the vertebra (figs. 2 and 3) comes from the posterior region of the back. The neural canal (fig. 4, «) is small and triangular ; a sharp longitudinal ridge rises from the middle of its floor, and on each side of this there is a vascular canal descending vertically into the substance of the centrum ; this substance presents a coarse fibro- cancellous texture ; the areolae extended longitudinally, and decreasing much in size at the ends of the centrum. The outer surface of the vertebra is smooth ; the margins of the anterior articular concavity are sharp. The vertebra (fig. 2) shows, by the lower position of the diapophysis {d), that it CRETACEOUS LIZARDS. 189 comes from a more posterior position of the spine than that represented in fig. 3. Figs. 5 and 5 a give views (upside down) of a caudal vertebra, which demonstrates another Mosasaurian character in the anchylosis of the hsemapophyses or chevron- bones to the centrum, as in the posterior caudal vertebrae of Mosasaurus Hoffmanni ; but the haemal canal (fig. 5 a, h) is relatively wider, and the entire centrum is much longer than in the corresponding kind of vertebra figured by Cuvier* or by Faujas St. Fond.t Three views of the body of a vertebra of the Mosasaurus gracilis, discovered by the Rev. H. Hooper, M.A., distinguished by his geological researches in the neighbourhood of Lewes and Brighton, are given in PI. 9, figs. 7, 8, and 9. This specimen is from the Sotheram Chulk-pit, near Lewes. From the genus Leiodoii\ (PL 10, fig. 5, 5**) the Mosasmirus gracilis (lb. fig. 9) differs, like the Afosasaurus Hoffmanni (lb. fig. 7), in the inequality of the two sides of the crown of the teeth, which are bounded or divided by the anterior and posterior ridges. The Mosasaurus MaximUiani (lb. fig. 8) differs from the genus Leiodon in the polygonal character of the crowns of the teeth. The interest which must be excited in the Naturalist and Palaeontologist by an extinct Saurian, essentially organised according to the Lacertian type, but developed on a scale surpassing that of the largest existing Crocodiles, and especially modified, as it seems, for aquatic life, leads me to believe, that any additional facts tending to complete its restoration will here be acceptable, although they may not have been afforded by fossils from British strata. \n the formations of the Cretaceous Period in North America, answei'ing in mineralogical characters to our Gi'een-sands, though probably contemporaneous with the newest chalk deposits of Europe, many fine examples of Mosasaurus, of the species called by Goldfuss, Mos. MaximUiani, have been found, and the discovery affords a highly instructive instance of the coexistence of particular forms of fossil Reptilia in remote parts of the earth, at the same geological epoch. In a series of remains of the Mosasaurus MaximUiani, from a Green-sand formation at New Jersey, United States, kindly submitted to my examina- tion by Professor Henry Rogers, of Pennsylvania, I detected the basioccipital bone of the cranium, which gave additional evidence of the Lacertian affinities of the Mosasaurus, and new proof of the Cuvierian law of correlation of organic structures. This basioccipital bone, which is figured in the ' Quarterly Journal of the Geological Society,' November, 1849, pi. x, fig. 5, was three inches and a half in length, and four inches nine lines in extreme breadth. It resembled the centrum of the " vertebra dentata" of the Crocodilia, in being convex behind and flattened in front. The convexity formed the inferior and major part of the occipital condyle, which must have been reniform, the angles being superior, and formed by the * Cuvier, loc. cit., pi. xix, fig. C, A, B. f Loc. cit., pi. viii. X Odoutography, 4to, p. 20 1, pi. 72, figs. 1 and 2. 190 BRITISH FOSSIL REPTILES. exoccipitals. The rough sutural surfaces for the articulation of these elements were divided by a deep and narrow channel, which gradually expanded towards the condyle. The anterior flat vertical articular surface of the basioccipital was smooth, indicative of a persistent harmonia between it and the basisphenoid, analogous to that which exists between the centrum of the axis and the odontoid process. Two very thick and short exogenous processes (hypapophyses) diverge from the under part of the anterior half of the basioccipital, and terminate in oblique and slightly convex surfaces, irregularly pitted ; they resemble the hypapophyses sent off from the basisphenoid in the great Monitor (Varanus), against which the pterygoids abut. This form and structure of the basioccipital of the Mosasaurus harmonizes with the other indications of its Lacertian affinities. The basi-occipital in the Crocodilia sends down a single hypapophysis. No part of the organisation of the Mosasaurus is so little known as that of the locomotive extremities. Cuvier gives copies of drawings which had been transmitted to him of a portion of the scapula,* clavicle,! and coracoid,;}; of a portion of a long bone, which he likens to the cubitus of a Monitor,'^ and of an os pubis, || all of which he believes to have belonged to the Mosasaurus. The portion of the ulna would indicate, Cuvier remarks, that the Mosasamiis had moderately elevated extremities ;^[ but he adds that " the bones of the fore and hind feet, so far as they are known, would seem, on the contrary, to have belonged to a kind of contracted fin, like that in the dolphin or Plesiosaur.^* He, however, figures two bones comparable with the two principal bones of the carpus of the Crocodile,tt and which one would scarcely expect to be associated with metacarpals and phalanges like those of the Enaliosaurs. And if the ungual phalanx, figured in pi. xx, fig. 21, of the * Ossemen's Fossiles,' be rightly attributed to the Mosasaurw-:, it determines the question in the negative, as to whether that Lacertian reptile had plesiosaurian paddles ; the phalanx in question much resembles that in the British Museum (No. 384, Mantellian Catalogue), which has been described as "The Horn oi the Iffuanodon." The phalanx represented in PL xx, fig. 5, of the same work, with almost flat articular ends, must have belonged to a natatory form of foot ; but as large Chelonians were associated with the Mosasaurus in the Maestricht beds, it would be rash to conclude that this phalanx absolutely belonged to the Mosasaurus. Cuvier, in fact, sums up by admitting the hesitation which he feels in offering his conjectures as to the nature of the extremities of the Mosasaurus, which were founded on the inspection of drawings * Ossemen's Fossiles, torn, v, jot. 2, 4to, pi. xLx, fig. 9. t lb., fig. 14. X lb., fig. 15. § lb., pi. XX, fig. 24. II lb., pi. xLx, fig. 10. ^ "11 annoncerait que ses extremites etaient assez 61evees." (lb., p. 336.) ** "Les OS des mains et des pieds, autant qu'ou les coniiait, semblernieut au coutraire avoir appartenu k des espfeces de nageoires assez coiitractees, et plus ou moius seuiblables a celles des dauphins ou des plesiosaurus." (lb. p. 386.) -j-j- lb., pi. xx, figs. 4 and 5. CRETACEOUS LIZARDS. 191 only, for he says the immediate comparison of the bones themselves would hardly suffice, so great is the diversity and so small the precision of the forms of those bones in reptiles.* M. Pictet, in the second volume of his ' Traite Elementaire de Paleontologie,' 8vo., 1845, terminates his brief summary of the characters of the Mosasaurm, by stating : — "Les membres paraissent avoir ete termines par des nageoires aplaties," (p. 62.) In the collection of Saurian fossils submitted to me by Professor Henry Rogers were some bones of the extremities, showing the Lacertian type of structure, and agreeing in colour, petrified condition, and proportional size with the vertebrae and teeth of the Mosasauriis from the same Green-sand formation. They were too large to be attributed to the Crocodilian species indicated by the vertebrse from the same formation. 1 subjoin, therefore, a brief description of these interesting fossils which appear to me to throw additional light on the structure of the locomotive organs of the Mosasuurus. The first of these bones gave the following dimensions : — Feet. Inches. Extreme length 2 8 Extreme breadth of the broader eud ..... 0 8 Breadth of narrower end of the same bone (imperfect) . . 0 A^ The best preserved extremity of this long bone is expanded and subcompressed, like the lower end of the fibula of the Varanus, one part of this extremity being pro- duced into an obtuse angle. The extremity is smooth, slightly concave transversely on one side, more irregular on the opposite side, with a thick prominent border opposite to the produced angle. The shaft of the bone has an irregular full, oval, transverse section with dense walls of concentric plates of bone, eight or nine lines thick, surrounding a medullary cavity, one inch nine lines in diameter. The shaft is very slightly bent. The opposite extremity which gradually expands, preserving the general form of the shaft, exhibits a strong longitudinal ridge of six inches in extent, but which subsides before it reaches the articular end. Only a portion of this end is preserved, which is slightly and irregularly convex. The second long bone of the extremity yields the following dimensions : — Teet. Inches. Extreme length ......... Breadth round the upper (?) articulating surface Depth of articulating surface ...... Breadth of lower (?) end (imperfect) ..... This bone, therefore, equals in length the preceding, but becomes more attenuate in the middle than any of the long bones in the existing Saurians ; one extremity is * Loc. cit., p. 357. 2 5 0 ^ 0 H 0 3 192 BRITISH FOSSIL REPTILES. compressed, and terminates in a slightly convex, thick, smooth articular border. Nine or ten inches below this, the shaft, slightly increasing in breadth and decreasing in thickness, presents a thick, rough, and prominent ridge, three inches and a half in length, apparently for the attachment of some strong muscle ; behind this ridge the shaft contracts to a diameter of one inch nine lines, and to a circumference of four inches six lines. At ten inches from the distal end it increases in thickness, assumes a trihedral form, with one edge produced and convex, subsiding above the articidar end, which is in the form of a simple convex condyle, not excavated for a trochlear joint in the middle, but with an irregular branched impression or smooth groove at that part : the articular surface extends upon the fore and the back part of the shaft, ahont two inches six lines from the end, contracting posteriorly, and with a convex border anteriorly above, where there is a shallow semilunar depression. There is a very deep large hemispheric pit on each side above this condyle. There is no medullar)^ cavity in this bone. These two long bones are more like the tibia and fibula of the larger lizards than the radius and ulna : there can be little doubt that they belong either to the leg or to the antibrachium, but they differ too much in shape from any of the bones of those segments in the larger lizards, with which I have been able to compare them, to encourage me to hazard a positive determination. I should be disposed to ascribe them, from their length and slenderness, to the hind leg. They are more Lacertian than Crocodilian in their general character ; and they belong with great probability to the Mosasmirus. A metacarpal or metatarsal bone of the same reptile gives the following dimensions : — 'Feet. Inches. Extreme length ......... 1 8 Extreme breadth of the broader articulating surface or upper end 0 4| Central depth of ditto 0 3^ Breadth of lower end ........ 0 3 The proximal or upper end is suddenly expanded, with an undulated or partly convex partly concave articular surface, nearly flat, at right angles to the shaft ; sub- triangular with the angles rounded off, or reniform on account of the deep notch posteriorly, below which there is a depression. A ridge is continued from the shaft upon two of the angles, which gives a subhemispheric section of the shaft at six inches from the head. Here a medullary cavity nine lines in diameter is exposed. One half of the parietes of the middle third of the shaft of this bone is preserved, which shows a continuation of the medullary cavity and the development of an angular ridge from the shaft, which subsides about sLx inches from the distal end. This end slightly expands into a simple convex condyle, with the articular surface CRETACEOUS LIZARDS. 193 irregularly grooved, and with a large deep hemispheric pit on one side above the surface, but not on the other. The above-described long bones were taken back by Professor Rogers to America ; the following specimen he liberally permitted me to retain. A metacarpal or metatarsal bone rather larger than the preceding, with the notch at the proximal end much less deep. The angular border or ridge, continued from one of the posterior rounded angles of the articular surface, quickly subsides ; that from the other angle is continued down from the middle of the shaft, giving it an oval transverse section. The fracture of the shaft, nine inches from the head of the bone, exposes an oval medullary cavity, nine lines in the long diameter. The longitudinal ridge is developed from the distal half of the bone, as in the former, and it terminates in a simple convex condyle with the grooved sculpturing upon the articular surface, and with the large deep hemispheric pit for a ligament, on one side of the trochlea, and a large shallow notch on the opposite side. The following two bones of the toes conform to the Lacertian type, and not to that of the Enaliosauria. The first is a proximal phalanx of a toe of apparently the same Saurian as the bone last described. The prcjximal articular surface appears to have been subcircular, very slightly concave, with a few shallow pits and grooves in the middle, like those on the end of the metatarsal. The shaft gradually contracts, and becomes more convex in front than behind ; it subsides into a shallow depression above the forepart of the distal trochlea, on each side of which there is a large and deep ligamentous pit. Its dimensions are as follows : Inches. Extreme length .......... 5 Breadth of upper articulating surface ...... 2| Depth of ditto 2\ Breadth of lower articulating surface ...... If Depth of ditto 2 The second specimen is a second phalanx of apparently the same toe ; having an expanded, concave, proximal, articulating surface, adapted to the distal surface of the preceding bone ; and terminated by an oblique broad convex trochlear articulation. Its dimensions are as follows : Inches. Extreme length 3J Breadth of upper articulating surface ...... 2\ Depth of ditto 2 Breadth of lower articulating surface ...... 2 Depth of ditto .... - U On the highly probable supposition that the above-described long bones belong to the Mosascmrus, they indicate the extremities of that gigantic lizard to have been 194 BRITISH FOSSIL REPTILES. organised according to the type of the existing Lacerfilia and not of the Enaliosauria or Cetacea. But a foot so organised for crawling on land might, nevertheless, by the webbed union of the large and long unguiculate claws, have been well adapted, like the feet of the Amblyrhynchus and Alligator, for swimming ; and the modifications of the vertebral column, especially of the long and deep tail of the Mosasawr, clearly prove it to have been more strictly aquatic in its habits than any known existing lizard.* The vertebra from the Chalk near Lewes (PI. 1, figs. 1 and 2) above alluded to, which is the subject of the cut. No. 2, p. 146, of Dr. Mantell's 'Geology of the South- East of England,' is one of those posterior dorsal or lumbar vertebrae, in which the diapophysis {d) arises from near the middle of the side of the centrum, and has a depressed flattened form, at its origin, instead of the thicker subcompressed form that characterises the same process in the anterior dorsal vertebrae. The specimen in question is much mutilated ; both the neurapophyses, 7i, the diapophyses, d, and part of the left side of the centrum, are broken away ; but the rarity of such evidences of the Mosasaurian genus in our English Chalk, and the historical interest attached to this, which is one of the first specimens discovered, has induced me to give an accurate figure of it in PI. 1, fig. 4, together with one of the homologous vertebrae of the Macstricht species (fig. 4), which is preserved in the British Museum. The specimen from Lewes presents the following dimensions : — Inches. Lines. Length of the centrum 2 0 Vertical diameter of ditto ....... 1 4 Transverse diameter of ditto ....... 1 6 Length of the base of the neural arch ..... 1 8 The neural arch, n, has completely coalesced with the centrum : it terminates behind, about four lines from the convex articular end of the centrum. The marginal circumference of that surface, fig. 2, has been worn away, but it evidently presented a more obovate and less triangular figure than in the Mosasaurus Tloffmanm, fig. 5. The fractured base of the diapophysis, shown at (/, fig. 1, is situated lower than half- way down the side of the centrum. The two caudal vertebrae (PI. I, fig. 3) have been retained in natural juxtaposition in the same block of Chalk. Both the neural (») and haemal (A) arches have coalesced with the centrum without any trace of the primitive sutures, the antero-posterior extent of the neurapophysis is relatively shorter than in the more advanced vertebra, * M. Hermann von Meyer, in his comprehensive and useful summary of Fossil Eemains, entitled ' Palseologica,' 8vo, 1832, classifies the Mosasaurus with the Plesiosaurus, in the Order of Sauria, characterised by fins. ("Saurier mit flossartigen Gliedmassen," p. 201.) CRETACEOUS LIZARDS. 195 as is shown by fig. 6 as compared with fig. 4, and by the following admeasurements of one of the caudal vertebrae : — Length of the centrum Vertical diameter of the convex end Transverse diameter of ditto . Length of the base of the neural arch Length of the base of the hsemal arch Inch. Lines 1 7 1 5 1 3 1 0 0 9 The hsemapophysis (h) swells outwards at its origin, before it bends downwards, backwards, and inwards to unite with its fellow in order to complete the arch. The area or span of this arch has been considerable, as in the vertebra, fig. 5 a, PI. 2, and as it is in the Ilosasaurus Ilojfmanni : it is probable that the spinous process continued from it had a corresponding remarkable length, but of this the fractured condition of the specimen afi"ords no proof. The lateral surface of the centrum is smooth, with many small vascular perforations. There is a slight but well-marked rising above the base of the hsemapophysis, at d, fig. 3, PI. 1, which seems to indicate a last rudiment of the diapophysis. A narrow vertical ridge (r) extends about two lines from the border of the posterior convex surface, as if it were indicative of the limits of an epiphysis which had formed that surface. The border of the anterior concave surface has been worn or broken away. A linear impression gives also an indication of an epiphysis in the dorsal vertebra of the Mosasaurus Hoffmanni. The slight degree of concavity and convexity of the terminal articular surfaces of the centrum in these vertebrae is characteristic of the genus. In their special characters, the small vertebrae from Lewes correspond with the vertebrae attributed to the Mosasaurus gracilis, which are longer and more slender than those of the Mosasaurus Hoffmanni. Genus. — Leiodon, Owen. 'Odontography,' p. 261, pi. kxii, figs. 1 and 2. ' Report on British Fossil ReptUes,' Trans. Brit. Association, 1841, p. 144. The teeth from the chalk of Norfolk, surmised by Dr. Mantel!, from "their symmetrical, conical form, and other characters," to belong to an unknown reptile, or to a sauroid fish ;* and described and figured in my ' Odontography'! as character- istic of a new genus of Mosasauroid Reptiles, under the name of Leiodon,\ presented * Wonders of Geology, ed. 1 839, vol. i, p. 339. f Vol. i, p. 261, pi. Ixxii. figs. 1 and 2. X Aetos, smooth, oiott, tooth. / 196 BRITISH FOSSIL REPTILES. the same acrodont type of dentition as in Mosasaurus and Geosaurus, but differed in their closer arrangement and from the former, especially, in the shape of the crown, of which the outer side was as convex as the inner side, the transverse section being an ellipse with pointed ends, which latter corresponded with two opposite trenchant edges dividing the outer from the inner side of the crown. This was covered by a smooth enamel without any indications of minor ridges or facets : the apex of the crown was sharp-pointed ; the body of the crown slightly recurved ; and its base expanded into a thick fang of a circular form, which was anchylosed to a short conical process of the alveolar border of the jaw. Deducing the generic dental characters of 3Iosasaurus from the magnificent example of the jaws and pterygoid bones, which passed from Dr. Hoffmann's collection to that of the Canon Goddin, and ultimately to the Museum of the Garden of Plants at Paris, the deviation in the teeth in question from the inequilateral facetted character of the crowns of the maxillary and mandibular teeth of that specimen was so great, as to lead me to infer that these teeth from the English chalk belonged to a distinct genus of the same family of the Lacertine order ; unless, indeed, they might be pterygoid teeth of a species of Mosasaurus, distinct from the Mosasaurus Hoffmanni. After a rigid comparison in reference to this question, I was led to the conclusion that they were not pterygoid, but maxillary teeth, and I therefore described them under the name of Leiodon anceps. The general results of that comparison, which would have been out of place in a systematic Treatise of Teeth in general, will here be requisite. Leiodon anceps, Oioen. Lacertians, Plate 10. 'Odontography,' 1840, vol. i, p. 261 ; vol. ii, pi. 72, figs. 1 & 2. Mosasaurus stenodon. Charlesworth. The London Geological Journal, 18-16, p. 23. pis. 4 and 6. Baron Cuvier, after a close and accurate description of the pterygoid bones of the great Mosasaurus Hoffmanni, concludes by stating, that " each of these bones seemed to have supported eight teeth, which grew, became attached, and were replaced, like the teeth of the jaws, but were much smaller."* They also differ from the jaw-teeth by having their two sides less unequal in regard to their convexity ; the inner side is almost as convex as that side of the maxillary teeth, but the outer side of the * " Get OS paroit avoir portu dans notre animal fossile huit dents qui croissoient, se tixoient et se rempla^oient comme celles des machoires, quoique beaucoup plus petites." (Ossemens Fossiles, toni. v, pt. ii, p. 324, 4to, 1824.) CRETACEOUS LIZARDS. 197 pterygoid teeth is more convex than the nearly flat outer side of the maxillary teeth. They resemble, in fact, in their transverse section, the lower maxillary teeth of the Mosasaurus Bixoni. The alveolar border to which the pterygoid teeth are attached in the Mosasaurus Hoffmanni, is moderately convex towards the cavity of the mouth ; the alveolar tract is relatively thicker or broader than on the jaws, and the germs of the new pterygoid teeth appear almost like a second small row on the outer side of that row which is in place, being less close to the teeth they are destined to replace than they are in the maxillary series. The teeth in question from the English Chalk, differed in the shape of their crowns from the pterygoid teeth of the Mosasaurus Hoffmanni, and the alveolar border to which they were attached, more resembled that of the dentary piece of the lower jaw. In the smoothness of the enamelled crown, its compressed elliptical form and trenchant borders, (PI. 10, figs. 5, 6,) which, when magnified, presented a fine serration, the teeth in question, approached to the characters of those of Geosaurus, as much as they deviated from those of Mosasaurus. Both Mosasaurus and Geosaurus afford types of the acrodont mode of dental attachment. Had only the teeth and portions of the jaws of the Geosaurus been known they might have been registered, on such limited evidence, as having belonged to a species of Mosasaurus distinct from the Mosasaurus Hoffmanni, and the Anatomist, Soemmerring, even supposed that the Geosaurus might be merely the young of that species. But the differences in the shape of the teeth are associated with differences in the structure of the cranium, of the sclerotic, and, what is still more important, in that of the vertebrae themselves, which are sub- biconcave and contracted in the middle of the centrum. With these evidences, therefore, of the importance of the differences indicated by different forms of the teeth of the acrodont Sauria, one may be justified in the expectation that the Leiodon will prove to be a genus alike distinct from both Mosasaurus and Geosaurus, and, as probably tending to fill up the hiatus that divided those genera in the series of Acrodonts, as it was knowii to Cuvier. The additional evidence which has been received in elucidation of this highly interesting family of Saurians, since the publication of my ' Odontography,' has tended to confirm the conclusions stated in that work relative to the Leiodon anceps. The Mosa- saurus oi the Green -sand Formations in North America, (PI. 10, fig. 8,) has been satis- factorily shown in Professor Goldfuss's Memoir, to be a species distinct from that of the Cretaceous Deposits at Maestricht, (ib. fig. 7.) The maxillary teeth show the same generic characters, the two sides being unequal, but with specific modifications. The ptery- goid teeth are ten in number on each pterygoid bone, attached in like manner to an alveolar border, which is convex both downwards and outwards : all the crowns of these pterygoid teeth had been unfortunately broken off and lost. Mr. Charlesworth has described and figured in the first part of the 'London Geological Journal,' a portion of jaw-bone, with five teeth, of the Leiodon anceps, which 198 BRITISH FOSSIL REPTILES. he states to have come into his possession from " one of the numerous chalk-pits on the Essex side of the Thames" — the side on which the county of Norfolk lies ; and it appears that the teeth described and figured in my ' Odontography ' are not only specifically identical, but once formed part of the same specimen, with that which he has since figured. This may well be, for in the mass of materials which I had been collecting for six years previous to the publication of my ' Odontography ' I found the drawings, which are engraved in PI. 72, figs. 1 and 2 of that work, marked ' from the chalk of Norfolk,' without any other memorandum, and I feel obliged to Mr. Charles- worth for having publicly supplied in 1846, what my memory in 1840 failed to do, viz., the reference to the individual to whom I had been indebted in 1835 for the loan of the originals of those drawings. With regard to the question of the nature and affinities of the Leiodon, the additional evidence which the figures published by Mr. Charlesworth afford, is of value. The teeth in that specimen can only be referred to the genus Mosasaurus, as characterised by Cuvier and Goldfuss, on the supposition that they are ' pterygoid teeth.' But, in an extent of an alveolar tract of seven inches, and including five teeth, (PL 10, fig. 1,) that tract is slightly concave lengthwise, instead of being convex : and it wants the horizontal platform extended to the outside of the teeth in place, and supporting the nidus of their successors, which characterises the pterygoid bones (see fig. 4) . In my ' Odontography,' I have briefly noticed one of the most common conditions of fossil teeth, in which the pulp-cavity has not been obliterated by calcification of the pulp itself in the lifetime of the animal. Thus, in the section on the teeth of the Ichthyosaurus, it is described in the following passage. "The remains of the pulp, after the formation of the due quantity of dentine, became converted, as in the pleodont lizards, by a process of coarse ossification, into a reticulate, fibrous, or spongy bone ; but it continued open at the crown after the basal part of the tooth was thus consolidated, as is shown in the longitudinal section, (PI. 73, fig. 8,) wherein a is the pulp-cavity, filled with crystallized spath, h the ossified pulp at the base of the tooth." p. 279. In fig. 2*, PI. 10, is reproduced Mr. Charlesworth's figure of the mass of similar siliceous spath, that, in like manner, filled the uncalcified part of the pulp-cavity of the tooth of the Leiodon anceps. Although I should not have called this " a very unlooked for condition of the interior of the tooth," I concur with the Editor of the ' London Geological Journal ' in his hypothesis of the precipitation of the siliceous matter from a fluid. But, at the same time, I am fully conscious how trans- parent a veil such an hypothesis is to our ignorance as to the precise conditions of the precipitation of such matter in the interior of fossil teeth, in the medullary cavities of fossil bones, and in the closed chambers of many polythalamous shells. The only wonder connected with the fact illustrated in PI. 10, figs. 2 and 2*, is, that any Geologist should deem it an unlooked for or extraordinary one. I have described and figured some small detached crowns of the teeth of the Leiodon, CRETACEOUS CROCODILES. 199 from the Chalk-pits of Sussex, in my friend Mr. Dixon's Geology of the Tertiary and Cretaceous Deposits of that County, Tab. XXXVII, figs. 10, 11, and 12. One of the finest and most characteristic teeth of this genus was discovered in the Chalk, during the cutting of the Brighton and Lewes Railway : it is figured in PI. 10, figs. 6 and 6*, of the present Work, and is now in the fine Collection of Henry Catt, Esq., of Brighton. CHAPTER III. Order. CROCODILIA. Genus. — Crocodilus ? Crocodilia, Plate 30. In the Museum of Mr. Saull, F.G.S., there is a small block of green-sand from the County of Sussex, containing several parts of a small, and apparently very young crocodile. The portion of the upper jaw, and of the right ramus of the lower jaw, (PI. 30, figs. 1 and 2,) demonstrate the crocodilian shape and mode of implantation of the teeth, which have thick, subconical, obtuse crowns, and present proportions most resembling those of the GoniophoUs crassidens* The alveolar border of the jaw has a similar wavy outline, and so differs from that in the Gavials and Teleosaurs, in which the alveolar border is straight. The sockets of the teeth, which are distinct at the anterior half of the jaws, run together at the posterior half, as in the Alligators and the young Crocodiles of the existing species. Several bony scutes are preserved, as, e. g., at m fig. 3 ; none of which show the tooth-like process at one angle, which characterises many of the scutes in the GoniophoUs: and as there is not a single centrum, or body of a vertebra to give the characters of the articular ends of that part, I am unable at present to determine the species. The femur, 65, is longer and more slender in proportion to the ischium, 63, than in the Nilotic or Indian Crocodiles : and the tibia, 66, and fibula, 67, are longer in proportion to the femur. This species evidently had the hind legs proportionably more developed than in existing Crocodilia, and better adapted for swimming,— a character which is observable in the Teleosaurs and some other Crocodiles of the secondary formations. At the same time it should be remembered that, in the Green-sand Formations of New Jersey, vertebrae of two species of Crocodiles or Alligators have been discovered by Professor Henry Rogers, con- structed on the same procoelian type as those of existing species. See ' Quarterly Journal of the Geological Society,' January, 1849, p 380, pi. x. * Report ou British Fossil Reptiles, Trans. Brit. Association, 18-11, p. 09. 200 BRITISH FOSSIL REPTILES. Genus. — Polyptychodon, Owen. ' Odontography,' 1840, vol. ii, p. 19, pi. 72, figs. 3 and 4. 'Report on British Fossil Reptiles,' Trans. Brit. Association, 1841, p. 156. Having described in the preceding pages of the present Section the fossil remains of the Class Reptilia, from the Chalk-formations, which, as in the case of the Mosasauroids, are either referable or most nearly allied to species long known as characteristic of those Formations ; or which, as in the case of the Chelonia, and the smaller Lacertilia with procoelian vertebrae, are nearly allied to the Turtles and Lizards of the present day ; I next pass to the consideration of those fossils which indicate a greater deviation from modern types of the order, and which are either new, or comparatively new to Science. In collecting the materials for my ' Report on British Fossil Reptiles ' I soon found that among the evidences of that class in the Cretaceous Deposits of England, a large species of Saurian was indicated by thick conical teeth, having the general characters of the teeth of the Crocodile, but distinguished by the more regular circular transverse section of the crown, the absence of two opposite larger ridges, and the presence of numerous close-set, narrow, longitudinal ridges, continued, in some specimens, of nearly equal length to within a short distance of the apex of the crown, but in more specimens, of unequal length ; a comparatively small number only of the ridges extending to near the apex : a few of the largest specimens of the teeth presented fewer and more minute ridges, and a greater degree of smoothness and polish of the enamel. Without venturing to say how far this latter character in the largest tooth might be due to age, there was a general adherence of all these teeth to a type of form and structure, which differed to such a degree from the type of any other recent or fossil teeth, as to induce me to signify such difference by applying a generic name to the extinct Reptile to which they belonged ; and I accordingly described and figured them in my ' Odontography ' under the name of Polyptychodon* in reference to their many-ridged or folded exterior. Some of these teeth in their size, and most of thcni in their general aspect, re- semble at first sight the teeth of the great Sauroid fish Ilyjjsodon, of Agassiz, which are also found in the chalk : but those of Polt/pfi/chodon may be distinguished, generally, by the greater solidity of the crown, and the conformity of the structure of the dentine with that of the Crocodiles and Plesiosaurs : the ridges also on the exterior of the crown of the Hypsodon's teeth are alternately long and short, and end abruptly at different, but commonly greater distances from the apex of the tooth than in Poli/jjfj/- * Vol. ii, p. 19 : from ttoXus, many, itriil, a fold, ohnii, a tooth. CRETACEOUS CROCODILES. 201 chodon, the interspaces between the longer ridges widening as they approach the apex. The teeth of the Polyptycliodon never offer any approach to opposite trenchant edges of the crown : but this part, presenting throughout its extent a transverse section of an almost circular form, {Crocodilia, PL 26, fig. 7, PI. 29, fig. 3,) is slightly and regu- larly bent lengthwise, and is invested with a moderately thick layer of true enamel, of which substance the ridges are wholly composed, the surface of the outermost layer of dentine being quite smooth, (PI. 29, fig. 4.) The teeth of the Polyptychodon may be distinguished at once from those of the Mosasaiirus or Pllosaurus by the absence of the less convex, or almost flattened facet of the crown, which is divided by strono- ridges from the remainder of the crown. ■'o'- PoLYPTYCHODON coNTiNuus, Otoen. Plate 29, figs. 4, 5, 6. 'Odontography,' vol. ii, p. 19. The first evidence of this species was a single tooth, which was discovered by W. H. Bensted, Esq., of Rock Hall, near Maidstone, September 16th, 1834, in what is called the ' Trigonia-stratum ' of Shanklin Sand, in the Kentish Rag Quarries near that town, this stratum being a member of the Lower Green-sand Formation. The tooth in question (PI. 29, figs. 5 and 6,) has a crown upwards of three inches in leno-th, and one inch four lines in diameter across its base. The compact dentine has been partially resolved by decomposition into a series of superimposed thin hollow cones fig. 6, and the short and wide conical pulp-cavity is confined to the base, and beginning of the fang, which has been broken away. The cavity of the crown of the tooth in Hypsodon would seem to have been always much larger, as it is in many other predatory fishes in which the teeth are more rapidly shed and renewed than in the Crocodilian Reptiles. In the Collection of Henry Catt, Esq., of Brighton, is preserved tlie crown of a nearly equally fine specimen of the Polypty chodon continuus, from the Chalk of Sussex: this specimen is figured of the natural size in PI. 29, fig. 4. A portion of the ridged enamel has scaled ofi", exposing the smooth surface of the dentine which it protected. The teeth of this species of Poly pity chodon differ from those supposed to have belonged to PoiJdIopleuron, in the ridges of the crown being more numerous and close set, and in the transverse section being circular instead of elliptical. Gigantic Fossil Saurian from the Lower Green-sand at Hythe. Crocodilia, Plates 27, 28. 'Proceedings of the Geological Society of London, June 16th, 1841.' I propose to describe these remarkable and highly interesting fossils under the . present section, on account of the identity of the Formation in which they were dis- covered, with that of the tooth qI Polypitychodon continuus above described, and because 202 BRITISH FOSSIL REPTILES. no other teeth have as yet been found in the Cretaceous Series to which the fossils in question could be referred. These are at present, however, the chief grounds of the probability that such teeth and bones of a large Saurian, may have belonged to the same genus. The bones about to be described, are unquestionably the remains of a Saurian of marine habits, but most probably of the Crocodihan order, as gigantic as the Cetiosaurus or Poli/pfi/chodon, but, in the absence of any associated parts yielding the dental and vertebral characters, not certainly referable to any known genus. They were discovered, in 1840, by H. B. Mackeson, Esq., of Hythe, in the Green- sand Quarries, near that town, and include portions of the coracoid, humerus, and ulna, of the iliac, ischial, and pubic bones, a large proportion of the shaft of a femur, parts of a tibia and fibula, and several metatarsal bones, four of which exhibit their proximal articular surfaces. The remains occupied a space in the quarry, of about fifteen feet by twelve, where it would seem that a proportion of the skeleton of this gigantic Saurian, including the pelvis with one hinder extremity, and a part of the fore-limb had been exposed. In consequence of the absence of vertebrae and teeth, the present observations will be limited to indicating the characters by which these remains differ from previously known extinct genera of Saurians. In the first place, as the femur and other long bones have no medullary cavities, but a central structure composed of coarse cancelli, it is evident that the animal of which they formed part was of marine habits, and did not belong to the Binosauria ; but the best-preserved bone being a femur, this circumstance, independently of the size and shape of the metatarsals, at once negatives the idea that these remains belonged to the Cetacean order, whilst the form and proportions of the metatarsals equally forbid their reference to any other Mammalian genus, or to the Reptilian order Enaliosauria. The cells of the cancellous tissue are about a line in diameter : the compact outer crust or wall of the bone is from four to five lines in thickness. In the recent state, the cells of the cancellous structure of the marine Saurian's bones were doubtless filled with a fluid oil, as in the similarly coarsely cancellous bones of the Cetaceans, and thus the specific gravity of the animal would be nearly accommodated to that of the fluid in which it principally, if not exclusively existed. Femur. — The portions of this bone, PI. 27, fig. 1, secured by Mr. INIackeson include about the two distal thirds, excepting the articular extremity ; its length is 2 feet 4 inches ; its circumference in the middle, or smallest part of the shaft, is 1 5 inches 6 lines, and at the broken distal end, 2 feet 5 inches. These dimensions prove that the animal was equal to the most gigantic described Iguamdon* If the supposition of the proportion of the femur which has been preserved be right, this bone differs from that of the Iguanodon, not only in the want of a medullary cavity, * The length of the largest femur yet obtained of this Saurian is 4 feet 6 inches, its smaller circumference 1 foot U) inches. CRETACEOUS CROCODILES. 203 but also in the absence of the compressed process which projects from the inner side of the middle of the shaft. The bone also expands more gradually than in the femur of the Ir/uanodon, and the posterior part of the condyles must have been wider apart in consequeijce of the posterior inter-condyloid longitudinal excavation being longer and wider. The middle part of the shaft of the femur is subcompressed, with a nearly quadrilateral contour of the transverse section, the line bounding the outer side being less convex and longer than that which circumscribes the inner side of the bone : the anterior surface is flatter than the posterior one. The anterior and outer surfaces meet at a more marked angle than do any of the others ; the angle being formed by an obtuse ridge. The concavity of the posterior surface begins about 6 inches above the broken distal end of the present fragment, and gradually increases in both width and depth as it descends. The width of the inter-condyloid groove at the fractured distal end is 5 inches 4 lines. The same admeasurement in the largest Iguanodoii s femur gives 2 inches. The convex ridge leading to the inner condyle is more prominent than the outer one ; and on the tibial side of the inner ridge there is a second slight concavity. On the anterior surface of the distal end of the femur there is a broad shallow depression of the surface, corresponding to the deeper one behind, and there is not the nan-ow and deep groove which characterises the corres- ponding part of the femur of the Ic/uanodon. The texture of the distal end of the bone presents the same coarse cancelli as occupy the middle of the upper part of the shaft, but with a thinning of the outer laminated compact crust. The following are admeasurements of the bone not given in the above description : — Inches. Lines. Transverse diameter of the middle of shaft .... 5 6 Antero-posterior or lesser diameter of ditto .... 3 9 Greater diameter of the distal end . ..... 12 0 Smaller diameter of ditto at middle of the inter-condyloid groove 5 0 Tibia and Fibula. — The portion of a tibia, PL 28, fig. 1, t, which has been pre- served, is compressed near its head, and the side next to the fibula is slightly concave. The longest transverse diameter is 8 inches 9 lines, and the two other transverse diameters at right angles to the preceding give respectively 3 inches 3 lines, and 2 inches 6 lines. The bone soon assumes a thicker form, its circumference at about one third from its proximal end being 16 inches 6 lines. The compact laminated outer wall of the bone is 4 lines thick. The cancelli occupying the central portion of the bone are arranged in a succession of layers around a point nearest the narrower end of the transverse section. Lower down the tibia again becomes compressed, and towards the distal end the transverse section exhibits the form of a plate bent towards the fibula, and its narrowest transverse diameter is 1\ inches. The portion of the fibula, PI. 28, fig. 1, f, is 11^ inches long. In the middle it is flat on one side, slightly concave on another, and convex on the two remaining sides. 9 204 BRITISH FOSSIL REPTILES. Fig.Z. An outline of a section of this part is given at Fig 1 . It presents the same can- cellous structure as the tibia, but the concentric arrangement of the layers of cells is more exact. Towards the op- posite end of the bone the concave side becomes first flat, and is then produced into a convex wall, terminating one end of a transverse section of a compressed and bent thick plate of bone. The long diameter of this section is 6 inches 6 lines at the end of the fragment ; 4 inches from that end it measures 5 inches 6 lines : the shorter diameter of the compressed bone at the same part is 1 inch 10 lines ; an outline of the transverse section of this part is given in Fig. 2. Of several long and strong bones, which from their form and relative size represent metatarsals, there are considerable portions of four, detached, with their proximal articular surfaces preserved ; a fifth, wanting the articular extremities ; and two others longitudinally split and imbedded in a mass of the Green-sand matrix ; these latter exhibit the characteristic inequality of length of the Crocodilian metatarsals, and are probably the innermost and second metatarsals of our present gigantic Saurian. The innermost and smallest measures one foot in length ; the adjoining metatarsal two feet. Their position in the rock shows that the part of the skeleton had been separated through decomposition before they were per- manently imbedded, the proximal articular extremities being 3 inches apart, but on the same transverse line. The outline of the larger of these imbedded meta- tarsals is subjoined at fig. 3 ; its transverse diameter at a, is 8 inches, at 6, 4 inches 5 lines, and at c, 6 inches. The smaller metatarsal is more contracted at the shaft which presents a triedral contour : the diameter of its greater end is 5 inches ; that of the narrow part of the shaft is 1 inch 1 1 lines ; its compact outer crust is between one and two lines thick ; all the rest of the substance presents a cellular texture, the cells having a diameter of one half to two thirds of a line. Outline of an irabcikled metatarsal of the Toliifly- choioH. Seal 2{ inches to a foot. CRETACEOUS CROCODILES. 205 Fig. 4. Fig. 6. i- h Fig. 5. Fig. 7. Proximal end and section of shaft of a metatarsal of Poti/pti/cfwiion ! Proximal end and section of shaft of a metatarsal of PoJi/pii/cIiodon ! Of the detached metatarsals I subjoin outHne sketches of the articular end, and the transverse section of the shaft for facilitating the comprehension of their form and their comparison with other remains. The chief of these is the proximal portion of a metatarsal bone 1 5 inches, 6 lines in length. Figure 4 is the contour of the articular end, which is slightly convex at the smaller side, nearly flat at the wider one, and with a very irregular superficies, being pitted all over with depressions admitting the end of the little finger, these depressions at some parts of the circumference of the articular end being continued into as broad grooves, which soon subside to the level of the surface of the shaft. Figure 5 is the outline of the fractured end, nine inches from the articular end of the same bone : the angle indicates a ridge which runs .obliquely down the bone towards the middle of the surface, and subsides near the broken end, fifteen inches down the shaft. The dotted line indicates the thickness of the laminated wall, which gradually becomes less compact, and encloses a coarse cancellous structure. The outer surface of the bone is smooth. Figure 6 gives the contour of the articular end of a proximal portion of a metatarsal bone 11 inches long. The articular surface is pitted with cavities, as in fig. 4, the size of the same, as if for a coarse ligamentous articulation : the cavities are continued into grooves at bb- Figure 7 gives the contour of the broken surface, six inches 206 BRITISH FOSSIL REPTILES. below the proximal end : the whole thickness of the bone, within the compact outer wall, being occupied by a coarse cancellous structure. Fig. 8. Fig. 10. Fig. 9. Fig. 11. Proximal end and section of shaft of a metatarsal ijone of Pohjphjchothn. Of a fragment, 12 inches long, of the proximal portion of a metatarsal bone, figure 8 gives the contour of the articular end ; and fig. 9 of the fractured end of the shaft; the dotted outline indicates where the outer crust of the wall prevented an exact figure of the contour being made ; but the shaft of the bone seemed to have been flat on that side. A fourth fragment of a long bone measured 10 inches in length. Figure 10 gives the contour of the proximal articular end of this bone (the outer wall having scaled off). Figure 11 is the contour of the fractured end of the shaft, 5 inches beyond the articular end. It is occupied by a coarse cancellous structure throughout. There remain to be noticed some less perfect fragments of huge flat bones im- bedded, or indicated by their impressions, in masses of the Green-sand Rock. In three of these I recognise the ilia, ischia, and pubes : they are broader than in the Crocodiles, but would be conformable to the Crocodilian type, if the cartilaginous parts of some of those bones in the recent species were ossified : by this greater extent of ossification of the large fossils in question, the pubis and ischium approach somewhat to the Plesiosaurian type. The ilia are imbedded in the same block of stone : they are flat, CRETACEOUS CROCODILES. 207 nearly straight, and become gradually wider and thicker towards the end attached to the sacrum : of these bones a portion 25 inches long is preserved of the one, (PI. 27, fig. 6,) and 20 inches of the other : the broadest end of the longer portion measures across 10 inches. In a second block, the mesial extremities of the pubis and ischium are preserved. The exposed surface of the pubis is principally convex, but becomes concave towards the opposite or median margin : it measures across at its broadest part 13 inches; the length of the fragment preserved is 17 inches. The diameter of the corresponding expanded extremity of the ischium is 9 inches: its expanded extremity is obliquely truncated ; that of the pubis is rounded. In another block the expanded extremity of the opposite pubis is preserved ; it measures 14 inches across, and is 22 inches in length. In a third large mass of rock, the fragment of an enormous, apparently sub- quadrilateral flat bone, is exhibited, which most probably belongs to the pectoral arch, and, in that case, must be the coracoid bone, PI. 27, fig. 5, p. The length of this fragment is two feet, its greatest breadth 1 7 inches : its thickness varies from 3 to 5 inches. On one side there is a slight submedian ridge, from which the surface slopes away with a gentle concavity. The breadth of this bone indicates the great development of the muscles destined for the movement of the fore-leg, whence it may be inferred that the anterior extremities were more powerfully and habitually used in progressive motion than in the Crocodiles. In the existing species of this family, the anterior extremities are used chiefly for the support and movements of the body on land ; they are apphed to the sides of the chest when the animal swims, which is chiefly effected by the actions of the strong and long vertically compressed tail. The lateral movements of the fore- legs being much restricted, the coracoid bone and the muscles arising from it are comparatively slender. In the Enaliosauria, where the fore-legs are converted into paddles for swimming, the coracoids are vastly expanded, both for the increased strength of the shoulder-joint and the increased surface for the attachment of the muscles, which effect the lateral movements and the stroke of the paddle-shaped limb upon the water. We may infer, therefore, that the anterior extremities of the present gigantic Crocodilian were, by some webbed modification of the hand, better adapted, and more energetically used for swimming than in the existing Crocodilians. The shaft of a long bone somewhat similar to, but shorter and more slender than the femur, and crushed, is preserved with that of a smaller bone, tapering more gradually to one end, in the same block of stone : these are figured in PI. 28, fio-. 2 ; the larger bone is probably the humerus, h, the smaller one the ulna, u. Other less intelligible fragments of the long bones of the same great Saurian are represented in PI. 27, figs. 2, 3, and 4 ; and in PI. 28, figs. 2 and 4. Fig. 3 probably shows two of the metacarpals in the same block of stone. The principal parts above described are preserved in the British Museum, to 208 BRITISH FOSSIL REPTILES. wliich Institution they were liberally presented by their discoverer H. B. Mackcson, Esq. They were mutilated in the attempt to disencumber them of the massive blocks of the matrix in which they were imbedded, and are less characteristic than when I took the foregoing description and sketches of them on the spot where they were found. It has been shown that the texture of the femur, tibia, fibula, and the other long bones, is conclusive against the identity of the Saurian of the Hythe Lower Green- sand with the great ambulatory Dinosaurian reptiles, viz., Iguanodon and Megalosaurus, the former discovered in the Lower Green-sand at Maidstone, and both species also in the Wealden and Oolite Formations ; there then remains to be considered its relation- ship with the Enaliosaurians, the Crocodilians, the Mosasaur, and Poikilopleuron. The length, thickness, and indication of condyles in the femur, and the length, thickness, and angular form of the metatarsals, place the Plesiosaurs, and, a fortiori, the Ichthyosaurs, out of the pale of comparison. The superior expanse of the pubis, and the broad coracoid (?) with the form of the femur, and the gigantic proportions of all the bones, forbid a reference of the Saurian in question to any subgenera, recent or extinct, of the Crocodilian Reptiles, of which the bones of the extremities were previously known. If it were true that the Mosasaurus had locomotive extremities in the form of flattened paddles, like the Plesiosauriis, the identity of our present Reptile with the Maestricht species would be at once disproved, by the unequivocal remains of the metatarsal bones, wliich indicate a form of foot, corresponding, as far as the skeleton is concerned, with that of the Crocodile : and if, as is most probable, the metatarsals of the Lacertian tyjDe from the Green-sand of New Jersey appertain to a Mosasaurus, the metatarsals from the Green-sand at Hythe differ from them in size, shape, and the absence of any medullary cavity. With regard to the Crocodilians, the extinct genus which most closely agrees with the characters of the bones of the Hythe Saurian is that which I have named Cetio- saurus, the vertebrae of which have been found in the Wealden and Oolite formations, and the long bones of which are devoid of a medullary cavity. Unfortunately no vertebra referable to Cefiosaurus has yet been discovered in the Cretaceous deposits. It is possible that the teeth on which the genus Pol^j^tychodon has been founded may belong to Cetiosuurus ; but hitherto such teeth have not been discovered in the strata where the remains of Cetiosuurus are common. The gigantic Saurian discovered by M. Deslongchamps, in the Oolite at Caen, and which he has named Poikilopleuron BticMandii, yields for comparison with the Hythe Saurian the femur, fragments of the tibia, fibula, and metatarsal bones. In the form of the condyles of the femur, and their posterior intervening channel, the Hythe Saurian resembles the Poikilopleuron more than it does the Iguanodon ; but the large medullary cavity in the femur of the Poikilopleuron distinguishes it as CRETACEOUS CROCODILES. 209 much as it does that of the Iguanodon from the Hythe Saurian. The medullary canal is described as being very great in the tibia of the Poikilopleuron.* The absence of vertebrae and teeth in the Hythe specimen prevents the establish- ment of a comparison of these instructive parts of the skeleton of the tvi'o extinct Saurians, and the question of the dental characters of the Poikilopleuron remains in the same doubtful state as it is left by M. Deslongchamps, who describes and figures a detached large Crocodilian tooth from the Oolite near the village of Allemagne, as corresponding in size with the remains of the Poikilopleuron. f M. Deslongchamps conceives it may be useful to make known these teeth at the same time with his Poikilopleuron, leaving to subsequent discoveries the determination of the truth or otherwise of the approximation. For the same motive I have prefixed to my account of the Hythe Saurian a description of the teeth of a gigantic, and hitherto unknown Saurian from the Green-sand at Maidstone, and shall append to it an account of similar teeth from the Chalk Formation in Sussex, Kent, and Cambridgeshire. Since the bones of the extremities of Mr. Mackeson's large reptile from the Green- sand afford sufficient evidence of their distinctness from the tallying parts of any previously described Saurian genus, and since we have evidence as satisfactory of an equally gigantic Saurian genus from the teeth which occur in the same Formation, it may be allowable, for the purposes of the present record, to regard both the bones and the teeth as parts of the same animal. UntU, therefore, further evidence is obtained, showng the Hythe skeleton to have been furnished with differently-formed teeth, or the teeth from the Maidstone Green-sand to have been associated with a differently constructed skeleton, I shall apply to the Hythe fossil the name of Pohjptyckodon, under which the genus of gigantic Saurian, hitherto known only in the Green-sand and Chalk strata, was first indicated. PoLYPTYCHODON iNTERRUPTus, Owcn. Lacertia, Plate 2, figs. 16, 17. PI. 8, fig. 3. Crocodilia, Plates 26 and 29, figs. 1 and 2. 'Odontography,' vol. ii, p. 19, pi. 72, fig. 4; and in Dixon's 'Geology and Fossils of the Tertiary and Cretaceous Deposits of Sussex,' p. 3/8. The majority of the specimens of the teeth of this species have been found in the middle and lower Chalk or Chalk-marl : one large tooth of this species has been * "Le canal medullaire etait fort grand ; I'epaisseur du tissu compact, en d, est d' environ O™- 015." (Deslongchamps, 'Surle Poikilopleuron,' 410, p. 55.) "Dans ce tiers inferieure, le femur est un peu plus etendu transversalemeut que d'avant en arrifere." (Deslongchamps, loc. cit.) f "On a trouve, h. diverses epoques, dans les carrieres du Village d' Allemagne de grandes dents, toujours isolees, offrant tous les caracteres de celles des Crocodiles. J'en figure une, pi. vi, (de grandeur 210 BRITISH FOSSIL REPTILES. discovered by the Rev. Peter Brodie, M.A. F.G.S., in the upper Green-sand at Barnwell, near Cambridge, and a few other specimens have been obtained by James Carter, Esq. from the Green-sand of another locality, near Cambridge. The fine examples of teeth figured in PI. 26 (with the exception of fig. 8) were discovered in 1847 by Mr. Potter, of Lewes, in the lower bed of Chalk-marl, just above the Green-sand, in the vicinity of that town. They formed part of as many as from twenty to thirty teeth of nearly the same size which were scattered at no great distance from each other. No part of the jaw-bones could be detected ; and as the teeth are fully formed, and some of them retain their long fangs, it may be inferred that they were originally implanted freely, like the teeth of the Crocodile, in loose sockets, and have dropped out as easily, after the decomposition of the gums and other soft parts. The crown is about two sevenths the length of the entire tooth, and its enamelled striated coat terminates by an abrupt and well-defined border ; the fang continues to expand to about its middle part, whence it gradually contracts to an obtuse end, which is perforated by the entry to the pulp-cavity. The general shape of the crown agrees with that of the Polyptycliodon continuus ; the difference is shown by the greater proportion of the ridges which stop short of the apex of the crown, espe- cially on the convex side of the tooth. In using the term convex or concave as applied to the crown, allusion is made to the slight bend of crown in the direction of its axis. Around the entire basal part of the crown the ridges are close together : their inter- spaces are only the clefts that separate them. On the concave side of the tooth a large proportion of the ridges extend nearly to the apex, as is shown in PI. 26, fig. 1 ; but on the convex side a greater number extend only one third or two thirds towards the apex, these shorter ridges alternating with the longer ones, between which, there- fore, at the apical part of the tooth, there are intervals of flat tracts of enamel. The apex of the tooth is rather obtuse. On one side of the crown there is a long ridge, towards which contiguous shorter ones have a convergent inclination. The long fang of the tooth is covered by a layer of smooth cement. The dentine is compact, and corresponds in microscopic structure with that of the crocodile's teeth. In the frac- tured specimens of the teeth from Lewes, the dentine had become resolved into super- imposed conical layers, as in the larger tooth from the Green-sand of Maidstone : this effect of long interment is represented in figs. 1,3, 5, and 7, of PI. 26. There is no trace of the absorbent action excited by pressure of a successional tooth in any of these specimens of teeth. Although the detached state of the above-described teeth with well-developed fangs would have suggested and sustained the inference that they had been implanted like naturelle, fig. 8, reduite au quart, fig. 9.) EUes out interiurement vine cavity conique; leur surface couverte d'email jusqu'a uue certain distance de leur base, est ornee des stries en relief, longitudinales, de longeur in^gale, dont deux seulement, situees aux extreniites du meme diametre, arriveut jusqu'a la pointe." (p. 80.) CRETACEOUS CROCODILES. 211 the teeth of the Crocodile, direct evidence to that effect had not been obtained at the time of the publication of my ' Report on British Fossil Reptiles ;' and it has been objected that the mode of fixation of the teeth of the Polyptychodon might have been the same as in the Mosasaurus, and that those teeth might belonff to a second extinct genus of gigantic Sea-lizards. The specimen, however, which is represented of the natural size in PI. 8, fig. 3, inclines the balance in favour of the Crocodilian affinities of the Polyptychodon, by proving that its teeth were implanted in distinct sockets, and not anchylosed to the summits of processes of the jaw, as in Mosasaurus and Leiodon. In the figure cited, taken from an unique specimen of part of the lower jaw of the Polyptychodon interruptus discovered in the lower chalk-deposits of Kent, and now in the collection of Mrs. Smith, of Tonbridge Wells, the letter b shows the smooth cement-covered cylindrical base, and c the enamelled conical crown ; « is an adjoining vacant alveolus, from which a tooth similar to that in place has slipped out, hke the teeth from the Lewes Chalk-marl. The crown of the tooth in place is rather longer in proportion than in most of the detached teeth from Lewes ; and it may, therefore, indicate a certain inequality in the length of the crowns of the teeth in the same jaw, as in the Crocodiles, and it may have answered to the tooth which is some- times called, on account of its greater length, the " canine tooth" in the Crocodile. The socket anterior to the one with the completed tooth contains the germ of a young tooth, and shows that the teeth succeeded each other from the same sockets as in the modern Crocodiles. The crown of a much larger tooth of the Polyptychodon interruptus, which is figured in PI. 2, figs. 16 and 17, was found near Valmer, during the cutting of the Lewes railway, and is now in the museum of Henry Catt, Esq., of Brighton. It shows well that alternate and interrupted character of the longitudinal ridges of the enamelled surface which distinguishes the present species ; but the ridges have been more worn down, especially towards the apex, in Mr. Catt's specimen, than in the one originally figured in my ' Odontography.'* The body of the crown consists of a hard compact dentine, partly resolved in the specimen by incipient decomposition into superimposed hollow cones, like the similarly-sized tooth of the Polyptychodon continuus from Mr. Bensted's Green-sand " Iguanodon" quarry at Maidstone. f The cylindrical base of the tooth is excavated by a wide conical pulp-cavity with an obtuse summit, into which a small central process projects from the base of the crown (fig. 17). The enamel is very thin at the base of the crown. Figure 8 in ' Crocodilia,' PL 26, is the crown and part of the base of a still larger tooth of apparently the same species of Polyptychodon, obtained by Mr. Catt in October 1850, from the grand and picturesque chalk-pit, or rather chalk-cliff, at Houghton, near Arundel. * Odontography, pi. Ixxii, figs. 4, 4', t lb. fig. 3, and 'Report on British Fossil Reptiles,' p. 156. 212 BRITISH POSSIL REPTILES. One or two of the long ridges of this tooth are more than usually prominent, and most of the shorter ones are fainter than usual; but I cannot regard those differences in any other light than as individual varieties. The pulp-cavity at the base of the tooth, filled up in the specimen by the white chalk, appears to have been unusually large, as if the specimen had been in an incompletely developed state. If this were the case, it must have come from a very large specimen of the present species of extinct reptile. To such a specimen must have belonged the anterior end of the left ramus of the lower jaw, (' Crocodilia,' PI. 31,) discovered in the Burham Chalk-pit, in Kent, and now in the choice and instructive Collection of J. Toulmin Smith, Esq. The fragment is upwards of a foot in length, but contains only three alveoli, and corresponded, probably, to the premaxillary part of the upper jaw of the same animal. The first socket, « i, is nearly three inches from the fractured end of the jaw, and two inches from the larger socket, s 2, behind it ; the third socket, s 3, is closer to the second. These are filled up by the chalk, the teeth having fallen out. The outer surface of the jaw is convex and promi- nent ; a solid mass of the bone extends horizontally inwards from the anterior socket, to form the symphysis, which seems to have been ossified, with the opposite ramus. The substance of the bone has the same coarse cancellous tissue as that of the portion of the smaller jaw of Polyptychodon, (' Lacertilia,' PI. 8, fig. 3); and, as it shows a similar inequality in the intervals of the alveoli, it may be concluded to belong to the same genus, if not species, of extinct Crocodilian reptile. The present fragment (PI. 31) indicates an individual as large as the great Mosasaurus, the skull of which was discovered in the Maestricht Chalk. Fine specimens of crowns of the teeth of both species of Pohjptychodon, have been obtained by James Carter, Esq., M.R.C.S., of Cambridge, from the Upper Green- sand near that town, and also at Horn-sea, in the same county. These specimens present a darker colour than those of the chalk, by reason of the modification of their matrix. The ridges are remarkably well defined on the enamel ; the dentine presents the same well-marked division into layers, cone within cone, as in the Chalk specimens, and that from the Shanklin sand near Maidstone. The crown of one of the specimens of the Polyptychodon interruptus, from the Cambridge Green-sand, equals in size that of the Polyptychodo7i continuus, discovered by Mr. Bensted in his quarry near Maidstone. 213 CHAPTER IV. Order— ENJZIOSA UBIA. Genus. — Plesiosaurus, Conyleare. Besides the teeth which, according to their form and structure, were referable to the different genera and species of Iteptilia above described, — viz. to Baphiosatcrus, (PI. 9, fig. 2;) to Coniosaurus, (PI. 2, fig. 19a;) to Mosasaurus, (ib., fig. 1;) to Leiodon, (PI. 10, fig. 1 ;) and to Poli/pti/chodon, (' Crocodilia,' PL 26 and PI. 29,)— we now, for the first time, in our progressive researches, descending through the strata which indicate the changes which the part of the earth's surface, forming England, has undergone, meet with teeth of different and peculiar type, remarkable, viz., for their length and slenderness, and with a circular transverse section, not subcompressed or with opposite trenchant margins, as in the Gavials of the Tertiary deposits. The tooth represented of the natural size in PI. 2, fig. 8, is a good example of one of those of the form in question. Its enamelled crown, if entire, would exceed an inch and a half in length, yet it is but half an inch in diameter at its base ; the crown is slightly curved and tapers gradually to a point ; the enamel presents some slender but well-defined longitudinal ridges of different lengths, and none of them extending to the apex. The fang or root is cylindrical, smooth, and covered by a thin cement. The tooth above described was obtained from the Scaddlescombe Chalk-pit, near Lewes, Sussex. A similar specimen, rather more fractured, PL 2, fig. 9, was found in a Chalk-pit at Southeram, Sussex. A smaller tooth, (PL 2, fig. 13,) of the same type, but with more numerous longi- tudinal ridges, seems to indicate a different species. This specimen was also found at Southeram. If satisfactory and abundant evidence of the nature of the extinct reptile to which the above-described teeth belong had not been obtained from Secondary Formations of a more ancient date than the cretaceous ones, the Comparative Anatomist would have inferred, and correctly, the generic distinction of the Reptile to which they belonged ; but he could have had no suspicion of the truly extraordinary nature ctf the animal, the entire race of which, after flourishing under a variety of specific forms from the epochs of the Muschelkalk and Lias, finally perished at the time of the deposition of the Chalk. The anatomical description of the Plesiosaurus, discovered and restored by CoNYBEARE and De la Beche, will be reserved for the Monograph descriptive of the fossil Reptiles of the formations in which its remains are most abun- 214 BRITISH FOSSIL REPTILES. dant ; and I shall here limit myself to quoting the brief but graphic definition of it which Dr. Buckland has given in his interesting and instructive ' Bridgewater Treatise :' — "To the head of a Lizard it united the teeth of a Crocodile ; a neck of enormous length, resembling the body of a Serpent ; a trunk and tail having the proportions of an ordinary quadruped ; the ribs of a Chameleon ; and the paddles of a Whale. Such are the strange combinations of form and structure in the Plesiosaurus," (p. 102.) I may add, that of all existing Reptiles the Chelonians make the nearest approach to the present remarkable extinct genus in the length and flexibility of the neck, in the size of the true body of the atlas, which resumes its normal relations with the neural arch of that vertebra in Cheli/s and Chelodina, as in Plesiosaurus ; in the natatory form of the extremities as exemplified in the paddles of the Turtle, which besides being four in number, come much nearer those of the Plesiosaurus in structure than the paddles of the Whale do, and in the great expanse of the ischium and pubis : whilst the Plesiosaurs exhibit, next to the Turtles, the greatest deve- lopment of the abdominal ribs (hsemapophyses and their spines), which form a kind of interwoven flexible " plastron " beneath the abdomen. Plesiosaurus Bernardi, Oiven. ' Enahosauria,' Plate 26. Dixon's 'Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex,' p. 396. In my ' Report on British Fossil Reptiles,' one species of Plesiosaurus, viz. Plesio- saurus pachyomus, was defined from remains discovered in the green-sand division of the Cretaceous series ;* and the existence of the genus Plesiosaurus, at the period of the deposition of the latest member of that series, was inferred from the discovery of the femur of a large species in the chalk which forms the well-known " Shakespeare's Cliff" near Dover.f This indication has been since confirmed by the discovery not only of the teeth above described, but of vertebrse of the Plesiosaurus in the same formation ; and the cervical vertebra figured in PI. 26, which was obtained from the Upper Chalk at Houghton, near Arundel, Sussex, indicates a species allied to the Plesiosaurus pachyomus from the green-sand of Cambridge. The following are the dimensions of the vertebra from Houghton, and of the most perfect of those of the above-cited species from the green-sand. Antero-posterior diameter of centrum Transverse diameter Vertical diameter PI. pachyomus. P/. Bernardi. Inches. Lines. Inches. Lines. 2 0 1 9 2 9 3 0 2 6 2 0 The breadth of the centrum is proportionally greater in the vertebra from the chalk, which further differs from that from the green-sand in the lower position, and * Report on British Fossil Reptiles, Trans. Brit. Association (1839), p. 74. t Ibid., p. 193. This specimen was kindly transmitted to me by J. Wickham Flower, Esq. CRETACEOUS PLESIOSAURS. 215 the anchylosis of the pleurapophyses, jd (hatchet-bones or cervical ribs) ; which, if they presented the characteristic expansion of their extremities, must have supported the hatched-shaped head on an unusually long body or pedicle. The articular surfaces of the centrum are more concave than in most Plesiosauri, and deepen to a central pit, in which they resemble those of the Pksiosaurus pachi/omus ,- but the circumference of the articular surface is more extensively rounded or bevelled off, so that its convexity is seen, as at ca, cp, upon a side view of the vertebra, fig. 3, PI. 26. Both neurapophyses, fig. 3 («), and pleurapophyses {pi) are anchylosed to the centrum. The neurapophyses coalesce together, and send almost vertically upwards a spinous process, which exceeds in length the whole vertical diameter of the vertebra below it, and is more than twice its own antero-posterior diameter ; it is compressed and gradually decreases in thickness as it rises ; it presents a rough shallow tract along its fore part (fig. 1), and a wider, deeper, and smoother excavation behind (fig. 2). Two small zygapophyses are developed from both the fore-part [z) and back part {z') of the neural arch. The pleurapophyses {pi) are long, sub-depressed, slightly expanded as they extend downward, outwards, and backwards ; but the fractured ends do not show how far they have extended forwards and backwards into a hatchet- shaped extremity. They have coalesced with the lower part of the sides of the centrum, an extent more than their own vertical diameter intervening between them and the base of the anchylosed neurapophyses. The articulated cervical ribs in the PI. pachyomns (PI. 28) have not quite so low a position on the centrum, and are thicker vertically. The under part of the centrum presents two deep pits from which the vascular canals ascend, divided by a moderately thick, convex, longitudinal bar (fig. 4). The non-articular surface of the centrum is smooth, and the sides of the centrum are slightly concave. A very interesting and well-marked species of the singular genus Plcsiosaurus, in addition to those from the older secondary strata, is thus indicated by the present unusually perfect fossil vertebra. As it was discovered on one of the estates of his Grace the Duke of Norfolk, I avail myself of the opportunity of fulfilling a wish of my lamented friend Mr. Dixon, and of gratifying my own, by dedicating this new species to the memory of Lord Bernard Howard, a young nobleman of great promise and most amiable disposition, and who had given much attention to the science of geology : he died suddenly in Egypt at the early age of twenty-one years, whilst pursuing his travels in order to acquire a knowledge of the antiquities, the arts, and policy of distant countries. Plesiosaurus constrictus, Owen. ' Lacertians,' Plate 2, figs. 6 and 7. Dixon's ' Geology and Fossils of the Tertiary and Cretaceous Formations of Susse.x,' p. 398. The species oi Plesiosaurus from the Chalk-pit at Steyning, Sussex, indicated by the centrum of a middle cervical vertebra, which is figured in the above-cited Plate, figs. 6 216 BRITISH FOSSIL REPTILES. and 7, differs from that of the Flesiosaurus Bernardi, {' Enaliosauria,' PI. 26,) in its great length, as compared with the height and breadth of the articular surfaces of the centrum, and in the small size of the costal articulation (pi), the pleurapophyses having been unanchyloscd to the centrum ; it also differs from all the species of Plesiosaur hitherto defined in the degree of lateral constriction of the centrum between those surfaces, if this be natural. The free or non-articular surface of the centrum is rugose, showing the coarsely fibrous texture of the bone. The under surface (fig. 6) is slightly concave, both transversely and longitudinally, is subquadrate and oblong, with two approximated vascular orifices at its centre, separated by a slight rising, which is not developed into a ridge. The small costal surfaces (pi) are elliptic, situated at the middle of the ridge dividing the vinder from the lateral surfaces of the centrum, twice their own vertical diameter below the neurapophysial surfaces, and equidistant from the two ends of the centrum. The articular surfaces here are convex at their circumference, slightly concave in the rest of their extent, with a feeble longitudinal rising at the centre, in- terrupted by a transverse linear groove. The neurapophyses terminated below in a very open angle. The vertebra appears to have been subject to pressure, and is slightly distorted ; but it is difficult to conceive how this could have operated so partially as to have produced the compressed character of the middle of the centrum and have left the two articular ends of their natural form. The following are its principal dimensions. Antero-posterior diameter of centrum .... Transverse diameter of articular surface of ditto Vertical diameter of ditto ...... Distance between the neurapophysial and costal pits Transverse diameter of middle of centrum above the costal pits .......... 1 7 It is most probable that the teeth of the Plesiosaiirus, PI. 2, figs. 8 and 9, belong, by reason of their size, to the Plesiosaurus Bernardi. A much-fractured tooth, (PL 2, fig. 15,) as thick as those of figs. 8 and 9, but diminishing more rapidly to the apex, shows similar unequal but more numerous ridges all round the enamelled surface ; its crown is composed of the same kind of hard dentine as in the Crocodiles and Plesiosaurs, with a moderately thick covering of enamel. The tooth may be a variety of the Plesiosaurian type, or it may have belonged to a Stencosauroid Crocodilian. It was obtained from the same chalk-pit, at Houghton, near Arundel, as the vertebra of the Plesiosaurus Bernardi. The teeth, ' Enaliosauria,' PI. 28, figs. 7 and 8, present more slender proportions, and so far, are more strictly Plesiosauroid. The fang is round, smooth, and deeply excavated by the pulp-cavity, which is indicated by the dotted line at p; the enamelled crown supports numerous fine longitudinal ridges: it is rather more compressed at its fractured Inches. Lines. 2 4 2 2 1 7i 1 0 CRETACEOUS PLESIOSAURS. 217 end than in the typical Plesiosaurian teeth. These specimens were found in the lowest bed of the Lower Green-sand beneath Shanklin Chine, Isle of Wight ; I am indebted for the drawings of them to John Edward Lee, Esq., of the Priory, Caerleon, Mon- mouthshire. VERTEBRA OF A PLESiosAURUs. ' Enaliosauria,' Plate 27. The subject of the above-cited Plate is a mutilated vertebra, there figured of the natural size, which was obtained from the Chalk-pit at Burham, in Kent, and is now in the Collection of Mrs. Smith, of Tunbridge Wells. The centrum, slightly concave at both ends, with a large vertically oval depression, fig. 3, pi, for a rib on each side, and with a pair of vascular foramina on its under surface, fig. 2, c, c, shows the characters of the genus Flesiosauriis, with which the structure of the neural arch is conformable. The followin"- are the chief dimensions of this vertebra. a Inches. Liues. Antero-posterior diameter of the centrum .... 2 2 Transverse diameter of its articular cud ..... 3 0 Vertical diameter of ditto ....... 3 0 This vertebra differs from that of the Plcsiosainifs Ber/uirdi, not only in ihe proportions indicated by the dimensions above given, but likewise by the non- anchylosis of the rib, and by the shape and position of the surface for its attachment to the centrum : and if the value of these differences were to be questioned on the ground that tlie present vertebra might be one nearer the back than the vertebra figured in PI. 26, at which part of the spine the cervical ribs increase in size, have their jimction raised nearer to the neural arch, and retain longer their individuality in the species in which they become anchylosed in the more advanced vertebr;c, there would still remain the following difi'erences : — the vascular foramina on the under surface are not situated in such deep and wdl-defined pits ; the concave terminal articular surfaces have not the central depression : the sides of the centrum are not bevelled off at the border of these articular surfaces, but are divided from them at a right angle by a well-defined margin. jNIy present experience of the constancy of such secondary characters in the cervical vertebnc of the same species of Plcsiosanrtiff, leads me to conclude that the vertebra figured in PL 27 is of a distinct species of Vlcxio- saurm from that figured in PI. 26, a conclusion to which we are also led by the consideration that the vertcln'al l)odies usually gain in breadth as they approach the back, whilst the vertebra, (PI. 26,) with a lower placed rib, is relatively broader than the present one. From the FJcHiomnruH pachi/omns, from th(> (Jrccn-sand of Ileaeli. near Cambridge,* the present specimen differs in the form of its costal surface, whicii * Report on Britisli Fossil Reptiles, IS.'i!), p. 71. 218 BRITISH FOSSIL REPTILES. is vertically instead of being transversely elliptical : it is still more obviously distinct from the Plesiosaurus cojistrictifs, from the Chalk of Stcyning, in Sussex. Although the sutures connecting the neural arch with the centrum are traceable, there has been a certain degree of anchylosis, which has helped to maintain the arch in its natural connection, notwithstanding the degree of pressure and distortion to which the whole vertebra has been subject. Each neurapophysis, which measures one inch five lines in antero-posterior diameter at its narrowest part, is smoothly rounded off at both its free borders, of which the anterior one is the thickest ; the posterior zygapophysis is developed at rather more than an inch above the base of the neurapophysis ; its flat oval articular surface looks downwards, and a little outwards : the neural canal is relatively wider than in the Plesiosaurus Bernardi, and its area is oval, with the great end downwards. The spinous process, of which nearly four inches is preserved, has an antero-posterior diameter at its base, of nearly two inches, and is strengthened behind by two buttress-like ridges, which rise converging from the summit of each posterior zygapophysis : bounding an angular depression at the back part of the spine, as in the Plesiosaurus Bernardi, and many other species. The total height of this vertebra, as far as the spine is preserved, is seven inches and a half, and the total length of the Plesiosaurus, to which it belonged, was probably not less than sixteen feet. There are preserved in the same block of Chalk with the vertebra above described, the summit of the neural arch, with the base of the spine of another vertebra, and a portion of one of the long ribs of the thorax, fig. 1, pi. Plesiosaurus pachyomus, 0?w«. ' Enaliosauria,' Plates 28 and 29. ' Report on British. Fossil Reptiles,' Trans. Brit. Association, 1839. This species of Plesiosaurus was founded on certain remains discovered in the Upper Green-sand at Reach, about six miles from Cambridge, and placed by the Rev. Professor Sedgwick in the Wordwardian Museum of that University. The specific name "■ pacliyomus'' relates to the unusual thickness of the humerus, the distal flattened end of which is one inch and a half thick, the breadth of the same part being only four inches and a half, and the length of the entire bone nine inches and a half. The contour of the articular head is transversely oval. The central part of the bone is occupied by a coarse cellular structure, one inch and a half in diameter, surrounded by dense osseous walls, three lines thick. In the rich and instructive collection of Reptilian fossils, from the Cretaceous deposits in Cambridgeshire, in the possession of James Carter, Esq., M.R.C.S., of Cambridge, there are several vertebral bodies or " centrums" of the same species of Plesiosaurus which show the change of proportion in the breadth and depth of the * riaxi's, thick, w/Lios, humerus, or arm-bone. CRETACEOUS PLESIOSAURS. 219 centrum which the vertebrae undergo as they pass from the region of the neck to that of the back, without corresponding alteration in the length of the centrum. The following are dimensions of the most perfect specimens of these vertebrae : Anterior Middle Posterior Last Cervical. Cervical. Cervical. Cervical. In. Lines. In. Lines. lu. Lines. Li. Lines. Antcro-posterior diameter, or length 1 9 2 0 2 0 1 10 Transverse diameter, or breadth 2 3 2 3 2 9 3 0 Vertical diameter, or height . 1 9 2 3 2 6 2 7 Breadth of neural surface (midtUe) . 0 2J 0 5 0 6 Breadth of neurapophysial pit — 1 1 1 3 1 9 Breadth of costal surface . — 1 0 1 Oi — Height of ditto .... — 0 10 1 0 — Distance between neurapophysial and costal pits 1 0 0 9 0 7J — The above dimensions show that whilst the centrums retain the length of two inches in the middle and towards the posterior parts of the long neck, they become shortened in the penultimate and last cervicals to the length of the smaller vertebra towards the anterior part of the neck ; the diiference, however, is but' slight, and whilst an almost uniform length is retained, the vertebral centrums augment in height, and still more in breadth, as they approach the region of the back. With the increased breadth of the centrum, there is a concomitant increase in that of the rough depressions (PI. 29, figs. 3 and 4, np) for the articulation of the neur- apophyses, and, at the same time, the bases of these vertebral elements become wider apart, and the breadth of the surface (ib. w n) supporting the neural axis, increases. This smooth surface which occupies the middle of the upper part of the centrum is contracted in the middle by the approximated neurapophysial pits, where there is on each side the orifice of the canal for the vertebral vein or sinus which traverses the centrum vertically. The lower openings of these canals are shown in PI. 29, figures 2 and 5, and their whole course is displayed in the fractured vertebra rrepresented in fig. 6, cc'. The costal pits in the greater proportion of the cervical vertebrae present the form of a full transverse ellipse, as in PI. 28, fig. 1, and are situated below the neurapophysial pit at a distance about equal to their own vertical diameter. They are nearer the posterior than the anterior surface of the vertebra, and thus difi'er in position as in shape from the costal surface in PI. 27, fig. 3, j,i. As the cervicals approach the dorsal region the costal pit increases in vertical extent, assumes a circular form, and, as in all Plesiosauri, begins to rise towards the neurapophyses. The commencement of this 220 BRITISH FOSSIL REPTILES. change in form and position of the costal pit, pi, is shown in PI. 28, fig. 3, and its borders are here seen to be rather prominent. In none of the vertebrae has the costal pit presented the groove which, in most Plesiosauri, crosses it in the axis of the vertebra and divides it into tw^o subequal parts. The articular ends of the centrum are slightly- concave and are impressed by a circular pit at the centre ; the peripheral margin is rounded off; it appears in the side view of the vertebra, PI. 28, fig. 3, but not to such an extent as in Plesiosmirus Bernardi, PI. 26, fig. 2. The lower apertures of the venous canals are closely approximated in all the cervicals except the most pos- terior ones, in which the canals diverge, as they descend, with a proportionate breadth between their lower outlets, c' d, fig. 2, PI. 29. They are divided by a narrow ridge, as in fig. 5, in the ordinary cervical vertebrae, and are not situated in fossse, as in the Plesiosaurus Bernardi, PI. 26, fig. 4. In the vertebra which I take to be the penultimate or antipenultimate cervical, the upper half of the costal surface has passed upon the base of the neurapophysis, and, from w^hat remains upon the centrum, as at pi, fig. 5, PI. 28, we may see that the surface has undergone a further change of form, and has exchanged the circular (as in fig. 3) for a vertically elliptical or oval figure. In the centrum of the last cervical vertebra figured in PI. 29, figs. 1, 2, 3, the last trace of the costal surface is shown at pi, fig. 1. A.nd I may here remark, that, as there is no definite natural distinction between the cervical and dorsal regions of the Plesiosaurus; the vertebrae in both supporting ribs, and the transition in the size, shape, and position of these being more gradual than in the Crocodiles, I have selected the arbitrary character of the impression of the costal articular surface, or any part of it, upon the centrum, as the character of the cervical vertebras in i\\Q Plesiosaurus, and I count that to be the first dorsal in which the costal surface has wholly ascended upon the neurapophysis. In PI. 29, fig. 7, one of the caudal vertebrae is figured showing the longitudinal channel, at the middle of the under surface, bounded by the ridges which terminate on the articular surfaces for the hasmapophyses : those surfaces are here worn away. The neurapophyses have coalesced with the centrum ; and the ribs have also coalesced, forming the ' transverse processes' of this caudal vertebra. Plesiosauroid Paddle. Enaliosauria, PI. 30. The block of Chalk from the pit at Burham, in Kent, figured in PI. 30, in- cludes parts of four digits of the same foot, the phalanges of which had the opposed . ends flattened, and joined together by ligament, the whole formmg part of the bony framework of a large fin, most resembling that of the Plesiosaurus. This fine specimen forms part of the I'ich Collection of Chalk-fossils belonging to Mrs. Smith, of Tonbridge CRETACEOUS PLESIOSAURS. 221 Wells. Had Cuvier's conjecture, that the extremities of the Mosasaurus resembled those of the Plesiosaurus, been supported by the evidence of such remains of extremities referable to Mosasaurus as have been discovered since his time, the present remarkable specimen from the Chalk Formations of Kent, might have been ascribed with some degree of probability to the great Lacertian of the Maestricht Chalk. But the evidence which has been adduced from the remains of extremities of the Mosasaurus from the Green-sand of New Jersey, in the United States,* is incompatible with the supposition that the phalanges of the Mosasaurus were united by flattened surfaces and syndesmosis. No remains of the Mosasaurus, so far as I know, have been discovered in the Chalk- pit at Burham, but some vertebrae of Plesiosaurus have been obtained from thence, including the fine one figured in PI. 27. In the specimen figured in PI. 30, fig. 1, three phalangeal bones, and part of a fourth are preserved in one digit, three phalanges in the adjoining digit, and one phalanx of the next, which, if it be in its natural relative position, would belong either to the outermost or the innermost digit; and this is the more likely, as the phalanx of a fourth digit is on the same parallel with the proximal phalanges of the two best preserved digits. In the paddle of the Plesiosaurus the phalanges of the three middle digits are on the same transverse parallel, whilst those of the outer and the inner digits are on a higher or more ' proximal ' plane. I conclude, therefore, that the phalanges marked /;, Ui, and iv, are the middle ones of a pentadactyle paddle, and that the phalanx marked v has belonged to either the inner or the outer terminal digit. If the fragment of bone that closely adheres by a flat surface to the proximal end of the phalanx a, belong to the small carpal bone which articulates with the second digit in the paddle of the Plesiosaurus, we must consider the phalanx to which it is attached, and the two parallel phalanges, as appertaining to the proximal series : but that fragment may be a remnant of a proximal phalanx itself. The proximal surface of the three phalanges is slightly concave : the shaft of the phalanx is thick and strong ; rather compressed from before backwards ; gradually contracting to the middle part. Their substance presents a coarse cancellous texture throughout, with the cells or intervals widest at the middle of the bone. The parts being represented of the natural size, it is unnecessary to specify the dimensions of the phalanges. If the length of the proximal phalanx be taken with the compasses in digits m and u-, it will be found that the two following phalanges progressively decrease in length. On the supposition that the phalanges of these digits are the first, second, and third, we may estimate the length of the entire paddle, according to the proportions of that of the Plesiosaurus Hawkinsii, at sixteen inches ; which would accord with the proportions of the vertebra of the Plesiosaurus from the same pit, figured in PI. 27. * Quarterly Journal of the Geological Society, Jan., 1849, See also, ante, pp. 191 — 193. 222 BRITISH FOSSIL REPTILES. In the instructive Collection of Thomas Charles, Esq., of Maidstone, is part of a single digit of the paddle of apparently the same species of Plesiosaurus. It includes three phalanges, and part of a displaced small phalanx of an adjoining digit. In comparison with the more perfect paddle in Mrs. Smith's collection, I regard the phalanges in the present specimen as being the third, fourth, and fifth of their digit. Genus, Ichthyosaurus. If the investigation of the fossil remains of the Chalk-beds had been undertaken by the Comparative Anatomist, without previous knowledge of the fossils of the lower secondary formations, he would have perceived in the teeth which form the subjects of ' Enaliosauria,' PI. 1, characters not only specifically, but generically, distinct from any of the teeth that have been previously described and figured in the present Work. The thick conical crown covered by enamel, raised into numerous longitudinal ridges, would have offered, it is true, a repetition of the general character of that of the teeth of Polypty- chodon ; but the continued expansion of the base or fang of the tooth, and the coarser longitudinal ridges and grooves with which most of the surface of that part is sculp- tured, would be a peculiarity distinguishing the present from any of the previously noted teeth from the Cretaceous or Tertiary series, and still more so from the teeth of any known existing Reptile. It is only, indeed, those of the largest Crocodiles or Alligators that can compete with the present fossil teeth from the Chalk-formations in point of size ; and the crowns of these, as in the teeth of the Poli/pti/chodon, differ from the teeth of the Crocodilia in the absence of the two opposite ridges, forming or indi- cating the edges of the crown ; whilst their base also differs from that of the Crocodile's tooth in the structure above defined, — a difference which becomes more manifest when a section of that part is made, demonstrating that the expanse of the fang is due to the unusual thickness of the osseous external crust called ' cement.' The Anatomist, I say, would be justified in deducing from these characters the generic distinction of the Reptile to which they had belonged, but he could have formed no suspicion of the truly extraordinary modifications of the entire reptilian organisation that had been associated with such generic modifications of the teeth. Such fossil teeth, having a conical, enameled, and commonly striated crown, offering a considerable range of variation in its proportions, and supported by an expanded, usually solid, and coarsely-grooved fang, covered by a thick coat of cement, have been recognised, since the publication of Sir Everard Home's Paper ' On the Remains of an Animal linking the class of Fishes to that of the Crocodile,' published in the Philosophical Transactions for 1814, as belonging to that genus of animal to which Home gave the name of Proieomurus, but to which Naturalists have concurred in applying the more classically CRETACEOUS ICHTHYOSAURS. 223 constructed and appropriate name of Ichtbjomums, suggested for it by the estimable and accomplished keeper of the Mineralogical Department of the British Museum, Charles Konig, K.H., F.R.S. Remains of species of IcJdhi/osaurm are found in secondary strata from the Chalk down to the Muschelkalk, and most abundantly in the Oolite and Lias. In my 'Report on the British Fossil Reptiles,' I recorded the discovery of " portions of the lower jaw with teeth of a large species of Icldhyosaums from the lower Chalk between Folkstone and Dover, which was closely allied to the Icldhyosuimis communis. And in the description of the Fossil Reptilia m Mr. Dixon's work ' On the Geology of Sussex, some teeth from the Chalk of Kent, now preserved in the Museum of William Harris, Esq., F.G.S., are figured in T. XXXIX, fig. 10, where they are stated to belong to the genus IcJdhyosaurHs, and to correspond so closely in form and size with those of the Icldhyosaurim communis, that I did not presume, in the absence of any knowledge of the skeleton, to pronounce them to belong to a distinct species. I have since been favoured with the opportunity of studying and comparing the required parts for yielding more satisfactory characters, and have arrived at a convic- tion of the distinction of the species of Ichthyosaur of the Chalk-epoch from that of the Lias, which it most resembles in the general shape and proportions of the teeth, a distinction first recognised by James Carter, Esq., M.R.C.S., of Cambridge, who proposed for the species the name of Icldhjosaurus campi/lodon, at the 'Meeting of the British Association' at that University in 1846, on the occasion of the exhibition of some fine remains of the species obtained by him from the Lower Chalk, in the vicinity of Cambridge, in 1845. Before describing these remains, I shall give an account of the additional specimens from the locality VN-hence I derived the first evidence of the presence of remains of the Ichthyosaurus in the Cretaceous strata. Ichthyosaurus campylodon, Carter. Lower jaw, ' Enaliosauria,' Plate 4. In the operations upon the Chalk-clifi's connected with the Dover Railway, a considerable proportion of the lower jaws and fragments of the ribs of a large Ichthyo- saurus were brought to light ; they were dislodged from the hard gray chalk at the end of the Round Down Tunnel, about two miles and a half from Dover, under the clifi", four feet from the beach beyond " Shakespeare's Cliff," towards Folkestone. The specimens are now in the collection of H. W. Taylor, Esq., of Brunswick Place, Brixton Hill, to whose kindness I am indebted for the present opportunity of describing and figuring them. The principal portion consists of four coadaptable fragments of the left ramus of the lower jaw, including nearly the whole of the dentary piece and fragments of the splenial and angular pieces, the whole measuring two feet seven inches in length, but 224 BRITISH FOSSIL REPTILES. ■without the natural anterior termination, and wanting all that extensive hinder part of the ramus formed by the angular and surangular pieces. The inner alveolar plate of the dentary is broken away ; but the vertical diameter of the outer part of the bone, from being 2 inches 6 lines at the hinder end, gradually decreases to 1 inch 9 lines at the fore part. A few teeth have been cemented to the alveolar plate in the anterior fragments, and perhaps in the places near which they were found, for numerous scattered teeth of the Ichthi/osaitrus campyhdon, and doubtless of the same individual as the jaws, were exposed in the fragments of the Chalk rock containing those parts. The outer surface of the dentary bone, PI. 4, fig. 1, is convex, the inner surface at the part where the second joins the third fragment, about 1 foot 6 inches from the anterior end, is divided into two longitudinal channels by the base of the inner alveolar wall; which base is perforated lengthwise by the dental canal. As we trace this part of the dentary backwards, the alveolar groove progressively shallows and diminishes, and the lower groove widens and increases ; the section of the dentary at the back part of this fragment, two feet from the fore end of the whole portion of the bone preserved, presenting a sort of hour-glass form, the upper and under portion being connected by a very thin plate. The form of the section displayed -at the fractured end is given in PI. 4, fig. 1*. The coarser central osseous texture appears to have been included within a thin, dense, exterior crust, about a line in thickness, and the same crust suri'ounds the canal c. The outer surface of the dentary piece shows a shallow groove about two thirds of an inch below the outer alveolar border, into which groove the several vascular foramina open which are continued from the canal, fig. I c. The portion of the right ramus of the same lower jaw, PI. 4, fig. 2, includes the termination of the splenial pieces with the commencement of the symphysis, and includes an extent of the dentary piece, 32, measuring one foot three inches in length. The vertical diameter of the dentary at the hinder fractured end, fig. 2*, is three inches, and at the front end, fig. 2**, is two inches two lines. The inner alveolar plate is sent off about an inch below the upper border of the thick outer plate ; and forms the floor of the groove before it rises to form the inner wall ; it slightly increases in thickness in forming the rounded border of that wall ; the diameter of the floor of the socket is three lines : the depth of the alveolar groove is two inches three lines, its breadth is ten lines and a half. Portions of both splenial bones, somewhat dislocated, shown at 31, 31. The cavity in the dentary beneath the alveolar wall is reduced to a mere groove midway between the fractured ends, with the exception of whicli the whole of the now flattened inner surface of the dentary is in contact with its fellow, forming the strong and long " symphysis raenti." At the fore part of the fragment the alveolar groove is reduced to a depth of eleven lines, and a breadth at its outlet of nine lines. One of the transverse canals is exposed at the anterior fracture, which passes from the inner longitudinal canal to the outer groove. Wherever the bone is broken, that modification CRETACEOUS ICHTHYOSAURS. 225 of its outer surface is shown, which gives it the appearance of forming a crust about a line in thickness, of a different texture from the rest of the bone. The fragment, PI. 4, fig. 3, is a portion of the right premandibular bone, showing a cast of tlie dental vasculo-nervous canal, and the outlets terminating at the orifices on the outer side of the bone. The teeth, supposing them to have been correctly restored, decrease in size, as in the Ichthyosaurus communis, near the anterior end of the dentary piece. The largest tooth in this portion of the jaw, placed one foot from the anterior end, has a crown eleven lines in length, straight, conical, rather obtusely pointed, five lines and a half in diameter, with numerous, not very sharp, but close-set ridges, narrowing as they approach the summit, and subsiding before they attain it. The cement- covered base continues to expand as it descends, with a smooth exterior for about one third of its extent from the crown, and with coarse longitudinal striations or wrinkles over the rest of its extent. The surface of the base in most of the teeth, like the surface of the bone, is coated by a firm crust, sparkling with minute crystals of pyrites. In the attempt to remove this coating, the parts have been more or less injured, so that the precise character of the external markings, and original shape of the thickened fang, cannot be ascertained. The transverse section of the crown of the tooth is circular at its apical half, but widens into a full ellipse towards the base ; that of the smooth beginning of the base is a modified ellipse, which in the rougher and more expanded part of the base, seems to take on a subquadrate form. The teeth differ in size at different parts of the jaw ; in the first or foremost of the series the crown of the tooth is only four lines in length in the lower jaw, and it gradually increases to eight and ten lines in length, — the total length of the longest tooth being two inches and a half. Some of the scattered teeth adherent to the present fragments having very short and thick crowns. In fig. 4, the crown is as wide at its base as it is long : a portion of the thick cement has been removed from the fang just below the crown, and exposes the grooved exterior surface of the dentinal base of that part of the tooth. In the Ichthyosaurus communis, the teeth of which most resemble those of the present species from the chalk, the crown of the tooth tapers more gradually to the apex ; and the enamel ridges are immediately continued upon broader rounded ridges of the cement- covered fang, which become more strongly marked as the fang recedes from the crown, and are divided by deep grooves, giving a fluted character to the base of the tooth, which is proportionally less expanded, and retains more of the circular form in transverse section. (See ' Enaliosauria,' PI. 1, fig. 17.) In the few more or less imperfect teeth of the Ichthyosaurus from the chalk, which I had seen whilst drawing up, in 1838, my Report on 'British Fossil Reptiles,' the differences above specified were not manifested so clearly as in the more numerous and complete examples which have since been submitted to me. The smooth exterior 226 BRITISH FOSSIL REPTILES. of that part of the fang next the crown, in the IMhi/osaurus campylodon, is due to a thick coat of cement ; the dentine so covered shows a fluted character, only differing from that of the teeth of the Ichtlnjommiif< communis in being more regular and some- what finer. This is shown in PI. 4, fig. 4. Not any of the detached teeth discovered with the above-described portions of jaw present any well-marked curvature of the base. The characteristics of the teeth of the IcIifJii/osaiirus campylodon are best displayed in those specimens that have been obtained from the cretaceous deposits in Cambridgeshire. Teeth of Ichthyosaurus campylodon, ' Enaliosauria,' Plate I. The detached teeth from the Cambridge Chalk and Green-sand present two modifications of form : the majority are straight, the rest curved, chiefly owing to a slight inward bending of the thickened fang. These latter have been proved to come from the lower jaw, and the curvature relates, as Mr. Carter has well remarked, to the more oblique direction outwards of the alveolar groove in that jaw, which is compensated by the curvature of the teeth, the crowns of which are thereby bi'ought into more direct apposition with the teeth above.* The enameled crown in all the teeth (figs. 1, 2, 6 c) is a cone, short and thick in the largest teeth, with a circular or very full elliptical transverse section; it is a longer and narrower cone in most of the smaller teeth. The ridges of the enamel are numerous and fine, not always of equal thickness ; the intervening grooves are rather narrower than the ridges. In some teeth, shorter and narrower ridges are seen in the basal intervals of the longer ridges : in other teeth the ridges are thicker at the base of the crown, and are occasionally impressed or divided there by a shorter longitudinal groove. All the ridges subside before they reach the apex of the crown, which is smooth. The enamel terminates at the base of the crown by a thin well-defined border. The tooth continues to expand be3^ond this border, and, for an extent varying from one third to one fifth of the entire fang. The surface is smooth ; not any of the longitudinal furrows or ridges of the enameled crown being continued upon that part of the cement-covered fang. In a few^ teeth, the base of the crown is well defined, as Mr. Carter has remarked, by an annular projection, Plate 1, figs. 3 and 4. The rest of the base or fang of the tooth, beyond the smooth part, presents coarse longitudinal ridges and grooves, is much expanded in most of the teeth, and in many it presents, as in the tooth figured and described by Mr. Carter,! a square shape. This character is best marked in the straight teeth from the upper jaw ; it arises out of the progressive growth of the osseous cement of the fang, which seems to have * London Geological Journal, vol. i, p. 9. f Loc. cit., p. 8, figs, a and h. CRETACEOUS ICHTHYOSAURS. 227 been only checked by the resistance of the alveolar walls on the outer and inner sides of the tooth, and by the contiguous teeth before and behind. Thus, by this thickening of the fang, the teeth must have become wedged together in the common alveolar groove, and the absence of partitions completing the sockets must have been in some measure compensated by this firm impaction. This is shown in the part of the fractured jaws. (PI. 3, fig. 2.) Figs. 3 and 4, PI. 1, give two views of a portion of the alveolar groove with one tooth thus squarely wedged in its place, part of the adjoining tooth on one side, and part of the socket on the other, in which a thin bony partition had been formed for a short extent of the base of the tooth. The extent of the square root in the direction of the long axis of the jaw, fig. 4, is commonly greater than the transverse diameter of the same root, fig. 3. The tooth is never wholly consolidated even in this fully developed state of the fang : a remnant of the uncalcified pulp has always been retained in the central dentinal part of the enlarged fang, after the crown has been completed. This is shown in the fractured specimen, fig. 5, in which the square fang beyond the cavity, o, is one solid mass of coarse cement ; and more clearly in the transverse section, fig. 6, in which c is the cement, (/ the dentine, and a the pulp-cavity. The view given at fig. 6' shows the consolidated base of the thickened fang, — a character by which the teeth of the Ichthyosaurs diifer from those of almost all other Saurians, and especially from the Crocodiles, in which the base of the tooth always remains widely open. Notwithstanding, however, the resistance which must be opposed by the thickened and consolidated root of the tooth of the Ichthyosaur, it is affected by the germ of the succeeding tooth in the same way as in the Crocodilia. I have seldom, indeed, seen the process better illustrated than in a series of the teeth of the IcJdhyosaunis cam- pylodon in Mr. Carter's collection, obtained from the Chalk in the neighbourhood of Cambridge. Fig. 7, PI. 1, is a tooth with a thick, straight, square fang ; probably, therefore, from the upper jaw, which shows on one of the broader sides of the base a shallow elliptical depression, o. This is caused by the progressive absorption excited by the pressure of the soft matrLx of the successional tooth which was in the course of development at the angle of the alveolar groove on the inner side of the base of the tooth in place. In the Ichthyosaur's tooth the absorption causes a simple excavation in the substance of the thick cement ; but in the Crocodile's the same process speedily penetrates the thinner wall of the large cavity in the base of the tooth, as is shown in the figure of that of an Alligator (fig. 11), where a circular aperture is the result of the pressure. As the new tooth of the Ichthyosaur grows, the thick cement of the old tooth yields, and the reduced pulp-cavity in the centre of the fang is penetrated, as is shown at fig. 8, o, where the absorbent process has extended nearly across the whole solid base of the fang, fig. 8'. In fig. 9 the germ of the tooth is preserved, which has penetrated k 228 BRITISH FOSSIL REPTILES. the breach so excavated ; and as both this and the preceding tooth (fig. 8) are from the lower jaw, the direction in which the fang is bent demonstrates that the germs of the new teeth were developed from the inner angle of the bottom of the alveolar groove, and affected the inner side of the base of the fully formed teeth, as in the Crocodiles. In fig. 10 the crown and the smooth beginning of the fang of the successional tooth have been completed, and it is seen enclosed by part of the debris of the old tooth which it is about to replace. As in all young teeth, the crown is a thin shell of the first-formed layers of dentine, with a thin coat of enamel, the ridges of which seem not to have been quite completed. The teeth of the Ichthyosaurus are smaller at the two extremes than at the middle of the series in both jaws ; and some modifications of form are presented in these teeth, which do not, however, overpass the recognisable limits of the specific characters. Fig. 13 is a tooth probably from the back part of the series in the upper jaw, in which the crown is less broad at its base and relatively longer than in the large teeth from the middle of the series ; the rough expanded fang presents in transverse section a long ellipse, with its angles truncated, making but a slight approach to the quadrate figure of the fang of most of the larger teeth ; but in the fine striation of the conical enamelled crown, in the smooth tract of unenamelled fang which precedes the roughly striated expanded portion, and in the degree of expansion of this part, all the distinctive characters of the IcJtthyosauriis campylodon are preserved. Figure 14 is an incompletely formed tooth from the opposite end of the dental series, in which the enamelled crown is unusually short and thick ; but the smooth surface of the portion of the fang which has been formed, which continues to expand to the widely open pulp-cavity, gives the character of the same species as fig. 1 3. In fig. 15, from the Upper Green-sand, we have a tooth in a more advanced stage of formation : the roughened thickened part of the base has begun to be added ; but this is still widely open, as is shown in fig. 15'. In Figure 16, a greater proportion of the rough expanded fang is completed, and the basal outlet of the pulp-cavity is beginning to be encroached upon : but in these young teeth the cement has not increased in such quantity as to be moulded into the square form that is so characteristic of the old teeth. Jaws of the Ichthyosaurus campylodon, from the Cambridge Chalk. ' Enaliosauria,' Plates 2 and 3. The portions of the upper and lower jaws discovered with the teeth above described, and containing several teeth of the same character in situ, are, as their possessor, Mr. Carter, truly describes, the most characteristic relic of the Ichthyo- saurian genus hitherto obtained from the Cretaceous Formations. The portion of the upper jaw includes an extent of two feet of the premaxUlary CRETACEOUS ICHTHYOSAURS. 229 bones, including at the back part about three inches of the exposed, and apparently pointed terminations of the nasal bones (PI. 2, fig. 2, 15.) These, however, extend much further forwards than they appear to do externally, their anterior ends being overlapped by the premaxillaries, 22. The breadth of the premaxillaries at the fractured hinder end of this specimen is 5^ inches, at the distance of one foot from that fractured end it is 3| inches, and the decrease seems to have been rather more gradual in advance of this part. The total length of the jaws from the point of union of the premaxillaries above the nasals, may therefore be estimated at about three feet. The breadth of each nasal, where they dip beneath the premaxillaries, is one inch three lines : the upper surface presents a longitudinal furrow midway between the margins of the bone, into which furrow a longitudinal ridge at the under surface of the premaxillary fits, thus strengthening the union between the two bones. The nasal bone forms a parallel ridge, or angular projection, from its own under surface, which divides the inferior concavity into two parts, the median and broader concavity being somewhat angular in form. The actual pointed ends of the nasals are visible at a fractured surface, (PI. 3, fig. 2, 15,) nine inches in advance of the point where they are concealed by the median junction of the premaxillaries : their section here presents the form of a curved lamina of bone, thickest at its median border, and half an inch in breadth, and this may be traced beneath the fractured portion of the premaxillary three inches further forwards. The breadth of the nasal cavity at the back part of the fractured end, (PI. 3, fig. 1,) is rather more than two inches : at the anterior fracture, fig. 2, it is reduced to ten lines. The median borders of the premaxillaries, (PI. 3, fig. 1, 22,) before their junction above the nasals, (ib. 15,) are about one line thick, and the bone increases to a thickness of three lines, above the part where it sends off, inwards and downwards, the inner alveolar border, (ib. al,) which is at a distance of an inch and three fourths from the upper median border. On the outside, opposite the origin of the inner alveolar plate, the premaxillary is traversed by a straight longitudinal groove, (PI. 2, fig. l,y,) four lines in breadth, which contracts, as it advances forwards. The outer alveolar plate, (PI. 3, fig. 1, «,) increases in thickness to six lines, and terminates below in a convex border. The inner alveolar plate, (ib. al,) forms the chief part of the arched roof of the upper dental groove, and has there scarcely a line in thickness ; but as it descends, it rapidly gains a thickness of five lines at its inferior convex border. There is a slight solution of continuity between the arched and descending portions of the inner alveolar plate, (ib. al',) at the hinder fractured end of the specimen, and the descending plates might at first sight be taken for the palatine bones ; but these, in other Icldliyosauri, are vertical plates, which lie parallel with, and on the inner side of the descending alveolar plate of the premaxillary, and do not reach so far forwards as where the nasals are wholly overlapped by the premaxillaries. The inner alveolar 230 BRITISH FOSSIL REPTILES. plate descends eight lines lower than the outer one, and the outlet of the alveolar groove has a corresponding oblique aspect downwards, and a little outwards : the breadth of the groove at the outlet is 1 inch 2 lines : the depth of the groove, to the inner border, is 1 inch 6 lines : the breadth of the alveolar part of the preraaxillary, including the plates, is 2 inches and a half. At the anterior fractured end of the left premaxillary, (PI. 3, fig. 2, 22,) ten inches in advance of the hinder fracture, the vertical diameter of the bone is 2 inches 10 hnes, the breadth of the lower alveolar part is 1 inch 9 lines, the depth of the alveolar groove is 1 inch 5 lines, the breadth of its outlet 1 inch 1 line. Here the two preraaxillaries are in contact at the upper borders, which have progressively increased, after overlapping the nasals, to a thickness of 7 lines, The inner alveolar plate is sent off about half an inch below the upper border, extending inwards and downwards, and dividing the nasal from the alveolar groove, then descending, in contact with the same plate of the opposite premaxillary, for about an inch of vertical extent : the thickness of the plate near its origin is 3 lines, whence it increases to 7 lines at its lower rounded border, ib. d' . The elliptical area of a canal, 4 lines in diameter, o, is exposed above the origin of the inner alveolar plate. The narrow exterior groove, g, sinks 3 lines into the substance of the bone, and slightly expands towards its bottom. The outer groove and the inner canal communicate by transverse anastomosing channels at certain parts. The whole of the upper surface of the premaxillaries forms a smooth arch of bone, describing in transverse section a semicircle, and impressed only by the longitudinal groove each side, for the lodgement of a vessel on and probably also a branch of the fifth pair of nerves. The portion of the lower jaw consists of the dentary and splenial pieces,* both dislocated, the former slighly. At the back part of the left ramus, (PI. 3, fig. 1,) the lower border of the splenial, (ib. 31,) has been pressed inwards and downwards from that of the dentary, (ib. 32,) and slightly rotated so as to incline its inner vertical wall outwards, where it is pushed into the groove or concavity of the dentary, which it naturally closes, applying itself to the side of the inner alveolar plate of the dentary. Tlie right splenial, (ib. 31,) has been still more displaced, its lower border being pushed against the base of the inner alveolar plate of the left ramus. Both splenials are exposed at the anterior fracture of the rami, (PI. 3, fig. 2,) six inches in advance of the preceding, the right being here, also, above the left, and removed from its own ramus to contact with the base of the inner alveolar plate of the left ramus. The vertical diameter of the splenial.. which is two inches at the hinder fractured part, has diminished to little more than one inch at a distance of five inches * See the Cut, fig. 13, p. 9, of the ' Fossil Reptilia of the Tertiary Formations,' Chap, ii, Crocodilia, in which tlie different pieces of the complex lower jaw of the Alligator is figured : and where 29 is the "articular," 29' the " surangular," 30 the "angular," 31 the "splenial," 31 the " complemental," and 32 the " dentary." CRETACEOUS ICHTHYOSAURS. 231 in advance of this. The splenial has the same shape as in other Ichthyosauri, being a longitudinal plate, with its lower margin bent outwards at a right angle ; this margin forms the lower border of a great extent of the ramus, underlapping the dentary at the situation of the posterior fracture, which is a little prior to the junction of the two rami forming the symphysis ; it is withdrawn to the inner side of the dentary at the anterior fracture. The ascending or vertical plate of the splenial forms the largest part of the bone, and is much thicker than in the Crocodile with a jaw of the same depth : its transverse diameter in the present Ichthyosaur is 3 lines. The dentary is a long bone which, at the hinder fractured part, (PI. 3, fig. 1, 32,) appears as if it were folded lengthwise twice upon itself, forming a sigmoid transverse section ; but the outer part of the bone increases in thickness as it advances forwards, and the inner alveolar wall presents, at the anterior fracture, more the appearance of an accessory plate or process sent off from the inner side of the body of the bone. The vertical diameter of the dentary pieces is 2 inches 3 lines. The outer part of the dentary at the hinder fracture is 6 lines in thickness, smooth and convex on its outer side, which is traversed by a longitudinal groove, g, which also slightly narrows as it advances. The alveolar plate is continued downwards and inwards at an angle of about 50°, diminishing in thickness as it descends, and again increasing after it has risen, to form the inner wall of the alveolar groove. The depth of the groove is 1 inch 5 lines ; its width is 1 inch. At the anterior section, 5 inches in advance, (PI. 3, fig. 2,) the alveolar groove {ac) has contracted to a diameter of 8 lines, and is 1 inch 2 lines in depth ; the inner alveolar wall, (a/,) has increased in thickness. The lower jaw, in the present fine fragment of skull, appears to have been broken across just anterior to the meeting of the two rami, where they form the symphysis. What is wanting in the specimen of the Ichthyosaurus campylodon in Mr. Carter's collection to give, ex visu, the proportions of the jaws of that species, is, in great part, supplied by the fragments from Mr. Taylor's collection, which had been previously discovered in the Grey Chalk near Dover. The hinder end of the portion of the left ramus in that specimen, which measures 2 feet 7 inches in length, has been broken away from the part which corresponds with the front end of the portion of the same bone in Mr. Carter's specimen, and this end is nearly 1 foot distant from the hindmost part of the same specimen. We thus gain an extent of jaw by this addition of nearly 3 feet, and at least I foot more would be required to complete the whole length of the jaw. Owing to the partial dislocation of the rami, the aspect of the alveolar groove is more outwards than is natural ; but in the proper relative position it is turned more obliquely outwards than that of the upper jaw, and the roots of the lower teeth, as Mr. Carter has well remarked, present a curvature which compensates for the obliquity of this alveolar groove, and gives a more vertical direction to their crowns. 232 BRITISH FOSSIL REPTILES. This characteristic of the present species is well shown in the group of upper and lower teeth preserved on the right side of the present instructive fragment of the skull, (PI. 2 and PI. 3, fig. 2.) It includes, in an extent of 6 inches and 9 lines, six teeth of the upper jaw ; and, in an extent of 4 inches and a half, four teeth of the lower jaw. Besides the teeth which have preserved nearly their natural positions in respect of each other, there are three or four displaced teeth or fragments of teeth. Of the four teeth of the lower jaw, the three largest, while they have kept nearly their natural position to the teeth above, have slipped out of the groove of the lower jaw during its downward displacement, instead of being separated to the same extent from the upper teeth. In the lower jaw of the Cachalot, where the teeth are lodged in a wide groove, and with the alveoli incompletely developed, they are easily dislodged when decom- position has commenced, and may be stripped away with the firm gum, to which the necks of the teeth adhere more strongly than their fangs do to the rudimental sockets. The first of the six teeth of the upper jaw is completely formed, and shows the quadrate root a little compressed in the transverse direction. The rough part of the fang is that which is embraced by the sides of the alveolar grove ; the smooth portion was probably surrounded by a soft slimy gum as far as the enamelled crown. The tooth opposed to this in the lower jaw, and the crown of which passes, as usual, external to it, is a young tooth, with the fang as yet incompletely formed and rounded : its inferiority of size to the tooth above depends on this circumstance. The second tooth above is not so far advanced in growth as the one which precedes or the four that follow it ; the crown and part of the fang of the last, m, of these are broken away, and expose the germ of the young tooth, t, which had penetrated its cavity and was about to displace it. The curve of the rough expanded fangs of the lower teeth is well exhibited in the last two of these teeth. The teeth of the Ichthyosaurus campylodon are large in proportion to the slenderness of the elongated jaws, and ofi"er, in this respect, a great contrast with those of the Ichthyosaurus temiirostris : they are even larger in proportion than the teeth of the shorter and thicker jawed Ichthyosaurus communis and Ichthyosaurus lonchiodon, and both the proportions and the form of the teeth determine the specific distinction of the present Ichthyosaurus of the Chalk and Green-sand from any of the known species from the older secondary strata. But there is no modification indicative of a departure from the generic characteristics of the great Fish-lizard : on the contrary, so far as these are manifested by the structure of the jaws, especially the undivided alveolar groove, by the great proportional size of the premaxillaries, and by the thickly cement- covered fangs of the teeth, these characters are rather in excess, and the last of the Ichthyosaurs, far from progressing towards any higher and later form of reptile, might be cited as a type of its peculiar genus. CRETACEOUS ICHTHYOSAURS. 233 Vertebra of Ichthyosaurus Campylodon. 'Enaliosauria,' Plate 7. Had no other part of the Ichthyosaurus been discovered in the Chalk Formations than the centrum of a vertebra, that alone would have sufficed to convince the investigator, who had commenced his researches by descending from the more recent to the older Formations, that some marine Saurian had existed totally distinct from any other Reptile the remains of which he might have previously met with in the chalk ; if, indeed, a vertebra so far departing from those of the Reptilia in general had not been mistaken for the vertebra of a Fish. The most fish-like character of the Ichthyosaurus is the deep concavity of both articular extremities of the centrum, fig. 3, and the shortness of the vertebra, fig. 1, as compared with its breadth and height, fig. 2, in which proportion it resembles the vertebrae of the shark tribe. But the peripheral non-articular or free surface of the vertebra is smooth and entire : the articular depressions for the neurapophyses are shallow, and those for the ribs are situated on either one or two tubercles on each side of the centrum. Such pair of costal tubercles would alone suffice to distinguish the vertebra of the Ichthyosaurus from the biconcave vertebra of any fish. All the general characters of the Ichthyo- saurian vertebrae are manifested by the specimen figured in PL 7. It was discovered in the same mass of grey chalk at the base of Shakspeare's Cliff as the jaws and teeth figured in PI. 4, and forms with these part of the collection of W. H. Taylor, Esq. It corresponds in its dimensions with those fine fragments of jaw, and might well have formed part of the vertebral column, which supported a head four feet in length. The substance of the bone is decomposed, and the surface studded with firmly adherent pyritic matter. It appears to have come from the base of the tail, where the costal tubercles become single. The surface of the articular concavity has the gentle undulating disposition, convex at the periphery, before the deeper central concavity is scooped out, as shown in the section, (PI. 7, fig. 3,) which is common to some other species of Ichthyosaurus ; but no specific character could have been deduced from this fragment of the skeleton. The vertebra figured measures 4 inches vertically across the articular concavity; and 1 inch 10 lines longitudinally across the side. A smaller vertebra from the middle of the tail measures 3^ inches transversely, and 1^ inch in antero-posterior extent. The concavity deepens rather suddenly towards the centre. Three more or less mutilated bodies of vertebrae, having similar proportions to those of the Ichthyosaurus campylodon from the Dover Chalk, have been obtained from the Upper Green-sand near Cambridge, where they are also associated with teeth of the same species. They are preserved in the cabinet of James Carter, Esq., M.R.CS. 234 BRITISH FOSSIL REPTILES. In the Iclithyosaurus tenuirostris, the length of the lower jaw equals at least fourteen times that of the vertical diameter of the centrum of an anterior caudal vertebra ; in the Ich. communis and in the Ich. loncModon eleven times ; in the Ich. Iniermeduis ten times the same diameter. The jaws of the Ichthyosaums camjjylodon must have approached more nearly to the proportions of those of the Ich. tenuirostris, than the other species above named, and it is not unlikely that the lower jaw was thirteen times the length of the vertical diameter of an abdominal or anterior caudal centrum. Assuming such proportions, we may reckon the lower jaw to have been upwards of four feet in length ; and this calculation accords with that founded upon the proportions of the fragments of the lower jaws above described. One of the masses of chalk contains portions of several ribs, the longest being about ten inches in length ; the transverse section of these portions of rib is a regular full ellipse, the fractured end of one of the least mutilated is 9 lines in its long diameter, 6 lines in its short diameter ; but some parts of the ribs are 1 inch in breadth. Not any of these fragments show the opposite longitudinal impressions that characterise some of the ribs in the Iclithyosaurus communis. CHAPTER V. Order. PTEBOSAUBIA, Owen. Genus — Pterodactylus, Cuvier. The honour of having first made known the existence of remains of Pferodactyles in the Chalk belongs to the able Secretary of the ' Paleeontographical Society,' James Scott Bowerbank, Esq., F.R.S. This indefatigable Collector had the good fortune to receive, in 1845, from the Chalk of Kent, the characteristic jaws and teeth, with part of the scapular arch and a few other bones of a well-marked species of Pterodactylus, and the discovery was briefly recorded in the ' Proceedings of the Geological Society of London' for May 14th, 1845,* with an illustrative plate. Mr. Bowerbank concludes his Paper by referring to a large fossil wing-bone from the chalk, which I had previously figured and described in the ' Geological Transactions,'! and remarks that " if it should prove to belong to a Pterodactyle, the probable expansion of the wings would reach to at least eight or nine feet. Under these circumstances," he says, " I propose that * The author there states that the specimens were " obtained from the Upper Chalk of Kent :" Mr. Toulmin Smith, in his able paper " On the Formation of the Flints of the Upper Chalk" in the •Annals of Natural History,' vol. xx, p. 295, affirms that no Upper Chalk exists in the localities whence those specimens came. They are from the Middle Chalk. •\ Second Series, vol. vi, 1840, pi. 39, fig. 1. CRETACEOUS PTERODACTYLES. 235 the species described above shall be designated Pterodacfylus ffit/antcus,''' (loc. cit., p. 8.) Subsequent discoveries and observations have inclined the balance of pro- bability in favour of the Pterodactylian nature of the fossils to which Mr. Bowerbank refers. These fossils are not, indeed, amongst the characteristic parts of the flying reptile ; one is the shaft of a long bone exhibiting those peculiarities of structure which are common to birds and Pterodactyles ; the other shows an articular extremity which, in our present ignorance of the different bones of the Pterodactylc, has its nearest analogue in the distal trochlea of the bird's tibia. These two specimens, which are figured in the above-cited volume of the ' Transactions of the Geological Society,' PI. 39, figs. 1 and 2, were, in fact, as I acknowledged in the Memoir, read April 26th, 1840, transmitted to me by the Earl of Enniskillen and Dr. Buckland, as being the bones of a bird (p. 411), and my comparisons of them were limited to that class. The idea of their possibly belonging to a Pterodactylc did occur to me, but it was dispelled by the following considerations. The act of flight — the most energetic mode of locomotion — demands a special modification of the vertebrate organisation, in that sub- kingdom, for its exertion. But in the class Aves, in which every system is more or less adapted and co-adjusted for this end, the laws of gravitation seem to forbid the suc- cessful exercise of the volant powers in species beyond a certain bulk ; and when this exceeds that of the Condor or Albatross, as, for example, in the Cassowary, the Emeu, or the Ostrich, although the organisation is essentially that of the vertebrate animal modified for flight, flight is impossible ; and its immediate instruments, to the exercise of which all the rest of the system is more or less subordinated, are checked in their development, and, being unfitted for flight, are not modified for any other use. There is, perhaps, hardly a more anomalous or suggestive phenomenon in nature than a bird which cannot fly ! A small section of the Mammalia is modified for flight ; but the plan of the organisation of that warm-blooded class being less directly adapted for flight than that of birds, the weight and bulk of the body which may be raised and transported through the air, are restricted to a lower range ; and the largest frugivo- rous Bat {Pteropus) does not exceed the Raven in size. The Reptilian modification of the vertebrate type would seem to be still less fitted for any special adjustment to aerial locomotion ; and, in the present day, we know of no species of this class that can sustain itself in the air which equals a sparrow in size ; this species, moreover, the little JDraco volans, sails rather than flies, upborn by its outstretched costal parachute in its oblique leaps from bough to bough. Of the remarkable Reptiles now extinct, which, like the Bats, had their anterior members modified for plying a broad membranous wing, no species had been discovered prior to 1840, which surpassed the largest of the Pteropi, or "Flying-foxes," in the spread of those wings, and there was a priori a physiological improbability that the cold-blooded organisation of a Reptile should, by any secondary modification, be made I 236 BRITISH FOSSIL REPTILES. to effect more in the way of flight, or be able to raise a larger mass into the air, than could be done by the warm-blooded mammal under an analogous special adaptation. When, therefore, the supposed bird's bone, ' Pterosauria,' PI. 4, fig. 4, was first submitted to me by Dr. Buckland, which, on the Pterodactyle hypothesis, could not be the humerus, but must have been one of the smaller bones of the wing, its size seemed decisive against its reference to an animal of flight having a cold-blooded organisation. The subsequent discovery of portions of the skull of the Pterodactyles figured in ib., PI. 3, shows that the manifestations of Creative power in past time surpass the calculations that are founded upon actual nature. It is only the practised Comparative Anatomist that can fully realise the difficulty of the attempt to resolve a Palseontological problem from such data as the two fragments of bones first submitted to me in 1840. He alone can adequately appreci- ate the amount of research involved in such a generalization, as that " there is no bird now known, north of the equator, with which the fossils can be compared ;" and when, after a wearying progress through an extensive class, the species is at length found to which the nearest resemblance is made by the fragmentary fossil, and the differences are conscientiously pointed out — as when, e. g., in reference to the humerus of the Albatross, I stated that " it differs therefrom in the more marked angles which bound the three sides," — the genuine worker and searcher after truth may conceive the feelings with which I find myself misrepresented as having " regarded the specimens as belonging to an extinct species of Albatross." My reference of the bones even to the longipennate tribe of natatorial birds, is stated hypothetically, and with due caution. " On the supposition that this fragment of bone is the shaft of the humerus, its length and comparative straightness would prove it to have belonged to one of the longipennate natatorial birds, equalling in size the Albatross," (loc. cit., p. 411.) Since the discovery has been made of the manifestly characteristic parts of the genus Pterodacfi/lus, in the Burham Chalk-pit, it has been objected that these bones first discovered there, and described by me as resembhng those of birds of flight, " are so extremely tJiin as to render it most improbable that they could ever have sus- tained such an instrument of flight as the powerful wing of the Albatross or of any other bird : their tenuity is in fact such," says the objector, " as to point out their adaptation to support an expanded membrane, but not pinions."* This assertion needs only for its refutation a simple reference to nature ; sections of the wing- bones of birds may be seen in the Museum of the Royal College of Surgeons, and have been exposed to view, since the discovery of their structure by the founder of that Collection, in every Museum of Comparative Anatomy worthy to be so called. To expose the gratuitous character of the objection above cited, I have selected for * Mantell, 'Wonders of Geology,' 1848, vol. i, p. 441. CRETACEOUS PTERODACTYLES. 237 llustration in ' Pterosauria,' PI. 5, fig. 1, a section of the very bone that directly sus- tains the large quill-feathers in the Pelican : its parietes are only half as thin as those of the anti-brachial bone of the great Pterodactyle, figured in ib., PI. 4, fig. 1 : they are thinner than those of the humerus figured in ib, PL 2, fig. 1. Hunter, who had obtained some of the long bones, with thin parietes and a wide cavity, from the Stonesfield Slate, has entered them in his MS. Catalogue of Fossils, as the " Bones of Birds :" and perhaps no practical anatomist had had greater experience in the degree of tenuity presented by the compact walls of the large air-cavities of the bones in that class. Of all the modifications of the dermal system for combining extent of surface with lightness of material, the expanded feather has been generally deemed the consummation. Well might the eloquent Paley exclaim : — " Every feather is a mechanical wonder — their disposition, all incHned backwards, the down about the stem, the overlapping of their tips, their different configuration in different parts, not to mention the variety of their colours, constitute a vestment for the body, so beautiful and so appropriate to the life which the animal is to lead, as that, I think, we should have had no conception of anything equally perfect, if we had never seen it, or can imagine anything more so." It was reserved for the author of the ' Wonders of Geology,' to prefer the leathern wings of the Bat and Pterodactyle as the lighter form, and to discover that such a structure, as is displayed in PI. 4, fig. 4, was "a most improbable one to have sustained a powerful wing of any bird." Let me not be supposed, however, to be concerned in excusing my own mistake. I am only reducing the unamiable exaggeration of it. Above all things, in our attempts to gain a prospect of an unkno-mi world by the difficult ascent of the frag- mentary ruins of a former temple of life, we ought to note the successful efforts, as well as the occasional deviations from the right track, with a clear and unprejudiced glance, and record them with a strict regard to truth. The existence of a species of Albatross, or of any other actual genus of Bird, during the period of the Middle Chalk, would be truly a wonder of Geology ; not so the existence of a bird of the longipennate family. I still think it for the interest of science, in the present limited extent of induction from microscopic evidence, to offer a warning against a too hasty and implicit con- fidence in the forms and proportions of the purkingean or radiated corpuscles of bone, as demonstrative of such minor groups of a class, as that of the genus Pterodactylus Such a statement as" that these cells in Birds " have a breadth in proportion to their length of from one to four or five ; while in Reptiles the length exceeds the breadth of ten or twelve times,"* only betrays the limited experience of the assertor. In the dermal plates of the Tortoise, e. g., the average breadth of the bone-cell to its length is as one to six : and single ones might be selected of greater breadth. * Mantell, 'Wonders, &c.,' vol. i, p. 441. 238 BRITISH FOSSIL REPTILES. With the exception of one restricted family of Ruminants, every Mammal, the blood-discs of which have been submitted to examination, has been found to possess those particles of a circular form : in the Camelidee they are elliptical, as in birds and reptiles. The bone-cells have already shown a greater range of variety in the vertebrate series than the blood-discs. Is it, then, a too scrupulous reticence, to require the evidence of microscopic structure of a bone to be corroborated by other testimony of a plainer kind, before hastening to an absolute determination of its nature, as has been done with regard to the Wealden bone, figured in the ' Geological Trans- actions," vol. V, pi. xiii, fig. 6 ?* As a matter of fact, the existence of Pterodactylian remains in Chalk was not sur- mised through any observation of the microscopic structure of bones that are liable to be mistaken from their more obvious characters for those of birds, but by the dis- covery of the characteristic portions of the Pterodactyle, defined by Mr. Bowerbank, as follows, in his original communication of their discovery to the ' Geological Society of London,' May 14th, 1845. " I have recently obtained from the Upper Chalkf of Kent, some remains of a large species of Pterodactylus. The bones consist of — 1. "The fore part of the head, as far as about the middle of the cavifas narhnn, with a corresponding portion of the under jaws, — many of the teeth remaining in their sockets, (see PI. 1, fig. 1.) 2. " A fragment of the bone of the same animal, apparently a part of the coracoid, (fig. 2.) 3. " A portion of what appears to be one of the bones of the auricular digit, from a Chalk-pit at Hailing, (fig. 3.) 4. " A portion of a similar bone, from the same locality as No. 1, (fig. 4.) 5. " The head of a long bone, probably the tibia, belonging to the same animal as the head, No. 1, (fig. 5.) 6. " A more perfect bone of the same description, not from the same animal, but found at Hailing," (fig. 6.) In a subsequent communication, dated December 1845, Mr. Bowerbank states, with regard to the specimens, Nos. 5 and 6, which he supposed to be parts of a tibia, that " on a more careful comparison with the figures of Fterodactylm by Goldfuss, I am inclined to believe they are more likely to be portions of the ulna." * I would request the reader who may be desirous to exercise an independent judgement ou such facts as have been published on this point, to compare, for example, some of the cells figured by Mr. Bowerbank, in PI. i, fig. !), of the ' Quarterly Journal of the Geological Society,' vol. iv, as being those of the bone of a bird, with some of the wider cells, fig. 1, of the same plate, as being those of the bone of a Pterodactyle ; and contrast the want of a parallelism in the cells of the Wealden bone, fig. 9, with the parallelism of the long axes of the cells in the bone of the Albatross, fig. 3. f See the Note, ante, p. 80. CRETACEOUS PTERODACTYLES. 239 With respect to the long bone, figured in the present work at ' Pterosauria,' PI. 6, fig. 11, comparing it with that figured in ib., PI. 4, fig. 4, Mr. Bowerbank writes : — " Although the two specimens differ greatly in size, there is so strong a resemblance between them in the form and angularity of the shaft, and in the com- parative substance of the bony structure, as to render it exceedingly probable that they belong to the same class of animals ;" and he concludes by remarking that " if the part of the head in my possession (see fig. 1), be supposed similar in its proportions to that of Pterodactylm crassirostris, — and there appears but little difference in that respect, — it would indicate an animal of comparatively enormous size. The length of the head, from the tip of the nose to the basal extremity of the skull of P. crassirostris, is about 4|- inches, while my specimen would be, as nearly as can be estimated, 9^ inches. According to the restoration of the animal by Goldfuss, P. crassirostris would measure, as nearly as possible, three feet from tip to tip of the wings, and it is probable that the species now described would measure at least six feet from one extremity of the expanded wings to the other ; but if it should hereafter prove, that the bone described and figured by Professor Owen belongs to a Pterodactyle, the probable expansion of the wings would reach to at least eight or nine feet. Under these circumstances, I propose that the species described above shall be designated Pterodactylus giganteusr (p- 8.) In a subsequent Memoir, read June 9th, 1 847, and published in the ' Quarterly Journal of the Geological Society,' February, 1848, Mr. Bowerbank gives figures of the "bone-cells" from the jaw of a Pterodactyle (PL i, fig. 1), from the shaft of the bone in question (ib., fig. 2), and from the femur of a recent Albatross (ib., fig. 13), in corroboration of the required proof ; and he adds : — " Fortunately the two fine specimens from the rich collection of Mrs. Smith, of Tonbridge Wells, represented by fig. 1, PI. ii, in a great measure justify this conclusion, and in the bone a, which is apparently the corresponding bone to the one represented by fig. 1 in Professor Owen's Paper, the head is very nearly in a perfect state of preser^^ation," (Op. cit., p. 5.) Mr. Bowerbank, in his explanation of PI. ii, describes the two specimens above mentioned, as : — " Fig. 1. Radius and ulna of Pterodactylus yiganteus, in the Cabinet of Mrs. Smith, of Tunbridge W^ells," (Tom. cit., p. 10, 'Pterosauria,'' PI. 4, fig. 5, of the present work.) He proceeds to state, " there are two other similar bones imbedded side by side in the Collection of Mr. Charles, of Maidstone, of still greater dimensions than those from the Cabinet of Mrs. Smith," and he assigns his grounds for the con- clusion, that " the animal to which such bones belonged could, therefore, have scarcely measured less than fifteen or sixteen feet from tip to tip of its expanded wings." These bones are represented in ' Pterosauria,' PI. 4, of the present Work. The Committee of the British Association, for the Reform and Regulation of Zoological Nomenclature, amongst other excellent rules, have determined, that : — " Names not clearly defined may be changed. Unless a species or group is 240 BRITISH FOSSIL REPTILES. intelligiljly defined when the name is given, it cannot be recognised by others, and the signification of the name is consequently lost. Two things are necessary before a Zoological term can acquire any authority, viz. definition and puhlication. Definition properly implies a distinct exposition of essential characters, and in all cases we conceive this to be indispensable.* Now with regard to the Pterodadylus giganteus, I always understood Mr. Bowerbank to apply the term to the species to which the long wing-bone first described by me might appertain, under the circumstances of its being proved to belong to a Pterodactyle, and my belief in this definition of his species was confirmed by the fact of his subsequently figuring the two similar and equal-sized bones in the ' Quarterly Journal of the Geological Society,' Vol. IV, pi. 2, fig. I, (Proceedings of the Society for June 9th, 1847,) as the "radius and ulna oi Pterodadylus giganteusr So far as a species can be intelligibly defined by figures, that to which the term giganteus was, in 1845, provisional^, and in 1847 absolutely applied, seemed to be clearly enough pointed out by the Plate 2, in the Work above cited. But with the large bones appropriately designated by the term giganteus, some part of a smaller Pterodadgle, including the portions of jaws first announcing the genus in the Chalk, had been associated under the same name. Supposing those bones to have belonged to a young individual of the Pterodactylas giganteus, no diflBculty or confusion would arise. After instituting, however, a rigid comparison of these specimens, I was compelled to arrive at the conclusion that the parts figured by Mr. Bowerbank, in Plate I, figs. 1 and 2, of Vol. II of the ' Quarterly Geological Journal,' and the parts figured in Plate 2, figs. 1 a and b of Vol. IV, of the same Journal, both assigned by Mr. Bowerbank to the Pterodactyhs giganteus, belonged to two distinct species. The portions of the scapula and coracoidof the Pterodactyle (PL l,fig. 2, vol. ii, op. cit.) indicates, by its complete anchylosis, that it has not been part of a young individual of the species to which the large antibrachial bones (PI. 2, fig. 1, a and b, vol. iv, op. cit.) belonged, although it might well appertain to the species to which the jaws (PL 1, fig. 1, vol. ii,) belonged. Two species of Pterodactyle were plainly indicated, as I have shown in the Work by my lamented friend, Mr. Dixon, ' On the Tertiary and Cretaceous Deposits of Sussex,' 4to, p. 402. The same name could not be retained for both, and it was in obedience to this necessity, and not with any idea of detracting an iota from the merit of Mr. Bowerbank's original announcement of the existence of a Pterodactyle in the Chalk, that I proposed the name of conirostris for the smaller species, then for the first time distinctly defined and dis- tinguished from the larger remains, to which the name giganteus had also been given by Mr. Bowerbank. I proposed the name, moreover, provisionally, and with sub- mission to the Committee for the Reform of Zoological Nomenclature, according to whose rules I believed myself to have been guided. * See their 'Report,' Trans, of the British Association for 1842, 113. CRETACEOUS PTERODACTYLES. 241 As, however, I have no personal feeUng with regard to mere names, I shall apply to the specimens of the jaws of the Pterodactyles, described in the present Work, the names by which Mr. Bowerbank first made those parts known to Geologists, and before entering upon their descriptions shall premise a few remarks on the Pterodactyles in general. The Order Pterosauria includes species of flying reptiles, so modified in regard to the structure and proportions of the skull, the disposition of the teeth, and the deve- lopment of the tail, as to be referable, even according to the partial knowledge we now possess of this once extensive group, to di0"erent genera. M. von Meyer, e. g., primarily divides the Order into : — A. Diarthri. With a two-jointed wing-finger. Ex. Pterodacfylm {^Ornithopterus) Lavateri. B. Tetrarthri. With a four-jointed wing-finger. Ex. All the other known species of the Order. These again are subdivided into : — 1 . Bentirostres. Jaws armed with teeth to their ends : a bony sclerotic ring : scapula and coracoid not confluent with one another :* a short moveable tail. Ex. Pterodactylus proper. 2. Subulirostres. Jaws with their ends produced into an edentulous point, pro- bably sheathed with horn : no bony sclerotic : scapula and coracoid confluent : a lone; and stiff tail. *o Ex. Tterodadylus {Bamphorhyndms) Gemminyi.\ The extremity of the upper jaw of the Ptcrodactyli's Ciwieri, Bowerbank, is sufficiently perfect to demonstrate that it had a pair of approximated alveoli close to its termination, and we may, therefore, refer it to the Dentirostral division. In this division, however, there are species which present such different proper tions of the beak, accompanied by differences in the relative extent of the dental series, as would, without doubt, lead to their allocation in distinct genera, were they the living or recent subjects of the modern Erpetologist. In the Ptcrodartylus longirostris, the first species discovered, and made known by Collini in 1784,]; the jaws are of extreme length and tenuity, and the alveoli of the upper jaw do not extend so * The condition of the scapular arch in the P. giyanteus. Bow., P. conirostris, Mihi, demonstrates the fallacy of this character. •f Palaeontographica, Heft I, 4to, 1846, p. 19. X Acta Academise Theodoro-Palatinse, v, p. 58, Tab. v. 242 BRITISH FOSSIL REPTILES. far back as the nostril, ' Pferosawria,' PI. 1, fig. L In the Pterodacft/Jus crassirostris* , (ib. fig. 2,) on the other hand, the jaws are short, thick and obtusely terminated ; and the alveoli of the upper jaw reach as far back as the middle of the cavity which intervenes between the nostril and the orbit, and which Goldfuss terms the " cavitas ntiermedia." In the solid or imperforate part of the upper jaw anterior to the nostril the Pterodacti/lus longirostris has twelve long subequal teeth, followed by a few of smaller size : the same part of the jaw in the Fter. crassirostris has but six teeth, of which the first four are close together at the end of the jaw, and the first three shorter than the rest. The " cavitas intermedia" in P. longirosfris is much smaller than the nostril : in the P. crassirostris it is larger than the nostril. Were these two species of dentirostral Pterosauria to be taken, as by the modem Erpetologist they assuredly would, to be types of two distinct genera, the name Pterodacti/lus should be retained for the longirostral species, as including the first-discovered specimen and type of the genus ; and the crassirostral species should be grouped together under some other generic name. Pterodactylus CuviERi, Bowerhanh. 'Pterosauria,' Plate 3, figs. I — 7 ; Plate 4, figs. 1 — 3. 'Proceedings of the Zoological Society,' January 14th, 1851. The specimen of gigantic Pterodactyle, exhibited and so named by Mr. Bowerbank at the meeting of the Zoological Society, January 14th, 1851, and which he has confided to me for description in the present Monograph, consists of the solid anterior end, i. e., of the impei'forate continuous bony walls, of a jaw, compressed, and decreasing in depth, at first rapidly, then more gradually, to an obtusely pointed extremity. As the symphysis of the lower jaw is long and the original joint oblite- rated, and its depth somewhat rapidly increased by the development of its lower and back part into a kind of ridge in some smaller Pterodactyles, the present specimen, so far as these characters go, might be referred to the lower jaw, and its relatively inferior depth to the upper jaw in the Pter. giganteus, would seem to lead to that conclusion. But the present is plainly a species which has a relatively longer and more slender snout, and the convex curve formed by the alveolar border, slight as it is, decides it to be part of the upper jaw. The lower jaw, moreover, might be expected by the analogy of the smaller Pterodactyles to be flatter or less acute below the end of the symphysis. The specimen of Pferodactijlm Cuvieri consists of the anterior extremity of the upper jaw of seven inches in extent, without any trace of the nasal or any other * Goldfuss, Beitrage zur Kenntniss Verschiedener Reptilien der Vorwelt, 4to, 1831, sec. i. Tabs, vii, viii, ix. CRETACEOUS PTERODACTYLES. 243 natural perforation of its upper or lateral parietes, and corresponds with the parts marked a, b, PI. 1, figs. 1 and 2. From the number of teeth contained in this part, the Pter. Ciwieri presents a much closer resemblance to the Pter. longirostris, (ib., fig. 1,) than to the Pter. crassirostris, (ib., fig. 2;) and, if the entire skull were restored according to the proportions of the Pter. longirostris, it would be twenty- eight inches in length. But nature seems never to retain the same proportions in species that differ materially in bulk. The great Diprotodon, with the dental and cranial characters of a Kangaroo, does not retain the same length of hinder limbs as its living homologue ; the laws of gravity forbid the saltatory mode of locomotion to a Herbivore of the bulk of a Rhinoceros ; and accordingly, whilst the hind legs are shortened, the fore limbs are lengthened, and both are made more robust in the Diprotodon than in the Kangaroo. The change of proportions of the limbs of the Sloths is equally striking in those extinct species which were too bulky to climb : e. g., the Megatherium and Mylodon. We may therefore infer, with a high degree of probability, when a longi- rostral Pterodactyle much surpassed in bulk the species so called " par excellence," that the same proportions were not maintained in the length of the jaws, and that the species to which the fine fragment, (PL 3, fig. 1,) belonged, far as it has exceeded our previous ideas of the bulk of a flying reptile, did not sustain and carry through the air a head of 2 feet 4 inches in length, or double the size of that of the Pelican. We see, in fact, that the size of the teeth was not increased in the ratio of that of the jaws. Although the fractured hinder part of the jaw shows no trace of the commence- ment of the wide nasal aperture, there is a plain indication that the jaws were less prolonged than in the Pt. longirostris, in the more rapid increase of the depth of the jaw. Opposite the ninth tooth, e.g., the depth of the jaw equals two fifths of the length of the jaw in advance of that tooth, whilst in the Pt. longirostris it is only two sevenths. The contour of the upper border of the jaw in the Pterodactglus Cuvieri differs from that in both the Pt. longirostris, Pt. crassirostris, and Pt. Gemmingi, in sinking more suddenly opposite the ninth, eighth, and seventh teeth, than along the more advanced part of the jaw — a character which, while it affords a good specific distinction from any of those species, indicates the hinder parts of the head, that are wanting in the present specimens, to have been shorter, but relatively much deeper, than in the Pt. longirostris. The first pair of alveoli (figs. 1 and 4, a) almost meet at the anterior extremity of the jaw, (PI. 3, fig. 3,) and their outlet is directed obliquely forwards and downwards ; the obtuse end of the premaxillary above those alveoli is about two lines across. The palate, (ib., fig. 4,) quickly expands to a width of three lines between the second alveoli ; then to a width of four lines between the fourth alveoli ; and more gradually, after the ninth alveoli, to a width of six lines between the eleventh alveoli, a! .■ here the palate appears to have been slightly crushed ; but in the rest of its extent it 244 BRITISH FOSSIL REPTILES. presents its natural form, being traversed longitudinally by a moderate median ridge, on each side of which it is slightly concave transversely. It is perforated by a few small irregular vascular foramina ; but the bony roof of the mouth is continued for an extent of six inches without any trace of its interruption by the naso-palatal aperture. There are no orifices on the inner side of the alveoh : the successional teeth, as will be presently shown, emerge as in the Crocodile, from the old sockets, and not as in certain Mammals and Fishes, by foramina distinct from them. The second and third alveoli are the largest ; the fourth, fifth, and sixth the smallest, yet they are more than half the size of the foregoing ; with which the rest are nearly equal. The outlets of the alveoli are elliptical, and they form prominences at the side of the jaw, or rather the jaw there sinks gently in between the alveoli, and is con- tinued into the bony palate, without any ridge, the vertical wall bending round to form the horizontal plate. The greatest breadth of the under surface of the jaw, taken from the outside of the alveoli, varies only from seven lines across the third pair to nine lines across the eleventh pair of alveoli ; and from this narrow base the sides of the jaw converge with a slight convexity outwards at the anterior half of the fragment, but are almost plane at the deeper posterior half, where they seem to have met at an acute superior ridge ; indeed, such a ridge is continued to within an inch of the fore pai't of the jaw, where the upper border becomes more obtuse. The whole portion of the jaw consists of one uninterrupted bone — the pre- maxillary ; the delicate crust of osseous substance, as thin as paper, is traversed by many irregular cracks and fissures, but there is no recognizable suture marking off the limits of a maxillary or nasal bone. The bone offers to the naked eye a fine fibrous structure, so fine as to produce almost a silken aspect : the fibres or striae being longi- tudinal, and impressed at intervals of from two to six lines by small vascular foramina. The first socket on the right side contains a young tooth which protrudes about a third of an inch obliquely downwards and forwards, (fig. 1, a ••) the fifth socket on the right side and the eighth on the left contain the germ of a younger tooth, the point of which does not protrude beyond the socket ; it lies close to the inner wall of the socket of the old tooth, from which it would have emerged, as in the Crocodile. Two fully developed teeth, (figs. 5 and 6,) are preserved in the same block of chalk with the jaw. One of these is 1 inch 4 lines in length, sabre-shaped, subcompressed, slightly bent, and gradually diminishing in breadth from the widely-open base to the apex : this part is broken off in both specimens, showing the crown to be composed of a compact hard dentine, sheathed by a thin coat of shining enamel : about 9 lines of the basal part of the present tooth, (fig. .5,) is coated by a thin layer of cement. The enamel is marked by extremely fine longitudinal ridges, with an irregular or thready course, of unequal length and with wide intervals, as shown in the magnified view, (fig. 7.) The second, (fig. 6,) is a somewhat smaller tooth ; having the same structure. The unique specimen above described was obtained from the Burham Chalk-pit, Kent, and forms part of the fine Collection of James S. Bowerbank, Esq., F.R.S. CRETACEOUS PTERODACTYLES. 245 Ptkrodactylus giganteus, Bowerhank. ' Pterosauria' Plate 6. Ptekodactylus giganteus. Bowerhanh. Proceedings of the Geological Society, May 14, 1845; in the 'Quarterly Journal of the Geological Society,' February, 1846. — CONIEOSTEIS. Owen. Dixon's ' Geology and Fossils of the Tertiary and Cretaceous Formations of Sussex,' 4to, p. 401, T. XXXVIII. This specimen consists of the upper jaw, as far as the commencement of the nostril, (PI. 6, fig. 2, w,) with the corresponding part of the lower jaw. The upper jaw is a subcompressed, three-sided cone, with a more obtuse apex than in Ptero- dactylus Cuvieri, and more rapidly and regularly increasing in depth as it approaches the nostrils, the sides converging at an acute angle as they ascend from the alveolar border, arching over the apex of the jaw, but meeting within an inch from this part at a ridge, which is rather more obtuse than that in Pt. Cuvieri, and formed at a somewhat less acute angle, (figs. 3 and 4.) The surface of the bone appears naturally to have been less even or level than in the larger species, and the thin osseous plate is similarly fissured and cracked. The part appears, however, to have suffered little compression ; the palate, where it is exposed at the back part of the jaw, being entire, and presenting a concave longitudinal channel on each side of a prominent median ridge : its breadth opposite the ninth alveolus is 8 lines ; the depth of the jaw at that part being 14 lines ; the breadth of the base of the jaw, there, outside the alveoli, is 1 1 lines. The sides of the jaw are plane, but sink in a little between the alveoli, where they become continuous with the palatal surface. The alveolar border of the jaw is slightly convex lengthwise along its anterior third, and is continued straight along the rest of its extent. There are ten pairs of alveoli in the part of the upper jaw anterior to the bony nostril, the alveoli being separated by intervals about equal to their own diameter. In the Pt. Cuvieri there are at least twelve pairs of alveoli anterior to the nostril, and there may have been more, as there are in the Pt. longirostris. In the Pt. crassirostris there are only six pairs of alveoli in the corresponding part of the upper-jaw, and the fourth, fifth, and sixth, are separated by intervals of thrice the diameter of the alveolus. Such characters as these place in a strong hght the specific distinctions of the Pterodactyli compared. The species under consideration exemplifies in the Cretaceous epoch the crassirostral group of the older secondary Pterosauria, as the gigantic Pt. compressirostris docs the longirostral group ; the Pt. Cuvieri approaches nearer a middle term between the two types of the groups in question. The length of the jaw anterior to the nostril in the Pt. crassirostris, described by Goldfuss,* is 13 lines, * Nova Acta Acad. Nat. Cur., torn, xv, pt. i, p. 63. (See Plate 1, fig. 2.) 246 ' BRIIISH FOSSIL REPTILES. that of the Pt. giganteus is 2 inches 3 Hncs ; the total length of the head of the Pt. crassirostris is 4 inches 8 lines, that in the Pt. giganieus, restored on the same scale, would be 9 inches, and the proportions on which this calculation is made are much more likely to have been maintained, than those of the Pt. longirostris in reference to the more gigantic Pt. Cuvieri ; but the teeth are absolutely shorter, and relatively much smaller, than in the Pt. crassirostris. The lower jaw, fig. 5, has an obtuse rounded termination anteriorly like the upper one, fig. 4, but is a little narrower there, and is flatter, its under part being less convex than the corresponding exposed part of the upper jaw is above : the median inferior ridge behind this part is more suddenly developed than that upon the upper jaw, and the progressively deepening sides of the lower jaw are bent inwards before they form the ridge, being convex near the alveoli, and becoming concave at the base of the ridge, in the transverse direction : and this modification does not appear to be the result of accidental pressure. The sohd or confluent symphysis has an extent of more than 2 inches, but the bone is too much broken away at its back part to determine its precise extent: it is evident, however, that the rami diverging from it were of less vertical extent than the ridged part of the symphysis from which they diverge, and this character is also shown in the lower jaw of the Pt. longirostris, and Pt. Gemmingi. On the right side of the lower jaw, which is best preserved, there are nine alveoli, and part of a tenth, corresponding in size and spacing with those above. The inner alveolar wall extends so far inwards, horizontally, that if discovered alone, it might well be mistaken for the palatal plate of an upper jaw. It is not united with that of the opposite side to an extent corresponding with the bony palate above ; but to what extent the symphysis of the jaw is continued backwards, the specimen does not allow to be precisely determined. This broad inner alveolar plate of the lower jaw is slightly concave transversely, forming a wide longitudinal channel about two lines and a half in breadth along the inner side of the alveolar border : to the extent to which it may be united to the opposite plate, a median longitudinal ridge will be formed dividing the two channels ; and presenting a structure closely corresponding with that of the palate above. The teeth are preserved, in situ, in some of the alveoli, of both the upper and lower jaws. The enamelled crown is a less elongated and narrow cone than in either the Pt. Cuoieri, or the Pt. crassirostris, and it is less compressed ; it does not exceed one line and a half in length. The fang is longer, and after a slight expansion main- tains the same diameter, or contracts a little towards its basal termination. The smooth polished coronal enamel shows the same extremely fine raised striae, with an irregular course and wide intervals, as in the teeth of Pt. Cuvieri. The basal cement has a more irregular external surface. The fractured tooth in the sixth alveolus of the left side shows well the form of the transverse section at the base of the crown, and the proportional size of the pulp-cavity. This, as usual, is occupied by a sparkling CRETACEOUS PTERODACTYLES. 247 siliceous spath. I am not at present aware of any species of Pterodactyle in which the teeth are so short and thick as in the Pf. giganteus, (see the magnified view, fig. 6.) Those figured in PI 27, Vol. iii., 2d Series, of the ' Geological Trans- actions,' on the supposition that they might belong to the Pterodactyle, appertain to a species of Fish. The point of a successional tooth projects from the fore part of the ninth socket on the right side of the upper jaw, from which its predecessor has fallen ; proving, as in the larger species, that the crowns of the successional teeth do not emerge, as Cuvier surmised to be the case in Pt. longirostrls,^ from a distinct orifice on the inner side of the socket of the old tooth, as in the Mammalia. The substance of the osseous walls of the above-described portions of jaws is as thin and delicate as in the foregoing species : it does not present the same fine longitudinally striated surface as in the Pt. Cuvieri ; but it is similarly perforated by numerous minute vascular foramina, which are largest and most abundant near the alveolar border at the fore part of the jaw. The unique specimen above described was discovered in the Burham Chalk-pit, Kent, and is in the Collection of James Scott Bowerbank, Esq., F.R.S. Scapular Arch and Bones of the Extremities of the Pterodactylus GIGANTEUS, Boioerhanlc. ' Pierosauria,' PI. 6, figs. 7, 8, 9, 10 — 13. Perhaps no part of the skeleton of the Pterodactyle more closely resembles in form that of the bird, than the scapular arch : and in no specimen has this arch been better preserved than in the Pterodactylus macronyx.^ The scapula is shown in those specimens to be long, sabre-shaped, and to form a moiety of the articular concavity for the head of the humerus, and the coracoid to be stronger, straighter, and shorter than the scapula, and with a subbifid protuberance near the articular surface for the humerus : the opposite end of the coracoid terminates by a rather oblique truncation, but without expanding : both the elements of the arch are anchylosed together, where they meet at rather an acute angle to form the shoulder-joint. In the Pt. crassirostrisX the two bones appear not to have been anchylosed, the more slender and slightly curved bone, 17, in Prof. Goldfuss's plate, is called the coracoid, the stronger and straighter one, 16, the scapula : but this determination seems to have been based upon the crushed specimen, in which there has been sufficient displacement of parts to render it very probable that the scapula and coracoid have suffered some change of position : the fore part of 1 7, which I believe to be the scapula, shows a tuberosity near the articular end, which forms an angle between that and the shaft of the bone : the coracoid, ic, * Ossemens Fossiles, torn, v, pt. ii, pp. 3S4, 3G7. t See Dr. Buckland's Memoir, 'Geological Transactions,' 2d Series, vol. iii, pi. xxvii, X, 9; and Vou Meyer, in tlie 'Nova Acta Acad Nat. Curios, torn, .tv, pt. ii, Tab. Ix, fig. 8. X Goldfuss, ut supra, T. VII, 16, 17. 248 BRITISH FOSSIL REPTILES. exhibits a stronger tuberosity near the same part; the sternal end of this bone is sHghtly expanded and rounded. The length of the scapula is rather more than one- third of that of the entire skull. In the same block of chalk as that which contained the fore part of the jaws of the Ft. giganteus, is preserved the confluent extremities of the right scapula and coracoid, one third larger than the coiTesponding parts in the Ft. crassirostris, and one-fourth larger than those in the Pf. macronyx. The portion of scapula, (PI. 6, figs. 7 and 8, 51,) includes thirteen lines of the humeral end of that bone ; the fractured part of the body showing that part to be subcompressed, with the side next the ribs slightly concave, the opposite side convex ; the long diameter of this section of the bone is 3 lines ; its short diameter 1 line ; it expands as it approaches the shoulder joint, and developes an obtuse oval tubercle, a, from its upper and inner border about 4 lines from the articular end ; a low acromial ridge is extended from the outer side of the bone, from near the origin of the tubercle, to the outer and fore part of the glenoid cavity : the inner and posterior border is expanded into a third ridge which joins a corresponding one from the same part of the coracoid. Of this bone, 52, about ten lines is preserved : the transverse section exposed at the fractured end is oval, and measures 3^ lines by 2 lines ; the expansion of the bone to form the shoulder- joint is rapid. Besides the ridge sent off from the inner and back part to join the one above mentioned from the scapula, there is a much stronger process, c, developed from the under and fore part of the coracoid, as in that of the Ft. macronyx, between which and the glenoid surface the bone is perforated by a narrow canal, the inner outlet of which is just above the inner ridge. If we carry forwards the two straight lines respectively parallel with the outer borders of the scapula and coracoid, they will meet at an angle somewhat less acute than those in the Ft. macronyx. By a trace of the original suture we may see that the coracoid has formed about two thirds of the glenoid cavity, (fig. 7, g .) the long diameter of that cavity measures 6 lines, its short diameter 2>\ lines ; in the direction of which it is flat above and slightly convex below ; being concave only in the direction of its long axis ; its contour is reniform, the convex border being extended upon the acromial ridge. The long diameter of the glenoid cavity in the Ft. macronyx measures 4 lines ; and the absence of the tuberosity on the scapula makes that end of the bone relatively more feeble than in the present instance. As the parts are fully one third larger than those in the Ft. crassirostris, we may estimate the skull of the present species according to the pro- portions of the scapula to the skull in Ft. crassirostris, as having been about 7 inches in length. Both the scapula and coracoid are hollow, the cavity being surrounded by a very thin compact wall, and being subdivided by a few much thinner plates. There is a fragment of a bone, (PI. 6, fig. 9,) in the same block of chalk, which, from its rapid expansion, I am induced to suspect to be part of the sternum: its thickest part presents a coarse cancellous structure : from this part it expands into a thin plate, of which, however, not enough remains to indicate its original form. CRETACEOUS PTERODACTYLES. 249 Several portions of long bones figured in PI. 6, may well belong, by their size, to the same species as the portion of jaws, figs. 1 and 2, in the same plate : two of them, figs. 11 and 12, are from a different locality, Hailing pit, but from the same formation — the Middle Chalk of Kent. As all these fragments, however, consist only of the simple hollow shaft, I shall proceed with the description of the better preserved specimens from the chalk which are referable to the genus Pterodadylus. Pterodactylus compressirostkis, Owen. ' Pterosauria,' Plate 3, figs. 8, 9, and 10. This species is represented by two portions of the upper jaw, obtained from the Middle Chalk of Kent, the hinder and larger of which includes the beginning of the external nostril, (fig. 8, n.) The depth of the jaw at this part is 14 lines, whence it gradually decreases, so as, at a distance of 3 inches in advance of this, to present a depth of 10 lines, indicating a jaw as long and slender as in the Pterodacti/lus lon(/irosfris, (PI. 1, fig. 1,) supposing the same degree of convergence of the straight outlines of the upper and alveolar borders of the jaw to have been preserved to its anterior end : that this was actually the case is rendered most probable by the proportions of the smaller anterior part of the jaw, (PI. 3, fig. 8' and 9',) obtained from the same pit, if not from the same block of Chalk, and which, with a vertical depth of 7 lines at its hinder part, decreases to one of 6 lines in an extent of 1^ inch in advance of that part. The sides of the jaw as they rise from the alveolar border incline a little outwards before they converge to meet at the upper border. This gives a very narrow ovoid section at the fore part of the larger fragment (fig. 9*), the greatest diameter, at its lower half, being 4 lines, and the sides meeting above at a slightly obtuse ridge. This very gradually widens as the jaw recedes backwards, where the entireness of the walls of the smoothly convex upper part of the jaw proves that the narrowness of that part is not due to accidental crushing. Had that been the case, the thin parietes arching above from one side to the other would have been cracked. The only evidence of the compression to which the deep sides of the jaw have been subject is seen in the bending in of the wall above the alveoli, close to the upper ridge, at the fore part of the fragment, in the crushed state of the palate at that pail, and in a slight depression of the left side of the jaw anterior to the nostril. In an extent of alveolar border of 3^ inches, there are eleven sockets, the anterior one on the right side retaining the fractured base of a tooth : the alveoli are separated by intervals of about one and a half times their own diameter ; their outlets are elliptical, and indicate the compressed form of the teeth : they are about 2 lines in long diameter, at the fore part of this fragment, but diminish as they are placed more backwards, the last two being developed beneath the external nostril. 250 BRITISH FOSSIL REPTILES. The bony palate is extremely narrow, and presents, in the larger portion, fig. 10, a median smooth convex rising between two longitudinal channels, which are bounded externally by the inner wall of the alveolar borders. There is no trace of a median suture in the longitudinal convexity. The breadth of the palate at the back part of the fragment is 8 lines, at the fore part it has gradually contracted to less than 3 lines, but it is somewhat crushed here, (fig. 10, a.) The naso-palatine aperture commences about half a line in advance of the external nostril, 3 inches behind the fore part of the larger portion of the skull : its form and extent, so far as it is preserved, are accurately shown in fig. \0,p, and it well exemplifies, in this specimen, the charac- teristic extent of the imperforate bony palate formed by the long single premaxillary bone in the present order of Saurians. The fragment from the more advanced part of the jaw, fig. 8, contains five pairs of alveoli, in an extent of 2 inches, these alveoli being rather larger and closer together than in the hinder part of the jaW; Owing to the compression which the present portion has undergone, the orifices of the alveoli are turned outwards ; the bony palate being pressed down between the two rows, and showing, probably as the result of that pressure, a median groove between two longitudinal convex ridges ; but the bone is entire and imperforate. The form of the upper jaw in the present remarkable species diifers widely fi'om that of the two previously described specimens from the Chalk, in its much greater elongation, its greater narrowness, and from the Pi. Cuvieri, more especially, in the straight course of the upper border of the jaw, as it gradually converges towards the straight lower border in advancing to the anterior end of the jaw. The alveoli, and consequently the teeth, are relatively smaller in proportion to the depth of the jaw than in the Pt. Cuvieri, and are more numerous than in the Pt. (jiyanteus : they are, probably, also, more numerous than in the Ft Cuvieri; although, as the whole extent of the jaw anterior to the nostril is not yet known in that species, it would be premature to express a decided opinion on that point. As we may reasonably calculate from the fragments preserved, (PI. 3, figs. 8 and 8',) that the jaw of the Pterodactylus compressirostris extended seven inches in front of the nostril, it could not have contained less than twenty pairs of alveoli, according to the number and arrangement of those in the two portions preserved. The osseous walls in both portions present the characteristic compactness and extreme thinness of the genus : the fine longitudinal striae of the outer surface are more continuous than in the Pt. Cuvieri, in which they seem to be produced by a succession of fine vascular orifices produced into grooves. The conspicuous vascular orifices are almost all confined to the vicinity of the alveoli in the Pt. compressi- rostris. This species belongs more decidedly than the Pt. Cuvieri to the longi- rostral section of the Fterosauria : whether it had an edentulous prolongation of the fore part of the upper and lower jaw, as in the Ft. Gemminffi, remains to be proved. CRETACEOUS PTERODACTYLES. 251 In attempting to form a conception of the total length of the head of the very remarkable species of Pterodactylc, represented by the portions of jaw above described, we should be more justified by their form in adopting the proportions of that of the Pt. longirostris than in the case of the Ft. Cuvieri : but, allowing that the external nostril may have been of somewhat less extent than in the Pt. lonrjirostris, we may still assign a length of from 14 to 16 inches to the skull of the Pterodactyle in question, of which I have attempted an analogical restoration in ' Pterosauria,'' PI. 1. It could not have been anticipated that the first three portions of Ptcrodactylian skull, and almost the only portions that have yet been discovered in the Cretaceous Formations, should have presented such well-marked distinctive characters one from the other as are described and illustrated in tlie present Work. Such, nevertheless, are the facts ; and however improbable it may appear, on the doctrine of chances, to those not conversant with the fixed relations of osteological and dental characters, that the three corresponding parts of three Pterodactyles, for the first time discovered, should be appropriated to three distinct species, I have no other alternative, in obedience to the indications of Nature, than to adopt such determination. The portions of the skull of the Plerodactt/lus cotnpressirostris, like those of the Pt. Cuvieri and Pt. r/if/anteus, were discovered in the Chalk-pit at Burham, Kent, and are in the Collection of James Scott Bowerbank, Esq., F.R.S., to whose skill is due the exposure of the palatal surface and the left side of the portion of the jaw, figured in PL 3, figs. 8 and 10. Long Bones of Pterodactylus Cuvieri. ' Pterosauria,'' Plate 4, figs. I, 2, and 3. The bone which, from its size, and from the character of its external surface may be, with most probability, referred to the largest of the above-defined species of Cretaceous Pterodactyles, is that which forms the subject of figures 1, 2, and 3, PI. 4. It was discovered in the Chalk-pit, at Burham, Kent, and is now in the Collection of J. Toulmin Smith, Esq., of Highgate. The length of the bone in proportion to its thickness is too great to be compatible with its being the humerus ; it indicates it to be either one of the antibrachial bones, or, more probably, from its similarity in shape to the long bones of most frequent occurrence in smaller species, the first or the second phalanx of the elongated wing-finger. One end of the bone is nearly entire, the other end is wanting, the total length of the specimen being 14^ inches. The longest diameter of the preserved extremity is 2 inches 3 lines, whence the shaft decreases to a diameter, in the same direction, of 1 inch, and then more gradually expands to a diameter of 1 inch 3 lines at the fractured end. Tlie shaft soon assumes a triedral figure, with the angles rounded ofi", and the breadth of the narrowest side is shown in fig. 3. The contour of the best 253 BRITISH FOSSIL REPTILES. preserved end is shown at fig. 2*, where a and h may give the form and position of natural articular surfaces, but there seems to have been some slight restoration here : c is a vacuity where the bone is deficient : the contour of the border of the bone at a, fig. 2, which is obviously entire, satisfactorily indicates, however, the concavity of the articular surface as shown at a. This, were the bone an ulna or a phalanx of the wing-finger, would determine the end preserved to be a proximal one : but, if the bone were a radius, the concavities a and b might be adapted to some of the small carpal bones. The presence of a pneumatic foramen, at p, figs. 1 and 3, would seem, however, to show the extremity near which it is situated to be a proximal one, and if any trust could be jjlaced in the analogy of the bones of birds, the position of this pneumatic foramen, with the double articular concavity, a and b, and the three-sided shape of the shaft, would concur in leading to a reference of the bone to the ulna. The side of the expanded proximal end shown in fig. 2 is slightly convex : that shown in fig. 1 is almost flat : whilst the pneumatic foramen is situated in a deep and narrow concavity or groove which forms the beginning, or the end, of the narrowest of the three sides of the shaft of the bone ; but the concavity is speedily changed, as it passes down the shaft, for a convexity, which subsides to a flattened surface at the middle of the shaft, as shown in fig. 2. The broadest side, shown in fig. 2, becomes flattened in the shaft of the bone : the transverse section of which, four inches from the entire end, is shown in fig. 3*, which gives the thickness of the compact osseous walls of the large air-cavity of the shaft : the thickness of these walls is also shown at their fractured borders in figs. 1, 2, and 3 ; it exceeds, as might be expected, that of the similarly sized pneumatic wing-bones of the gigantic Crane and Pelican. The character of the surface of the bone closely resembles that of the portion of the jaw of the Fterodactijlas Ciwieri. Long Bones of Pterodactylus compressirostris. ^ Pterosauria,' Vlaies, 2 and 4, figs. 4 and 5. In the reference of the long bones from the same locality or division of the Chalk Formations as those from which the jaw-bones of the Pterodactyles have been derived, the chief guide, at present, is the relative size of the parts. It is not likely that one can err in associating the largest specimens of the wing-bones, such as that above described, with the Pterodactyle with the largest and strongest jaw, especially when we find the same fine furrows and foramina giving a silky appearance to the surface of both. The smaller specimens seem by their more compact and smooth surface to belong to the smaller species ; but they may have been parts of smaller or younger individuals of the larger species : this, however, is the least likely of the conjectures to which, in the detached and fragmentary condition of the parts of the skeletons of these huge-winged CRETACEOUS PTERODACTYLES. 253 reptiles that have hitherto reached us, we are reduced in the attempts at their restoration. In a mass of wliite chalk, about thirteen inches in length, in the collection of Thomas Charles, Esq., are imbedded three portions of long-bones ; one of these (PI. 2, fig. ],) is seven inches in length, and shows a crushed articular extremity, 2 inches 2 lines in diameter, the shaft at the opposite fractured extremity being 1 inch 3 lines in the longest diameter ; a second fragment (PI. 2, fig. 3,) is 6 J inches in length, with a diameter of 8 lines at its smaller fractured end, and a diameter of 1 inch 3 lines at its larger fractured end, to which it gradually expands ; the third jiortion (fig. \, a a,) may be a part of the same bone, as fig. 3 ; it extends from close to the smaller fractured end of that bone in the opposite direction, but in the same line, gradually expanding ; its length being 5 inches, and its diameter at the broader fractured end about one inch. The largest portion of bone (PI. 2, fig. 1,) presents at its expanded end two surfaces, divided by a strong ridge, about one inch in length, the prominent summit of which has been broken away. One of the surfaces is three times the breadth of the other and is slightly concave transversely, becoming flat as it recedes from the ridge to the tuberosity which terminates the end of the bone furthest from the ridge. This tuberosity is subcompressed ; many linear impressions, indicative of the insertion of an aponeurosis or ligament, radiate from it upon the flat surface of the bone : a slight concavity on the end of the bone bounds the tuberosity opposite to the ridge ; the rest of that end, including the articular surface, is, as usual, destroyed. The second surface is flat, and slopes away at an open angle from the broader one. Below these surfaces, the outer layer of the thin, compact, osseous wall, has scaled ofi", and the shaft has been fractured across obliquely, about three inches from the expanded end. The thin wall of the shaft is then continued in broken portions for about three inches lower down, and the rest of the shaft is represented by the cast of its interior in the white chalk. This cast shows, on the surface which was next the bone, several impressions, chiefly in an oblique direction, and nearly parallel with one another ; they are shallow and smoothly rounded at the bottom, and may be presumed to have been left by ridges on the inner surface of the medullary or pneu- matic cavity of the bone : blood-vessels merely would have perished before the chalk, which must have been introduced into the cavities of these bones in a soft state, could have hardened sufficiently to retain the impression. With regard to the two other fragments, which are probably parts of an anti- brachial bone of the same wing, there is even less character to be obtained from an articular end than in the preceding fragment. On the supposition that the two portions belong to the same bone, it must have been upwards of fourteen inches in length. In the portion, PI. 2, fig. 3, a part of the inner surface of the thin com- pact wall of the medullary cavity of the bone is exposed : its smoothness is broken by feeble linear elevations, which are reticularly disposed : it is in appearance very 254 BRITISH FOSSIL REPTILES. similar to what may bo seen on the smooth inner surface of an air-bone in a large flying-bird, the Pelican or Adjutant Crane, for example : but it is not peculiar to bird's bones. I find something of the same character on the smooth inner surface of the medullary cavity of the tibia of a young gavial, and on the same inner surface in a femur of a lion ; only here there are minute vascular perforations lead- ing to the thick parietes of the bone, which do not exist in the bird's bone, or in the fossil in question. The enlarged end of the portion of bone, PL 2, fig. 3, shows evidence of a light open cancellous structure. The thickness of the compact wall of the large medullary cavity does not exceed half a line, as is shown in fig. 3 ; it is a little thicker towards the smaller end of the large bone, figure 1 . In neither case does it exceed the thickness of the shaft of the humerus or ulna of the Pelican. The transverse section of the smaller end of the portion of the largest bone, PI. 2, fig. 1, is a moderately long ellipse, rather more pointed at one end than at the other, indicating an approach to something like a ridge or angle along the corresponding side of the bone. The transverse section of the slender part of the smaller fragments also gives a long ellipse. Neither of the bones show the three- sided figure which characterises the long bone ascribed to the Pferodacfi/hts Cuvieri, PI. 4, figs. 1 — 3, or that, fig. 4 of the same plate, originally figured in the ' Geological Transactions,' 2d series, vol. vi, PI. 39, fig. 1. The bone with which the larger portion, fig. 1 , PL 2, is best comparable, is the humerus, of which it may be the distal portion ; but much is wanted in order to attain to a satisfactory determination of it. On the supposition that it is part of the humerus, and that the other two portions on the same block of chalk are parts of one bone, this bone may be the shaft of the radius. PL 4, fig. 5, represents, of the natural size, in the same block of chalk, portions of two longitudinally juxtaposed bones, of nearly equal size, and of similar form, and in this respect resembling the radius and ulna of the Pterodactyle, as they are shown in the Pt. lonc/irostris of Colhni and Cuvier,* in the Pt. medius of Count Munster,t and in the Pt. crassirosfris of Goldfuss. | Of one of these bones an extent of upwards of nine inches is preserved in three successive portions, in the present specimen. About four inches of the other bone is preserved. Both this and the chief part of the adjoining bone gradually expand to the natural articular end, of which, however, only a small part is preserved in each, showing a shallow smooth concavity; this which is best preserved in the bone, fig. 5*, d, obliquely overlaps a small part of the longer bone. The long diameter of the extremity of the shorter portion of bone is one inch five lines ; from * Annales du Museum, t. xiii, pi. .31. f Xova Acta .\cad. Nat. Curios., vol. xv, pt. i, T. VI. : lb., T. Yll and VIII, 22, 23. CRETACEOUS PTERODACTYLES. 255 which the shaft gradually decreases to a diameter of nine lines. The side imbedded in the chalk is convex ; that exposed to view is nearly flat ; but it is somewhat crushed ; the longer portion of the other bone is also too much crushed to give an idea of its natural shape. Like the portions of bone in PI. 2, these also present a thin wall of compact bone encompassing a very wide medullary or pneumatic cavity ; the thickness of the wall equals that of the same part of the ulna of the Pelican; PI. 5, fig 1 . In the long bone, fig. 4, PI. 4, the original of the fig. 1, PI. 39, of the ' Geological Transactions,' 2d series, vol. vi, the natural shape of the bone is better preserved ; but, unfortunately, only one small portion of the articular surface is preserved at the expanded end, and this merely exhibits part of a shallow concavity, with a thin well-defined border, fig. 4*, a- From this articular end to the opposite fractured end of the shaft, the bone measures twelve inches. The breadth of the expanded end is one inch and a half, whence the shaft gradually diminishes to a diameter of nine lines at its middle part, and more gradually increases to a diameter of eleven lines at the broken end. The bone is very slightly bent lengthwise at its expanded end ; it is straight in the rest of its extent ; its shaft is unequally three-sided, with the sides smooth and flat, and the angles rounded off. The compact osseous wall is about the third of a line in thickness, and incloses, as in the other specimens, an uninterrupted wide cavit3^ One of the sides of the bone equals the extreme breadth of the shaft; a second measures seven lines across, the third five lines ; the second side increases in breadth, at the expanded end, in a much greater degree than the third or narrowest side ; and this seems to have been indented by a natural fossa, and to have been perforated, atj9, for the admission of air to the cavity, before terminating at the border of the articular concavity, 'ilie true nature of this perforation, which I formerly apprehended might be accidental in the fractured state of that end of the bone, and before the discovery of other specimens, is illustrated by the presence of a similar perforation in the larger sized corresponding bone fig. I, p; and gives additional evidence of the remarkable fact of the agreement of some of the flying-reptiles with birds in the extension of the air-cells into the cavities of the bones. PI. 2, fig. 2, is the terminal portion of a long bone, with the articular end again unfortunately destroyed, so as to deprive us of one of the best guides to the determination of the fragment. So much of it as is preserved corresponds pretty closely with the proximal end of the foregoing bone : it is subtriedral, with the angles rounded off; the broadest side is imbedded in the chalk ; the expansion of the exposed surface is chiefly due to that of the next broadest side ; and the narrowest side, as it approaches the articular end, is impressed by a deep and narrow fossa, in which there is an interruption of the thin walls of the bone in the corresponding position of that, which, in the foregoing specimens, I have called a "foramen pneumaticum." A portion of the bone indicates the extension of a process beyond the articular cavity, which 256 BRITISH FOSSIL REPTILES. is a character of the proximal end of tlie first phalanx of the wing-finger, but no part of the articular surface has been preserved. A similar portion of the corresponding bone of the opposite wing is figured in PI. 5, fig. 2, and the more frequent occurrence of long bones with the subtriedral shaft, showing a contraction and deepening of the narrowest of the three sides towards one of the expanded ends of the bone, and the presence of the pneumatic foramen in the groove so formed, would indicate them to be one of those bones that are present in greatest number in the framework of the wing of the Pterodactyle, viz., phalanges of the singularly long and strong wing-finger. The fragment of the shaft of a bone, with a wide cavit}^, PI. 5, fig. 3, shows a different shape from most of the long bones above described ; its transverse section is given at fig. 3' ; and from its shape, and the presence of a longitudinal ridge at one side of the flatter and probably posterior part of the shaft, I am inclined to regard it as having been part of a femur ; it bears the same proportion to the diameter of the humerus, PI. 2, fig. 1, as the femur of the Pterodadylm crassirostris does to the humerus, in the beautiful plates of the Memoir by Goldfuss, above quoted. The fragments of long bones, with the best preserved articular extremity, are those represented of the natural size in PI. .5, figs. 4 and 5, the former of which was originally figured in the ' Geological Transactions,' 2d Series, vol. vi, pi. 39, fig. 2, the latter in the ' Quarterly Journal of the Geological Society,' vol. iv, pi. ii, fig. 4. Both these bones offer the closest resemblance to the trochlear modification of the lower end of the tibia in the bird ; and, if we might presume on that analogy, it would be to the same bone in the gigantic Pterodactyle, that we should, also, refer them, with the present indubitable evidence of the existence of volant reptiles of such dimensions in the formation and localities whence the specimens in question have been derived. But it is not likely that a reptile with distinct tarsal bones would have the same modification of the distal end of the tibia as in the bii'd, which does not possess them. The specimen which is the subject of fig. 5, in PL 5, was obtained by J. Toulmin Smith, Esq. from a chalk-pit near Maidstone, and has not suffered the degree of com- pression which distorts the specimen, fig. 4, PL 5, which was obtained by the Earl of Enniskillen from the same pit. The obliquity of the two parallel, convex, narrow condyles, which I suspected might be the effect of crushing in fig. 4, is shown to be natural in fig. 5 ; the back part of each condyle is broken away, but their antero- posterior extent is fortunately shown in fig. 4. The shaft is naturally compressed from before backwards, as is shown by the section, fig. b", and by the side view fig. 5'. There arc two depressions and two rough elevations on the surface of the bone, fig. 5, and between the latter a groove extends longitudinally, as if for the passage of a strong tendon ; the vacuity in the thin parietes of the bone above the condyle is, I am assured by Mr. Smith, a natural one, which he himselfexposed upon carefully removing CRETACEOUS PTERODACTYLES. 257 the chalk ; and it closely resembles the character of the " foramen pneumaticum" in a bird's bone, but I am not aware of any in that class which is situated on the back part of the distal end of the tibia. On the opposite side of the bone it presents a concavity, which, however, is deepened by the yielding of the thin parietes of the bone at that part. In the crushed specimen, fig. 4, the convex contour of the condyles bounding the deep trochlea, describes three fourths of a circle, and hitherto not any of the few well- preserved articular ends of the bones of the Ptcrodactyles have exhibited this structure. This remarkable trochlear joint may terminate either the femur, or the short and thick metacarpal bone of the wing-finger, from the degree of obliquity of the joint I incline to regard it as part of the latter. Figures 6 and 7, PI. 5, exhibit two portions of a long bone of a gigantic Pterodactyle from the Green-sand near Cambridge, the shaft of which repeats the same inequilateral triedral form as that of figs. 1 and 4, in PI. 4. The smaller fragment of Pterodactylian bone, also from the Green-sand of Cambridge, fig. 8, PL 5, indicates, by the strong and broad ridge, that it formed part of the proximal end of a humerus ; either of a younger individual, or of a species not larger than that called Pterodadylus giganteus, by Mr. Bowerbank, and of which some of the long bones are figured in PI. 6. The natural length of the difl^erent segments of the wing of the great Ptcrodactyles of the Chalk may be estimated, according to their proportions in better preserved specimens of the genus, if we can gain approximatively that of any one of the bones, and more especially of the humerus. Tliis I have endeavoured to do, with the following results. In the Fterodadi/lus macronyx, Pt. crassirostris, Pt. longirostris, the breadth of the distal end of the humerus equals rather more than one fifth of its length, and according to this proportion, the humerus, assigned to Pt. com2iressirostns, PI. 2, fig. 1, may be restored, and would give a total length of ten inches and a half. In the Pt. macronyx, the length of the humerus is equal to three fourths of that of the ulna ; in Pt. crassirostris it nearly equals one half ; in the Pt. longirostris it equals two thirds of the ulna ; in Pt. longicaudatus it equals three fifths of the ulna. Taking the mean of these proportions, which is nearly that in the Pt. longirostris, we may assign fifteen inches as the probable length of the antibrachial bones of the Pt. compressirosfris. If the bone, PI. 4, fig. 1, be the ulna of the Pt. Cuvieri, it must have been longer by some inches. The species of smaller Ptcrodactyles above cited show a greater difference in the proportions of the metacarpal bone of the wing-finger. In the Pt. macronyx this bone is one half the length of the humerus : in the Pt. longirostris it is at least of equal length with the humerus ; the Pt. crassirostris and Pt. longicaudatus come nearer the Pt. macronyx in the proportions of this bone : we may therefore assign, without hazarding an exaggeration, the length of six inches to both carpus and metacarpus of the Pt. compressirostris. 258 BRITISH FOSSIL REPTILES. With regard to the first phalanx of the wing-finger, this bone in Ft. macronyx is to the humerus as 31 to 26 ; in the Pt. crassirosfris it is as 22 to 16; in the Ft. loiiffirostris as 17 to 10; va.Ft.lonfficaudatusSiS2 to 1. In two of the above-cited species it is longer than the ulna, in the other two it is shorter : we shall probably not greatly err if we adopt the mean, and assign an equal length to the first phalanx with the ulna itself in the Ft. comprcssirostris, viz. fifteen inches. In the Ft. macroni/x the second phalanx of the wing-finger a little exceeds the length of the first : in the other species cited, it is a little shorter ; we may assign, therefore, a length of 14 inches to the second phalanx in the Ft. compressirostris. Supposing the long bone of the Ft. Cuvieri (PL 4, fig. 1) to be a phalanx of the wing-finger, it equals the dimensions above assigned to those of the Ft. compressirostris in its present mutilated state. With regard to the proportions of the third phalanx, the Ft. wacroni/x off'ers a marked difference from the three other species here compared : its length being to that of the first phalanx as 5 to 4, whilst it presents the reverse proportions in the rest. So likewise, with regard to the last slender pointed phalanx of the wing- finger, this exceeds the length of the penultimate phalanx in Ft. lon(/icaudatus, but falls short of that length in Ft. longirostris, the difference being very small in both cases : the last phalanx is not preserved in the specimen of the Ft. macronyx,* nor in that from which Professor Goldfuss has conjecturally restored the Ft. crassirostris.^ If we assume the penultimate and last phalanges of the Ft. comjivessirostris to have been of equal length, and restore them according to the- proportions of those of the Pt. longirostris, we may assign the length of 26 inches to the two bones ; but if the proportions of the Ft. macronyx were preserved in the gigantic species, the last two phalanges would be 30 inches in length. According to the former restoration the length of the bones of one wing, in a straight line, would be 7 feet 2 inches ; accord- ing to the latter restoration, 7 feet 6 inches. We may be assured that we are within the bounds of moderation in assigning an expanse of 7 feet to each wing of the smaller of the two great Pterodactyles of the Chalk, and supposing it to have had a breadth of chest from one humeral joint to the other of 1 foot, it would measure 15 feet from the tip of one wing to that of the other, an expanse of pinions rarely equalled, and still more rarely exceeded by the largest Albatross.;}: The FteroJactyliis Cuvieri was probably upborne on an expanse of wing not less than eighteen feet from tip to tip. * Geol. Trans., 2d Series, vol. iii, pi. xxvii. f Nova Acta Acad. Nat. Curios., torn, xv, pt. i, Tab. IX. \ Latham cites the following testimonies to the extent of the wings of the Albatross : — " Above ten feet, (Foster's Voyage, i, p. 8".) Ten feet two inches, called an enormous size, (Ilawkesworth's Cook'. Voy., iii, p. 627.) Eleven feet seven inches, (Parkinson's Voyage, p. 82.) Twelve feet, MS., at Sir Joseph Banks's. One in the Leverian Museum expanded thirteen feet ; and Ives mentions one, shot off the Cape of Good Hope, measuring seventeen feet and a half from wing to wing, (See Voyage, p. 5.)" (Latham's History of Birds, vol. x, p. 48, ed., 1824.) CRETACEOUS DINOSAURS. 259 CHAPTER VI. Order. DINOSAURIJ. Genus — Iguanodon. ' Dinosauria," Plates 1 — 5. Mr. W. H. Bensted, of Maidstone, the proprietor of a stone-quarry of the ShankHn-sand formation, in the close vicinity of that town, had his attention one day, in May 1834, called by his workmen to what they supposed to be petrified wood in some pieces of stone which they had been blasting. He perceived that what they supposed to be wood was fossil bone, and with a zeal and care which have always characterised this estimable man in his endeavours to secure for science any evidence of fossil remains in his quarry, he immediately resorted to the spot. He found that the bore or blast by which these remains were brought to light, had been inserted into the centre of the specimen, (which is figured in 'Dinosauria,' Plates 1 and 2,) so that the mass of stone containing it had been shattered into many pieces, some of which were blown into the adjoining fields. All these pieces he had carefully collected, and proceeding with equal ardour and success to the removal of the matrix from the fossils, he succeeded after a month's labour in exposing them to ^^ew, and in fitting the fragments to their proper places.* The quarry in which these remains were brought to light consists of many strata, regularly alternating, of compact lime-stone, and of sand more or less loose. Each stratum is of the thickness of from eight inches to twelve or fourteen inches, and the alter- nation of the two beds is remarkably regular and equal. The bed in which the fossil turtle Protemi/s serrata, described at pp. 169 — 1 73 of the present Work, was discovered, lies about fiifteen feet below the Iguanodon bed, and is remarkable for the accumu- lations of the spiculse of sponges, with which it abounds. Not far below this is the " Atherfield clay," which joins the " Wealden," the junction of the two being scarcely discoverable, owing to the similarity in texture and colour of the two clays. * In a contemporary notice of this discovery, written with evident knowledge of the facts, and within a month after they occurred, it is stated : — " By the great care bestowed upon them, however, by the very intelligent proprietor of the quarry, Mr. W. H. Bensted, nearly all the detached pieces have been collected, and the various bones carefuUy cleared from the rock which forms their matrix." (Philosophical Magazine, July, 1834.) Dr. Mantell, referring, in 1848, to this specimen in his 'Wonders of Geology,' vol. i, p. 427, states : — - " The rock was shattered to fragments by the explosion, and the bones were broken into a thousand pieces : but after much labour, I succeeded in uniting the several blocks of stone, and ultimately cleared and repaired the bones, and restored the specimen to its present state." As the specimen was presented to Dr. Mantell, from whom it was purchased, with the rest of his Collection, by the British Museum, we are probably indebted to his skill as well to that of its discoverer for the actual condition in which it may now be studied. 260 BRITISH FOSSIL REPTILES. Amongst the portions of the skeleton recovered by Mr. Bcnsted, were fortunately a portion of one tooth and the cast of a second in the matrix. These were recognised by him as being the teeth of the Iguanodon, which had previously been discovered in the Wealden of Tilgate Forest,* and which had been described by Dr. Mantell in a Paper printed in the 'Philosophical Transactions' for 1825; where that assiduous explorer of the Wealden acknowledges the mode by which he obtained the required information respecting them. " As these teeth were distinct from any that had previously come under my notice, I felt anxious to submit them to the examination of persons whose knowledge and means of observation were more extensive than my own. I therefore transmitted specimens to some of the most eminent naturalists in this country and on the continent. But although my communications were acknowledged with that candour and liberality which constantly characterise the intercourse of scientific men, yet no light was thrown upon the subject, except by the illustrious Baron Cuvier, whose opinions will best appear by the following extract from the correspondence wdth which he honoured me : — " ' Ces dents me sont certainement inconnues ; elles ne sont point d'un animal carnassier, et cependant je crois qu elles appartiennent, vu leur pen de complication, leur dentelure sur les bords, et la couche mince d'email qui les revet, a I'ordre des reptiles. A I'apparance exterieure on pourrait aussi les prendre pour des dents de poissons analogues aux tetrodons, ou aux diodons : mais leur structure intericure est forte diffcrente de celles-la. N'aurions-nous pas ici un animal nouveau ! un reptile herbivore ? et de meme qu'actuellement chez les mammiferes terrestres, c'est parmi les herbivores que I'on trouve les especes a plus grande taille, de mume aussi chez les reptiles d'autrefois, alors qu'ils etaient les seuls animaux terrestres, les plus grands d'entr'eux ne se seraient-ils point nourris de vcgctaux ? Une partie des grands os que vous possedez appartiendrait a cet animal unique, jusqu'a present, dans son genre. Le temps co«lirmera ou ?/ rest of the vertebra in one that lies between the humerus and femur ; although it has there suffered fracture ; in the other specimens the broken summits of the spines have not been preserved. In the characters above defined we may plainly recognise a vertebra differing from any of those that have been previously described ; from those of the Crocodiles and Gavials (' Crocodilian Pis. 1 D, 3, 3 A, 3 b,) in the flattened articular ends of the centrum ; and by the same character from those of the Ophidian, {'Ophidian Pis. 2 and 3,) and Lacertian {'Lacertia,' Pis. 1, 2, 8 and 9,) reptiles, which we have hitherto met with in the Tertiary and Cretaceous deposits ; it is equally distinct from the biconical and short ver- tebrae of the Ichthyosaurus, {' Enaliosauria,' PI. 7.) Were the centrum of the Iguanodon's vertebra {' Di/iosaifria," PI. 3,) to be found detached from the neural arch, it might not be so easy to distinguish it from that of a dorsal vertebra of a Pksiosaurus, which is similarly 264 BRITISH FOSSIL REPTILES. characterised by nearly flattened articular extremities; but although the vertebrae are very variable in their proportions as to length and breadth in the different species of Plesiosanriis, I have hitherto found none that combine the same antero-posterior diameter with the nearly flattened, inferiorly converging, sides of the dorsal centrum, as in the Iguanodon. When, however, the entire vertebra can be compared, or the chief characters of the neural arch of the Iguanodon, with the talljang parts in the Plesiosanriis, important difi'erences present themselves. In the cervical region of the Plesiosaiirus, the neural arch is comparatively low and simple, and sends off no other processes save the zygapophyses and spine : in the dorsal region a diapophysis is superadded ; but this alone ofiers an articular surface for the rib, and there is not any rudiment of parapophysis or of a parapophysial articulation for the head of the rib, such as is shown at p, PI. 3. In the presence of this lower transverse process with the surface for the head of the rib, in the Iguanodon, developed either from the side of the centrum (as in the anterior dorsal vertebrae), or from the side of the neural arch (as in the middle dorsal vertebrae), we have a character* distinguishing it from Ophidia, Lacertilia, and Enaliosauria, whilst in the strong bony platform, in which the summit of the neural arch expands, with its supporting buttresses, we have an additional character distinguishing it from all known Crocodilia ; and indicative of a distinct order of i^eptiles. The importance of the characters deducible from Mr. Bensted's invaluable dis- covery, will be plainly manifested when the detached vertebras and other fragmentary remains of large Saurians come to be described in the ' Monograph on the Wealden Reptiles,' and I proceed next to notice those of some caudal vertebrae which are well- preserved in the Maidstone specimen; they are marked ' c. vertebrce' va PI. 2, and one of the most perfect is figured of the natural size in PI. 5. The centrum is more compressed than in the trunk, its articular ends are less expanded, but the flattened character of the inferiorly converging sides of the centrum being retained, this part presents in a more marked degree the wedge-shaped figure ; the converging * First made known in my 'Report on British Fossil Reptiles,' Trans. Brit. Association, 1841, p. 127. "In the interspace of the two buttresses of the anterior dorsal vertebrae there is a large oval artScular surface, convex at the anterior, and concave at the posterior part, which has afforded a lodgement to the head of the rib." The nature of the part affording this surface is described in the next page as " the transverse process " which " extends from the side of the neurapophysis." At the commencement of my 'Report' I defined the "transverse processes" as being "of two kinds, superior and Inferior," (p. 48,) but I did not, in that 'Report,' specify them by the names "diapophysis'' and "parapophysis:" the process in question for the head of the rib is the "parapophysis." The author of the Appendix to Dr. ManteU's Paper, in the 'Philosophical Transactions,' 1849, assuming the " upper transverse process " to be the one indicated in my description of the fractured vertebra. No. 2160, imputes to me what he conceives to be an error (p. 291) ; but the error lies in his assumption. It is one amongst many instances of the necessity of abandoning the vague term ' transverse process,' and the advantage and propriety of the definite names "diapophysis" and "parapophysis," which I have been in the liabit of using since the pubhcation of my 'Report' in 1841. CRETACEOUS DINOSAURS. 265 sides, however, are separated below by a broader quadrate tract which is shghtly concave transversely, and more so lengthwise, with each of its angles developed into an articular hypapophysis, y y, for the junction of a portion of the base of a haemal arch. This part, which is shown in Pis. 1 and 2, near the middle of the upper border of the slab, consists, as usual, of a pair of " haemapophyses," but they are confluent with one another, not only where they form the base of the long haemal spine, but also at their opposite extremities ; and the hinder hypapophysial surfaces, y y,' which are the largest, also run into one another across the middle line. The articular end of the centrum, fig. 1, presents somethivig between a quadrate and an elliptical form, with the long axis vertical ; it is a little depressed within the border. The neural arch is anchylosed to the centrum ; a rudiment of a parapophysis appears at the side of its base (fig. 2) ; the diapophysis, d, rises above and behind this, and extends obliquely upwards, outwards, and backwards ; its extremity is broken off. The zygapophyses, z, are reduced to short tuberosities, without articular surfaces in this region of the spine ; and the neural platform and its buttresses are quite suppressed. The summit of the neural spine is broken away. Amongst the portions of ribs that are preserved, some show clearly not only the head but the neck and an articular tubercle ; superadditions, which at once remove the I(/uanodon from the If^uana and all its Lacertian congeners, and show the nearer afiinity of the great Dinosaur to the Crocodiles. In one of tlie specimens near the upper part of the slab, as figured in PI. I, there is an indication of the upper part of the neck of the rib rising and bifurcating near the tubercle, whence it is continued as two ridges which form an anterior and posterior margin, as it were produced and overhanging the body of the rib. This character may not be without its value in detecting and determining fragments of ribs, which are common among the fossils of the strata containing the remains of great reptiles. Both the bones, answering to those from the Wealden of Tilgate, which Cuvier thought " might be a clavicle,"* are preserved in the Maidstone specimen, having the same long, slender, triedral shaft slightly expanded, flattened and bent at one extremity ; more expanded, flattened, and bent at an open angle at the opposite end ; with a short pointed process sent off at the angle, and a broad subquadrate flattened plate projecting from the same border of the bent and expanded end, which has a truncate termination. In the Ci/clotlus\ lizard I find the clavicle is bent at an open angle, but nearer its middle part ; and the difference between this and the nearly * Quoted by Dr. Mantell, in ' Geology of the South-East of England,' 18.33, p. 308. t This is the Lizard referred to in the following passage of Dr. Mantell's Paper, in the ' Philosophical Transactions,' 1841, p. 138. "In a very small Lizard in the Hunteriau Museum, Mr. Owen pointed out to me a boue attached to the coracoid aud oinoplati', that bore some analogy to the one iu question: " it bears sufficient analogy to support the conclusion in the te.xt, but lends no countenance whatever to tiie idea of the fossil in question being a peculiar superaddition to the Saurian skeleton, requiring a new name. The "OS Cuvieri" is, in fact, abandoned in the Paper, in the 'Phil. Trans.,' 18'49. 266 BRITISH FOSSIL REPTILES. straight clavicle of the Ljuana, Aiiibli/rhi/nchus, and some other lizards, justifies the expectation of some unexampled modifications of that variable bone in a great extinct reptile of a dififerent order. For a knowledge of the bone, called "scapula" and "humerus," in PI. 2, I am indebted to Mr. George B. Holmes, of Horsham, who, in March, 1847, transmitted to me a beautiful drawing of both bones, together with the coracoid in natural juxta- position w ith the humerus, discovered " in one block of stone, with other bones of the same individual" in Tower Hill Pit, near Horsham. That gentleman, whose collection of the Wealden Fossils in his neighbourhood is one of the most instructive extant, had correctly determined their nature, and named them in the drawing which he sent to me " Humerus, Scapula, and Coracoid bone of the Iguanodon." Dr. Mantell published similar determinations of homologous bones, in the ' Philo- sophical Transactions' for 1849. This part of the skeleton of Iguanodon may, therefore, be regarded as definitely restored. The scapula in the Maidstone specimen, PL 1 , lies broken across the femur : it is a long, narrow, flattened bone, gradual^ expanding to its free end, more suddenly towards its articular end ; but this is too much mutilated to give its true character in the specimen in question : it will be described from Mr. Holmes's beautiful specimen in Section III, ' On the Fossil Reptilia of the Wealden Formation.' The humerus (see PI. 2) is shorter than the scapula, and much shorter than the femur, its relative proportions to which are the same in the Iguanodon, as in the Teleosaurus, (see 'Crocodilia,' PI. 1,) and, with the vertically developed tail of the Iguanodon, indicate the aquatic habits of that gigantic reptile. The head of the humerus is hemispheroid, and projects between two sub-equal tuberosities; a deltoid ridge is continued nearly half way down the bone fi'om the outer tuberosity, and, where it subsides, the shaft is bent a little inwards, contracts, and then again expands to the distal condyles, which are rounded and prominent, wdth a moderately deep depression between them at the back, which is the part of the bone exposed in the Maidstone specimen. The radius and ulna lie with their proximal ends next the right hand upper comer of the slab of the Maidstone specimen ; the latter being distinguished by its prominent olecranon, which is rounded as in the great Monitor {Varanus nUoticus). I shall reserve the description of the metacarpal and metatarsal bones for the succeeding Section ; and shall only observe, here, that the claw-bones marked " ungual phalanx," in PI. 2, though varying in their proportions in the two specimens preserved, are broader, more depressed, and less incurved than those of other known Saurians. The ilium which lies detached near the lower border of the slab in the Maidstone specimen, is the left one, with its sacral articular surface or inner surface uppermost, the extent of which plainly indicates the great length of the sacrum in the Iguanodon, as compared with existing Lizards, since it equals the antero-posterior diameter of five CRETACEOUS DINOSAURS. 267 of the dorsal vertebrae ; the part of the bone which is prolonged backwards beyond the articular part is slender, and terminates in an obtuse point. The right ilium, which is overlapped by one of the clavicles, shows that the anterior end bends outwards in the form of a thick tuberosity, and the expanded portion contributes by its lower border the usual share in the formation of the acetabulum. The two femora (PI. 2, femur,) well exemplify the characteristic peculiarities of this bone in the Iguanodon : its inwardly projecting hemispheric head, its much flattened trochanter, the compressed ridge-like process from the middle of the inner surface of the shaft, and the deep and narrow fissure between the distal condyles. This part of the femur had been figured and referred by Dr. Mantell to the Iguanodon, in his ' Geology of the South-East of England,' Nov. ] 833, p. 310, pi. IV, figs. 3 and 4 ; and the subsequent discovery of the Maidstone specimen confirmed the accuracy of that determination. The bone which is figured in PI. II, fig. 8 of the same work, as the tibia of the Iguanodon, is also shown to be correctly so called by the Maidstone specimen, ' Dliiosaiiria,' Pis. 1 and 2. The following are the dimensions of the principal and best-preserved bones in that specimen : — Dorsal Vertebra. Inches. Lines. Antero-posterior diameter of centrum . . . . . . . 3 10 Vertical diameter of articular end ........ 4 0 Transverse diameter of ditto ........ 'i \ From the base of the neurapophysis to the fore-part of that of the spinous process ............ 3 0 From ditto ditto back part of ditto ... 4 0 Antero-posterior extent of neural platform ...... 4 (J Caudal Vertebne. Antero-posterior diameter of centrum ....... 2 5 Vertical diameter of articular end ........ 2 5 Transverse diameter of ditto . . . . . . . . . Ill From the base of the neurapophysis to the fore-part of that of the spinous process ............ 1 3 From ditto ditto back part of ditto ... 1 6 Clavicle. Length of the bone .......... 37 0 Breadth across the process at the broader end ...... 8 0 Breadth across the narrower end ........ 4 0 268 BRITISH FOSSIL REPTILES. Scapula. Inches. Lines. Length of the bone 29 0 Breadth across the middle of the shaft ....... 3 0 Humerus. Length 19 0 Breadth of proximal end .........GO Breadth of distal end . 4 0 Ulna. Length 18 0 Breadth of proximal end ......... 3 0 Ilium. Length 30 0 Breadth across the enlarged end . . . . . . . .10 0 Extent of sacro-iliac articulation . 19 0 Femur. Length 33 0 TiUa. Length 31 0 The detached teeth and bones of the Iguanodon successively discovered in the Wealden strata of Sussex, and afterwards found associated together to the extent of nearly half the skeleton of one and the same individual in the Green-sand quarries of Mr. Bensted, offer not the least marvellous or significant evidences of the inhabitants of the now temperate latitudes during the later secondary periods of the formation of the earth's crust. With vertebrae flat or subconcave at their articular extremities, having, in the dorsal region, lofty and expanded neural arches, and doubly articulated ribs, and characterised in the sacral region by their unusual number and complication of structure ; with a Lacertian pectoral arch, crocodilian proportions of the fore-limbs, and unusually large bones of the hind limbs, excavated by large medullary cavities and adapted for terrestrial progression, as well as for natation ; — -the Iguanodon was distinguished by CRETACEOUS DINOSAURS. 269 teeth, resembling in shape those of the Iguana, but in structure differing from the teeth of that and every other known reptile, and unequivocally indicating the former existence in the Dinosaurian Order of a gigantic representative of the small group of living lizards vi'hich subsist on vegetable substances. The important difference which the fossil teeth presented in the form of their grinding surface was pointed out by Cuvier,* of whose description Dr. Mantell adopted a condensed view in his ' Illustrations of the Geology of Sussex,' 4to, 1827, p. 72. The combination of this dental distinction with the vertebral and costal characters, which prove the Ic/uamdon not to have belonged to the same group of Saurians as that which includes the Iguana and other modern lizards, rendered it highly desirable to ascertain by the improved modes of investigating dental structure, the actual amount of corres- pondence between the Iguanodon and Iguana in this respect. This I have done in my general description of teeth of reptiles,! from which the following description is abridged : — The teeth of the IgHanodon, though resembling most closely those of the Iguana, do not present an exact magnified image of them, but differ in the greater relative thickness of the crown, its more complicated external surface, and, still more essen- tially, in a modification of the internal structure, by which the Iguanodoii equally deviates from every other known reptile. As in the Iguana, the base of the tooth is elongated and contracted ; the crown expanded, and smoothly convex on the inner side ; when first formed it is acuminated, compressed, its sloping sides serrated, and its external sui'face traversed by a median longitudinal ridge, and coated by a layer of enamel, but beyond this point the descrip- tion of the tooth of the Iguanodon indicates characters peculiar to that genus. In most of the teeth that have hitherto been found, three longitudinal ridges traverse the outer surface of the crown, one on each side of the median primitive ridge ; these are separated from each otlier, and from the serrated margins of the crown by four wide and smooth longitudinal grooves. The relative width of these grooves varies in different teeth ; sometimes a fourth small longitudinal ridge is developed on the outer side of the crown. The marginal serrations, which at first sight appear to be simple notches, as in the Iguana, present under a low magnifying power the form of trans- verse ridges, themselves notched, so as to resemble the mammillated margins of the unworn plates of the elephant's grinder : slight grooves lead from the interspaces of these notches upon the sides of the marginal ridges. These ridges or dentations do not extend beyond the expanded part of the crown : the longitudinal ridges are continued further down, especially the median ones, which do not subside till the fang of the tooth begins to assume its subcylindrical form. The tooth at first increases both in breadth and thickness ; it then diminishes in breadth, but its thickness ffoes on &"- * Ossemens Fossiles, 1824, vol! v, part ii, p. 351. t Odontography, part ii, p. 249; and Transactions of the British Association, 1838. 270 BRITISH FOSSIL REPTILES. increasing ; in the larger and fully formed teeth, the fang decreases in every diameter, and sometimes tapers almost to a point. The smooth unbroken surface of such fangs indicates that they did not adhere to the inner side of the maxillte, as in the Iguana, but were placed in separate alveoli, as in the Crocodile and Megalosaur : such support would appear, indeed, to be indispensable to teeth so worn by mastication as those of the I(/uanodon. The apex of the tooth soon begins to be worn away ; and it would appear, by many specimens that the teeth were retained until nearly the whole of the crown had yielded to the daily abrasion. In these teeth, however, the deep excavation of the remaining fang plainly bespeaks the progress of the successional tooth prepared to supply the place of the worn out grinder. At the earlier stages of abrasion a sharp edge is maintained at the external part of the tooth by means of the enamel which covers that surface of the crown ; the prominent ridges upon that surface give a sinuous contour to the middle of the cutting edge, whilst its sides are jagged by the lateral serrations : the adaptation of this admirable dental instrument to the cropping and comminution of such tough vegetable food as the Cluihrarice and similar plants, which are found buried with the Iguanodon, is pointed out 1)y Dr. Buckland, with his usual felicity of illustration, in his ' Bridgewater Treatise,' vol. i, p. 246. When the crown is worn away beyond the enamel, it presents a broad and nearly horizontal grinding surface, and now another dental substance is brought into use to give an inequality to that surface ; this is the ossified remnant of the pulp, which, being firmer than the surrounding dentine, forms a slight transverse ridge in the middle of the grinding surface : the tooth in this stage has exchanged the functions of an incisor for that of a molar, and is prepared to give the final compression, or comminution, to the coarsely divided vegetable matters. The marginal edge of the incisive condition of the tooth, and the median ridge of the molar stage, are more effectually established by the introduction of a modification into the texture of the dentine, by which it is rendered softer than in the existing Iguanae and other reptiles, and more easily worn away : this is efifected by an arrest of the calcifying process along certain cylindrical tracts of the pulp, which is thus con- tinued, in the form of medullary canals, analogous to those in the soft dentine of the Megatherium's grinder, from the central cavity, at pretty regular intervals, parallel with the calcigerous tubes, nearly to the surface of the tooth. The medullary canals radiate from the internal and lateral sides of the pulp cavity, and are confined to the dentine forming the corresponding walls of the tooth : their diameter is y^fj-oth of an inch : they are separated by pretty regular intervals equal to from six to eight of their own diameters ; they sometimes divide once in their course. Each medullary canal is surrounded by a clear space ; its cavity was occupied in the section described by a substance of a deeper yellow colour than the rest of the dentine. The calcigerous tubes present a diameter of Trj-.Vo-otli of an inch, with interspaces CRETACEOUS DINOSAURS. 271 equal to about four of their diameters. At the first part of their course, near the pulp cavity, they are bent in strong undulations, but afterwards proceed in slight and regular primary curves, or in nearly straight hues to the periphery of the tooth. When viewed in a longitudinal section of the tooth, the concavity of the primary curvature is turned towards the base of the tooth : the lowest tubes are inclined towards the root, the rest have a general direction at right angles to the axis of the tooth ; the few calcigerous tubes, which proceed vertically to the apex, arc soon worn away, and can be seen only in a section of the apical part of the crown of an incom- pletely developed tooth. The secondary undulations of each tooth are regular and very minute. The branches, both primary and secondary, of the calcigerous tubes are sent off from the concave side of the main inflections ; the minute secondary branches are remarkable at certain parts of the tooth for their flexuous ramifications, anastomoses, and dilatations into minute calcigerous cells, which take place along nearly parallel lines for a limited extent of the course of the main tubes. The appear- ance of interruption in the course of the calcigerous tubes, occasioned by this modification of their secondary branches, is represented by the irregularly-dotted tracts in the figure. This modification must contribute, with the medullary canals, though in a minor degree, in producing that inequality of texture and of density in the dentine, which renders the broad and thick tooth of the Iguanodoji more efficient as a triturating instrument. The enamel which invests the harder dentine, forming the outer side of the tooth, presents the same peculiar dirty brown colour, when viewed by transmitted light, as in most other teeth : very minute and scarcely perceptible undulating fibres, running vertically to the surface of the tooth, form the only structure I have been able to detect in it. The remains of the pulp in the contracted cavity of the completely-formed tooth, are converted into a dense but true osseous substance, characterised by minute elliptical radiated cells, whose long axis is parallel with the plane of the concentric lamellae, which surround the few and contracted medullary canals in this substance. The microscopical examination of the structure of tho Iguanodon's teeth thus contributes additional evidence of the perfection of their adaptation to the offices to which their more obvious characters had indicated them to have been destined. To preserve a trenchant edge, a partial coating of enamel is applied ; and, that the thick body of the tooth might be worn away in a more regularly oblique plane, the dentine is rendered softer as it recedes from the enameled edge by the simple con- trivance of arresting the calcifying process along certain tracts of the inner wall of the tooth. When attrition has at length exhausted the enamel, and the tooth is limited to its function as a grinder, a third substance has been prepared in the ossified remnant of the pulp to add to the efficiency of the dental instrument in its final capacity. And if the following reflections were natural and just after a review of the external characters 272 BRITISH FOSSIL REPTILES. of the dental organs of the If/tianodon, their truth and beauty become still more manifest as our knowledge of their svibject becomes more particular and exact. " In this curious piece of animal mechanism we find a varied adjustment of all parts and proportions of the tooth, to the exercise of peculiar functions, attended by com- pensations adapted to shifting conditions of the instrument, during different stages of its consumption. And we must estimate the works of nature by a different standard from that which we apply to the productions of human art, if we can view such examples of mechanical contrivance, vmited with so much economy of expenditure, and with such anticipated adaptations to varying conditions in their application, witliout feeling a profound conviction that all this adjustment has resulted from design and high intelligence." — (' Buckland's Bridgewater Treatise,' vol. i, p. 249.) In pursuing the search after the remains of Reptiles below the actual surface of the soil, through the Formations of the Tertiary deposits in this island, it was found, as has been shown in the First Section of the present Work, that the number and variety of those remains rapidly increased when we had arrived at the oldest or " eocene " division of the deposits ; the general character of the organic remains in which demonstrate a warmer or more equable climate to have prevailed here during their formation. Under conditions so favorable to the existence of the cold-blooded class of air-breathing vertebrate animals, not only were the Reptilia larger and more numerous, but they were distinct from any of the few small species now existing in the British Islands ; and most of them belonged to orders which, as, e.(/., the Chelonia, are either represented only by rare examples of the Marine Order, casually floated near or cast on our shores, or which, as, e.g., the CrocodiUa, are no longer represented by any indigenous species in Europe. All the species of Eocene Reptilia, nevertheless, belonged to orders and families of the class which still exist in the warmer latitudes of the globe; and if some of the fossils may seem to have been distinct from corresponding parts of actual Genera, it was not from any of those great natural groups to which Linnaeus restricted the term genus, but from the modern and less important sub-divisions of such, like those into which the Linnean CoJubri have been dispersed, and to which sub-genera the FalcEophis and Paleryx were correlative. In short, to the bottom of the Tertiary Deposits, or, in other words, from the very commencement of that epoch in Geological time, we found only forms of the Reptilia so little modified from those now existing as irresistably to impress us with the conviction that they played the same parts, under very similar influences and circum- stances, which are performed by the Gavials, Crocodiles, Alligators, Turtles, Terrapenes, Mud Tortoises, Lizards, and Serpents of the present day. CONCLUDING REMARKS. 273 But this aspect of Reptilian life rapidly fades away as we pursue our course through the dark vistas of the past. The slow and massive Chdonia, indeed, characterised by their tenacity of life and the sluggishness of its manifestations, continue to retain the characteristic forms of the principal modifications of their Order, but little altered. The Chelone Camperi and Chelone Benstedi do not differ more from the modern Turtle of gastronomic repute than do the numerous forms that paddled about the estuary of Sheppey in the oldest Tertiary times. The modifications of the Emydian from the Green-sand of Maidstone are not of greater value than may be expressed by a sub-generic name, in accordance with the adopted practice of modern Herpetologists. When, however, we look for species of the modern Crocodiles, Alligators, and Gavials, in the strata that immediately follow the Tertiary beds in descending order, we nowhere find an unequivocal trace of them. Not a fragment of the numerous vertebrae that enter into the composition of the much- prolonged spinal column of the procselian Crocodilia has yet been discovered in any of the widely-dispersed Formations of the Chalk or Green-sand periods, although some of the latter were so situated as to have received occasional evidences, as in the case of the Protemys, of the Reptilian inhabitants of the Fresh-waters or Estuaries. The only Saurian vertebree with a cup at the front and a ball at the back part of the body, from the Cretaceous deposits, belong to the Lacertian not to the Crocodilian Order ; and the most remarkable of these vertebrae show a modification of the Lacertian type very distinct from any existing form, being adapted more expressly for aquatic, and without doubt marine, life, and, attaining, under favour of that medium of existence, a bulk surpassing the largest of the modern Crocodilia. The Mosasaurus combined a carnivorous form of teeth with an anchylosed mode of their attachment, as in many Fishes and in the Acrodont Chameleons and Agamian Lizards, and with a disposition of the teeth on the maxillary and pterygoid bones, as in many of the true Lizards, and in the Anolian, Scincoid, and Iguanian famihes. The vertebral column was modified for the act of swimming, by being unfettered by zygapophysial joints along more than the hinder half of its extent, as it is in the Cetacea ; and by the anchylosis of long haemal arches to the vertically-extended caudal vertebrae, as we find in many Fishes : and the trunk, composed of one hundred and thirty-three vertebrae, which supported a skull of four feet in length, cannot be reasonably calculated at less than from twenty to thirty feet in length. The extremities, though doubtless webbed and adapted for swimming, like those of the Gavial, yet appear, from the evidence adduced in the text, to have been formed, as in the Crocodilian type, for occasional locomotion on land ; yet the absence of any trace of a sacrum combines with the ascertained modifications of the vertebral column, in indicating a more strictly marine life in the Mosasaurus than in any modern Lizard. The ascertained modifications in the structure of the skeleton of this large extinct Lacertian demonstrate, in fact, that 274 BRITISH FOSSIL REPTILES. it had no such near affinities to any of the existing genera, as to have constituted a link intermediate between any two of them ; but tliat it manifested a type of the Lacertian organisation, representing a division of the Order Lacertilia, adapted for marine hfe, equivalent in character to the remainder of the Order as represented by the existing terrestrial species ; and I have, therefore, indicated those two divisions or tribes of the Order Lacertilia by the terms Natantia and Bepentia. The Lacertian Order expands as our survey of its existence in past time extends backwards; and the same direction of development becomes more striking as we carry our retrospect over the whole Reptilian Class. A new Order, with an organisation more expressly adapted for marine life than in the Mosasaurus, comes into view when we descend to the Chalk-beds, where it is represented by the remains of the Ich- thyosauri and Plesiosauri described in the Fourth Chapter of the present Section. Evidence of another Order of Reptiles, distinct from any now left to us, was given by the discovery of the Iguanodon in the Green-sand of Maidstone. But the most striking modification of the Reptilian structures is afforded by those remarkable specimens of Pterodactyles, discovered in the Middle-chalk itself, and described in the Fifth Chapter of the present Section. Succeeding Sections devoted to the Fossil Reptiles of still older Strata will bring to light additional and varied forms of Enaliosauria, Ptcrosauria, and Dinosauria, and also of tribes of Crocodilia no longer existing. All these modi- fications of the once richly developed Class of Reptiles perished, according to our present evidence, during the period of the deposition of the Chalk Formations, after which we know that the seas of our Planet were peopled with carnivorous fish-like animals of the warm-blooded Mammalian Class, and its dry land with large herbivorous and carnivorous quadrupeds of the same highly-organised type. In considering the marvellous fact of the disappearance or extinction of the Orders Enaliosauria and Pterosauria, we must bear in mind that the last Ichthyosaur of which we have been enabled to get cognizance preserves as strictly the type of its peculiar genus as any of its predecessors, and that in respect to the extent of cement outside its teeth, which is such as to lead to their being wedged squarely into their common alveolar groove, the Ichtlnjosavrus cami^jlodon, instead of showing any approach or affinity to later forms of larger Peptilia, manifested a distinctive characteristic of its peculiar genus in an exaggerated degree. So likewise with regard to the Flying Reptiles, these seem at no period to have been represented by species so gigantic and formidable as during the most recent of the Secondary Formations ; and the Order Pterosauria, instead of showing signs of progressive decay or transmutation, seems to have attained its highest and most typical development at the eve of its final extinction. 275 SECTION III. THE FOSSIL EEPTILIA OF THE WEALDEN FORMATIONS. Chapter I.— Order DINOSAUBIA* (Cervical and anterior dorsal vertebra; with parapophyses and diapophyses ; dorsal vertebrae with a neural platform ; sacral vertebrae exceeding two in number ; body supported on four well-developed unguiculate limbs.) *, fig. 2, PL 16. What may have been the length of the entire jaw, as completed by the splenial, angular, surangular, and articular elements' must remain conjectural, until either this part of the mandible, or an entire upper jaw with the tympanic part of the same cranium, may be discovered. In the Iguana the dentary element forms about three fifths of the length of the lower jaw ; in the Cyclodus it forms rather more than half, in the Varanus a little less than half of the lower jaw ; in the Crocodile it forms more than two thirds the length of the jaw. As the dentary piece in the Iguanodon itself contributes to tlie formation of the coronoid process, it is probable that the entire jaw may more nearly resemble tlie Crocodilian than the Lacertian type in the proportion of the ramus formed liy'the dentary element. The length of the corresponding element of the lower jaw of probably a mature Iguanodon, now in the British Museum, PL 18, fig. 1, is 21 inches; its vertical diameter, in a straight line, where the alveolar wall is best preserved, is 4 inches, 7 lines, so that it is relatively deeper than in the younger Iguanodon, and this probably in reference to a deeper implantation of tlie large teeth of mature age, and to the greater strength of the jaw required for the more vigorous mastication at that period of life. The coronoid process, PL 18, / being a part of the dentary bone, has also been preserved with the rest of that element in Capt. Brickenden's specimen, and shows the same abrupt curve upwards. The nervo-vascular foramina, y, y, are 2yS BRITISH FOSSIL REPTILES more numerous than iu the younger jaw, but are arranged, as in that jaw, along the outside of the alveolar wall, beginning near the base of the coronoid process, and extending down the edentulous sloping part of the jaw ; their size is exaggerated in the figure given in the ' Philosophical Transactions,' and there is no particular anterior foramen, larger than the rest, and meriting, as in the mammalia, the name of " foramen mentale." The exterior marginal groove of the edentulous border is better marked in Capt. Brickenden's than in Mr. Holmes's specimen, but the alveolar wall has suffered more injury in the Tilgate specimen than in that from Stammerham ; in the latter, indeed, it seems to be entire, and so much of the thin inner border is preserved as to show that there was not any internal alveolar wall co-extensive with the outer one. I cannot discern evidence of more than 18 dental depressions on the outer alveolar wall of the large lower jaw from Tilgate ; the number, therefore, is the same as in the specimen from the younger Iguanodon, just as we find the same number of teeth in the same species of Crocodile at all ages of the individual, no additional teeth being added to the series from behind, like the true molars in the Mammalia, in the course of the cliange of dentition as the animal advances to maturity. So much of the inner surface of the dentary bone as is preserved entire in the Tilgate specimen, corresponds with the same portion in the younger specimen from Stammerham ; no part is absolutely flattened : the part sustaining the upper division of the mandibular canal has been broken away. If we pass now to the consideration of the inferences as to the nature of the soft or perishable teguments of the jaw, which are deducible from the characters of the bone itself, it may be first remarked, that the disposition of the vessels and nerves, supplying such teguments, differs according to their nature in different existing air- breathing vertebrate animals, and the jaw-bone exhibits corresponding differences in relation to such modifications of the mandibular vessels and nerves. To those who may not have ready access to Cabinets of Comparative Osteology, a glance at the plates of the well-known and widely distributed ' Ossemens Fossiles,' of Baron Cmaer, will show that the rami of the lower jaw in Mammalia usually present one large, rarely two or three, foramina, on the outside of each ramus at its fore-part ; but that, in rei)tiles, as may be seen in the Crocodiles, PI. 1 ; the Lizards, PI. 16; the Tortoises, PI. 11 ;'■" the nervo-vascular foramina are more numerous, smaller, and arranged, in a more or less linear series along nearly the whole extent of the outside of the ramus of the jaw. The first modification relates to the concentration of the nervous and vascular influences upon thick, muscular, soft, sensitive, extensile and retractile lips, covering the jaws, and extending beyond their fore part, where such lips are most developed. The second modification relates to a more diffused and equable supply of the nervous and vascular, but especially the latter, influences, to salivary follicles opening along the * The 4th editiou, 1824, torn, v, pt. ii, is here cited. WEALDEN DINOSAURS. 299 alveolar parapet, and to rapidly worn and renewed horny scales covering the outside of the rami of the lower jaw. The like differences of the condition of the soft parts external to the upper jaw govern corresponding modifications of the nervo-vascular foramina of the bones of that part. It will be obvious, on the slightest reflection, that the horny scales or scutes covering the borders of the jaws in reptiles must be those that are subject to most abrasion, moistening, and other influences accelerating their decay ; and in the living Saurians it may be generally seen that the marginal scales or scutes of the jaws exhibit the effects of such destructive influences contingent on their position. As these scales are more quickly worn away than those of other parts, so they are more rapidly renewed ; their progress of growth is quicker, and their formative beds in the cutis have a greater supply of both vessels and nerves : the greater vascularity of this part of the integument is shown by injecting the head of a crocodile or lizard, and macerating away the cuticular scales. The labial muco- salivary follicles are arranged commonly in a linear series, and their orifices may be seen in a row along the narrow and shallow groove between the alveolar border and the scaly integument forming the margin of the mouth : these follicles, in most Saurians, perform the oflices assigned to the more compact and localized salivary glands in Mammalia ; and consequently require and exhaust a good supply of blood. The arteries emerging from the serial foramina resolve themselves each into a brush of small branches which are spent in the vascular matrices of the labial scales and on the secreting surfaces of the labial glands. In the great Mosasaurus, as is shown in PI. XVIII, of the ' Ossemens Fossiles,' of Cuvier,* the linear series of nervo-vascular foramina along the outside of the ramus of the lower jaw indicates plainly that such jaw was covered by a firm scaly integument protecting a long series of muco-salivary follicles, as in existing Saurians. In the great Megatherium and Mylodon the single or double large nervo-vascular outlets confined to the fore part of the mandibular rami equally attest the existence of fleshy and sensitive lips produced beyond the fore part of the jaw, and capable of being further protruded and retracted. It needs only a comparison of the lower jaw of the Iguanodon with that of the Mosasaurus and of any recent reptile, and with that of the Megatherium and of any recent Mammal, to arrive at a correct conclusion as to whether the Iguanodon resembled the Saurians in the covering of its jaws, or presented the monstrous combination of mammalian lips with a reptilian skeleton. I have only to add that the form of the anterior termination of the jaw of the Iguanodon is diametrically opposite to that of the Mylodon : in the former, the upper border slopes downwards and forwards at an angle of 45° to the straight inferior border ; in the latter the inferior border bends upwards and forwards at nearly the same angle to the straight upper border. In the reduced figure of the lower jaw of * Ed. 4to, 1824, torn, v, pt. 2. t ,300 BRITISH FOSSIL REPTILES. the Iguanodon in PI. XVII, fig. 4, of the memoir above quoted in the ' Philosophical Transactions' for 1848, the nervo-vascular foramina are not diminished in the same proportion as the jaw itself: they are accurately delineated both as to number and size, in PI. IS, fig. 1, y, g, of the present Section. The angle, also, at which the two rami of the lower jaw are conjecturally united in PI. XVII, ' Phil. Trans.,' 1848, is much too acute ; and the restoration of the lower jaw in the Mantellian collection, British Museum, accordingly leaves a transverse space equalling little more than one half the breadth of the upper jaw, to the description of which I next proceed. Fragment of the Tipper Jaw of the Iguanodon. PI. 18, figs. 2, 3, 4. After the tympanic bone and lower jaw, the most instructive and intelligible part of the skull of the Iguanodon, as yet obtained, is a portion of the upper jaw, consisting of so much of the back part of the left superior maxillary bone, with the alveolar groove, as includes ten dental recesses, seven of which contain teeth. This specimen was washed out of the submerged Weal den deposits off Brook Point, Isle of Wight, and is now in the British Museum. The alveolar groove opens widely and obliquely upon the inner and under aspect of the fragment, a, a, fig. 3 : the outer side or parapet, fig. 2, is formed by the chief osseous mass with the outer compact wall of the jaw, fig. 4, i, & ; this w^all sends off from its upper and outer side a process, m, directed backwards and a little outwards, with the end broken and blunted by attrition, or water- worn ; the bone is then continued backwards, slightly expanding in the vertical direction, and terminating in a point, p, also obtusely rounded by attrition subsequent to fossilization. Both this extremity and the malar process show unequivocal evidence of sutural surfaces upon their outer and upper side ; that upon the malar process is oblong and depressed ; that upon the upper and outer part of the hinder end of the maxillary is broad, oblique, and divided into two parts by a longi- tudinal elevation. Between this extremity and the malar process the canal, c, for the nerves and vessels of the upper jaw enters the substance of the bone, immediately above the deep rounded groove that divides the process from the body of the bone ; a fossa is continued forwards above the canal, for an inch and a half, in advance of the entry of the canal, and continues the separation of the process from the body of the bone in that direction. The smaller anterior end of this fragment is of a trihedral figure ; the inner and under side is formed by the dental groove, the inner and upper side is flat ; the outer side is slightly convex. At the angle where the last two sides meet there is a narrow sutural or fractured surface continued forwards from the sutural depression upon the upper part of the malar process. A transverse section of the anterior extremity of the fragment, fig. 4, taken through the foremost tooth, i, and its successor, 2, shows com- WEALDEN DINOSAURS. 301 pact bone from three to four lines in thickness, forming the outer surface, h, h, and a similar la3'er from one to two lines thick, forming the inner surface, ;, and increasing to near three lines in thickness, where it bends down to form the shallow inner boundary of the alveolar groove, >, a ; the compact substance is not continued over the alveolar groove itself; the intermediate substance is an areolar osseous tissue, the meshes being most open along the inner and upper surface of the bone. The maxillary canal, c, exposed in this section is nearer the outer surface; it measures 14 lines by 8 lines in its diameters, sending off branches which perforate obliquely, outwards and forwards, the compact outer wall of the jaw. Of the three oval nervo-vascular foramina, g, ^, preserved in the present fragment upon the outer surface, two are 4 lines, and the third 3 lines in long diameter; they are included in a space of 16 lines, are situate about an inch above the worn outer border of the alveolar groove, and are the last three of the sei'ies of such foramina. They correspond nearly in size and relative distance from the alveolar border with those at the back part of the similar series of nervo-vascular foramina in the lower jaw of the Iguanodon ; and like them the obliquity of their course indicates the relation of the fragment to the anterior and posterior extremities of the jaw. The corresponding foramina are present on the same part of the bone in the more mutilated homologous portion of a dentigerous bone of the Iguanodon figured in Dr. Mantell's ' Memoir,' above quoted, PI. XIX, and equally prove the part to which those orifices incline as they open outwards to be the anterior end of the fragment, and not the posterior end, as the anatomist conjectured of whose aid Dr. Mantell availed himself in the interpretation of this fragment. The vertical extent of the slightly convex outer surface of the maxillary, in front of the malar process, in the present fragment, is 3 inches, but a portion has been broken away from the border, to which the smooth and flat inner surface of the maxillary convertres as it ascends ; it is possible, therefore, that the outer wall of the maxillary of the Iguanodon may have been continued relatively as high vertically as in the Iguana, Varanus, Tejus, and most other Lizards: anterior to this broken upper surface is a portion of a wide smooth depression, or of a canal laid open. The alveolar groove, as it extends backwards, curves outwards, in the same degree as the alveolar groove does at the same part in the lower jaw, PI. 17, fig. 3. The extent of the alveolar groove in the present fragment of the upper jaw is 8 inches ; the antei-o-posterior diameter of the crown of the largest tooth is 1 inch ; it seems to answer, therefore, to the posterior half of the dentary part of the lower jaw of the Iguanodon. The first tooth, i, is a fully developed or old one, with its cement-covered base apparently continuous or confluent with the cancellous bottom of the groove, «'. The crown of the tooth, 2, which is about to succeed it, and which has in part undermined and excavated the old tooth, is on the inner and posterior side of its base ; the crown of the new tooth is widely and deeply excavated, as shown in the section, fig. 4, 2, where the hollow base of the crown has sufi'ered a slight fracture and displacement : 302 BRITISH FOSSIL REPTILES. a thin layer of dentine has been formed beneath the enamel; the mineral matter now occupies the place of the original vascular pulp of the dental matrix. The flattened side of the crown of this tooth is turned towards the outer alveolar wall, the convex surface looks inwards and downwards ; in the lower jaw the teeth, PI. 16, fig. 2, /, /, have the reverse direction, as stated in Dr. Mantell's Memoir on the lower jaw, from Tilgate.* Next, behind the young tooth, 2, is the recess from which an old tooth has been expelled ; and behind the recess is a fully formed crown of a tooth, 3, with the beginning of the fang, which tooth had come into use, but its grinding surface has been worn down by the rolling of the fragment after fossilization and extrication of the specimen from the matrix ; a narrow recess follows this tooth, and then comes the fang and base of the crown of an old tooth, 4, partly undermined, and about to be pushed out by the crown of a successor, r> ; next follows an empty recess ; then the base of apparently a fully developed tooth, 6, the projecting crown of which has been broken away ; close behind this tooth is the base of a narrower and smaller tooth, 7, followed by the recess for a similar sized tooth, which terminates the series. We thus see that, as in the lower jaw of the Iguanodon and in the upper jaw of the Iguana and Tejus, the teeth decrease in size at the hinder end of the series ; and that this end of the series in the Iguanodon inclines outwards, as does the same end of the alveolar series in the lower jaw, to which it was opposed. As a similar portion of bone, recognised by Dr. Mantell as a " fragment of the upper jaw of an Iguanodon," when first discovered in 1838, in a quarry near Cuckfield, has been referred to the opposite end of the jaw, in the Memoir in which it is figured, 'Philosophical Transactions,' 1848, PI. XIX, pp. 190, 191, with an appeal to the osteology of the recent Iguana, as confirmatory of that determination, I may be excused for concluding by a summary of the facts which seem to me to determine rightly the nature and relative position to the rest of the skull of the present very interesting part of the fossihzed skeleton of the Iguanodon. The size of the teeth forbids the suppo- sition that the fragment in question can have formed part of a pterygoid or palatine bone, — such a dentigerous bone, viz., as is shown in the skull of the Mosasaurus and, amongst existing Saurians, in the Iguana : l)oth the shape of the pterygoid and the relative size of the teeth discourage the idea that the present fragment can be part of the homologous bone : it would be contrary to all known analogies to refer it to the palatine bone ; and there remains, tliereforc, only the superior maxillary bone with which to compare it. Of this bone the specimen is evidently that part or extremity containing a natural termination of the alveolar groove ; this is shown by the suddenly diminished size of the teeth and alveoli, and by the portion of bone, p, fig. 2, which is continued beyond the last alveolus. The question next arises : — Does the fragment include the anterior or posterior end of the alveolar groove ? In answer to this I may first remark, that the outer and inner * PLilos. Trans., 1818, p. 187. WEALDEN DINOSAURS. 303 sides of the fragment are determined by the relative depth of the walls of the alveolar groove, and by the relative position of the new and old teeth. In no pleurodont lizard is the deeper wall the innermost ; and in no lizard or crocodile does the germ of a successional tooth appear on the outside of the base of the one it is about to succeed. The philosophy of Zootomy compels one to be guided by so great a number of observed instances, as is impHed by the above generalized statement, as by a rule; and we know that the lower jaw of the Iguanodon conforms to that rule, by direct observation. In the upper jaw of the Iguanodon the successional tooth-germ is not situated directly on the inner side, but is also behind the tooth about to be displaced, at least in most of the specimens in the present fragment. The extremity of the alveolar series, therefore, exhibited in the present fragment, must be either the fore end of the right maxillary bone or the back end of the left maxillary bone. The expansion and bifurcation of the bone, as it approaches towards the end of the alveolar series, are opposed to every analogy presented by the fore part of the maxillary in the Lacertian and Crocodilian reptiles. The foramina, grooves, and sutural surfaces become utterly unintelligible in this supposition ; which is opposed, moreover, by the direction of the nervo-vascular outlets on the outer side of the bone, and by the curvature of the extremity of the alveolar series, as compared with the anterior extremity of that series in the lower jaw. In favour of the conclusion that the fragment in question is from the back part of the upper jaw, the expansion of the bone as it recedes from the tricdral fractured end, a, a', the direction of the neiwo- vascular outlets, ) the crown is unequally convex; on the opposite side (cut i), at the apical two thirds, it becomes a little concave : one margin is gently convex, WEALDEN CROCODILES. 421 the other is very shghtly concave at the apical half. The convex side of the crown is covered by smooth enamel, which forms four low ridges on its most pi'ominent part, and terminates inferiorly, by a delicate rugous structure, in a well- defined border, concave toward the root. The opposite side of the crown, flattened below and concave above, has the enamel smooth, except at the base, where it is rugous, and is extended nearly half an inch lower down the crown, where it terminates by a border convex toward the root. The margins of the crown are obliquely abraded toward the concave side of the crown, and, near the base of the straighter border, there is an oblique depression. The root is subcylindrical, and shows the remains of a pulp-cavity : it appears as if it had been implanted in a complete alveolar cavity ; but the unequal extent of the enamel on the two sides of the crown indicates a corresponding inequality in the outer and inner alveolar walls of the jaw which supported this tooth. Assuming the thecodont mode of its implantation, it w^ould in this respect resemble the teeth of the Crocodiles, and of certain Enaliosaurs and Dinosaurs. The shape of the crown of this tooth, especially the degree of compression of the crown (cut c) and its expansion above the root into opposite borders, which become trenchant, accords best with the characters of the teeth in the carnivorous Sauria. Of such teeth as have hitherto been discovered in the Wealden strata, those that have been referred to the Hylaosanrus* make the nearest approach to the form of the tooth in question ; but, besides the difference of size, the crown has a more symmetrical shape in Hylccoscmrus, and its broadest part is nearer the apex : the opposite worn margins which converge to the tip are both relatively shorter and thicker, and are not obliquely abraded so as to be trenchant, as they are in the larger Wealden tooth here described. It is a tooth of allied form to that of the Hylaosaurus, and, like it, was implanted by a cylindrical fang, apparently in a distinct socket : the few specimens that have been discovered of the teeth ascribed to Hi/lcrosmmis appear to have been broken from the socket, not to have been naturally shed so as to show the traces of absorption ; and the same is the case with the larger tooth in question. The difference of form between the tooth of the Blegalosaurus f and the present large piercing and cutting tooth is too obvious and strongly marked to need particularising ; and it departs still further, both in shape and mode of implantation, from the tooth of the Iguanodon.;}: The present tooth, therefore, indicates a reptile equal in size to any of those above cited from the Wealden strata, but of a distinct genus : and vertebral evidence has been adduced, in the present ' Monograph,' of at least two genera — independently of * 1= " Dlnosauria," Plate 39, figs. C— 9. f Ibid., Plates 33 and 34. t Ibid., Plate 23. 422 BRITISH FOSSIL REPTILES. Streptospondylus — of large Wealden reptiles equally distinct from those originally made known by Buckland and Mantell. The tooth in question may, very probably, belong to either Cetiosanrus or Pelorosaurus. Fu- ture discoveries of teeth or of jaws with teeth, associated with the characteristic vertebrae of one or other of these large reptiles, will determine this question. The tooth here described was first made known to geologists, and figured by Dr. Thomas Wright, F.G.S., an indefatigable explorer of the geology and fossils of the Isle of Wight, in a paper on the Palaeontology of the Island, in the ' Annals and Magazine of Natural History' for August, 1852. Tooth of large Wealden Reptile. — Veliosaurm or Pelorosauros (?). Genus — Poikilopleuron. Eudes-Deslongchamps. This genus was first proposed, under the above name, by the accomplished Pro- fessor of Natural History in the Lyceum or University of Caen, Normandy, in his description of portions of a fossil skeleton of a Crocodilian reptile discovered in the oolitic quarries near that town. This reptile was distinguished from the Cetiosanrus by the more complete protection afforded to the abdominal cavity through the greater development of the posterior ribs, and, as the author then believed, by the greater diversity of form presented by the whole series of ribs, a peculiarity which suggested the generic name.* Perhaps the most truly distinctive character of this genus, so far as its organization is known, is the texture of the bones, and especially of the vertebral centrums, which show unusually large cavities in their substance, with a very compact outer crust, polished externally, and recalling the character of the skeleton in the Pterosauria. It is this character which has led me to conclude that a species of the genus Poikilopleuron has left its remains in the formations of the Wealden period. * rioniXos, varied; TrXcvfjov, rib. WEALDEN CROCODILES. 423 Vertebra of Poikilopleuron. ' Crocodilia,' Plates G, 19. In the Museum of the Royal College of Surgeons, London, is a portion of a caudal vertebra (No 59 of the ' Fossil Reptilia,' PI. G, figs. 5, G), presented by me, and obtained from the submerged Wealden beds at Brook Point, Isle of Wight.* The terminal articular surface (fig. 5) is elliptical, with the long diameter vertical, and is slightly concave ; the middle of the centrum is contracted ; the fractured surface (fig. 6) exposes a medullary cavity, surrounded by large, cancellous vacuities, which have become filled with siliceous spar and pyritic matter. There is a small depression on each side near the base of the neural arch, which seems to lead, like a pneumatic foramen, into the cavities of the bone. The thin, outer wall of this open, cancellous structure consists of very compact bone. This vertebra agrees in shape and structure with those of Poikilojjieuron. To the genus Poikilopleuron it is most probable that the specimen No. -irh: '" the Mantellian Collection, British Museum, belongs, as it agrees in size, in texture and especially in the character of the external surface, with the caudal vertebra above described. As it consists of the annular part or neural arch only, the test of the medullary cavity of the body cannot be applied. It belongs to one of the ante- rior dorsal vertebrae, and is distinguished by well-marked and peculiar characters from the corresponding vertebrse of the Iguanodon, Megalosaurus, IlylcEosaurus, Getiosauriis, and Streptospondi/lus ; and in the chief of these differences it approxi- mates to the sub-biconcave Crocodilian type of vertebrae. By the characters here given of this fragment it may be compared with more perfect vertebrse from the Oolite of Maladrerie, near Caen, in the event of the remainder of the vertebral column of the Poikilopleuron ever falling into the hands of its original discoverer. The present fossil is imbedded in the ferruginous sand of the Tilgate strata; its antero-posterior diameter, from the extremity of the anterior to that of the posterior zygapophysis, is 5 inches 4 lines. The neurapophyses (PI. 19, figs. 1 and 2, d) instead of rising and expanding to form a broad platform, as in the Dinosaurian vertebrse, support the spinous (fig. 4, e) and transverse («') processes by a longitudinal plate not more than from 3 to 6 lines in transverse thickness ; from each side of this plate a horizontal, flat, broad, lamelli- form diapophysis (e), supported below by a subvertical, triangular plate, extends outward and a little upward ; and a broad, thin, and moderately high spinous pro- cess arises, in a peculiar manner, by two laminse, from the whole antero-posterior extent of the ridge-like summit of the neural arch. The fossil is broken in two; a portion of the centrum adheres to the anterior part of the neural arch, demonstrating the anchylosis of the two parts without trace of suture. In this respect the fossil * ' Catalogue of Fossil Reptiles and Fishes,' 4to, Loudou, 1S54, p. 15 2o 424 BRITISH FOSSIL REPTILES. agrees with Poikilopleuron and differs from Iguanodon, in which the neural arch is anchylosed with the centrum, but evident traces of the suture remain, at least in the dorsal vertebrge. The anterior part of the side of the centrum is impressed by a large surface for the head of the rib ; the surface is concave in the axis of the vertebra, convex vertically, and is bounded above by a well-defined ridge. The anterior zygapophysis (figs. 1 and 2, «) supports flat, articular surfaces, of an elliptical form, IG lines by 9 lines, looking upward and inward ; the lower edges of the pair of surfaces converging at an angle of 50°. These edges are separated from each other by a fissure 3| lines broad, continued to the base of the anterior oblique processes. In the Iguanodon the corresponding surfaces incline to each other at a right angle, and the lower margins of the processes are united by a continuous tract of bone. Each anterior articular surface is supported by a stout process, convex externally, inclining forward and slightly expanding, so as to overhang and extend beyond the anterior end of the centrum. A deep and narrow excavation commences immediately behind tlie upper and posterior origins of the anterior zygopophyses, and is continued backward, increasing in vertical extent, deep into the anterior part of the base of the spinous process. Immediately behind the columnar portion of the zygapophysis a conical cavity sinks into the neurapophysis, undermining the anterior part of the base of the diapophysis, and dividing the zygapophysis from it. The diapophysis commences from the summit of the neurapophysis immediately exterior to the anterior part of the base of the spinous process, by a ridge which is continued backward from the upper and outer margin of the anterior zygopophysis, in a gentle curve outwards and slightly upwards. The posterior margin of the base of the diapophysis is not continued, in like manner, into the posterior zygapophysis, but terminates or sub.^ides into a ridge above, and separated from that process by a wide groove. The bases of the two diapophyses are only separated from each other, owing to the modification of the neural arch above mentioned, by a thickness of bone not exceeding 4 lines; the interspace of the origins of the two diapophyses in a corre- sponding vertebra of the Iguanodon measures 4 niches ; the leugtli of the base of the neural arch being the same in the vertebra compared. The antero-posterior extent of the base of the diapophysis in this (presumed) vertebra of the Poikilojjleuron is 2 inches 2 lines ; the length of the diapopiiysis is 4 inches ; the vertical diameter, or thickness of the same process, where unsupported^ is from 2 to 3 lines. It is obvious, therefore, that this long, thin, lamelliform plate of bone must need lurther support, in order to sustain the rib which is appended by its tubercle to the extremity ; and the requisite strength is here given precisely as the carpenter supports a shelf by a bracket. The bracket-like process (fig. 5, c) is a vertical, triangular plate of bone, the breadth or depth of which, at its origin, is 1 inch 4 hues ; this gradually diminishes in depth and increases in thickness as it WEALDEN CROCODILES. 425 extends along the middle of the under part of the transverse process, until it is finally lost near the extremity of the process, which here has exchanged its lamellar for a prismatic form, terminating in the obtuse extremity against which the tubercle of the rib abutted. The supporting bracket is not quite vertical, but inclines a little forward, and behind it there is a deep, angular fossa. The posterior zygapophyses (figs. 4, 5, b,b) diverge from each other and from the neural arch immediately above the poste- rior extremity of the spinal canal ; each articular surface, which is directed downward and outward, forms, as it were, the base of a posterior root of the spinous process, which is convex externally, diminishing in breadth as it converges to meet its fellow at a very acute angle above a deep fissure extending forwards into the substance of the base of the spine, similarly to the fissure before described as extending backward from the opposite part of the spine into its substance. As far as I could detach the matrix, these fissures extended so that they seem to communicate, and the neural arch to be perforated by two longitudinal passages, one for the spinal cord, and the other, running above and parallel with the former, through the base of the spinous process. The anterior parts of each spinal plate are thickened and rounded, like those behind, and extend to the origins of the anterior zygapophyses. The diameter of this remarkable spinal fissure is from 4 to 3 lines. It does not exist in the vertebrae of the Iguandon, Megalosaurus, or other Dinosauria. The base of the spinous process in this (presumed) Poilcilopleuron's vertebra, instead of descending from behind forward in a graceful curve, as in the Dinosaurs, forms a straight and almost horizontal line, 3 inches in extent ; the spine maintains the same breadth to its summit, which is truncated rather obliquely ; its height is 4 inches 9 lines, measured from the upper end of the posterior zygapophyses ; it is thickened and rounded at its truncate summit. The height of the spine of a corre- sponding vertebra of the Iguanodon, with a centrum of the same length, is 9 inches. Thus the present vertebra more resembles, in the form and proportions of its spinous process, as in other characters, the vertebra3 of the Crocodilians. The posterior part of the neural arch, with the spinous process of the vertebra, here described, is figured in Mantell's ' Illustrations of the Geology of Sussex,' p. xii, fig. 1, as the "Lumbar Vertebra of the Iguanodon." It is not, however, a lumbar vertebra nor a part of the Iffuanodon ; if it does not belong to the Poikilopleuron, it indicates an unknown genus of Crocodilians. Nos. /2V4 ^nd -^2^, in the Mantellian Collection, are the two moieties of a fossil caudal vertebra, fractured obliquely across the middle of the body, the length of which is to the breadth of its articular extremity as 3 to 2 ; both extremities are slightly concave ; the body is gradually contracted from the t\\ 0 extremities towards the middle part ; bears a transverse process developed from the posterior and upper part of its side, behind which there is a shallow groove ; has tlie neural arch anchy- losed, without trace of suture, to nearly the whole of the longitudinal extent of its 426 BRITISH FOSSIL REPTILES. Tipper surface. The neural arch is provided witli anterior and posterior oblique processes, and a broad and thin spine developed at its posterior part, and strongly inclined backwards at its origin; lastly, the vertebra has a large medullary cavity in the centre of the body, filled, in the fossil, with spar. In all these particulars the Palseontologist acquainted with the excellent description by M. Eudes-Deslong- champs of the roikilopleuron Bucklandi* from the Oolite at Caen, will not fail to recognise the distinctive characters of that species in the present fossil. It is attached to a mass of the common Wealden stone which is quarried at Tilgate, and was associated with the bones of the Iguanodon. The length of the present vertebra is 3 inches 9 lines, or 9^ centimeters; that of the caudal vertebrae of the Poikilopleuron of Caen is about a decimeter.f We may conclude, therefore, that the individual from the Caen Oolite and that from the Wealden were of the same si^e, and, from this correspondence, it is most likely that the size — 25 French feet, which M. Deslongchamps assigns to the entire animal — is the common size of the species. From the size and position of the transverse process, the Tilgate vertebra corre- sponds with the second or third of the first series of caudal vertebrae of the Caen Poikiloplcuroti figured by M. Deslongchamps. There is one character in the Wealden vertebra which is not mentioned in M. Deslongchamps' description of the Caen species, viz. a longitudinal sulcus at the middle of the under surface of the body of the vertebra, at least, at its anterior half; the sulcus is not deep, and is 1 centimeter or 4 lines in breadth. The fortunate fracture which demonstrates the peculiarly large medullary cavity in the centre of the vertebral body gives the best proof that could be required of the generic identity of the Wealden vertebra with the Caen Poililojjlcuron ; and the absence of that cavity in the vertebrae of Megalosaurus, which I have determined by a section of one of the caudal vertebrae, establishes the distinc- tion between that genus and Poikilopleuron. In the form of its sub-biconcave vertebrae, and the simplicity of their neural arch as compared with the Streptospondylus and the Dinosaurians, the Poikilopleuron manifests its closer affinity to the amphicoelian Crocodiles. It agrees with the Teleosaurns in the comparative shortness of the fore legs ; the mode of articulation of the vertebral ribs a])pears to be the same, and there is no evidence that it differs ill the structure of the abdominal ribs. The number of caudal vertebrae would appear to be greater; but I know not in what material respect the Poikilopleuron resembles the Lizard tribe more closely than does the Teleosaurus, unless it should be proved to have five toes on the hind foot, and to want the dermal armour. Subsequent discoveries may prove it to belong, like the Megalosaurus, to tiie Dinosaurian order; but as the Poikilojjleuron is * ' Menioires de la Societe Linn, de Normandie,' 4to, 1836. f "Nos verlebres out chacune environ un decimetre de long." — Deslongchamps, loc. eit., p. 53. WEALDEN CROCODILES. 427 at present known, it seems to have most claim to be received into the Amphicoelian family of the Crocodilian order, and perhaps has the closest affinity in that family to the Crocodilus Bollensis, Jaeger {Macrospondylus, 11. v. Meyer). Genus — Goniopholis, Owen This genus was determined, and so named, from the characteristic form of the teeth, which had been discovered in the Wealden strata of Sussex. These are remarkable, for the thick, rounded, and obtuse form of the crown, the enamel of which is marked by numerous close-set and neatly defined longitudinal ridges ; two of these, larger and sharper than the rest, traverse opposite sides of the tooth from the base to the ape.x of the crown, midway between the convex and concave lines of the curvature of the tooth ; the cement-covered, cylindrical base of tlie tooth is smooth. Such teeth vary from a length of crown of 2 inches, with a basal diameter of 1^ inch, to teeth of one third these dimensions. In the British Museum is preserved a slab of Purbeck limestone, with a portion of both endo- and exo-skeletons of a crocodile, in the lower jaw of which are preserved two teeth (PI. 7), proving the specimen to have been identical with the Goniopholis of the Wealden strata. Goniopholis crassidens, Owen. ' Grocodilia,' Plates 7 — 13. Our knowledge of this remarkably well-defined Amphiccelian Crocodile has been derived from a study of its fossil remains, obtained from deposits of the Wealden and Upper Oolitic ])eriods. The first indication of the genus was given by detached teeth from the Tilgate quarry, which presented a thicker and more robust form of crown than in other Saurian teeth of that period, the proportions being rather those of the teeth of the Proccelian Crocodiles andAlligators of the tertiary and modern times. From these, however, the Wealden ones differed in the longitudinal ridges of enamel traversing the exterior of the crown, which are numerous, close-set, and neatly defined. Two of the ridges, larger than the rest, traverse opposite sides of the tooth, and in the larger specimens fioni the base to the apex, being placed midway between the convex and concave out- lines of the curve of the tooth (PI. 11, fig. 3) ; in the smaller teeth, which intervene between the larger ones in the mandibular series, these opposite ridges are limited to 428 BRITISH FOSSIL REPTILES. the apical half of the crown, to which they give somewhat of a trenchant character (PI. 12, fig. 4). At the hack part of the series the crown becomes obtuse (Pi. 7, fig. 2) ; as it also does in the Crocodilus HastingsicB (' Crocodilia,' PI. 1 b, fig. 1), and in the Groc. Spenceri (PI. 3, a, fig. 12). On these characters the present genus and species were founded in my ' Report on British Fossil Reptiles.'* In the British Museum is preserved the split slab of Purbeck limestone, quarried near Swanage, Dorsetshire, containing dislocated parts of a skeleton of a reptile, determined by the two teeth, fortunately retained in the part of the lower jaw preserved, to belong to the Goniopholis. The first character which attracts the palseoutologist's attention, in this remarkable specimen, is that which the numerous large, bony, dermal plates or scutes afi'ord (PI. 7. d). These are scattered irregularly over the slab, and in their number and relative size bring the species much nearer to the extinct Teleosaurs than to any of the existing Crocodiles ; they diff'er, however, from both the dorsal and ventral scutes of the Teleosaur in their more regular quadrilateral figure ; they are longer in propor- tion to their breadth than most of the Teleosaurian scutes, and are distinguished from those of all other Crocodilians, recent and fossil, that I have yet seen, by the presence of a conical, obtuse process (PI. 1, figs. 1 and 2, a) continued from one of the angles vertically to the long axis of the scute ; analogous to the peg or tooth of a tile, and fitting into a depression on the under surface of the opposite angle (ib., fig. 1, b) of the adjoining scute ; thus serving to bind together the plates of the imbricated bony armour, and repeating a structure which is highly characteristic of the large bony and enamelled scales of many extinct ganoid fishes. Some of the scutes in the Swanage specimen are 6 inches in lengtli and 2^ inches in breadth. The exterior surface of the scute (PI. 8, fig. 2) is impressed by numerous deep, round, oblong, or angular pits, from two to four lines in diameter, and with intervals of about two lines, formed by convex, reticularly disposed ridges of the bone ; but a larger proportion of the anterior part of the scute is overlapped by the contiguous scute that in the Teleosaur, and this part is smooth, and thinner than the rest of the scute. The whole of the inner surface of the scute (ib., fig. 1) is smooth, but on close inspection it is seen to be everywhere impressed by fine, straight lines, decussating eacli other at nearly right angles, and indicating the structure of the corium in which the scutes were imbedded. Thus, from the size and strength of these dermal bones, their degree of imbrication, and the structure for interlocking, we may conclude that the Goniopholis was better mailed than even the extinct Teleosaur, which Cuvier regarded as " I'esp^ce la mieux cuirassee de tout le genre. "f In the slab in question the vertebras (PI. 7, v, v) were unfortunately all at right * 'Reports of the British Association,' 18-11, p. G9. t ' Ossemens Fossiles,' torn, v, pt. 2, p. 1, 139. Inches. 1 Lines, 10 1 9 I 8 0 11 10 0 4 4 WEALDEN CROCODILES. 429 angles to the exposed plane, and fractured across the middle, one extremity being buried in one of the halves of the slab, and the other in the opposite half. B/ per- mission of the Trustees of the British Museum, I was able, in 1841, to remove the matrix from the two extremities of the same vertebra, and so demonstrated that both articular ends were equally but slightly concave. The length of the body of the vertebra examined was . Vertical diameter of the articular extremity . . . Transverse diameter of the articular extremity Ditto of middle of the body ...... Ditto of entire vertebra, including the transverse processes . Height of entire vertebra, including spinous process . From the lower part of the centrum to the base of the transverse process .......... 2 6 The suture which joins the neural arcli to the centrum is conspicuous ; it forms an ascending angle or curve at its middle part. The body of the vertebra expands in a greater degree to form the subconcave articular surfaces than in other biconcave vertebrae of the same length ; and both in this character and in its smooth surface and circular transverse contour at the lower part, the Goniojjholis resembles the Streptospondylus more than it does the Teleosaurus. The transverse processes of the lumbar and anterior caudal vertebrae are long, straight, and comparatively slender ; those of the sacral vertebrae (PI. 7, *. «) are relatively thicker, and the spaces enclosed by their expanded extremities are smaller than in either the Teleosaurs or Crocodiles. The antero-posterior extent of the two sacral vertebrae is three inches two lines. The ilium (ib., i) is broader than in the existing Crocodilians ; the bifurcation of the proximal end of the ischium (ib-, is) is more marked, and the iliac branch is more regularly rounded ; the pubic branch is longer, more slender, and its articular end is more regularly convex ; the distal or low^er part of the ischium expands into a relatively broader plate. This character is still more conspicuous in the pubis (ib., p), which equals the ichium in breadth, and begins to expand much nearer the proximal extremity tiian in the existing Crocodiles. In these modificatious of tiie pelvis, as well as in the biconcave structure of the vertebra, the Crocodilian of the Purbeck limestone approaches nearer to the characters of the Enaliosaurs ; and we may infer that its habits were more decidedly marine than are those of existing Crocodilians. The caudal vertebrae were provided with long, narrow, unanchylosed chevron bones. The portion of the lower jaw preserved belongs to that part of the left ramus included between the articular extremity, which is broken off, and the commence- ment of the dental series ; it measures 1 foot 6 inches in length, and 5 inches in greatest depth. In these proportions, and the curve of the lower margin, it deviates 430 BRITISH FOSSIL REPTILES. from the ancient Teleosaurs and Steneosaurs, and resembles the modern Crocodiles ; and although not quite equalling these in the robust proportions of the jaw, yet it much exceeds in this respect the Crocodilians with more slender teeth. Portions of the skeleton of a GonwphoUs, kindly submitted to my examination by G. B. Holmes, Esq., of Horsham, by whom it was discovered in a Wealden stratum at Cuckfield, Sussex, shows the symphysis of the lower jaw (Pi. 12, fig. 4) to have been as long in the Crocodilus Spenceri (' Crocodilia,' PI. 2, fig. 2), a transitional form between the modern Crocodile and Gavial. The fore part of the premaxillaries (PI. 1 1, figs. 1 and 2) shows a semicircular anterior contour, and a single subcircular nostril, placed rather nearer the termination of the muzzle than in existing Crocodiles, but yet above, not terminal, as Teleosaurus, not subterminal, as in Steneosaurus. Tiiere is not enough of the bone preserved to show whether there was a constriction of the upper jaw behind the nostril, as in the Gavial. The incisive foramen is not immediately beneath the nostril, as in the modern and tertiary Crocodiles (comp. PI. 1, c, with Pi. 11, fig. 2). The outer surface of the premaxillaries is convex, rather irregular, with vascular foramina and wrinkled impressions. The margins of the symphysis are a little produced. There are four alveoli in each premaxillary, as far as the bone is preserved ; they are proportionally larger, more numerous, and closer together than in the corresponding part of the Streptospondi/luii or Steneosaurus brevi- rostrus {' Ossem. Fossiles,' 4to, t. v., pt. ii, pi. x, fig. 6). The first and smallest socket is in contact with the second, which is the largest; the intervals increased beyond this socket (PL 11, fig. 2). The palatal surface shows a pair of large and deep approximate fossae, and a second pair of smaller fossae for lodging the crowns of the anterior teeth of the lower jaw. This is very slightly expanded at its anterior end, where the larger (third and fourth) tusks are implanted. The fragments of the mandible indicate a symphysis of, at least, eight inches in length ; at the anterior three inches the rami interlock by strong, radiating ridges and grooves (PI. 12, fig. 1). The teeth are well preserved in parts of these fossil jaws the cylindrical fang is invested by smooth cement ; the coronal ridges begin at the basal line of the enamel, and proceed nearly parallel to the apex of the cone. In a tootli with a crown one inch long and half an inch across the base four ridges are included in a space one line broad ; a few of tlie ridges are interrupted to preserve the parallelism of the rest. Towards the apex a number of shorter and finer ridges are present on each side of the two chief ridges, to which they obliquely converge. At the extreme apex of an unworn tooth the ordinary ridges terminate in fine, slightly wavy lines, forming a subreticulate surface. In the Jurassic Crocodilian, called Madrimosaurus by V. Meyer, the coronal ridges of the teeth are more numerous, are smaller at the base of the enamel, and more of the ridges are interrupted than in Goniopholis ; the entire tooth also seems to be shorter and thicker. WEALDEN CROCODILES. 431 Examples of the successional teeth are shown at a, fig. 3, PI. 11, and at «, fig. 2, PI. 12. Since the characters of the teeth in the Purbeck Goniopholis are only known by the two posterior ones of the lower jaw, the Wealden species may be distinct. The large intervals and unequal size of the teeth behind the anterior four or five mandibular teeth are shown in PI. 11, fig. 4, and 11, 12, figs. 3, 3, a, and 4, from the Wealden specimen. Cervical Vertehree {'Crocodilia,'' PI. 10, figs. 1 — 5.) The three vertebrae represented in the above-cited plate were obtained by Mr. Holmes from the same bed of Wealden clay, at Cuckfield, as the teeth and scutes characteristic of the genus Goniopholis, to which, therefore, I refer them. They correspond with the fourth, fifth, and sixth cervical vertebra? of the recent Crocodile, having a parapophysis similar in form, extent, and position, with traces of a short and thick hypapophysis (comp. fig. 1, PI. 10, with fig. 2, A, PI. 3, a) at the fore part of the under surface ; but behind this the under surface of the Wealden vertebra is less convex, the whole centrum is relativelybroader, and the more important difference of the concavity of the hinder as well as of the front articular end manifests the distinct family of Crocodilia to which the Goniopholis belongs. The depth of the concavity of these surfaces exceeds that in Teleomurus. The free surface of the centrum is smooth. The neural arch articulates with the whole length of the centrum, which is impressed by a neural channel, slightly widening behind, between the neurapophysial surfaces (PI. 10, fig. 5). Two vertical, venous canals open into the neural canal. Fig. 6 is the side view of a cervical centrum from the Purbeck beds, having the general proportions of those of Goniopholis, but differing in the smaller size of the parapophysis. Figs. 7 — 9 are views of the centrum of a dorsal vertel)ra of a Wealden Goniopholis, fig. 9, showing the texture as displayed by a vertical longitudinal section. This shows a close, cancellous structure throughout, whereas the centrums in the Teleosaurus (PI. 9, fig. 6) exhibit a more open, reticulate texture, with a cavity near the centre. One of the posterior caudal vertebrae, after the subsidence of the diapophyses and the great reduction of the zygapophyses, shows the spinous process rising from the hinder half the neural arch, as at ff, PI. 13. The coracoid (PI. 13, /') difi"ers from that of the existing Crocodiles in its greater relative breadth at the neck or part marked k, in the more gradual and minor expansion of its mesial end, and in the more regular convexity of its scapular border. It exhibits the same perforation near this border as in the modern Crocodiles. The humerus associated with the remains of Goniopholis from the Wealden of Cuckfield has the usual Crocodilian form and sigmoid flexure. Compared with one 2^ 432 BRITISH FOSSIL REPTILES. from a Crocodilus biporcatus, with the same-sized cervical vertebrae, it is a somewhat thicker and stronger bone (see p. 102). It has a broader and thicker ulnar tuberosity, and the angle at which the process is bent down upon the shaft is less marked, more rounded off. The radial crest is a triangular, compressed ridge, but is not produced beyond four lines from the surface of the shaft ; the distal part of the bone is proportionally thicker antero-posteriorly than in the modern Crocodiles, and the longitudinal, irregular ridges at the margin of the articular surface are stronger ; there is a similar ridge above the inner condyle. The femur of the Goniopholis (PI. 13, o) is relatively longer, and is less bent than in the existing Gavial or Crocodile. The tibia {m and », the latter bone presenting its narrower side to view) is also both longer and thicker. Dermal Scutes (Plates 9 and 13). In the slab of Wealden stone from Cuckfield, containing the parts of the dislocated skeleton shown in PI. 13, there were imbedded, not only the long, quadrate, toothed scutes (a, b), like those in the Purbeck slab (Pis. 7 and 8), but a second form of scute (PI. 13, d,d), of which no examples had been preserved in the Purbeck specimen. These scutes are hexagonal, marked as in the toothed kind, on the outer surface, by hemispheric, circular or subcircular pits, and on the inside by fine, linear, decussating lines on an otherwise smooth and plane surface (PI. 9, fig. 2). They have no articulat- ing process, but have a strongly marked sutural surface on the thick margin (ib., fig. 5), showing tliem to have been united together, like the neural and costal plates of the carapace, and like the elements of the plastron, in the terrapene and tortoise. From the association of hexagonal sutural scutes with the quadrate, oblong, toothed scutes in the specimen (PI. 13), it can hardly be doubted that they formed part of the same exo-skeleton. But to what part of such skeleton each kind was appropriated cannot be determined until more complete examples are discovered. In the sixth part of the sixth volume of the ' Palseontographica' of H. v. Meyer, the author has described and figured part of the dermal skeleton of what he believes to have been a Saurian reptile, consisting of bony plates, for the most part hexagonal and united by marginal sutures. These plates, however, do not present the uniformly pitted character of the external surface, as in Goniopholis ; but here and there in the series they show a few irregular, large depressions ; the more constant markings are smaller, apparently vascular foramina, and linear, usually radiated, impressions in character more like the markings of the dermal ossifications of the Labyrinthodont reptiles. The specimen described is from the " dachsteinkalk," under the Winkel- maass Alpe, near Ruhpalding, in Bavaria, and it is referred to the Psephoderma Alpinum. WEALDEN CROCODILES. 433 Genus — Suchosaukos,* Owen. SuCHOSAURUS ciLTRiDENS, Owcu. ' CrococlHia,' PI. 5. In the Wealden formations have been found detached teeth and vertebrae, indicat- ing the existence, at that period, of a large Amphicoelian Crocodile specifically and generically distinct from the Goniopholis ; for, since the discovery of associated bones and teeth of the latter genus have made us acquainted with its vertebral characters, the other remains, upon an exhaustive analysis of the reptilian fossils of the Wealden series, leave only the form of Saurian tooth (PI. 5, fig. 4) wherewith to associate the equally peculiar form of Saurian vertebra (Pi. 5, fiiis. I — 3). This vertebra is readily distinguishable, by the length of the centrum and the compressed, wedge- shaped character of its middle part, from all other known Saurian (Dinosaurian or Crocodilian) vertebrae of the Wealden period. The specimen is No. i^^is' Mantt-llian Collection of Wealden fossils in the British Museum (PI. 6, figs. 1, 2, 3), and is the body of a dorsal vertebra, with both articular extremities slightly and equally concave ; though narrower at the middle than at the ends, it is more uniformly compressed than in other Crocodilian vertebrae, the sides converging to an inferior obtuse ridge, which is very slightly concave in the antero-posterior direction. The sides are not flat in the vertical direction nor slightly concave, as in many of the Iguanodon's vertebrae, to which the present form approximates ; but are gently convex, so that a pencil laid vertically upon the side touches it only by its middle. A more decided difference between the present Crocodilian vertebrae and those of the Iguanodon is, that the former are longer in proportion to their height and depth. The external surface at the middle of the body of the vertebra is very finely striated, so as to present a silky appearance; near the margins it is sculptured by coarse, longitudinal grooves and ridges. The base of the neurapophysis (ib., fig. 3, b) which, when anchylosed, leaves an evident trace of the suture, is nearly equal in length with the body of the vertebra (ib., a) ; it does not wholly include the spinal canal, but leaves the impression of the lower third of that canal upon the upper surface of the centrum. On the outside of the neurapophysis are two slightly developed, broad, obtuse, ridges converging towards each other from the outer side of eacii angle or end of the base of the neurapophysis ; the ridge corresponding with the posteuior of these in the Iguanodon's vertebra rises more vertically, and is in higher relief. The neurapo- physial suture slightly undulates in its horizontal course, and rises in the middle instead of descending upon the centrum, as in the Plesiosaurs. * Greek liiv)^ns, an Egyptian name of the Crocodile, and aavpos, lizard. 434 BRITISH FOSSIL REPTILES. The present vertebra is alluded to at p. GO, and figured at pi. ix, fig. 11, of Dr. Mantell's ' Illustrations of the Geology of Sussex,' as a lumbar vertebra of the Megalosaurus. But in the ' Geology of the South-east of England,' the same author, speaking of this vertebra, observes, " It cannot, I now think, be separated from those figured in the same plate as belonging to a Crocodile." — p. 297. Fig. 8, PI. 9 (Tilgate Fossils) is, however, a caudal vertebra of the Getiosaiirus. The body of the Megalosaurian vertebra has a pretty deep, longitudinal depresssion belowr the neurapophysial suture, wanting in the Tilgate vertebra here described. This, however, is not the only distinction ; below the depression the centrum of the Megalosaur swells out, and is as convex below as it is laterally in the transverse section, so that the outline of a transverse section would describe five sixths of a circle ; a similar section of the vertebra of Suchosunrus would be triangular, with the apex rounded off. Tlie Megalosaurian vertebra is more contracted at the middle, and swells out near the articular ends, surrounding those articulations with a thick convex border ; in Suchosaurus the lateral meet the marginal surfaces at a somewhat acute angle ; but the silky, striated surface of the Suchosaurian vertebra, and the smooth and polished surface of the Megalosaurian one, would effectually serve to distinguish even fragments from the middle of the body of each. The following are dimensions of the vertebra of the large Wealden Crocodilian above described : — No. 138. Inches. Lines. Antero-posterior diameter of the body . . . . . 3 10 Vertical diameter of its articular end ..... 3 2 Transverse diameter of its articular end ..... 2 9 Transverse diameter of the middle of the body .... 2 0 The fossil teeth from the Wealden (PI. 5, fig. 4), which I provisionally associate with the foregoing vertebree, approach by their more slender and acuminated form to the character of those of the Gavial, but differ from the teeth of any of the recent species of that sub-genus of Crocodilians, as well as from those of the long and slender-snouted extinct genera, called Teleosauriis, Steneosaurus, &c. The crown is laterally compressed, subincurved, with two opposite trenchant edges, one forming the concave, the other the convex, outline of the tooth. In the Gavial the flattening of the crown and the situation of the trenchant edges are the reverse, the compression being from before backwards, and the edges being lateral.* The tooth of the Sucho- saur thus resembles in form that of the Megalosaur (PI. 5 fig. 5), and perhaps still more those of the Argenton Crocodile ; but I have not observed any specimens of the Wealden teeth in which the edges of the crown were serrated, as in both the reptiles * The tooth attributed by M. Deslougchamps to the Poikilupleuron agrees in form with those of the Gavial, and differs in the characters cited in the te.Yt from those of the Suchosaurus. WEALDEN CROCODILES. 435 just cited. The teeth of the Suchosaur also present a character which does not exist in tlie teeth of the Megalosaur, and is not attnbuted by Cuvier,* to tliose of the Crocodile d'Argenton. The sides of the crown are traversed by a few longitudinal, parallel ridges, with regular intervals of about one line, in a crown of a tooth one inch and a half in length ; these ridges subside before they reach the apex of the tooth, and more rapidly at the convex than at the concave side of the crown. Hitherto these teeth have not been found so associated with any part of the skeleton of the same species as to yield unequivocally further characters of the present extinct Crocodilian. From the above-mentioned well-marked differences between these teeth and those of all other known species, I regarded the extinct Crocodile as forming the type of a distinct genus and species, and proposed for it the term Suchosaums culfridens.f * Cuvier, ' Ossein. Fossiies,' 8vo, torn, ix, p. 331. ■f 'Report on Brit. Fossil Reptiles,' 1841, p. 67. 436 BRITISH FOSSIL REPTILES. Order— PlWi2 OS A TIBIA. SUPPLEMENT No. II. PTERODACTYLES OF THE CRETACEOUS FORMATIONS. Genus — Pterodactylus, Cuvier. In the first supplement to the present order, on the Pterodactyles of the Upper Green-sand of Cambridgeshire, I described,* figured,! or referred to, parts of a Pterodactyle from an individual surpassing in size that to which the portions of upper and lower javv| belonged on which the species dedicated to Professor Sedgwick was founded. Such fossil evidences of more gigantic flying reptiles, showing no better distinctive characters than size, were deemed, probably, to belong to the Pterodactylus Sedgwickii, the then largest known species of the genus. I am now, however, enabled to adduce, from the more recently acquired additions to the Woodwardian Museum at Cambridge, supplied to me by the same unfailing liberality of the eloquent Professor, evidences of a much larger Ptero- dactyle, distinct, in regard to the form of the skull, from any previously known, and one which, assuming that the portion of upper jaw of Fterodactylus Sed^tvickii (PI. 7, fig. 1) belonged to a full-grown specimen, must have acquired at least double the dimensions of that species. * Page 382. t Plate 7, fig. 6. J Ibid., p. 3/9, plate 7, figs. 1 and 2. CRETACEOUS PTERODACTYLES. 437 Pterodactylus simus, Owen. Jaws and teeth (PI. 11, figs. 1 — 10). The first evidence I have to offer of tliis truly gigantic flying reptile consists of the corresponding part of the upper jaw with that on which the Pterodactylus Sedgwic/di was founded, viz. the anterior extremity forming the muzzle (PI. 11, figs. 1—5), including the first four {a,b,c,d) and part of the fifth (e) sockets of the teeth. The comparison and appreciation of the specific distinctions of the two large Pterodactyles are thus rendered easy and satisfactory. In the specimen oi Pterodactylus simus (PI. 11, figs. 1 — 5), the first tooth («) on the left side remains in the socket; it is not larger than the corresponding tooth in Pterodactylus Sedc/ioickii, and, consequently, is relatively much smaller than in that species. Its socket and that of its fellow, moreover, are differently situated, opening downwards, like the succeeding sockets, and the position of the exserted foremost tooth is accordingly vertical and nearly parallel with tlie lower half of the anterior contour of the muzzle. In Pterodactylus SedyioicJcii, the sockets of the first pair of teeth open upon the fore part of the muzzle, and look almost directly forward,* and their teeth had, consequently, a nearly similar direction ; the same, viz. which they appear to have had in Pterodactylus suevicus, Qnst.f The contour of the muzzle in Pterodactylus Sedywickli rises at first vertically ahove these sockets before curving back into the upper part of the skull's profile, and gives an obtuse anterior termination to the upper jaw;]: but this character is much exaggerated in the present specimen (PI. 11, figs. 1 and 3), not only by the greater relative extent of the vertical part above the front sockets, but by the greater breadth of that part, which is flattened anteriorly, forming a surface (fig. 3) of nearly 2 inches in length, about 10 lines in breadth below, and contracting gradually above to a point, where the blunt ridge begins that forms the upper part of the profile of this portion of the skull. The name proposed for the species refers to this peculiarly obtuse and flattened fore part of the cranium. In Ptero- dactylus Sedywickii, the upper ridge of the fore part of the cranium is continued down to between the first pair of sockets,^ the muzzle being only obtuse vertically, and not transversely, as in Pterodactylus simus. The flattened anterior surface, in the specimen figured (PI. 11, fig. 3), is im- * Plate 7, fig. l,c. t ' Ueber Pterodactylus suevicus,' &c., 4to, 1855, tab. i. t Page 380, pi. 7. fig. 1. § Plate 7, fig. 2. 438 BKITTSU FOSSIL REPTILES. pressed by a very shallow and wide, longitudinal or vertical channel ; but this is scarcely marked in a second specimen of a muzzle of the same species. In both specimens the outer surftxce of the flattened part is less smooth than at the sides of the muzzle, being impressed by numerous irregular, linear grooves, seemingly vascular, affecting the vertical direction at the upper part, and the transverse direction at the rest of the surface. The ridge where the two sides of the muzzle meet, above and beyond the flattened surface, is more obtuse and is relatively thicker than in Pterodacti/lus Sedgwickii. Were the same curve to be continued from the part of the ridge preserved until it became horizontal, the vertical diameter of the skull at this part would be not less than three inches ; it may, however, have arisen to a greater height, for the contour is not regularly curved, but subangular, as shown in figs. 1 and 2, PI. 11. The facial part of the skull must have been narrow in proportion to its height, and, no doubt, also to its length. Tlie broadest pare of the present fragment does not exceed one inch and a quarter at the fourth pair of sockets ; the adherent matrix {m,m, figs. 4 and 5) gives a seeming greater breadth to this part of the skull. The sockets of the first pair of teeth («) are three lines apart, the interspace equalling the largest diameter of the socket ; the bone forming this anterior termination of the palate projects as a convexity below the level of the alveolar openings, the plane of which is a little inclined outwards. This inclination is increased in those of the second pair of sockets, which are nearly double the size of the first, and are five lines apart. The second is separated from the first socket by an interval of two lines ; its outlet has a full, oval form. The third socket is four lines distant from the second, and exhibits the same ratio of increase of size; there is a sliallow, vertical depression on the outer alveolar wall, between the second and third tooth, the socket of the latter appearing to have made a slight pro- minence on that part of the jaw. The palate at the interspace between the second and third pairs of sockets is flat, showing no trace of the median ridge charac- terising that part of the upper jaw, or of the groove at the corresponding part of the lower jaw, in the Pterodacf^Ius Sedgwickii. The upper jaw of the Pterodactylus siii/us, in the present specimen, has been partially fractured across the third pair of sockets (figs. 1 2, 5, «), of which only the fore part of the left one is here preserved, showing well-marked vascular grooves. Its outlet, from this fracture, appear to be of a larger oval or ellipse than in the second socket. The fourth socket {) ; it descends a short way obliquely palmad, decreasing in breadth, but still thick, convex, and terminating obtusely (fig. G, c). The radial crest (fig. G, i) better merits the name; it extends twice the length of the ulnar one, down the shaft, to the palmar side, towards which the whole crest is slightly bent; its margin describes a very open or low, obtuse, angle at its middle part. A ridge (') ui)on the palmar side of its distal half indicates the boundary of the insertion of the pectoralis major into the crest. At the middle of the anconal surface of the proximal part of the shaft there is a low, longitudinal ridge (fig. 7, /)• At the distal part of the humerus a ridge on the radial side of the palmar surface, and a rising of the bone on the ulnar side of the same surface, diverge to the opposite angles or tuberosities of the expanded end of the bone; they include a shallow, subtriangular concavity above the articular surfaces. These are two, and are convex. The radial surlace is a narrow, subelongate convexity, extending from near the middle of the palmar surface obliquely to the lower part of the radial tuberosity, where the convexity subsides; it is very prominent at its palmar end, with a groove on each side, the deeper one dividing it from the ulnar, articular convexity. This is of a transversely oval or elliptical shape, most prominent 450 BRITISH FOSSIL REPTILES. palmad ; all the part of the end of the humerus forming the two articular con- vexities is as if bent toward the palmar aspect. The ulnar end of the ulnar convexity is bent, and continued anconad to that end of the ulnar tuberosity. An oblique longitudinal channel divides the anconal end of the radial tuberosity from an almost longitudinal ridge, which is nearer the middle of the anconal side of the distal end of the humerus; a similar, but shorter, longitudinal ridge or rising of bone, terminates in the anconal part of the ulnar tuberosity. Between the above almost parallel ridges the anconal surface is nearly flat transversely ; it is traversed along the middle by a low, narrow, longitudinal ridge. Lengthwise the bone is here convex. The differences in the humerus of different birds are seen chiefly in the forms and proportions of the proximal crests ; the radial one in the CohnnbidcB, e.g. is shorter and more produced than in most birds of flight. The humerus in the swift and humming-bird is distinguished by special modifications. In the crocodile (PI. 13, figs. 9 — 12), the articular head of the humerus (fig. 12, a) is a transversely elongated, sub-oval convexity ; it is continued upon the short, obtuse, angular prominence (e), answering to the ulnar crest or tuberosity in the bird. The radial crest (fig. 9, 6) begins to project from the shaft at some distance from the head of the bone ; it is shorter, thicker, more prominent, and projects more directly palmad than in the bird. The humerus presents a similar sigmoid flexure lengthwise to that in the bird, but the ulnar contour of the shaft, as it descends from the ulnar end of the head of the bone, describes a concave line to the ulnar condyle; the radial contour is sigmoid, and not affected by the radial crest, as in the bird. There is a longitudinal ridge (fig. 10, d) on the anconal surface close to the radial border. The humerus of the Pterodactyle (ib., figs. 1 — 5) is shorter in proportion to the expanse of its proximal end than in either the bird or crocodile, and it appears to have a straighter shaft. It conforms at its proximal end more with the Croco- dilian than the Avian type. The ulnar crest, or tuberosity (c), is rather more prominent and better defined than in the crocodile, but the radial crest (6) is much more developed than in either the crocodile or bird. It resembles that of the crocodile in being more directly bent palmad, or what would be outward in relation to the side of the trunk, in the natural position of the bone at rest. The crest begins, above, at the radial and palmar end or angle of the articular head of the bone, and rapidly expands, bending palmad, with a base co-extensive with one fifth of the length of the humerus, inclining, as it descends (fig. 3), to the palmar side, ending below by a rough tuberosity, h, projecting at a right angle from the shaft of the bone; the lower sharp margin (fig. 1, i) of the tuberosity passes by a quick curve, and subsides upon the cylindrical shaft. The palmar surface of the proximal part of the humerus, by the production in that direction of the ulnar CRETACEOUS PTERODACTYLES. 451 tuberosity, but more especially by the direction of the large, radial crest («), is more concave across than in birds. Between b and c, in fig. 1, it is gently convex lengthwise, and is very smooth. A longitudinal ridge (fig. 1, '), along the distal half and palmar side of the base of the radial crest, indicates, as in birds, the insertion of the strong and large pectoral muscle. The articular head of the bone is reniform, not uniformly convex, as in birds, but slightly concave between the beginnings of the radial and ulnar crests or processes on that moiety of the head next the palmar side (fig. 3, «). At the opposite (anconal) side (fig. 2, «), the head-piece projects slightly beyond or over- hangs the shaft, the upper part of which, on the anconal side, is slightly concave lengthwise, very convex across, more so than in birds, and without trace of the median longitudinal ridge (/, fig. 7). It is equally devoid of the ridge which, in the crocodile (fig. 18, d), runs close to the radial side of the anconal surface. The shaft is more cylindrical than in birds. The pneumatic foramen (figs. 2, 5, p) is situated a little below the radial end of the head of the bone, on the palmar side of the bone; in the vulture, and most birds of flight, it is situated on the opposite side (fig. 7, p). The pneumatic texture of the shaft is as well marked as in any bird of flight. In looking directly upon the palmar side of the humerus in the bird one has an oblique, foreshortened view of the radial crest, the base of which lies wholly along the radial margin. Taking the same view of the humerus of the Pterodactyle as in PI. 13, fig. 3, we look almost directly upon the edge of the radial crest {h, b'), the base of which has inclined below from the radial upon the palmar surface. A corresponding view of the humerus of the crocodile (fig. 11) shows the whole base of the radial crest on the palmar surface, clear of the radial border, and the opposite side of the crest to that in the bird is obliquely brought into view. (In the figure 11 the radial side of the shaft is rather too much turned towards the eye.) In the position and shape of the radial crest the Pterodactyle is between the bird and the crocodile; in the transverse extent of the crest it exceeds both. The crest differs in extent and shape in different species of the Pterodactyle. In fig. 1 the ulnar side of the shaft is turned so far towards the eye as to permit the whole breadth of the radial crest {h) to be seen. The degree to which the radial crest projected in the humerus of the large Cretacean Pterodactyle (PI. 13, fig. 1) is only shown at its lower part, the upper, thinner portion being broken away. Relatively to the size of the head of the bone, the extent of the base is greater than in the smaller species of Pterodactyle, a corresponding portion of the humerus of which is represented in fig. 5, from the same aspect as fig. 1. The 452 BRITISH FOSSIL REPTILES. extent of the base of the radial crests in fig. 5 corresponds with that of Ptero- dadylus sueviciis.* In Bampliorhynchus Gemmingi the radial crest, with a similar short origin, has a remarkable transverse extent, and expands at its termination, so that both upper and lower margins are very concave. f The latter is of much greater relative extent than in the large Cretaceous Pterodactyle (PI. 13, fig. 1). The Wealden Pterodactyle {Pfcr. ornis) resembled Bamphorhynchus in the propor- tions of the radial or outer process {a, fig. 5, 'Quart. Journal of the Geol. Soc.,' 1845, p. 99). The determination of the homologies of the processes from the proximal end of the humerus of the Pterodactyle with those in the bird and crocodile enables one to recognise the specimen (figs. 1 — 3 and fig. 5) as part of the right humerus. Fig. 4 is part of the left humerus, from the Upper Green-sand and Cambridge- shire, but was drawn upon the stone without reversing, to facilitate its comparison with fig. 1, from the Middle or AVhite Chalk of Kent, which it resembles in the extent of origin of the radial ridge (*). Carpal Bones (PI. 12, fig. 6 ; PI. 14, figs. 5—9). The two bones {Pterosaiiria, PI. 14, figs. 5, 6, and figs. 7 — 10) correspond in size so much more with that of the distal extremities of the radius and ulna than with that of the same part of the tibia, as to leave a conviction that they are carpal bones, and they afford instructive evidence of the characters of those bones in the Pterodactyle. Specimens of more or less entire, but dislocated, skeletons of the smaller kinds of Pterodactyle from Oolitic strata, especially that of Pterodactylus suevicus from the lithographic slates of Wirtemburg,| and that of Bamphorhynchus Gemminyi from the same formation at Eichstadt,§ have demonstrated the presence of at least two large carpal bones, with one or two smaller ones, the two carpals forming a first and second row ; but the figures are two small and indefinite to permit the matching with them of either of the larger and probably better- preserved carpal bones from the Cambridge Green-sand. The first to be described in subdepressed, subtriangular in shape, with a general tendency to convexity on one articular surface (PI. 14, fig. 8), and to concavity * Quenstedt, op. cit., tab. i, cr, cl. t H. V. Meyer, op. cit., tab. ix. A. Wagner, 'Fauna des Lithogr. Scbiefers,' 4to, 1858, taf. xvi. X Well described and figured by Professor Quenstedt, in his treatise ' Ueber Pterodactylus suevicus,' 4to, Tubingen, 1855. § H. V. Meyer, op. cit., tab. ix, fig. 1. CRETACEOUS PTERODACTYLES. 453 on the opposite surface (fig. 7) ; but both these surfaces are irregularly undulated, as shown in the figures ; the more concave surface being also impressed by a deep hemispheric pit. I conjecture that this bone formed the proximal part of the carpus, and that the pit may have received a process of the distal end of one of the antibrachial bones. The opposite, probably distal, and more convex surface (fig. 8) is divided into two slight convexities, by a shallow, wide channel, crossing the bone obliquely. The convexity («) meets the concave surface on the other side of the bone («./) by their convergence to the basal border or margin, which presents a slight notch. The opposite end of the bone forms the obtuse apex ((/), whicli is a little bent down towards the concave side. On this side (fig. 7) the notch is continued into an angular channel, which divides the two shallow, concave sur- faces (e and /) occupying the basal half of this surface ; a little nearer the apex than the middle of the bone comes the hemispheric pit, with a small depression on one side of it. Fig. 9 shows the thickest or deepest, non-articular side of the bone, sloping to the end of the facet (/), and with the apical tuberosity (d) at the opposite end. Fig. 10 is taken looking upon the convex surface from the notched base (a). Fig. 8 may correspond with the surface of the carpal bone in Pterodactylus suevicus, marked 1, in the bones of the left wing in Professor Quenstedt's Plate ; and the side view of the same bone in the carpus of the right wing gives an indication of the produced apex. The outline of the large proximal carpal in Pterodadijlus {Eamphorlnjnchus) Gemmingi, in M. v. Meyer's Plate, accords in a general way with the profile of the narrower side of the present bone, which, for the convenience of indication and description, might be called the " scapho-cuneiform." I have no proof, however, from knowledge of its precise connexions, of the accuracy of this determination, but strongly suspect that the bone may represent more than one of the proximal carpals in the mammalian wrist, and probably the two proximal bones in the carpus of the crocodile. In PI. 12, fig. 6, a scapho-cuneiform bone is figured, which, from its size, might belong to Pterodadijlus simus ; it differs from that in PI. 14, fig. 7, not merely in size, but, apparently, in a greater relative breadth of the surfaces (e and /) ; their margins forming the base of the triangle have been, however, abraded. The second large wrist-bone (PI. 14, figs, 5 and 6), if the foregoing be rightly compared, will match with the carpal bone articulating with the proximal end of the metacarpal of the fifth or wing-finger in the plates of Pterodactt/his suevicus, and of BamphorJiyncJius Gemmingi, above cited ; and it will consequently answer to or include the " unciforme," by which name it will be here described and figured. 454 BRITISH FOSSIL REPTILES. Both proximal and distal surfaces show well-defined, concave articulations. On the more concave surface (fig. 5) there is an oblong, articular depression (tychodon and the associated large Plesiosauroid vertebrae from Kursk. I am indebted to the able engineer and zealous palaeontologist, Colonel KiprianofiF, for the opportunity of examining the specimens discovered by him in that locality. The centrum of one of these vertebae belonging to the dorsal region, from the Neocomian formations at Kursk, measures 4 inches in length and 5 inches 4 lines in breadth ; the terminal articular surfaces are flat ; between them the lower surface of the centrum is strai':;ht, but at the sides it is gently concave; there are two venous foramina, 2 lines apart, at the middle of the under surface of the centrum. Portions of ribs from the Upper Green-sand of Cambridgeshire agree in texture, and correspond in proportional size, with the cervical and dorsal vertebral bodies with which they were associated. I have selected one of these fragments for representation in PI. 31, fig. 3, because it shows a well-marked ridge («) on one side, a character I have not seen in the ribs of true Plesiosauri ; and these portions of ribs, of probably FoJypfychodon, present a less rounded transverse section. Atlas and Axis {Enaliosauria, PI. 32). The centrums of the first and second cervical vertebrae coalesced, as in Plesio- saunis, from the same locality and formation as the hinder cervical vertebra, p. 457, PI. 31, present the proportions, in regard to their antero-posterior diameter, of the cervical vertebras of Pliosaurus ; but they belong, in all probability, to the same Plesiosauroid reptile as the vertebrae previously described, and I refer them to the genus Polyptychodon. Like most of the fossils from the Haslingfield locality, they had been subject to attrition. The contour of the centrum of the atlas {Eiialiosauria, PI. 32, fig. 1) has been subcircular; its anterior articular surface (e, a,) is concave, and has afl'orded CRETACEOUS ENALIOSAURS. 459 a large proportion of the bottom or middle part of the cup for the occipital condyle. The lower part of the cup has been completed, as in Plesiosaurus, by a wedge-shaped hypapophysis, the articular surface for which is shown at ^, y ; the upper contour has been contributed by the neurapophyses, the articular surfaces for which may be discerned at n, />, on each side of the smooth neural tract, "> in figs. 2 and 3. The line of the original separation of the bodies of the atlas and axis may be traced ; the second hypapophysis, or part of it, remains anchylosed to their inferior interspace; it has been much smaller than the first. The posterior surface of the centrum of the axis vertebra (fig. 2, c, x) is almost flat, showing the Plesiosauroid nature of the bones. In the similarly short vertebrae of an Ichthyosaurus this surface would have been deeply concave. Having thus a proof of the plesiosauroid nature of these anchylosed vertebrae, the same grounds for referring them to FolyptychodoH apply as to the posterior cervical vertebrae (PI. 31, figs. 1 and 2) of more ordinary plesiosaurian proportions. Between that vertebras and the axis I infer, therefore, that the anterior cervicals rapidly diminished in length, and that the anterior ones exhibited the same Ichthyosaurian shortness as they do in Pliosaurus. The magnitude of the head, jaws, and teeth, o{ Polypti/cliodoii resembled that of its more ancient congener from the Kimmeridge Clay, and the supporting part of the spinal column appears to have been shortened and strengthened accordingly. It is probable that the large Plesiosauroid paddle, from the Chalk of Kent (p. 220), the phalanges of which are figured in ' Enaliosauria,' PI. 30, belonged to FoJypiijchodon. Thus the evidence at present obtained respecting the huge but hitherto problematical carnivorous .Saurian of the Cretaceous period proves it to have been a marine one — the rival and contemporary of the equally huge Maestricht lizard (p. 183), But whilst Mosasaurus, by its vertebral, palatal, and dental characters, foreshadows the saurian type to follow, Polyptychodon adheres more closely to the prevailing type of the sea-lizards of the great geological epoch then drawing to its close. The seas in which the English Chalk hills and cliffs were formed, and by which they were modified in the course of upheaval, must have teemed with life, and have been traversed by shoals of fishes needed for the sustentation of the numerous kinds of large marine reptiles now known to have existed during that period, and all of which were provided with jaws and teeth adapted, under diverse secondary modifications, to the capture and destruction of the finny races. Of these carni- vorous reptiles some, as e.g. Ichthyosaurus campylodon (p. 223) and Plesiosaurus Bernardi (214), were large species of genera represented throughout the oolitic period ; others, as e.y. Leiodon (p. 195) and Mosasaurus (p. 183), ofi"er generic or family modifications of the Saurian structure, unknown in any other than the Cretaceous 460 BRITISH FOSSIL REPTILES. deposits. The subject of the present section, as gigantic as the Maestricht Mosasaur, manifests an extreme modification of the Plesiosauroid type of structure. It is probable that the large Pterodactyles of the same geological period, soaring like albatrosses and giant petrels over the Cretaceous seas, co-operated with the marine reptiles, as those sea birds now do with cetaceous mammals, in reducing the excessive numbers of the teeming tribes of fishes, and in maintaining the balance of oceanic life. SUPPLEMENT NO. I. CRETACEOUS LIZARDS. Tribe — Natantia. The genus Leiodon was defined (p. 195) on a modification of Mosasauroid teeth in a fragment of jaw discovered in a Cretaceous formation in Norfolk.' The vertebral column of Leiodon anceps (Cut, fig. 1) exhibits the range of modifi- cation in its several regions which I deem to be characteristic of the great extinct Fig 1. "^^^mm^ Eestoeation and Type-veetebe^, Leiodon anceps. ' Lacertia natantia,' and offers a strong contrast with the comparative uniformity of the vertebras in Pi/tJion, PalaopJiis and other Ophidia (pp. 135 — 154). The atlas (fig. 2) consists of a pair of neurapophyses, n, and a detached hsemapophysis, h, simulating a centrum : of this the transverse exceeds the vertical 1 See 'Report of the British Association' for 1841, 8vo., p. 1-44. CRETACEOUS LIZARDS. 461 diameter, although the latter is extended by a short obtuse hypapophysial spine, less developed than in Mosasaunis. Each neurajjophysis presents a large sub- concave facet for articulating with part of the occipital condyle. The axis (fig. 3) consists of a long body, including the proper centrum of the atlas, c a, coalesced with that of the axis, c x. The latter develops a hypapophysis, y, to which is articulated a short haemapophysis, //. A compressed vertical ridge- like process (par-diapophysis, d) extends from each side of the centrum ; it may be for the support of a rudimental cervical rib. A few of the succeeding vertebrae are characterised by both diapophysis (fig. 4, d) and hypapophysis, y — the latter with a rough articular surface for ligamentous attachment of a haemapophysis, h. The diapophysis of the third cervical supports a rib ; and a similar costigerous process is present in the dorsal vertebrae. This series may be conveniently, though artificially, defined by the suppression of the hypapophysis. The zygapophyses (figs. 5 and 6, z z) disappear in the posterior dorsals as in fig, 7. The diminution in vertical and increase in longitudinal extent, together with a descent in position from the side of the centrum, reduce the transverse process to a parapophysis, jo, fig. 8, which characterises the lumbar vertebrae. The centrum here becomes triangular, in transverse section, with the base down- ward. There is no 'sacrum' by ankylosis; it is represented by a single vertebra supporting a pair of small rib-hke ilia (fig. 1, h). The pubis, u, is slender, nearly straight ; the ischium, m, is broader, with a short hind process, offering a syndesmosal surface for the ilium and the femur; it also unites with its fellow, completing the inverted ' pelvic arch ' below. The following table gives the kinds and numbers of the vertebrae. Number. Atlas and axis 2 Vertebrae (type 4) with hseraopopliysis, hypapophysis, diapophysis, and zygapophysis 5 „ (type 5) with hypapophysis, zygapophysis, and diapophysis 7 ,, (type 6) with zygapophysis and diapophysis 18 „ (type 7) with diapophysis 22 ,, (type 8) with parapophysis 15 ,, (type 9) with parapophysis and unankylosed hasmal arch 24 ,, (type 10) with unankylosed hEemal arch 14 „ (type 11) with ankylosed hsenial arch 44 „ (type 12) with centrum and neurapophyses, the latter rudimental or none ... 12 163 The vertebrfB of Leiodon are devoid of the accessory zygantral and zygosphenal articulations. In the {eyv Mosasauroids which show them they adhere to the iguanoid type (Ophidia, PI. 2, figs. 34, 35). 462 BRITISH FOSSIL REPTILES. All the ribs or pleurapophyses, where present or preserved, are monocipital. Iii Leiodo7i the basisphenoid is concave, almost canaliculate alons: the middle of the under surface, devoid of any ophidian median ridge; the pair of hypapophyses abut against the pair from the hasioccipital, but leave the broad truncate ends of these free, as in Amblyrliynchus. In Leiodon, as in Mosasauriis, there is a large 'foramen pineale' which, as in Mo7iifor, is wholly in the parietal. This bone bifurcates posteriorly ; its prongs extend backward, outward, and articulate with the mastoid, which curves outward and downward to join the squamosal, and, with it, forms the articular surface for the tympanic. Anteriorly the squamosal unites with the postfrontai, 12. The long and wide temporal fossje are bounded, externally, as in Lacertians, by a long and narrow zygomatic bridge, in the composition and proportions of which Leiodon most rescml)les the Monitors and Iguanas. Leiodon, like other Mosasauroids, has two pairs of limbs, of the natatory type ; the tegumentary sheath is supported by five digits, in both fore and hind fins. The phalangeal formula is, in the main, Lacertian (fig. 1). In the single occipital condyle and the composite structure of the mandible the Mosasaurians are Licptilian ; in the proccelian vertebrse they accord with the existing representatives of the class; in the double occipital hypapophyses, in the bifurcate and perforate parietal, in the columella, in the composite formation of the suspensory joint of tlie tympanic, in the type of the tympanic, in the frame of the parial nostrils, in the composition of the mandible, and in the structure and attachment of the teeth they are Lacertian; in one special dental modification they are lyuanian ; in another they are 3Ioniforial. In the broad cemental basis of the enamelled tooth? in the more extensive fixation of the pterygoids and ossification of the roof of the mouth, in the large proportion of the vertebral column devoid of zygapophyses, in the confluence of the haemal arch with the centrum of certain of the caudal vertebrae, in the natatory character of the fore and hind limbs, they are Mosasaurian. But they do not seem to me to be entitled, through the last category of modifications, to the rank of an order in the reptilian class. The order Lacertilia, in the class Reptilia, is a taxonomic equivalent of the order Carnivora or Ferse in the mammalian class. In the Ferae there is a group which, by modifications of the skull, teeth, vertebrae, and, especially, limbs, takes rank as a suborder or subordinate group, viz. the Pinnipedia or Phocida?. I estimate the Mosasaurians in the Lacertian on er to be equivalent to the Seals in the Ferine order. Ordeii— PTEROSAUEIA. PTERODACTYLES OF THE LIASSIC FORMATIONS. Genus — Dimorphodon, Owen. Species — Dimorphodon macronyx, Bucklcmd. Remains of volant Reptiles {Pterosatiria) were later recognised, and, save in the instance about to be recorded, in a more fragmentary or scattered condition, in England than in Continental localities. A single bone or tooth gives value to a slab of Stonesfield Slate, and the evidence of a Pterodactyle rarely goes beyond such specimen in that Oolitic deposit. A jaw with teeth, or a skull more or less entire, from the Chalk of Kent, or the Upper Green-sand of Cambridge, has been welcomed for the fuller information so yielded ; and such fossils, with a few detached vertebrae and wing-bones, have expanded our conceptions of the bulk attained by some of the Flying-dragons at the decline of the Mesozoic period. When the waters over which they flitted had a clayey or muddy bottom it afforded a quieter resting-place to the dead body of the Pterosaurian therein entombed. So the first discovered specimen of one of these in the upraised petrified ocean-bed now forming the Liassic cliff's of western Dorsetshire afforded Buckland'^ subjects, in the compass of a slab about a foot square, for a description and figures of the leg and wing-bones, with part of the vertebral column, of the species which he called Fterodacfylus macronyx — the first evidence of the genus from deposits so low, or ancient, in the Oolitic series. In 1858 I obtained the skull, with a few other parts of the skeleton of the same or a closely allied species, from the Lower Lias at Lyme Regis, and communicated a brief notice of it to the British Association, which that year met at Leeds.^ 1 " On the Discovery of a New Species of Pterodactyle in the Lias at Lyme Regis." By the Rev. W. Buckland, D.D., F.R.S., F.G.S. (Read Feb. G, 1829.) 'Transactions of the Geological Society of London,' second series, 4to, vol. iii, I83.i, p. 217, pi. xxvii. 2 "On a New Genus {Bimorphodon) of Pterosauria, with Remarks on the Geological Distribution of Flying Reptiles ;" in 'Reports (Sections) of the British Association,' 18,58, p. y?. 464 BRITISH FOSSIL REPTILES. This specimen confirmed the accuracy of Biicldand's conjecture, which I had doubted, viz., tliat the portion of lower jaw with the series of small lancet-shaped, close-set teeth,i in a second slab of Lias, belonged to the same Pterodactyle as the limb-bones he described ; but it also showed that these teeth, so like those of some Pishes, were limited to the lower jaw, and were associated, in the same mouth, with long, slender, trenchant and sharp- pointed laniaries, projecting with wide intervals, and set in advance ; which kind of teeth had, hitherto, alone been found in the different species of flying Reptiles. The chief result of the study of the second discovery of a Pterosaurian in Lias, viz., its evidence of a new generic form {Dmorjjhodo?i) in the order of volant Eeptilia, in addition to Rhamphorhjnclms, von Meyer, and Plerodactylus proper, was noted in the com- munication above cited. The third specimen about to be described confirms that taxonomic deduction, showing a combination of the caudal character, mainly differentiating Bhampjhorhynchus from Pterodactyl us, with the dental character above defined. I propose first to describe and figure the two specimens yielding the cranial and dental characters of Dimorphodon, and then to attempt a restoration of the Liassic species, D. mac.ronyx. The first specimen with the skull is figured in PI. 15. It is on a slab of Lias, mea- suring 11 inches by 7 inches. The right side of the head is exposed :" it has been subject to j)ressure and some degree of dislocation. Certain bones of both wings, and a few other parts of the skeleton are preserved, pell-mell, in this slab, pressed amongst and upon the bones of the head, especially at the back part of the skull. The right premaxillary (22), maxillary (21): and nasal (15), are almost in their natural positions, give the profile contour of that part of the skull, show most of the teeth of the right side upper jaw, and reveal the singular expansion of the nasal («) and antorbilal (a) vacuities. The alveolar part of the left maxillary (S'), with its ascending postnarial branch has been pushed obliquely downward, with fracture, but without much displacement, of the beginning of the alveolar ray, the inner surface of which is exposed. The mandible (.32) has been dislocated and pushed below the place of its articulation with the tympanic (28) : the left ramus has also been subject to the same force which has dislocated that side of the upper jaw ; the hind part of this ramus is obliquely depressed, so as to expose the inner surface (32). The anterior entire or undivided part of the premaxillary (22) is about 2 inches in length, and \\ inch in vertical height at its back part: it contains four pairs of teeth, which are the largest and longest of the series. The foremost tooth (1) is terminal, with a crown 5 lines in length, rather over 1 line in breadth (fore-and-aft) at its base ; it is subcompressed, 1 Bucklaiid, loc. cit., pi. x.wii, fig. 3. - Tlie specimen lias been drawn, in PI. 15 {Pterosauria), without reversing. LTASSIC PTERODACTYLES. 465 siibrecurved, and sharp- pointed. An interval of 4 lines divides it from the second tooth (2), with a crown 5i hnes long. After an interval of 7 lines projects the crown (3) of the third tooth, 7 lines in length and 2 lines in basal breadth, sharp-pointed like the first, but less bent. The socket and base (?) of the fourth tooth appear at an interval of 6 lines, and below is the entire and displaced homotypal tooth (4') of the left side, showing the cavity on the inner side of its root whicli wonkl liave received the successional laniary. This tooth measures 1 inch 2 lines in total length, of which the exposed enamelled crown forms two-thirds. In advance of the foremost tooth (1) is seen part of its honiotype (!') of the left side, also displaced from the socket, and showing the depression and vacuity on the inside of the base, in relation to the succeeding tooth. Beyond the fourth alveolus the maxillary (21) appears, underlapping the part of the premaxillary (22") which defines the lower and anterior part of the narial vacuity : the maxillary is continued straight backward, with feeble indications of two crushed alveoli (5, c) for 1 inch 9 lines, when the seventh laniary (7) projects almost straight downwai'd : the crown of this tooth is 5 lines long; the root, covered with rougher cement, slightly contracts to its implanted end, which has slipped a short way out of its socket. An interval of 4 lines divides this from the next laniary (8), which shows a crown of but 3 lines in length ; this projects opposite the fore part of the lateral post-narial branch (21O of the maxillary. The base of the left homotypal tooth (s') projects from the same part of the dislocated left alveolar branch of the maxillary; and above this, on the inner side of that bone, is exposed the coronal germ of a successor. In the right maxillary two other straight laniaries (9, 10) of rather decreasing length, project with similar or rather lessening intervals : then follows, after an interval of 3 lines, a pointed compressed crown Ig line in length (ii) ; and, at shorter intervals, two smaller pointed compressed teeth (12 and 13). These thirteen cuspidate teeth of tlie upper jaw are included in an extent of the alveolar border measuring 5 inches 2 lines. That border is continued backward, straight and edentulous, for 9 lines beyond the last tooth, when it is crossed by the large and long first phalanx (/, l) of the wing-finger. This edentulous part of the maxillary forms the lower straight border or base of the large triangular antorbital vacuity (a), at the back part of which it is overlapped by the fore part of the slender malar (20). Above this vacuity are parts of the nasal (15) and prefrontal (14), both somewhat displaced in this crushed part of the skull. The arched part of the frontal forming the upper part of the rim of the orbit (o) is recognisable at (11) PI. 15. Above its hind part are indications of the post-frontal (12) and mastoid (s), with the process of the latter descending external to its articulation with the tympanic (28). The metacarpus and dislocated unguiculate digits of the wing-limb are confusedly interblended with the crushed and dislocated back part of this skull; three phalanges {/r \,iv2,ir3) of the wing-finger are determinable. The two anterior teeth (i', 2') of the mandible show longitudinal angular depressions at their base, indicating exposure of their inner side, and that they belong to the left ramus. The corresponding part of the right ranuis may have been broken away : the third laniary 46G BRITISH FOSSIL REPTILES. (3') clearly belongs to this ramus, which is fractured beneath its socket. The point of this tooth is broken off: what remains of the body is cnrved, and is implanted more obliquely backward than the two preceding teeth. This at first led me to suspect it might be the foremost tooth of the mandible, and that the left ramus had lieen pushed in advance as well as downward : but my doubts on this point have been set at rest by the specimen (PI. 16) next to be described, and I view the tooth in question as the third of the mandibular series : it is divided from the second by an interval of 6 lines, and the second stands at a rather shorter interval behind the first. Five lines behind the third tooth is the base of a fourth laniary (j.'), and four lines further back is an indication of a fifth (s'). This is followed by the characteristic series of between thirty and forty very small, subcompressed cuspidate teeth, each less than a line in length, corresponding in extent with the maxillary part of the upper jaw. The entire series of mandibular teeth occupies an extent of alveolar border measuring 5 inches 1 line. The depth of the right ramus gradually increases from 5 lines below the last laniary to 10 lines below the last denticle. The inner side of the dislocated ramus (32') shows a strong longitudinal ridge projecting inwards about 3 lines above the lower border. The outer surface of the ramus seems to have been strengthened near its lower border by a similar but lower ridge. The distal ends of the antibrachial bones (54, 55) overlap the hind part of the mandible : that which shows the larger articular surface, op[)osite the three slender metacarpals, should be the radius. The base of the supplementary styloid bone appears near the distal end of the ulna, but is better shown in Buckland's original specimen. Indications of two carpals intervene between these and the metacarpus. This overlies and conceals the articular pedicle of the mandible and contiguous parts (squamosal, malar, &c.) of the skull. The metacarpus includes the three slender supports of digits /,//. »iij ///, and the strong and thick metacarpal of the wing-finger (/,). This bone, being almost con- cealed by the first phalanx in Buckland's specimen, was overlooked, and that phalanx was described as the metacarpal of the wing-finger, Avhich, accordingly, in the restoration, fig. 2, PL 27, of ' Buckland's Memoir,' is made thi-ee times the length of the other and more slender metacarpals (3')- In the original specimen, now in the British Museum, the true metacarpal may be distinctly traced. It corresponds with the same bone in previously described Pterosauria by surpassing in thickness, not in length, the other constituents of the metacarpus. In the specimen, PI. 15, the metacarpal of one wing-finger is clearly shown at ivm. That of the other, lying upon the cranium, is more obscure. The thin compact wall of this pneumatic bone has been crushed in upon the wide air-cavity, as with most of the other long bones, so that it looks like two metacarpals. The proximal articular surface of ^r,« is partly concave and partly convex : the distal articulation is trochlear, moderately concave from side to side at the middle, convex from behiiul forward, with a depression behind, above the ai-ticulation, for securing the olecranoid process of the proximal phalanx. This phalanx (/r, 1), in one LIASSIC PTERODACTYLES. 467 ■wing, is bent back npon the fore-arm, crosses the dislocated mandible, and has been pressed npon it, long and hard enough to leave a channel in the right ramus, where part of the phalanx has been removed : its length is 4 inches f) lines. The second, more slender and longer phalanx (/, 2), is bent at nearly a right angle with the first, and lies below and parallel with the mandible ; it is nearly 5 inches in length. The third phalanx (/,-. 3) is bent upward in front of both lower and upper jaws : 4^ inches of its length is preserved in the slab : from the analogy of the better pre- served specimens (PI. 16, ir. 3), about 1 inch 3 lines are wanting from the distal end. Of the three unguiculate digits the characteristic large claws are preserved : one (//) lies above the frontal (ii) with the penultimate phalanx ; the other two are between the upper and lower jaws, with some of the slender phalanges : all these parts of the ranuis having been dislocated and scattered. Parts of the distal ends of the radius and ulna (54', 55'), the metacarpal of the wing-finger (/',«'), and the proximal end of its first phalanx {i^'r'), of the opposite fore- limb, occupy a lower corner of the slab : carpal bones, one of the accessory styloid ossicles of the forearm, some of the slender metacarpals of the claw-fingers can be made out above these : and there are more obscure indications of vertebrae at that end of the slab, curving toward the cranium. All the osseous and dental textures are black, as if charred by slow combustion of the animal matter. UiMORrnoDON macronyx. pi. 16. In August, 1868, I was favoured by the Earl of Enniskillen, then at Lyme Regis, Dorsetshire, with a hst of parts of a Pterodactyle, in a slab of Lias al)out 20 inches by 1 1 inches, and of other parts in detached portions of Lias, including the entire tail with its bone-tendons, which his Lordship had observed at Messrs. James and Henry Marder's, the judicious and persevering collectors of the fossils of that rich locality. The result of this valuable and timely information was the securing for the British Museum the entire series of these Pterosaurian fossils. They proved to be parts of the Bimorphodon macronyx, confirmed many of the observations made on previously acquired specimens, corrected others, and added almost all that was required for the restoration of the skeleton of this remarkable genus and species, which I have accordingly attempted in Pi. 17 [Plerosanria). The slab of Lias with the second specimen, including the skull of Dimorjjhodon macronyx, is of larger size, shows more of the skeleton and in a more separated and definable state 408 BRITISH rOSSIL REPTILES. than ill PL 15. Nine dorsal vertebrae, third to eleventh inclusive, in natural juxta- position, with the twelfth slightly dislocated, are preserved at the upper part of the slab (PI. 16, d). The summits of the neurals pines (««) of most of these, and the disposition of many of the preserved ribs, show that they lie mainly with the dorsal aspect downward (as the specimen is figured). This explains and accords with the position of the parts of the pelvis, which lie a little way behind the dorsal vertebrae. The comparatively slender ilium (eg^es) is downward ; the broad ischium Q^), and the pair of spatulate pubic bones (cJ, are turned, like most of the ribs, upward, as I conclude the abdominal or ventral surface of the trunk was directed as the fossil lies in the figured slab. The bones of the hind-limb, in connection with the acetabulum, are turned outward, with their inner surface exposed. The projections of the trochlear terminations of the metatarsals {i, iv> eg), show that the sole of the foot is turned to view. Accordingly, we have here the bones of the left hind limb. On the hypothesis that the femur and tibia are seen from the outside, which at first suggests itself, they would belong to the right limb, viewed in profile. But then, the broad thin plate of bone contributing to the acetabulum, would represent the ilium, and the indi- cations of the pelvis below the acetabulum and head of the femur would represent ischium and pubis. This interpretation, however, gives to Dimorjiliodon proportions of pelvic bones very different from those determined by Wagner in Pterodacti/lus Kochii} and l)y Quenstedt- in Pterodactylus suevicus ; and, besides, it leaves undetermined the pair of bones (64, PI. 16) which closely resemble in form and proportion the 'pubic bones' {u,u) in Quenstedt's instructive plate.^ In this plate the ilia («, «) are represented as long slender bones, contributing the upper but smaller proportion of the acetabulum, and extending horizontally beyond it both forward and backward. The pelvis, in the position in which I conclude it to lie in the slab figured in PI. 16, might well afford such indications of the lire- and post-acetabular productions of the ilium as are there shown at 03,02- In Pterodactylus suevicus the ischium contributes the lower and major half of the acetabulum {tr, loc. cit.), and expands into a broad thin plate («, ib.), having the pro- portions to that of the spatulate pubis, which the bone 03 bears to c^, in PI. 16. The portion of the pelvis in the original specimen is preserved in natural connection with the sacrum and contiguous vertebrae ; and the constituent bones are rightly recognised by Buckland (op. cit., p. 222). It is interesting to note, that the pelvis of Pferosauria, so determined, resembles more closely that of the existing representatives of the section of Pepiilia with the 4-chambered heart and double-jointed ribs, viz., Crocodilia, than it does the pelvis in Chelonia and Lacertia. The ischium in Crocodilia, e. (/., sm-passes the pubis in size, and excludes that 1 " Ueher Ornitkocep/ialus Kochii," in 'Abhaiidl. d. niatli.-phvs. Klasse der Bayeiischen Akad.," ii, 'ito, Munchen, 1837- - ' Ueber Pterodactylus suevicus,' &c., 4to, Tubingen, 18.55. ^ In the Jlemoir above cited. LIASSIC PTERODACTYLES. 469 haemapopliysis from the acetabulum.i The ischium seems to contribute the hirger share of the acetabuhun in Bimorphodon, PI. 16, «. In Birds, as in Lizards, the pubis forms part of the acetabular cavity.^ In the specimen, PI. 16, a portion, cd, of a long tail, of which the vertebrae were smTormded by numerous slender bone-tendons, extends backward and downward beyond the pelvis : a better preserved portion with three caudal vertebrae (c d!) is preserved in a detached part of the matrix found in the vicinity of the larger slab. Ikit to this part of the vertebral column I shall return in describing the more perfect specimen of the tail of Dimorphodo?}, from another individual. Behind the skull are four cervical vertebrae (PI. IG, c), and part of a fifth in natural juxtaposition, or perhaps a little separated at the articular surfaces. The under surface of the centrums and articular processes of the neural arches are exposed. The sides of the centrums show a slight concavity, but their crushed state obscures the natural contour of the under surface. The hind part of the under surface, in the last two of these vertebrae, shows a pair of low obtuse processes, with an indication of a convex terminal articular surface. The centrum expands in breadth as it advances, and sends out a short thick process (parapophysis) from each side of the fore part ; to which, in the last three vertebrae, are indications of attachment, or parts, of a backwardly produced styliform rib. At the midline of the fore part of the last two of these vertebrae a fracture indicates a ridge or process there to have been broken off. The pre-zygapophyses are thick, and project far in advance of the concave anteiior articular surface of the centrum : the convex posterior articular surface of the centrum projects as far beyond the post-zygapophyses. Their joints are more vertical than horizontal : the posterior surfaces looking slightlv outward and downward. The superior breadth of the neural arch, as compared wMth that of the centrum, brings its articular processes into view, along each side of the vertebral bodies, in the degree shown in PI. 16, c. The character of the articulations indicate less extent and freedom of movement of the cervical vertebrae than in Birds, and more restriction in the lateral than in the vertical directions. The interlocking joints resulting from the different lengths of the fore and hind articular processes add strength to the part of the spine supporting the head. The cervical vertebrae of Dimorphodon, so far as their structure is exemplified in the present specimen, conform to the pterosaurian characteristics of these vertebrae, as shown in those of Pterodadylus /S'e(^?OTe/fM, described (p. 382), and figured in PI. 7, figs. 7 — 18 ; and in those of Pterodadylus simus (p. 437, PI. 11, figs. 1 — 5). The skull presei-ved in the present specimen agrees in size with that in the slab pre- viously received (PL 15), repeats the characteristics of the genus Bimorphodon, and shows no 1 'Anatomy of Vertebrates,' vol. v, p. 188, fig. I 19. 2 lb., p. 190. 470 BRITISH FOSSIL REPTILES. differences of greater degree or value than may be set down to individual modifications. The part defective and partly obscured by intrusive bones from other parts of the skeleton is un- fortunately that which leaves the precise determination of structure unsatisfactory in the pre- viously described specimen. A trace only of tympanic remains at 28, and of the descending styloid process of the mastoid at 8 : the thick metacaqial of the wing-finger (iv, ?«)) intrudes into the orbit, and overlaps the upper end of the malar (26). More of the part of the frontal forming the superorbital arch (ii) is shown than in PI. 15. Part of the concave surface of the orbital cavity beneath the superciliary ridge is here seen. The lacrymal (23) or descending branch of the prefrontal (i4) meets the ascending process from the combined malar and maxillary, dividing the orbital from the antoi'bital cavity. The true size and shape of the latter vacuity (") is here well displayed. The maxillary styloid process (21") rises, at the same angle backward as in PI. 15, to join the nasal (15). The medial branch or ray of the premaxillary (22'), the end of which is depressed below the prefrontal in PI. 15, preserves its position in the present specimen, and yields the true arched contour of the profile of this remarkable skull. The entire vertical extent of the vast narial vacuity, n, is here given, the longitudinal one, 3J inches, precisely agreeing with that in the first-described skull. The anterior part of the premaxillary (22) shows, also, the same proportions and shape, viewed side- ways, as in the first specimen. The conformity is instructively continued in the characters of the dental system. The apex of the crown of the laniary (PL 10, 1) from the fore end of the premaxillary shows the same curvature and proportions as in PI. 15; the same interval divides it from the second laniary (2) ; the longer interval, again, occurs between the second and the third laniary, with a longer and less ciu'ved crown. After an interval of seven lines comes the fourth tooth (4), corresponding in size and shape with the one which is displaced in PI. 15, 4'. After an interval of nine lines the apex of the crown of, seemingly, the successor of the fifth laniary (5) appears. It may be, normally, smaller than the rest; the socket of this tooth is feebly indicated in the subject of PL 15. The sixth laniary (e) shows the same size and relative position as in that subject, and the same may be said of the five succeeding teeth, save that the last is rather larger than in Pi. 15, which also shows an additional small hind cuspidate tooth. The suture between the premaxillary (22") and the maxillary (21) is more plainly discernible in the present specimen. The extent of alveolar surface of the left upper jaw occupied by the above- described dental series is 5 inches 3 lines. In the left ramus of the mandible two of the large anterior laniaries are in place ; one, answering to the second in PL 15, 2', projects across the diastema between the second and third tooth above ; in size, shape, and cm'vature, it resembles the second upper laniaiy, close to which it terminates. The next mandibular tooth is larger, less curved, and crosses the middle of the interval between the third and fourth upper laniaries. The tooth (I'j LIASSIC PTERODACTYLES. 471 displaced beneath the mutilated fore part of the mandible, I take to be the foremost of the mandibular series and suppose that its point would naturally project across the interval between the first and second of the upper teeth. The fourth laniary appears to be more displaced: its base or root, with a lateral depression, is shown behind the fifth tooth of the minute serial teeth, and the crown passes obliquely backward on the inner side of that of the sixth upper laniary, by which it is concealed. Of the serial teeth, with pointed crowns from half a line to a line in length, about thirty may be reckoned occupying an alveolar extent of 2 inches, 9 lines. At the hind part of the left mandibular ramus, here exposed, three longitudinal ridges define two vacuities, of which tlie inferior may be natural. The upper one seems more plainly due to loss of the thin outer plate of bone extended between the upper two ridges. The proportions of the ramus closely accord with those of the first- described specimen. The fore part of the mandible is too much mutilated for useful comparison. The dentition of Dimorpliodon, as displayed by the second specimen of skull, consists, in the upper jaw, of laniaries with wide intervals, eleven in number on each side ; in the lower jaw, of four, if not five, laniaries implanted at the fore part of each ramus of the mandible at intervals corresponding with three of the four anterior laniaries above ; then follows the long series of close- set and minute pointed teeth. The difference of dentition as compared with the first specimen (PI. 15) is, in the upper jaw, in the additional small laniary or cuspidate tooth at the back part of the series in that specimen. In the lower jaw there does not seem to be any noteworthy difference in the number, kinds, and position of the teeth. The longest laniaries are included between the second and fifth in both jaws : the upper laniaries after the fourth become small and straight. At the first view of the framework of the huge head of our Liassic dragon one is struck with the economy of bony material and the purposive skill with which it has been applied or disposed, so as to give strength where resisting power was most required. The lodgment of the poorly developed brain enUsts a miserably small proportion of the skidl : the cranium proper, or brain-case, is relegated to an out-of-the-way corner, so to speak, and there it is almost concealed by the projections for joints or muscular attachments. The orbits accord with the large eyes given to this volant and swift-moving Reptile. One can conceive no necessary interdependent relation between the wide external bony nostril (") and the organ of smell, nor be led to conjecture that the tegumentary inlets to the nasal chamber were.ilarger than is usual in Reptiles. The main pm-pose of the head is for prehension of prey. The jaws are produced far forward to form a wide-gaping mouth, and are formidably armed. We n)ay conceive, therefore, that the dragon may have occasionally seized an animal of such size as to 2 II 472 BRITISH FOSSIL REPTILES. require considerable force of jaw for overcoming its struggles. The means of resist- ance were afforded to the upper or fixed maxilla, not by a continuous wall of bone, but by curved columns or abutments. The chief of these is the upper medial arch of bone which overspans the skull lengthwise, from the short roof of the cranium to the fore part of the premaxillary (22); the froiitals (11) and nasals (15) combining with the mid-fork or branch of the premaxillary (22',) to constitute this arched key-ridge of the roof of the head. From it two piers or buttresses out-span on each side, to give strength and resistance to the upper jaw, and especially its alveolar tracts. One, proceeding from the nasal, meets the uprising process of the maxillary (21) ; this abutment, Curving from above outward and obliquely forward, expands and backs the part of the jaw where the second group of large laniaries project. The second buttress is continued from the pre- frontal (14), and arches more directly outward to meet the uprising process of the malo-maxillary. A third arch, due to the post-frontal (12) and malar (26), expands to abut upon the hind end of the maxillary arch, and gives support to the part of the skull which the temporal muscles tended to pull downward when they were giving to the mandible the power of a strong bite or grip. Finally, comes the strongest of the four piers, due to the mastoid (s) and tympanic (2S), for giving articular attachments to the rami of the lower jaw. Thus, four vacuities appear in the side-walls of the skull : the first („) is the largest, between the small consolidated or continuous fore part of the skull (22), and the naso- maxillary pillar (21% 15). This vacuity answers to the external bony nostril of the same side, in the Lizard's skull (PI. 17, fig. 3, «), where the nostrils are divided and more or less lateral. The second vacuity («) is somewhat less, ofa triangular form, with the base downward : it answers to the antorbital vacuity in Lyrioceplialus (ib., a) and a few other Lizards, and to that in Teleosaurus, where, however, it is very small. The third vacuity (o) still decreasing, is oval, with the narrow end or apex downward : it answers to the orbit, but is of large size compared with most Saurians ; it is, however, exceeded in relative expanse by the orbit in Lyrioceplialus (ib., 0). The fourth vacuity is the narrowest : it answers to the so-called ' temporal fossa ' and was occupied by the muscles of the same name. Extension of surface, for their origin, and additional strengthening of this back part of the skull are gained by laying horizontally across the temporal fossa the bony beams called ' upper and lower zygomata,' arching from the postfronto-malar to the masto-tympanic vertical columns. The heavy phosphate of lime, thus singularly economised by the disposition of the bones on mechanical prin- ciples plainly to that end, is made to go still further by the arrangement of the osseous tissue. Every bone is pneumatic, the abundant, open, cancellous structure being included in a very thin layer of compact osteine. The bones of the limbs are dislocated and dispersed in the way and degree common to the specimens of this animal hitherto discovered (Buckland, loc. cit., pi. xxvii; and pis. LIASSIC PTERODACTYLES. 473 15 and 16 of the present Monograph). The scapula (PL 15, si) and coracoid (ib., 52) in the same anehylosed condition as in the first-described specimen, are at the end of the slab opposite to that with the head. The corresponding humerus (53), preserved in a separate portion of the block of Lias, shows the entire contour of the pectoral process [i/]. The right humerus (53') lies below the dorsal vertebrae (d) ; the upper part of the pectoral process (5) is wanting, but the obtuse thickening of the end of that remarkable pro- duction is well shown. The ridge (c) called ' ulnar, '^ descending from the ' lesser tuberosity,' appears in this view of the ' palmar' surface of the bone." The sigmoid flexure of the shaft is much better marked than in the humerus of Fterodactijlas siievicus? The stronger walls of the humerus have resisted the pressure better than those of most of the other long bones. Of the antibrachial bones parts of the shafts, crushed, are seen at 54, 55, apparently of the right wing. With the distal ends of these, the right carpus (56) and metacarpus (57) appear to have retained their natural connections. The slender metacarpals of the first (i), second (n), and third (m) digits appear emerging from beneath the left hind foot which overlies their proximal ends. The phalanges of the first digit (r), two in number, preserve their natural articulations. As are also those of the second digit, three in number. The metacarpal of tiiis digit is longer by 2^ lines than that of the first. The additional phalanx would seem to be the proximal one, by its shortness : the second phalanx more nearly agrees in length with that supporting the claw-phalanx in the first digit; but it is thicker and a little longer. The four phalanges of the third digit (m) are dislocated ; but the penultimate, which is the longest, retains its connection with the ungual phalanx. The proximal phalanx is longer than the second, which resembles in length, and seems homotypal with, the proximal phalanx of the second digit. It may be concluded, therefore, that the additional phalanx to 11 and m was developed at the attachment of the digit to the metacarpus. The largely and abruptly expanded meta- carpal of the fourth digit is in great part covered by the correspondingly thickened and much elongated phalanx {jr^ 1) therewith articulated. The olecranoid process of this phalanx is well shown, and the entire bone is preserved : its length is 4 inches 2 lines : it is bent directly and abruptly back upon its metacarpal. To the distal end is attached part of the second phalanx (/,- 2). The proximal phalanx of the left wing-finger is preserved in a detached {ir, 1) part of the slab (PI. 16) containing the major part of the skeleton. The second phalanx (/^-o,) of the left wing-finger lies in that slab, is entire, and yields a length of 4 inches 9 Hues. The third phalanx (/,- 3) is 5 inches 6 lines in length ; near its distal end is part of the slender terminal phalanx of this digit {ir,^. There is no trace of a fourth unguiculate digit, and I return to 1 P. 449, pi. 13, fig. 1, c. 2 P. 451. ^ Queustedt, op. cit., c /, e r. 474 BRITISH TOSSIL REPTILES. Cuvier's view of the structure and homologies of the hand of the Petrodact3'le,^ which I had abandoned in favour of the seemingly more perfect evidence supporting Professor Goldfuss' restoration of Pterodadylm crassirostris,^ adopted by Buckland^ and myself.* The metacarpal of the left wing-finger (/,;,„, PI. 16) lies beneath the back part of the skull, and is over-lapped by the superorbital part of the frontal. Portions of two of the unguiculate digits of the same fore-paw (/ //) are seen in the wide narial vacuity. The definition and finish, so to speak, of the joints of the wing-finger are worthy of note, especially of that between the metacarpal bone and proximal phalanx. In Reptiles generally the articular extremities of the long bones are not very definitely sculptured, and do not manifest that reciprocal adaptation of their inequalities which are observed in the joints of Mammals and Birds. The difficulty of determining the coadapted extremities of detached bones of Reptiles is increased by the great thickness of the cartilage which covers them and renders their mutual contact more intimate, and which is always wanting in fossil bones. The Pterosavu'ian modification is, however, purely adaptive ; and the relation to Warm-blooded Vertebrates in this respect is one of analogy. An argument in favour of avian atfinity from the joint-structures could only be propounded by one not gifted with the judgment needed to deal with problems of this nature. The left femur (6.5') preserves its natural articulation with the acetabulum ; the head is bent forward from the line of the shaft for an extent like that at which the condyles are produced backward ; the shaft is straight, the great trochanter is feebly developed. There is no evidence of a modification of the distal condyle for the interlocking articulation with the fibula, which in Birds relates to their bipedal station and walk. The length of this femur is 3 inches 4 lines The left tibia {{]&), bent back at an acute angle upon the femur, measures 4 inches 10 lines in length. There is no trace of patella, nor has this sesamoid bone been found in any Pterosaur. The inner side of the bone being exposed, the styliform rudiment of the fibula is hidden from view. The trochlear termination of the distal end of the tibia is better marked than in Crocodilus, or even than in Scelidosaiirus (' Monograph on Oolitic Reptiha,' Palseontogr. Soc, Vol. for 1863, p. 16, PL X, cc), and consequently approaches more nearly to the characteristic form of the joint in Birds. The resemblance to the bicon- dyloid termination of the femur is instructively shown in the distal portion of every Ptero- saurian tibia, as may be appreciated in the distal half of the right tibia of Dimorphodon 1 'Ossemens Fossiles,' 4to, v, pt. ii, p. 371. - Beitrage zur Keutniss verschiedener Reptilien der Vorwelt, in 'Nova Acta Acad. Natur. Curios.,' Leopold Carol., &c., 4to, torn. xv. " Reptilien aus dem lithographischen Seliiefer, Pterodachjhis crassiros- tris, nobis, tabs. VII — X." 3 ' Bridgewater Treatise,' 8vo, 1836, pi. 2'J. * Owen's 'Palaeontology,' 8vo, 1861, fig. '.)/. LIASSIC PTERODACTYLES. 475 in the slab, PI. 16, at 60, which crosses the right antibrachium (54,55). The deflected posterior ends of the condyles are here shown, and beneath them three tarsal bones (o, /, b), with the characteristic short and thick metatarsal of the fifth toe (w, v)} The tarsal bone between the tibial trochlea and the three metatarsals [i, ii. Hi), answers to the astragalus, marked a, in Scelidosaurus and CrocodUus (Monograph and Plate above cited) ; two tarsals, of which the one representing the second row is the smallest, intervene between the tibia and the fifth metatarsal ; the larger of these ossicles answers to the calcaneum {I in Scelidosaurus and CrocodUus, Monograph, ut supra), the smaller and distal one to the cuboides {b, ib.). The bony frame-work of the left foot (69') is instructively preserved ; the first four metatarsals are, as usual, long and slender, and resemble those in previously described Pterosauria ; their under or plantar surface is exposed. The metatarsal of the first or innermost toe (/) is the shortest, that of the fourth toe (/w) is next in length ; the third {Hi) is the longest, but there is little difference in this respect ; their distal condyles project toward the sole, and are made trochlear by a mid-groove. The innermost digit shows the proximal and ungual phalanges in natural connection with each other and with the metatarsal : the ungual phalanx {i) is scarcely half the size of that of the corresponding digit (/) of the fore-foot. The ungual phalanges of the three other toes {H, Hi, iv) are preserved, showing the usual uniformity of size in the hind- foot of Pterosauria : the number and disposition of the contiguous but scattered phalanges best accord with the phalangeal formula (3,4, 5) presented by the second, third, and fourth toes respectively, in better preserved feet of other Pterosauria. There may be seen unequivocal evidence of a fifth toe, and that not merely rudimental but recognisably functional though without a claw. The tarsal bones (PI. 16, j, h) sup- port a metatarsal (/;?, v) directed parallel with the metatarsals [i — iv), but nuich shorter and also thicker : it is 6 lines in length, and expanded at both ends, the proximal one being 2^ lines in breadth, the distal one 2 lines, and the middle of the shaft \\ line. The imder or plantar side of the bone is exposed, as in the others, and shows a shallow oblique channel passing from the proximal end obliquely to the inner side of the shaft, dividing two elevations at that aspect of the proximal end. The distal end is a moderately convex condyle, the outer and plantar prominence of which is broken off. I regard this bone as the fifth metatarsal. It supports a digit of two phalanges : the first [\,v) is slightly dislocated, so as to show the concavity of its proximal joint close to the condyle to which it was articulated : it is 1 inch 3 lines in length, and is thicker as well as much longer than the corresponding phalanx of the other toes. The second phalanx (2, v) is 1 inch in length : it is bent back upon the first, and gradually tapers to a point. Both phalanges, 1 This throws e.xpository light on the idea, revived by Gegenbaur (' Vergleichend-anatomische Bemer- kungen iiber das Fussskelet der Vogel,' in Reichert's ' Archiv fiir Anatomie, Physiologie, und wissensch. Medicin,' 186.3, p. 445), viz., that the distal trochlear epiphysis of the Bird's tibia represents its pro.xitiial tarsal series, or astragalus. 47G BRITISH FOSSIL REPTILES. in the specimen described, pass obliquely across and beneath the four long metatarsals sup- porting the unguiculate claws. ^ From the position of this exunguiculate long and slender toe, as well as from its difference of structure, we may infer its application to a different office from that of the other toes. These obviously subserve the pm'poses of terrestrial locomotion, and perhaps of suspension : the fifth toe I infer to have helped to support, like the similarly shaped production of the calcaneum in certain Bats, the interfemoral expansion of alar integument, in the way indicated in the restoration (fig. 2, PL 17) of Dimorphodon macroiiyx. In the habitual mode of locomotion by vigorous act of flight this toe would be in action while the other four were at rest ; hence the necessity for greater thickness and strength of its bones, and the size of one of the tendons, as indicated by the groove in the metatarsal. Interesting, also, is it to note the analogy of this ' wing-toe' with the ' wing-finger,' though they be not homotypes, as shown in the shortness as well as thickness of the metapodial bone and the length of the pointed, claw- less, terminal phalanx. The fourth slab of Lias adding to our means of reconstruction of Dimorphodon, was observed by the Earl of Enniskillen in the collection of Henry Harder, Esq., jM.R.C.S., of Lyme Regis. It had been quarried from the same cliff as the preceding specimen (PL 16), and displayed the vertebra3 and bone-tendons of a long and stiff tail (PL 17, cd.). Indications of such a tail, in which the vertebrae were associated with ossified tendons, were apparent, and have been noted in the description in the second specimen with the skull (PL 16, cd) ; whereby one was able to show that the vertebrae in the originally described specimen supposed to be cervical (Buckland, loc. cit., pi. xxvii, a, a) were truly caudaL with similarly associated bone-tendons, as, indeed, Vo7i Meyer had recognised after the discovery of the caudal structure of his Bamphorhynchis: The specimen now to be described of the entire tail, as represented by its petrifiable parts, I conclude, from the identity of character of some of its vertebrse with the three shown in PL 10, c d' , and from the discovery of this specimen in the same formation and locality, to belong to Dimorphodon macronyx. The series of caudal vertebrae, to judge from the size of the anterior ones, comes from an individual as large as that represented by the fossils in Pis. 15 and 10, and, no doubt, from an adult or full grown one. This series is 1 foot 9 inches in length, following the curve, which is single and slight ; and it includes upwards of thirty vertebrae. These vertebrae, 3 ' " Cuvier, Wagler, unci Goldfuss lassen den Fuss aus fiinf ausgebildeten Zelien bestelien ; in alien Pterodactyln liabeich aber nie mehr als vier solchen Zelien uud hochstensnoch eineii Stummel voigefunden." Von Meyer, op. cit., p. 20. But see ' Osseniens fossiles,' 4to, torn, v, pt. ii, p. '3,7A — " Le cinquieme reduit a nn leger vestige," &c. ^ " Beitr'age zur naheren Kenntniss fossiler Reptilien," in Leonliard und Bronn's ' Xiues Jahrbucli fiir Minernlogie,' &c., 8vo, 1857, p. 536. LIASSIC PTERODACTYLES. 477 lines in length of centrum in the first five, progressively increase to a length of 1 inch at the twelfth, begin to shorten gradually after the fifteenth, the twenty-first being 11 lines, the twenty-fourth 9 lines, the twenty-eighth (i lines, and the thirtieth 5 lines in length. In breadth or thickness the vertebrse decrease from the first to the tenth; and then again gradually from the fifteenth to the last, which is filiform. The first caudal, or the first of the series here preserved, has the anterior articular surface of the centrum subconcave. The inferior surface describes a slight concavity lengthwise ; the upper part of the anterior half projects as a parapophysis, the end of which has been broken off, showing the open cancellous structure. A ridge from its upper part was continued to the fore part of the anchylosed neural arch. This arch developed zygapophyses, of which the anterior extend beyond the centrum ; but they are better shown in succeeding vertebrse. In the second caudal the base of the parapophysis has receded and now projects from the upper part of the side of the centrum, occupying more than its middle third. Part of a quadrate spinous process is here preserved, projecting above the centrum as far as the vertical diameter of that element. In the third caudal the base of the parapophysis, reduced in vertical thickness, occupies the same positions and longitudinal extent. The postzygapophysis, after a deep hind notch of the neurapophysis, curves over the prezygapophysis of the succeeding vertebra, which enters that notch. In the fourth caudal the base of the parapophysis has lost in longitudinal as well as vertical extent, and is more posterior in position. The subconvexity of the hind articu- lation of the centrum is here well shown. The confluent neural arch is low, attached to rather more than the fore half of the centrum. The postzygapophysis does not extend back beyond the centrum ; the prezygapophysis is continued beyond the front or concave surface of the centrum into the neural notch of the preceding vertebra. In the fifth caudal the parapophysis is smaller and more posterior. The neurapo- physis rises from the anterior half of the side of the centrum and continues to show the zygapophysis, though reduced in size. Between the fifth and sixth caudals a small, slender hsemapophysis (Ji) has been articulated to the under part of the intervertebral space. The reduced parapophysis is continued from the sixth caudal ; this vertebra shows a much reduced indication of neurapophysis. The base of a haemapophysis crosses the lower part of the space or joint between it and the seventh caudal, then expands both forward and backward, and more so in the latter direction ; the inferior border of this expansion is straight. In the seventh caudal the prezygapophysis is still indicated, though much reduced in size. The ha3mapophysis, similar in shape to the preceding one, is longer ; and three bone- tendons rise from the side of the hind projection of this haemal arch. In the eighth caudal the base of a reduced parapo[)hysis projects from the side of the 478 BRITISH FOSSIL REPTILES. centi'uru behind its middle ; a low prezygapopliysis projects from the neural arch : but beyond this vertebra all trace of that arch disappears, or is indicated by feeble prominences in the fasciculus of bone-tendons which seem to be attached to neural processes of the non-elongated centrums. Six or seven filamentary bone-tendons, one thicker than the rest, extend lengthwise above the centrum. Some of these may be traced over two centrums, then end in a point, their place being taken by another bone-tendon beginning by a similar pointed end. The parapophysis disappears in the tenth vertebra. The caudal vertebrae in the first discovered specimen of Bimorphodon ^ answer to the eighth — eleventh in the present series. The elongate centrums of the tenth and succeeding caudals, usually more or less uncovered by the bone-tendons, show a low lateral ridge, and a shght expansion at the ends. The hsemapophyses are traceable, much reduced in size, to the fifteenth — sixteenth vertebrae. The bone-tendons are in two fasciculi, one neural, the other haemal, in position. From five to eight may be counted in the side view given of each of these fasciculi. The seeming increase of thickness of some, usually the more peripheral of the filaments, may be due to this flattened form, and to more or less of the side coming into view, instead of the edge. Five or six may be counted in each fascicule, even beyond the twentieth caudal ; the number varying at parts through the formation of the bundle by successive tendons, as above mentioned. They are reduced to two or three at the thirtieth vertebra. The terminal joints of the elongate centrums appear to be flattened and closely adapted, allowing of very little motion. It is evident that, as in BawphorJiyncJius, the tail was stiff as well as long, and doubtless served as a sustaining ray of the parachute of membrane continued backwards from the wings and hind limbs. The vertical diameter of the second caudal showing its neural spine is five lines. The diameter of the ninth vertebra, including the neural and haemal fasciculi of bone- tendons, is the same ; and beyond this the vertebrae and their surroundings gradually diminish to the pointed end of the tail. § Restoration of Dimorphodon. Plate 17. The several parts of the skeleton of Bimorphodon preserved in the slabs of Lias described and referred to in the foregoing pages have ultimately yielded the desired result of their scrutiny and comparison, viz., a restoration of the extinct animal, such as I have endeavoured to exemphfy in Plate 17 ; and I propose to apply that plate in illustration of a summary of the osteology and dentition of Bliiiorphodon, comparing therewith the 1 Buckland, loc. cit., pi. 29, n, a. I have had these vertebra; carefully rtilrawn, from the specimen, ill PI. 17, cd. LIASSIC PTERODACTYLES. 479 previously known Pterosaiiria, and adding siicli deductions as to tbe status and affinities of the order as seem legitimately to flow from the facts. The first distinguishing feature of DiiiiorpIiodo?i, or of the present liassic type of the genus, is the disproportionate magnitude of the head — the more strangely dispro- portionate, as it seems, in an animal of flight. The head is large in proportion to the trunk, not only in respect of length but of depth, and probably, also, breadth ; nevertheless, the shape and disposition of the con- stituent bones are such that, perhaps, no other known skull of a vertebrate is constructed with more economy of material — with an arrangement and connection of bones more completely adapted to combine lightness with strength. So far as the skulls of Pterosauria have been sufficiently entire to show the shape of the head, no other known species resembles DimorpJiodon. The cranial part is singularly small : the rest is mainly devoted to the formation of the large, long, and powerful prehensile and manducatory jaws. Among the debris of the cranial bones, in specimens Pis. 15 and 16, the mastoid (s), parts of the occipital (paroccipital, 4), the parietal (7), post-frontal (12), frontal (11), prefrontal (14), and nasal (1.5), are recognisable : the last two bones, however, are concerned more with the scaffolding or buttressing of the upper jaw than with the protection of the brain or formation of its case. Though contributing their shares to the otccrane, the chief developments of the paroccipital (PL 17, 4) and mastoid (ib. 8) relate to the muscular connections of the head with the trunk : the mastoid joins the postfrontal to form an upper zygoma, giving origin to part of the temporal muscles; it also affords a fixed articulation to the tympanic, and sends down a pointed process external to the masto-tympanic articulation. The parietals (PI. 17, 7 ), confluent at the mid line, where they develop a low crest, swell out slightly at the temporal fossa, indicative of the size and saurian position of the mesencephalon. The frontal (11) is narrow and flat between the orbits, of which it contributes most of the upper part of the rim. This is continued by the postfrontal (12) behind, which sends down a long pointed process to unite with the malar (26), and a shorter and thicker one to join the mastoid (s). The prefrontal (14), of a triangular form, contributes to the upper and fore part of the orbit, and, either directly or by a connate lacrymal, unites with the ascending malo-maxillary process (21, 26), and the base of the pre- frontal articulates with the frontal and the nasal. The nasals (15), to the usual con- nections with the frontal, prefrontal, and medial process of the premaxillary (22'), superadd a union with the lateral ascending process of the maxillary (21>:), completing the bar between the nostril (w) and the antorbital vacuity [a). The nasal bone forms the upper part of the nostril ; the rest of the boundary of that singularly wide aperture is formed by the premaxillary and maxillary. Of the basis cranii and palate there do not appear to be any recognisable parts preserved. The maxillary is overlapped by the hind alveolar part of the premaxillary, and unites therewith by a long oblique suture (21")- The maxil- lary, receding, expands and sends upward a long slender pointed process to articulate 2 X 480 BRITISH FOSSIL REPTILES. with the nasal ; it then joins the malar and the prefronto-lacrymal, and descends internal to the mandible to join the palatine.^ Each maxillary (?i, 21') affords alveoli for eight or nine teeth. Tlie premaxillary is the largest of the bones of the head. The pair, by confluence or connation, constitute the fore part of the upper jaw (22), expanding from a sub-obtuse apex as it recedes, and preserving its entireness for an extent of about two inches. This tract seems to be arched above transversely, with a slightly convex upper longitudinal contour continued along the medial ray or process (22')- Of the configuration of the palatal surface the specimens give no evidence. Erom the analogy of Pterodactijlus Cuvieri and Pt. Sedgwichii^ we may infer that this (premaxillary) part of the bony roof of the mouth was entire, and strengthened by a median ridge. The lateral or alveolar borders formed alveoli for four teeth on each side. Thus the hind expansion of the premaxillary divides into three rays or processes. The upper medial or nasal ray is the longest : it is continued backward, continuing the initial curve of the upper contour of the face as far as the nasals, tiie mid suture or confluence of which bones it overlaps, and joins suturally to an extent precluding any movement of the upper jaw on that part of the head. The length of this ray is about 3| inches. The pair of lower or alveolar rays extend back for about I^ inches. The malar (26) forms the lower narrower end of the oval orbit, sending up dhe pointed process (united with that of the maxillary?) toward the prefrontal, and a longer and stronger one to join the postfrontal. The squamosal (27) continues the zygomatic bar backward to abut against the tympanic. Its precise position and direction are left doubtful in the specimens hitherto obtained, but it is unquestionably present, and contributes to the fixa- tion of the tympanic. This (28) is a moderately long and strong pedicle, immovably articulated to the mastoid, paroccipital, and squamosal ; thickest posteriorly, where it is strengthened by an outer marginal ridge, sending forward and inward a process which may articulate with the pterygoid (but of this I could not get clear evidence), expanding at its distal end to receive the abutment of the squamosal or lower zygoma, and to form the convex condyle for the articular element of the mandible. The dentary parts of the mandible are confluent at the symphysis, which is as long as the undivided fore part of the premaxillary. The ramal part of the dentary is compressed, and gains a depth of about 10 lines before it bifurcates. The alveolar border of the dentary extends as far as that of the maxillary, viz. about 5 inches, beyond which the upper prong (PL 17, 32') is continued above the mandibular vacuity, underlapphig the surangular (29) and terminating in a point. The lower prong (ib. 32") terminates in a point before attaining the vacuity ; it is underlapped by the fore part of the angular (so), with which it articulates. ^ This description is on a liomological hypothesis, subsequently discussed (p. J86). - Pterosauria, PI. 7, fig. 1 , b. LIASSIC PTERODACTYLES. 481 The divergence of the hinder prongs of the dentary exposes a small part of the splenial (31). The vacuity, if it be natural and not due to abrasion of a thin outer wall, is a long and narrow oval, 1 inch 8 lines in length, G lines in breadth. It is circumscribed behind by the confluent angular and surangular elements (29). The angular (30) forms a slight projection behind the articular concavity ; it expands vertically, and contracts transversely as it advances, contributing a small share to the lower border of the vacuity, and con- tracting to a point below the dentary, about 5 inches from the angular process. The range of variety shown by the skull is considerable in the order Pferosauria. In relative size, as in the expanse of the antorbital vacuity, Ptcrodacti/lus crassirostris^ comes nearest to Bimorphodoii ; but the orbit is relatively larger, and the nostril much smaller. In Bhamphorhi/nchus Gemmiriffi the nostril and antorbital vacuity are of equal size, and each is about one eighth the size of the orbit, which is proportionally larger than in Dimorphodon. \a. Fterodadyliis longirostris" the nostril is larger than the orbit; the antorbital vacuity is not half the size of the orbit. In Pterodacfi/Ius suevicus ^ the antorbital vacuity is still smaller. In Pterodacti/his Kochii * that vacuity is limited, as in Cldamydo- saurus, to the upper part of the boundary between the large orbit and the long and large nostril. In Pterodacfi/Ius longicollmn ^ it appears to be wanting. The shape of the skull offers many modifications in the several species, from the long and slender type of that of Pterodacti/lus scolopaciceps and Pt. longirostris to the shorter and deeper cone indicated by Pt. conirostris,^ and to the inflated and more or less anteriorly obtuse form exhibited by Dimorjihodon and the more gigantic Pterodactylus simus? The position of the tympanic pedicle varies from the almost vertical one in Dimorpho- don to the almost horizontal one in Plerodadylus longirostris and Pt. Kochii. In Pt. crassirostris it shows an intermediate slope or position. The mandible, conforming in relative depth and length to the general shape of the skull, has the symphysis longest in those species with long and slender jaws. In Pterodactylus suevicus the symphysis extends along the anterior third part of the mandible. In Pt. crassirostris it is shorter, and still shorter in Dimorphodon. The depth of the rami decreases behind the dentigerous part in Pterodactylus longirostris. The generic dental character of Dimorphodon has been given in detail in the special descriptions of the specimens figured in Pis. 15 and 16. The range of variety mani- 1 Pterosauriu, PL 1, figs. 2 — -4. 2 lb., fig. 1. ^ QUENSTEDT, Op. cit. * Von Meyer, op. cit., tab. i, fig. 2. ^ lb., ib., tab. vii, figs. 1 — 4. ^ Dixon's 'Geology and Fossils of the Tertiai-y and Cretaceous Formations of Sussex, 4to, 1846, PI. 38. ' Pterosauria, PI. 6, figs. 1 — 3. 482 BRITISH FOSSIL REPTILES. fested in this character is considerable in the present order, although in no species has any departure been observed from the predatory zoophagous condition. The teeth, always simple and pointed, vary in shape, in nund^er, in position, in relative size. Pterodactylus crassirosiris exemplifies the laniariform type of teeth, more or less elongate, and separated by intervals of varying extent. In this not uncommon condition the teeth are longest in the upper jaw, as offering more resistance than does the lower jaw in aid of the weapons most deeply implanted in the struggling prey. In Pterodactylus lonyirostris the teeth are rather small, subequal, with short intervals, a little widening toward the hind end of the series, which is restricted to the anterior half of the jaw, both above and below. In some Pterosauria a certain extent of the fore part of both upper and under jaws is edentulous, and from its shape has been inferred to have supported a horny sheath. The teeth are long slender canines, with wide intervals. They number from about 8 to 10 on each side of the upper jaw, and from 7 to 8 in each ramus of the mandible. Von Meyer proposed for this modification of mouth the generic name Rhamphorliyiiclius. Diinorphodon shows the combination of scattered laniaries, with small, more closely set serial teeth in the lower jaw ; it has more numerous teeth, occupying a greater extent of the alveolar margins of the jaws, than in any other Pterosaurian. The very small teeth which have been observed in tlie short jaws of the little Ptero- dactylus brevirostris^ are most probably characters of inmiaturity, not of species. In regard to the bony structure of the head and the dentition, the general result of observation and comparison of Pterosaurian fossils, and common consent of competent investigators, having excluded the volant Mammals from the claim of affinity, the question becomes narrowed to whether the skull in Pterosauria more resembles that in the cold- blooded or the warm-blooded oviparous air-breathing Vertebrates. Hermann von Meyer, who has contributed a great and valuable share to our know- ledge of the Pterosaurian order,^ quoting Oken's opinion, " that the skull is intermediate in character between that of the Chameleon and Crocodile," sums up his own conclusions on that head in the following terms :— " The skull oi Pterodactylus \?, essentially comparable only with that of Birds and Saurians. The preponderating resemblance with the Bird's skull cannot be contested. Against this, however, is a remarkable dissimilarity in certain parts which, on the other hand, approximates it to the type of Saurians." ^ The term Sauria is here used in the sense of Brongniart and Cuvier, and it is open ^ GoLDFUss, loc. cit., tab. .x, fig. 2. 2 Especially in the admirable summarv of his own and others' researches, in the part of his great work, 'Zur Fauna der Vorwelt' relating to " Reptilien aus dem lithographischen Schiefer," &c,, fol., 1860. "* "Der Schadel der Pterodactyln, der uach Oken zwischen Chamaleon und Crocodil stehen wiirde, lasst sich eigentlich nnr mit den Viigeln und den Sauriern vergleichen ; die iiberwiegende Aehnliehkeit mit dem Vogelkopfe kann nicht bcstritten werden ; ihr gegeniiber steht aber eine auffallende Uniibnlichkeit in gewissen Theilen, die dafiir ziim Zypus der Saurier hinneigen." — Op. cit., p. 15. LIASSIC PTEROSAURIA. 483 to the unbiassed investigator, and, indeed, becomes iplainly his business, to determine, not merely whellier Avian or Saurian characters predominate in the Pterosaurian skull, but to define the degree of affinity or correspondence of cranial structure therein traceable to such structures in Enahosauria, Binosaiiria, Bicynodontia, Crocodilia, Laceriilia, each of which may be a group, organically, of co-ordinate value vi^ith Aves. Greater respect to the memory of so unbiassed a seeker after truth cannot be shown than by weighing with due care and what judgment one may be able to bring to the task the value and significance of each well-determined evidence of the cranial structure which VoN jMeyer has described and reasoned upon. It is to be regretted that not in any of the numerous figures of the skull of Plero- sauria, original or copied, has Von Meyer indicated the bones which he describes. When he writes — " The temporal bone lies external to the parietal and principal frontal bones, and mainly forms the temporal fossa," ^ one much wishes he had indicated his ' Schliifen- bein ' in the skull of RhcaiiphorJipichus Geiniiiiriffi, pi. iii, fig. 4 ; pi. ix ; pi. x, fig. 1 ; or in the more insti'uctive example of cranial structure which he has borrowed from Goldfuss for the subject of his pi. v [Pferodacfj/lus crassirostris). By ' Schliifenbein ' Von Meyer may mean that element of the compound ' temporal bone' of anthropotomy which I have called 'squamosal.' No doubt in Man and most Mammals the squamosal does contribute a notable share to the formation of the temporal fossa, whence the name ' temporal ' given to the incongruous group of cranial elements coalescing in such warm-blooded Vertebrates with the squamosal, so exceptionally expanded in the Mammalia. But as to the value of the bed of the temporal muscles in determining the homology of the bones forming it, I would refer to the remarks in my work on the ' Homologies of the Vertebrate Skeleton.' ^ Some clue to the bone signified by Von Meyer may be got from the following remarks — " Anteriorly it seems not to take, as in Birds, a share in the formation of the orbital rim ; here, much more as in Saurians, it is pushed aside or supplanted by the postfrontal." ^ The term ' temporal bone ' (Schliifenbein) has been used in various senses, but whether it be applied to that element which I, with Cuvier, call ' mastoid ' in Beptilia, or to that which others,'' with Cuvier, call ' temporal ' (meaning squamosal) in Birds, there is no bone that Von Meyer can be supposed to mean by ' Schlafenbein ' whicJi forms any part of the rim of the orbit in Birds. VoN Meyer recognises a ' postfrontal ' (' Hinterstirnbein ') in Pterosauria, and states 1 " Das Schlafenbein liegt aussen an dem Scheitelbein und Hauptstirnbein, und bildet haiiptsiicblich die Scbliifengrube." — Op. cit., p. 15. 2 8vo, 1848, p. 33. ' "Vorn acheint es nicht wie in den Vijgeln an der Bildung des Augenhohlenrandes Tbeil zu nelimen hier vielmebr wie in den Sauriern durcli das Hinterstirnbein verdriingt zu werden." — Op. cit. p. 15. * Hallman, "Die vergleichende Oateologie des Scblafeabeins," p. 8, pi. 1. 484 BRITISH FOSSIL REPTILES. that it pushes away his temporal (Schiafenbein) from the orbit. In Pterosauria the post- frontal (PI. 17, 12) is undoubtedly interposed between the bone I determine as 'mastoid' (ib. S) and the orbit (ib. o) ; and my ' mastoid ' in Pterosauria answers to Cuvier's and Hallnian's 'temporal,' i.e. squamosal, in Birds. We may conclude, therefore, that Von Meyer's ' Schlafenbein ' in Pterosauria is that marked 8 in the skull of Pterodactylus crassirostris} Certain it is that no bone answering to 8 in Pis. 1.5, 10, 17 of the present Work contributes to the formation of the orbit in any Bird. In the great majority of that class, as is well known, the rim of the orbit is incomplete below ; it is formed above by the frontal, before by the prefrontal and lacrymal (' antorbital ' of ornithotomists), behind by the postfrontal (' postorbital,' ib.). Where, as in some Psittacidce,^ the orbital rim (' Augenhohlenrandes ') is complete, the lower complement is formed by an extension of ossification from the antorbital to the postorbital processes, independently of either Cuvier's temporal (s) or my squamosal (27) in Birds. I confess that the foregoing result of the analysis of a main ground of Von Meyer's assertion as to the " incontestable similarity between the Pterosaurian and Avian types of cranial structure " has not a little tended to shake my confidence in the grounds on which he has pronounced definite judgment on the matter. So far as we have yet got evidence of the structure of the skull in Pterosauria, it seems that, contrary to the rule in Birds, the orbital rim is entire ; and that its lower border is completed by the zygomatic arch, and chiefly, if not exclusively, by the malar element ; whereas, such arch passes freely beneath the orbital rim in the few Birds with that rim entire. Now, in this part of the cranial structure the Pterosauria agree with the Crocodilia : as in them the malar (26) sends up a process to unite with one descending from the postfrontal (12) to complete the orbital rim behind. In the small species of Pterodactyles (Pf. lonyirostris, Pt. scolopaciceps, and in the perhaps immature animal represented by Pt. brevirostris) the hind convexity of the cranial wall is not marked by the apophysiary developments of paroccipital and mastoid, and accordingly resembles that part of the cranium in Birds, especially the smaller Grallce ; but before this similarity of shape can be pressed into the argument for the Avian affinity of the Pterosauria, it should be shown to be common to or constant in the extinct volant order. But this is far from being the case. When a Pterosaur has gained the size of Pterodactylus crassirostris ^ or Pter. suevicus^ the back of the skull shows no cerebral swelling, but only the crests and processes for muscular attachments, as in other Reptilia 1 Pterosauria, PI. 1, figs. 3 and 4. - 'On the Archetype and Homologies of the Vertebrate Skeleton,' Svo, 1848, pi. i, fig. 1 {Calyplo- rJiynclms) ; 'Anatomy of Vertebrates,' Svo, vol. ii (1866), p. 51, fig. 30 {Psittacus), also p. 63. ^ Goldfuss, op. cit., pi. vii. Quenstedt, op. cit. LIASSIC PTERODACTYLES. 485 of similar size. Even in BhavipJiorhpichus Gemmingi the cranial convexity is not posterior, but is limited to the temporal fossae behind the orbit, as in the specimen figured by Von Meyer in pi. ix, op. cit. ; and this indication of the optic lobes is less conspicuous in the sul)ject of pi. X, fig. 1. In Bimorjjhodon there is still less trace of this alleged Avian characteristic. The bone which, in the Bird, as in the Pterosaur, forms part of the otocrane, articulates with the ex- and par-occipitals behind, with the alisphenoid in front, with the parietal above, and with the petrosal within, which contributes the articular surface to the tympanic and the upper rim to the meatus auditorius, also articulates in the Pterosaur, as in the Crocodile, with the postfrontal : and this character appears to be constant in the Pterosauria as in the Crocodilia, while it is exceptional in Aves. In the particulars in which the bone 8 differs in the Pterosaurian from that in the Bird, it agrees with 8 in Crocodilia ; as c.r/. in its high position in the cranium, owing to the low development of the cranial chamber; its greater degree of projection from the true cranial walls ; the extensive and suturally fixed character of its articulation with the tympanic as compared with the more definite and restricted glenoidal movable articulation which the mastoid (S) aff'ords to 28 in Birds. In all these circumstances, whether the bone 8 (PI. 17, tig. 1) be called mastoid or squamosal, it is Reptilian, not Avian, in the Pterosaur. Herr Von Meyer states, in another of his comparisons, that in the Monitor, Iguana, and SfeUio, the prefrontal (' Vorderstirnbein ') enters into the formation of the periphery of the external nostril (Nasenloch).^ This is the case with Varanus," not with true Monitors.^ In Tc'jiis nifjrojmncfatus some extent of the suture between the nasal and the maxillary intervenes between the prefrontal and the nostril. The non-extension of the prefrontal to the external nostril shows no Avian affinity in Pterosauria ; rather an agreement with the majority of Beptilia, as, for example, with the whole order of Crocodilia. In some Crocodilia {Teleosaurus) and Lacertilia {Chlami/dosauriis, Lyriocephalm) there is an antorbital vacuity, which, in the latter Lizard (PI. 17, fig. 3, a), is equal in size with the nostril (ib., n) and intermediate in position between that cavity and the orbit (ib., d), which is large. A process of the maxillary rises obliquely backward to join the nasal, and to separate the intermediate vacuity from the external nostril. The lacrymal and pre- frontal form the bar dividing the intermediate cavities from the orbit. In most Birds a small intermediate vacuity is partitioned off from tlje nostril by a process of the maxillary rising to join the nasal, and is similarly separated from the orbit by the lacrymal, which descends to join the malar. The great range of variety in the development of this I 'Zur Fauna der Vorwelt,' fol, 1860, p. Ifi. - See Cuvier, ' Ossemeus fossiles,' v, pt. 2, pi. xvi, lig. 1 ('grand Monitor da Xil, Lacerta miotica'), p. 259, the Varanus Draccena of Merreni, Varamis niloticus of most modern erpetologists ; also in pi. xvi, fig. 7, ' Monitor du Java,' p. 2G0 ; the Varanus bivittatvs, of Merrem. ^ As e.g. Tupinarnhis teyuixin, ' Sauve-garde d'.Amerique.' Cuvier, vol. cit., pi. xvi, figs. 10, 11, and Thorictes Draccena, ib., figs. 12, 1,3; " \m Uragone,' ib., p. l'G3. 486 BRITISH FOSSIL REPTILES. ' intermediate ' or ' antorbital vacuity,' in Pterosauria, has already been pointed out ; but tlie comparable structure is by no means peculiar, as Von Meyer would lead one to infer, to the skulls of Birds. ^ In no Pterosaurian has any obvious and unniistakeable suture been seen indicative of the respective shares taken by maxillary (21) and premaxillary (22) in the formation of the dentigerous part of the upper jaw^ : both hones combine to support the array of teeth ; they have coalesced, at least at their external or faci-alveolar plates ; as, likewise, have the right and left premaxillary portions forming the fore end of the upper jaw. The suture between this preuiaxillo-maxiliary bone and the suborbital portion of the zygomatic arch remains. Accordingly, there is a choice of analogies in the interpretation of the observed facts : a proportion of the compound bone may be assigned to the premaxillary, according to the analogy of the Crocodile and Lizard ; or the whole may be called premaxillary, according to the analogy of the Ichthyosaur. GoLDFUSs, guided by the Lacertian analogy, limits the premaxillary to the anterior part of the upper jaw, and to the upper part of the external bony nostril {n) ; and he illustrates this view by a dotted line representing the assumed suture in his restoration of Ptero- dactylm crassirostris, in pi. ix (op. cit.)." Von Meyer assumes, as arbitrarily, the Ichthyo- saurian analogy, but views it as a specially Avian one, and ascribes to the Pterosauria a bird-like premaxillary,'' and this determination is indicated by the numerals on the restora- tion of the skull of Ptcrodactylus compressirosiris, p. 249, PI. 1, fig. 5. Of the maxillary bone (my 21) Von Meyer merely remarks that "it does not follow the type of Birds" (" folgen nicht dem Typus der Vogel," ib., p. 15). And yet, if the Pterosau- rian premaxillary be interpreted according to that type, forming so large a proportion of the upper jaw as to include all the teeth, the edentulous maxillary must have had a correspond- ingly Avian proportion and position. Only, whereas in most Birds the small and slender maxillary sends up a process helping to define the back part of the nostril and fore part of the antorbital vacuity, the corresponding process in Plerosaiiria would be (as indicated in my PL 16, 22"), part of the premaxillary. I incline to believe, however, that it may prove to belong to the maxillary ; that the dentigerous part of the upper jaw is due, in Pterosauria, to the combined maxil- laries and premaxillaries, but that the latter take a larger share in the formation of the alveolar tract than Goldfuss conjectures. One ground of such opinion is this : the portion of upper jaw with six pairs of laniary teeth in the huge PlerodadyJus Sedywickii, in which the palatal surface could be clearly worked out,* showed that the anterior expansion, with the group of three pairs of teeth, could hardly have been ' " Zwischen Nasenloeh und Augenbohle licgt eine driUe Oeffimiig, die wiederum an den Vogel- si:badel erinnert." — Op. cit., p. 16. - Copied in PI. 1 {Pterosauria) of the present Work. 8 " Ein Vogeln-ahnlichen Zwisclienkiefers," v, p. If), op. cit. "t Monograph, Suppl. No. 1 (1859), PI. I, fig.s. 1, a, b. LIASSIC PTERODACTYLES. 487 separated by a suture, at the slight constriction suggesting that structure in Ft. crassi- rostris^ without leaving some indication of its original existence, especially on the palate. In the anterior confluence of right and left premaxillaries, and the backward produc- tion from their upper part of a bony bar uniting with the nasals and dividing the nostrils, we have a character of the Dicynodonts and of some Lacertians {Varanus) as well as of Birds, and the Saurian affinity is shown to be the truer one by the firmness of the naso-pre- maxillary union and the absence of any power of, or provision for, that hinge-like movement of the upper mandible upon the cranium which is peculiar to, though not constant in, the Avian class. Moreover, the outer surface of the premaxillary shows none of that spongy porosity and rugosity which relates to the sheath or horny covering of the beak character- istic of the Bird. Such structure has not even been detected in the feeble trace of eden- tulous anterior production of the upper jaw in Bhamphorhynchus, Von Meyer. I cannot, therefore, see, with Von Meyer, the beak of the Bird in an animal with a fixed and toothed upper jaw ;" for on every hypothesis of its bony structure it finds a closer resemblance among the toothed Reptiles than in the class of Birds. The mandible, or lower jaw, is supported, as in all Vertebrates below Mammals, by the tympanic, viz. the bone (28, Pis. 16 and 17) which is shown by its osseous connec- tions, its relations to the 'facial nerve,' ^ or its equivalent the 'ramus opercularis,' * and by its mode of formation, to answer to that which in Mammals is mainly reduced to the function of supporting the ear-drum. In air-breathing Ovipara it superadds this function to its more constant and essential use in non-mammalian Vertebrates, of supporting the lower jaw. In reference to the question of affinity before us, the tympanic gives valuable evidence by reason of the moveable articulation and peculiar connections with the upper mandible essentially correlated to a covering of feathers. In Pterosauria the tympanic at its proximal end resembles that of Lizards by its fixed sutural mode of union with the cranium, and it furthermore resembles that in Crocodiles by the abutment of the zygoma against its distal end, to which it is suturally attached. In Birds the tympanic enjoys a synovial moveable articulation by a single or double condyle at its proximal or cranial end, and presents a synovial cavity to a condyloid con- vexity of the hind part of the zygoma. By this test, therefore, the Pterosauria are shown to be not only ' Saurian,' but to be nearest akin to the existing orders which possess double-jointed ribs and the correlated cardiac structure. The difference of shape between the tympanic of the Pterodactyle and that of the Bird is too strongly marked not to have attracted attention ; but I do not find in that of the Chameleon the ' Goldfiiss, loc. cit. - "Wii- sehen also hier die Sclinaiitze der Vogel auf eiii Thier niit unbewegliclier uiid niit Z-ilinen bewaffneten Schnautze angewendet." — Op. cit., p. 15. ■' ' Anatomy of Vertebrates,' vol. ii, 8vo, 1SG6, p. 12-4, vol. iii, p. IJo. * lb., vol. i, p. 303. 2y 488 BRITISH FOSSIL REPTILES. most resemblance to the Pterosaurian tympanic.^ For, besides the Lacertian freedom of the bone from zygomatic abutment, the tympanic in the Chameleon has not the longitudinal strengthening ridges, nor the process turned toward the pterygoid. The dentigcrous mandible, like the maxilla, speaks for the Reptilian afhnity of Pterosauria ; the distinct sockets for the teeth ally them to the higher forms of Sauria. In reference to the generic modification of dentition in Dimorphodon, it has been remarked that this early form of flying dragon seemed to have derived one feature or modification from the Fish, and the other from the Crocodile or Plesiosaur.^ The length of the neck, which is not always equal to that of the head, is due, in Pterosauria, rather to the length than the number of the vertebra?. Counting the axis with the small coalesced atlas ^ as one, I give seven cervical vertebrae to the Dimorphodon macronyx (PI. 17, fig. 1, c). Of these a series of four are preserved in the specimen (PI. 16, c), showing, as described, the characteristics of the Pterosaurian cervical vertebrae which had been determined and illustrated in a former Monograph.* CuviER,^ in his searching analysis of the evidence at his command of the osseous struc- ture of the Pterodactylus lonyirosfris, concluded that the cervical vertebrae were not fewer than seven, as m Crocodilia and Mammalia, or not more than eight, as in Chclonia. GoLDFUSS was able to demonstrate the vertebral formula in his famous specimen of Pterodactylus crassirostris.^ The number, ' seven,' was, however, obtained by reckoning the atlas distinct from the axis, and the last cervical may have been relegated to the dorsal series. Quenstedt' shows seven cervicals in his instructive example of Pterodacfylus siievicus, reckoning the atlas and axis as one vertebra ; and this analogy I have followed in the restoration of DimorpJiodon. Rhamp/iorhynchus Gevimingi has six cervicals, counting the coalesced atlas and axis as one ; but in the specimen figured by Von Meyer in his pi. ix,^ there seems to be the centrum of a short ' seventh ' cervical between the longer ' sixth ' and the first (dorsal) vertebra supporting a long free pointed rib. It is certain that the number of cervicals does not exceed the latter reckoning or fall short of the first. Thus it is plain that the Pterosauria exemplify the Crocodilian affinity in the cervical region of the vertebral column. Lacer- ' " Dieser Knochen ist nicht wie in den Vogeln quadratisch, sondern cylindrisch stielformig beschaffem. — Hierin, so wie in eininpjen andern Tlieilen, zeigt das Tliier die meisle Aehnlichkeit niit Cha- maeleonT — Von Meyer, op. cit., p. 16. ^ 'Report (Sections) of the British Association for the Advancement of Scienre,' 8vo, 18.t8, p. 98. 3 Pterosauria, PI. 7, figs. 11—14. * PI. 8. PI. 12, figs. 1, 2 and 4. ^ 'Ossemens fossiles,' torn, cit., p. 367. ^ "Man ziihlt 7 Halswirbel, 1.5 Rippenwirbel, 2 Lenden, and 2 Kreuzbeiiiwirbcl," loc. cit., p. 79. 7 Op. cit., figs. 1—7. 8 Op. cit. LIASSIC PTERODACTYLES. 489 tians have fewer definite cervicals ; Birds have more. I have not seen any Bird with fewer than eleven cervicals.^ The length and flexibility of the neck is correlated with the covering necessitated by the high temperature of the Bird.^ The cold-l)looded flying Reptiles have a comparatively short and rigid neck, but of a thickness and strength proportionate to the size of the head, and adequate to the work to be performed by the jaws in over- coming and bearing away the prey they may have seized. The chief variety manifested hy the Pierosauria in the cervical region is in the relative length of the last six vertebra ; this is greatest in Fterodadiilus hngicollum and Pt. loiiffirostris ; it is least in Pt. crassirostris and DiniorjjJiodoii luacronyx, and apparently also in Pterodactylus simus, if we may judge by the breadth, compared with the length, of the vertebra figured in PI. 12, figs. 1 and 2. There seems to have prevailed a greater range of variety in the number of vertebrae between the cervical series and the sacrum. In Pterodactylus lonyirostris, Cuvier esti- mated at least twelve which supported moveable ribs/ and nineteen or twenty in the dorso-luuibar series. Von Meyer concluded that the number of dorsal vertebrae fell not below twelve in any species, nor exceeded fifteen or sixteen in Pterosauria. Pterodactylus Kochii shows fourteen dorsal vertebrae ; Pt. crassirostris not more than twelve, reckoned by the number of pairs of free ribs, which can be satisfactorily discerned. I have seen no specimen of Diniorphodon yielding definitely the number of the dorso- lumbar vertebrae, i. e. of the vertebrae between the cervical and sacral ; it is from the best considerations I have been able to give to the analogies of these vertebral formulae, in better preserved examples of other species of Pterosauria, that I assign thirteen to this series in my restoration of Bimorphodon macronyx (PL 17); and I conclude that the thirteenth was a true lumbar vertebra or without connection with a free ])air of ribs. If there should prove to be error in this estimate I cannot think it will extend beyond one vertebra, or at most two, in excess of twelve dorsals. The nine dorsal vertebrae, which have kept together, in almost a straight line, in the specimen (PI. 16, d), testify to the strength and closeness of their reciprocal articula tions, under disturbing influences which have afi'ected so great and general a degree of dislocation of most other parts of the skeleton. BucKLAND seems first to have observed the convexity of one of the terminal articular surfaces of the centrum of a dorsal vertebra, and to have deduced an affinity therefrom ; ' The Sparrow (Pi/rf/ita (/omesticn) hiis twelve (' Osteol. Catal. Coll. of Surgeons,' No. l.i/l, vol. i, p. 297). ^ " As the prehensile functions of the hand are transferred to the beak, so those of the arm are per- formed by the neck of the Bird ; that portion of the spine is, therefore, composed of numerous, elongated, and freely moveable vertebra?, and is never so short or so rigid but that it can be made to apply the beak to the coccygeal oil-gland, and to every part of the body, for the purpose of oiling and cleansing the plumage." — ' Annt. of Vertebrates,^ ii, p. 39. ' Vol. cit., p. 3fi8 : — " II senible qu'il en est reste au moins douze en place du cote gauche." The specimen figured by Von Meyer, op. cit. in pi. i, fig. 1, shows tliirteeu ribs on the left side of the trunk. 490 BRITISH FOSSIL REPTILES. (the specimen is marked d in the Plate 27 of his Memoir, loc. cit.), and is described "as the body of a vertebra showing a convex articulating surface, as in the Crocodile" (p. 221). Quenstedt's Pferof/ac^'y/ws .SMew/ra.s showed similar detached dorsals, in one of which it appeared that "the articular surfaces of the body were convex at the back end, and concave at the fore part. "i Ijuckland's specimen serves to dissipate any doubt on the point so important in reference to the Crocodilian affinity. It might be assumed that the Author viewed the convexity as posterior by the expression "as in the Crocodile;" and in the last of the dorso-lumbar series, which I regard, with Buckland, as ' probably lumbar,' in the sense of not being costigerous, the position of " its concave articulating surface '' is demonstrated by those of the articular processes (zygapophyses) at the same end of the vertebra, which prove them to be the anterior pair, slightly prominent, looking upward and inward. Buckland notes these as " two anterior spinous processes, an obvious typographical error for ' ol:)lique ' or ' articular,' venial in one not professedly an anatomist." With regard to the Crocodilian atRnity inferred from this structure, it must be remem- bered that the procoelian structure, though it has been observed in Crocodiles from the Greensand of New Jersey,' is characteristic of the Tertiary and existing species, rather than of the order at large, which had more abundant and diversified (amphicoelian and opisthocoelian) representatives in the Secondary ages of Geology. Moreover, the anterior concavity and posterior convexity of the vertebral body obtain in most recent. Tertiary, and Cretaceous Lacertilia ; and finally, the cup- and ball-joints of the centrum appear in the dorsal vertebrae of at least one genus of Birds, though with the ball in front.* In the series of nine dorsals, preserved in the subject of PI. 10, d, the centrums slightly lose length as they recede in position from the neck ; the anterior ones measure 0009 mm. = 44 lines ; the posterior ones measure O'OOS mm. = 4 lines ; the transverse diameter of the articular ends is 0007 mm. = 3 lines. The dorsal vertebra in Buck- land's specimen presents the same dimensions. These dimensions increase as the two or three anterior dorsals approach the neck, but the greater enlargement of the last cervical is somewhat abrupt. For the shape and proportions of the ribs (in the Restoration, PI. 17), I have those marked b, c in the original specimen,^ and the more numerous and better preserved ones ' " Die Gelenkflaclie der Wirbelkiirper war aiif der Hinterseite convex, wie beim Crokodil, vorn dagegen concav. So scheint es weiiigstens." — Quenstedt, Ueber Pterodactylus sueincus im lithographischen Scbiefer Wiirtembergs. -Ito, 1855, p. 4,5. 2 Buckland, loc. cit., pi. 27. [This vertebra is shown iu PI. Ill, fig. 2, of the present Mono- graph.] 3 "Notes on Remains of Fossil Reptiles discovered in the Greensand Formations of New Jersey," ' Quarterly Journal of the Geological Society,' vol. v, 1849, p. 388. * As in JptenoiJytes i "On the Vertebral Characters of tlie OrAn Pterosuurin," ' Phil. Trans.,' 1849, pi. X, fig. 22, p. Wi. ^ Buckland, loc. cit., pi. 27. \ LIASSIC PTERODACTYLES. 491 in the specimen figured in PI. 16. Their articulations with the vertebrae have already been noticed. The ribs increase in length to the fifth or sixth, with some diminution of breadth after the third, and acquire a characteristic tenuity beyond the sixth pair. On the outer surface a groove extends from the neck, or interspace between the head and tubercle downward ; the front border of the groove being somewhat prominent, but sub- siding in the hinder ribs. Epipleural appendages are indicated in some specimens ; but the indications are feeble, and, if rightly so interpreted, these appendages seem to have been but partially ossified. The sternal ribs, beyond the sternum, unite below with the free ends of the abdominal V-shaped, intermuscular styles. The irregular elongate mass (marked 18 in pi. xxviii of Buckland's Memoir) and conjectured to be " sternum — much broken, and its form indistinct " (loc. cit., p. 221) in- cludes two crushed cervical vertebrae, and part of a third. Of the sternum I have not been able to discern a satisfactory trace in any of the specimens of Dimorpliodon ; its propor- tions and position are, therefore, indicated in the 'restoration' (PL 17) according to the analogy of that in Pterodadylus suevicus} Pt. simus,^ and in Bhamphorhynchus? In the main, as regards breadth of the hind part and depth of the fore part, the breast- bone of Pterosauria is formed on the Ornithic pattern ; i. e. it is shield-shaped, and it has a keel. But the keel does not descend from the expanded portion ; it is formed, as shown in 'Pterosauria,' PI. 12, pp. 443 — 448, by the vertical development of the anterior production answering to the ossified sternum of Crocodiles and to the episternum of Lizards. I would recommend a comparison of the figures of the sternum in Iguana and Notornis, given at p. 21, vol. iii, of my ' Anatomy of Vertebrates,' to whosoever may desire to form an opinion of the evidence of affinity to Birds or to Reptiles, respectively, FiG. 1. I'IG. 2. Pterosaur. Crocodile. aff'orded by the Pterosaurian sternum, especially as this is illustrated in figures 7 to 12 of PI. 12, above cited. No one desirous of simply getting at the truth of the matter can ' Qiienstedt, loc. cit. (1855). = PI. 12, figs. 7—12. >* Vnn Meyer, op. cit. (18(i0), ]il. vii, figs. 1 and 3, and pi. ix, fig. 1. 492 BRITISH FOSSIL REPTILES. put aside the ' post-coracoid lateral eniarginations,' and other modifications defined in that Monograph as ' distinctive Pterosaurian characters.' No Bird has shown any approach to them. What modifications of the Pterosaurian sternum Bimorphodon may have presented, we have yet to learn. In all cases in which it has been observed, the sternum in Pterosauria (fig. 1) resem- bles in essential characters that of CrocodUia (fig. 2); its chief part is a longitudinal, com- pressed, deep bar (.59), expanding laterally, some way from the fore-end, for the articulation of the coracoids (5l),^ and having the posterior expansion (eo), which remains cartilaginous in the CrocodUia, more or less ossified, in the form of a thin semicircular plate : but the whole bone, though adaptively modified for attachment of muscles of flight, preserves the characteristic shortness compared with the trunk, and offers a striking contrast to the long and large subabdominal plastron in most birds of flight. There is no distinct T-shaped episternum, such as exists in most Lacertia, and no trace of clavicles as in Lizards and Birds. Distinct lateral elements for articulation with sternal ribs I have not satisfactorily made out in any specimen. The abdominal haemal arches consist of slender haemapophyses and of chevron-shaped haemal spines. There is evidence of one lumbar or ribless vertebra anterior to the sacrum, in Dimor- phodon ; and no Pterosaurian appears to have shown more than two such vertebras : in this character we are again directed to the true Reptilian relation of Pterosauria, and warned off the beguiling marks of Avian affinity. The indications of epipleural appendages of ribs, more or less bony, if rightly inter- preted, answer to the gristly ones in CrocodUia andi some LacerfiaJ' The restoration of the bony cage of the thoracic-abdominal cavity of Pimorp/iodon (PI. 17) is based on the analogy of better preserved specimens of Pterosauria in regard to this part of the skeleton. Scattered elements of the haemal arches, ' abdominal ribs,' &c., have alone been met with in the specimens of Bimorphodon hitherto obtained. The sacrum, on the probable hypothesis of retention of the length of centrum shown in the lumbar vertebra, would include at least four vertebras ; if, as by the analogy of the sacrum (figured in PI. 8, fig. 26), the vertebrae lost length at this confluent tract, there might be five or six sacrals articulating with the iliac bones in Bimorphodon. Von Meyer figures 5 — G anchylosed sacral vertebrae in his Pterodactjjlus dubius i^ and the sacrum appears to consist of at least six confluent vertebrae in Pliamphorhynchus grandi- pelvis, Von Meyer.* With all the evidence that the Pterosauria, like the Dinosauria and Bicynodontia, ' PI. 12, figs. 7—12. '-' As ill Hatteiiit, see Giiiither's excellent Memor, in ' PIpIo.s. Trans.,' Part II, 18G7, p. 13, pi. if, r.gs. 17,24. ^ Op. cit., p. 17, pi. vi, fig. 1. ■' Op. cit., p. 53, pi. viii, fig. 1. LIASSIC PTERODACTYLES. 493 exceeded the sacral formula prevailing in existing Crocodilia and Lacertilia, we should gain no firm ground therefrom for predicating Avian aifinity or for building thereon a derivative hypothesis of the class of Birds. Many existing Chelonian Reptiles have a sacrum composed of more than two vertebrae. ^ The perfect specimen of tail-vertebrae and associated bone-tendons in the specimen of Bhaviphorhpichus Meyeri completes satisfactorily the restoration of this part of the vertebral column in B'morphodon. Before the discovery of Rhampliorhptchus, the order Pterosauria was known only through species having the tail very short. Not only were the vertebrES comparatively few, estimated at twelve or thirteen in Ftcrodactylus lonyirosfris,^ at fourteen in Pt. spectabilis, at fifteen in Pt. scolopaciceps,^ and as low as ten in Pt. Meyeri* but they were very small and short. The great advocate of the Avian affinity of the Pterosaurs, Soemmerring, based his chief argument in this character. But CuviER was able to adduce instances of Beptilia with tails as short ; and he might now have cited a Bird with a tail-skeleton as long, as slender, and as many-jointed as in divers Saurians.'^ The earliest indication of a range of variety in this part of the bony frame- work of a Pterosaur was deduced, with his usual sagacity, by Buckland. In the original specimen of DimorpJiodon are three caudal vertebrae at the base of the tail, marked K, in pi. xxvii of his Memoir, from the size of which vertebrae, togetlier with the larger and longer legs, as compared with Pferodacfylus lonyirostris, Buckland inferred tliat the entire " tail was probably longer, and may have co-operated with the legs in expanding the membrane for flight." " " A long and powerful tail," he proceeds to remark, " is in strict conformity with the character of a Lizard " (ib.).' Buckland would have had further direct confirmation of the length and strength of the tail of his Lias Pterosaur, if he had recognised the series preserved at a, a, in his pi. xxvii, as caudal vertebrae ; but they were conceived to belong to the neck, notwithstanding their slenderness and length, and that around them were " small cylindrical bony tendons, resembling the soft tendons that run parallel to the vertebrae in the tails of Rats." ^ When the evidences of caudal structure were first recognised by Von Meyer, in BhampJiorhynchus Gemmingi, he detected the homologous structures in pi. xxvii of ^ ' Anat. of Vertebrates,' vol, i, p. 65. 2 By Cuvier, vol. cit., p. 368. ' Von Meyer, op. cit., p. 17. *Ib., p. 17. 6 Owen "On the ArchcBopteryx" ' Philos. Trans.,' 1S63, p. 33, pis. i— iv. * Buckland, loc. cit., p. 221. "1 Archaopteryx had not then been discovered ; else, it might have been objected to the above hint of affinity, not only that there had been short-tailed Pterodactyles, but also long-tailed Birds. 8 "Mr. Clift and Mr. Broderip have discovered that the remaining cervical vertebrae are surrounded with small cylindrical bony tendons of the size of a thread. These run parallel to the vertebrsE, like the tendons that surround the tails of rats, and resemble the bony tendons that run along the back of the pigmy musk and of many birds" (loc. cit., p. 218). 494 BRITISH FOSSIL REPTILES. Buckland's Memoir, and suggested tliat its subject might lielong to the same section or genus.i The subsequent discovery of the skull and dentition has, however, shown that another generic section of JPterosauria, or at least one species thereof, had a similar long and stiff tail. The modification involving that quality does not, however, extend throughout; the anterior caudal vertebrae retain the more normal character, and the appendage would be most moveable at its base. No doubt a small degree of yielding at the many persistent vertebral joints— for complete anchylosis has not been observed- would allow a slight curvature to the extent to which the tail is represented as yielding to a lateral force in the restored figure (PI. 17, fig. 2). The number of the cauda^l vertebrae in Dimorphodon macromjx was at least thirty ; the termination of the specimen figured in PI. 17, does not indicate a loss there of as many centrums as would brino- the number up to thirty-eight, which are assigned by Von Meyer to his Mhamplw- rhynclius Gemminffi. As we cannot, therefore, with Soemmerring, insist on the shortness of the tail in some Pterosauria as proof that they were Birds, so neither can we conclude from the length of the tail in other Pterosauria that they were Reptiles. The legitimate taxonomic deduction from such caudal modifications is, that they are not of sufficient importance for determi- nation of a class, and that they do not exclusively characterise the genus. Thev mdicate adaptations in an extreme and variable part or appendage of the body to special powers or ways of movement, or sustentation, in air of the present group of volant animals. So, likewise, it cannot be, as it has been, inferred from the length of tail in Archaopteryx, that it was a Reptile." What we learn from that Avian fossil is akin to what we have learnt from Pterosaurian remains, viz., that the tail is a seat of extreme modification, in respect of length and number of joints, within the limits of the feathered class. Mamma- logists, with a like drift, could add instructive evidence of corresponding caudal variability within the limits of the order, as in the volant Cheiroptera, and even within the bounds of the family {Bradi/pus and Megatherium, e.r/). The value of the discovery of Archmpteryx, in relation to Pterosauria, is enhanced by the peculiar nature of the matrix, conservative of cutaneous as well as of osseous characters ; showing casts of down and feathers,^ impressions of the fine foldings or wrinkles of thin expansions of naked skin, as well as delicate tendons surroun°ding, working, strengthening, and stifl"ening the caudal framework. With these parts the fine lithographic lime-marl should have preserved the plumose appendages of the long tail oi Rhamphorhynchus,ii that flying Reptile had possessed such ; and, along with caudal plumes and vertebrae, should have been preserved the bone-tendons of the tail, if Archaoptefyx had possessed that structure. It is probable, from the constancy with which caudal vertebrae of long-tailed 1 In 'Leouhard und Bronn's Neues Jalirbuch fiir Mineralogie,' &c., Jahrgang, 18,57, p. 53G. - E.g., as the Gnjphosaiiriis of Andreas Wagner. ^ A few of the delicate, downy body-feathers of Arcficpopten/x are clearly indicated near one side of the trunk in the slab witli most of the bones of the specimen of Archaeopteryx in the British Mnseiiin. LIASSIC PTERODACTYLES. 495 Pterosaurs have been found associated witli their tendons,^ that detached caudal vertebrae of ArchcEopteryx might he recognised through the want of them. We may confidently concluile that the Oolitic mud which has entombed the greatest number and variety of the flying reptiles of its period would have shown us, when petrified into lithographic slate, their feathers, if, as warm-blooded animals, they had needed such heat-conserving a covering. The plumose clothing of the long-tailed bird of the period proves its hsematothei-mal character, as the want of it shows the long-tailed pterosaur to have been cold-blooded. The tyro, fresh from the lecture-room of his physiological teacher, ambitious of soaring into higher regions of biology than were opened to him at the medical school, impressed with the relations of active locomotion to generation of animal heat, may be pardoned for inferring that the amount of work involved in sustaining a Pterodactyle in the air would make it, physiologically, highly probable that it was a hot-blooded animal. But a competent friend, finding him bent on rushing with such show of knowledge into print, would counsel him to provide himself with a thermometer adapted to the delicate testing of the internal heat of small animals. So provided, if he should chance to beat down a cliafer in full flight, the experiment, made with due care and defence of the fingers guiding the instrument, would teach him how fallacious would be the inference that, because an animal can fly, it must, therefore, be hot-blooded. Unless he happen, in introducing the bulb by the widened vent into the abdomen, to plunge it into a mass of ova, he will find the heat of the beetle, notwithstanding the amount of work involved in sustaining and propelling itself in air, not to exceed by more than one degree that of the atmosphere. If he has knocked down a female cockchafer prior to oviposition, the ovarian masses may indicate half a degree, or even one degree, higher of temperature (Fahr.). With the cooling of the air in the summer lu'ght the tem[)erature of the Melolontha concurrently falls. So, likewise, would that of the flying reptile, whatever " amount of oxidation and evolution of waste products in the form of carbonic acid " "" might have attended their exercise of flight. The constant correlative structure with hot-bloodedness is a non-conducting covering of the body. We may with certainty infer that ArchcBopterijx was hot-blooded, because it had feathers, not because it could fly. There is no ground, from observation of the Sharks and Porpoises that accompany swift-sailing vessels, maintaining themselves near the surface, exercising their several and characteristic evolutions in quest or capture of prey, for inferring that tlie amount or the energy of muscular action is very different in the two surface-swimmers. Sharks have and, no doubt, work a greater proportion of muscle than Cetaceans; a less proportion of their body is excavated into visceral cavities. Yet the Shark is cold- blooded ; its temperature rises and falls with that of its medium ; it has no provision, by 1 As seen in PI. 1 6, at cd. 2 'Proceedings of tlie Zoological Society,' April, 1867, p. 417, Prof. Huxley " On the Classificatiou of Birds." 2^ 496 BRITISH FOSSIL REPTILES. a blanket of blubber or other superficial modification, in aid of the maintenance of a fixed and high degree of blood-heat. There are conditions, it is true, in which a Reptile generates a higher degree of heat than is usual, but they are not those accompanying any unusual or excessive muscular work and waste ; they are attended with rest, not locomotion. The incubating Boa gives to the hand that may be insinuated between the coils surrounding the eggs the sensation of a warm-blooded animal. Valenciennes ' found, in the Reptile-house at the Jardin des Plantes, when its temperature, in the month of May, was 28° (Centi- grade), that the heat of the Python, between the folds and upon the eggs, was 41-5° (ib.); so also the heat of the incubating snrface of the Bird may rise to 10 degrees (Centicr.) above the ordinary temperature — higher in this passive state than it ever reaches during flight. The organic condition which determines the hot-blooded or cold-blooded nature of a volant Vertebrate is the separation or the commingling of the arterial and venous bloods in the course of their respective circnlations. From the demonstrated absence of any heat-retaining covering of the skin in Pferosawria — the kind and amount of negative evidence hereon being decisive — I infer that the black and red sanguineous streams were mixed by intercommunication of the aortic trunks of the right and left ventricles, as in the Crocodile.^ The plumose integument of Archaopteryx bespeaks the separation, not only of the pulmonic and systemic ventricles, but of the arterial trunks thence arising ; it was, consequently, hot-blooded, not because it coidd exert the muscular force required to sustain itself in the air. The- all-important condition of the circulating system Las wide correlations, not only with the extensive superficies acting upon the surrounding medium, and being reacted upon thereby, but with a rapid and uninterrupted respiration, with an advanced status of the nervous system, especially the brain, involving higher intelligence and more lively and varied instincts, especially the parental. In the organic character determining temperature, breathing, and psychical phenomena of life, Birds agree with Mammals and differ from Reptiles. Birds agree with Implacental Mammals {LyencepUala) in the development, by the embryo, of a vascular allantois devoid of villi for placental connection.^ They agree with the same Mammals and diff'er from Reptiles in the transversely and deeply folded cere- bellum, and in the larger proportion of that and of the cerebrum to the optic loljcs. Birds 1 "Faites pendant I'incubation d'une femelle du Python a deux raies {Python bivittutus, Kuhl)," &c. 'Cotnptes rendus de I'Acad. des Sciences,' Paris, 19 Juillet, 1841. Something akin to this occurs in the development of the generative elements in plants. = ' Anat. of Vertebrates,' i, pp. .510— ,512, figs. 339, 3-40. ■5 This character is affirmed to be " of extreme importance, and to define Birds and Reptiles, as a whole, very sharply from Mammals." — Prof. Huxley 'On the Classification of Birds,' loc. cit., p. 4IG. But, then, the emphatic assertion comes from a writer on Elementary Physiology, who infers tlie blood of the Ptero- sauria to have been hot because they were able to sustain themselves in air ! LIASSIC PTERODACTYLES. 497 resemble Reptiles in the absence, not only of a corpus callosnm, but of a fornix and hippocanipal commissure. The Lyencephala have the hippocampal commissure, but no corpus callosum ; this characterises the Placental Mammalia. Birds differ from other Oviparous Vertebrates in the chalaziferous ovum. The particulars in which Birds differ from all Mammals and agree with Reptiles are comparatively unimportant ones of the skeleton. The occipital condyles [e.g.] are more completely blended or unified than in Cetacea. The tympanic is interposed between the mandible and the mastoid, as in Reptiles.^ Two genera of Lyencephalous Mammals retain the osteological character common to Birds and Reptiles of the connection of the scapula with the sternum by the intermedi- ation of a fully developed coracoid, and it is one of several and more important characters disproving any sharp definition of the higher warm-blooded Ovipara, at least, from the Ovo-viviparous or Implacental jMammalia. The scapular arch retains, in Pterosauria, its crocodilian simplicity, modified in shape and in the angle at which the scapula meets the coracoid adaptively for the function of flight in the limb suspended thereto. There is, consequently, a close similarity to the same elements in Birds of Plight," but without any trace of the superadded furculum. The articular grooves on the sternum for the coracoids communicate or run into each other at the mid line. The articulation of the corresponding end of the coracoid must be as secure, and yet with as easy a motion, due to a well-turned synovial joint (shown first in Pterodactylus Woodioardi and Pt. simus)^ as in any Bird. The confluence of the scapula with the coracoid seems not to be constant in the order Pterosauria ; and where it has been found, as in BlmorpJiodon and Pterodacfj/lus Fittoni, traces of the original suture are present, as represented in the large Neocomian Pterosauria (PL 10). In some specimens of Rlmmpliorliyndim Gemmingi and in BhampJiorhynchi(s lonyicaudus the scapula and coracoid seemed not to have coalesced.* The coalescence is complete and constant (so far as may be inferred from two specimens) in Dimorphodon. For the analysis of the characters of the humerus in Pterosauria, I may refer to pp. 448—452, PI. 13. The chief seat of variety is the " radial crest " (PI. 16, 53, b, of present Monograph). In the shape and proportions of this extraordinary process Dimorphodon resembles Pterodactylus more than it does Phamphorhynclms. In the proportions of the humerus to the body there is little diversity in the several species. The antibrachium is commonly two sevenths longer than the humerus. It consists 1 Asa taxonomic character — whatever degree of vahie may be adjudged to it — this mode of connection of tlie lower jaw with the skull gains nothing; by calling the tympanic 'quadrate bone,' or by affirming it to represent the ' incus ' or the ' malleus ' of Mammalia, whichever may happen to be the favourite fancy of the day. 2 P. 395. 3 P. 444, pi. 12, figs. 7—12. ■* Von Meyeb, op. cit., p. 18. 498 BRITISH FOSSIL REPTILES. of two equal-sized, closely and extensively united bones, with one or two slender stylifonn ossicles attached lengthwise, having the base a little below the distal ends of the radius and uhia. The latter bone shows no pits for the attachment of quill-featiiers, as in the hot-blooded volant Ovipara. A carpus with one large and one small bone in a proximal row, and with a second large and at least one smaller bone in a distal row, is another character by which the Pterosauria manifest their closer affinity to Reptiles than to Birds. The remains of the gigantic species from the Cambridge Greensands have yielded the characters of the two larger carpal ossicles.^ Variation, as usual, begins to assert its sway as the segments of the limb recede from the trunk. This is mainly shown in the relative length of the metacarpus. In Rliampho- rhynchus Gemmivgi it is to the antibracliiura as 2 to 7, and to the first phalanx of the wing-finger as 1 to 5, or rather less. In Bimorphodon the metacarpus is to the antibrachium rather more than 2 to 6, and is little less than one half the length of the first phalanx of the wing-finger. In Pterodacfi/Iiis longirostris the metacarpus is two thirds the length of the first phalanx. In Pterodactylus lonyicoUum the metacarpus is almost four fifths the length of the first phalanx of the wing-finger. In Pt. suevicus the metacarpus is one eighth longer than the antibrachium. There are diversities also in the relative length of the phalanges of the wing-finger. In Dimorp/iodo?i they inprease in length from the first to tlie third. In Phamphorynchm Gemmiiiffi the first and second phalanges are of equal length, and the third is shorter. In Pterodactylus lonyiro^tris, Pt. scolojmciccps , Pt. Kochii, they decrease in length from the first to the third, and in a greater degree in Pt. suevicus. The most marked variety, however, if the structure has been rightly determined or be not due to some accidental mutilation of the individual, is that on which Von Meyer ^ has founded his genus Ornitliopterus, viz. a reduction in the number of phalanges of the wing-finger from four to two, and the articulation of the proximal one to two large metacarpals. The last pointed phalanx of the wing-finger in Rhamphorhyiichus is rather longer than the penultimate one ; in Ornitliopterus Lavateri it is only one third the length of the penultimate phalanx. The evidences of pelvic structure in other Pterosauria, already referred to, leaves no doubt as to that in Bimorphodon, as restored at s, 62, 03, 64, in PI. 17. The expansion of the ischial and pubic elements and the direction of the latter are strong evidences of Reptilian aflinity, and decisive differences in the comparison with Birds. Given the greatest number of vertebra; grasped by the ilia, it falls short of the least number presented in the class of Birds, as by certain Natatores, which concomitantly manifest a vacillating or waddling gait. Nothing in the structure, proportions, and con- nections of the pelvic arch squares with the notion of bipedal progression or erect sustentation of the body and wings of the Pterosaur. The share taken by the hind limbs 1 P. 452, PI. 12, fig. 6; PI. M, figs. .5—9. ^ Op. cit., p. 25, pi. vi, fig. 5. LIASSIC PTERODACTYLES. 499 in resting or moving on dry ground was tliat indicated in the restoration of the skeleton in PI. 17. The hind limbs of Bimorphodon are, nevertheless, larger and stronger in proportion than in other Pterosauria. The femur, in most species, equals the humerus in length, and, in Bimorphodon, also in thickness. Tu Pterodadylus longirostris and Pt. Xoc/iii the femur is the more slender bone ; in Rhampliorliynclms it is likewise shorter than the humerus. The tibia, more slender than the antibrachial bones, in Pterodadi/Iiis longirostris and Pt. Koc/iii, is of equal length therevi^ith. In Bimorphodon the tibia is less slender in pro- portion to the antibrachium, and is longer by one seventh. In Rhamphorhynchus it is much more slender than the antibrachium, and is nearly one third shorter. The ankle- joint works between the tibia and tarsus, which, as in other Reptiles and Mammals, is distinct from the metatarsus. There is no calcaneal prominence, and the foot admits of easy rotation, as in the ' Restoration,' PI. 17, fig. 2, where the inner toe is turned out- ward and the sole presented to view, to show the application of the wing-toe in flight to the interfemoral web. Whether the trochlear terminal joint of the tibia be ossified from a separate centre in the Pterodactyle as in the Bird requires a specimen of the requisite immaturity for deter- mining. If the hind limbs and pelvis presented the structure for sustaining and moving the animal erect on land, an epiphysial state of the articular ends of the long bones might be physiologically inferred. I conclude, from the absence of the modifications essential to bipedal station and progression in Pterosauria, that the articular ends of both femur and tibia, including the distal condyles of the latter bone, were co-ossified with the shaft as in other Saurians. Wlien in warm-blooded Vertebrates,whether Birds or Mammals, the metapodial elements of different toes coalesce, the epiphyses of such coalesced series, or ' cannon bone,' are usually connate, forming a single bone. As, e.g., at the proximal end of the Cow's and Bird's metatarsus (figs. 3 and 4, c)} and also even at the distal end of the cannon-bone in Ruminants (fig. 3, d). I demonstrated the fact in both the metacarpus and meta- tarsus of a young Giraife, in my ' Hunterian Lectures' of 1851. The specimens are Nos. 3631 and 3635 in the Osteological Collection of the Royal College of Surgeons (' Catal' 4to, 1853, p. 601). The distal trochlear end of the Bird's tibia, in its epiphysial state (fig, 4, d), answers to the distal trochlear epiphysis of the Ruminant's '^^^ tibia (fig. 3, a). In its anchylosed state the distal bicondylar troch- lear joint or end of the Bird's tibia answers to the distal bicondylar p^^j,,,;^^^, trochlear joint or end of the Pterosaur's tibia. The proximal 1 " The upper articular surface is formed by a single broad piece. The original separation of th? metatarsal bone below into three pieces is plainly indicated." — "On the Anatomy of the Southern Apteryx," •Trans. Zool. See.,' ii (1838), p. 293. Fig. 3. Fig. 4. 500 BRITISH FOSSIL REPTILES. epiphysis of the Bird's metatarsus (fig. 4, c) answers to the proximal epiphysis of the Ruminant's metatarsus (fig. 3, c). The interspace between the leg and foot is the seat of variable and inconstant centres of ossification, from zero, as in Proteus, Amphiuma, Aves, to the four ossicles in Crocodilus, and the seven ossicles in Chelone. The functions of the hind leg in Birds require peculiarly strong, firm, close-fitting, interlocking joints. Thus, the fibula articulates directly with the femvn-, and the meta- tarsus as directly with the tibia. No interposed ossicles are permitted to affect the simple efficiency of this tibio- metatarsal joint in the long-footed feathered bipeds. In quadrupeds and in the short- and broad-footed Bimana tarsal ossicles, interposed at the space b (fig. 3), have their use. But whether the tarsus exist or not, in the Hcematotherma the articular ends of the long bones begin as ' epiphyses ;' and when two or more metacarpals are to become massed into one bone, the epiphysis {c) is single — a very significant developmental guide to the homology in question. The strangest aberrations in homological aims have arisen from a non-recognition of the distinction between teleological and homological centres of ossification.^ Not only is a tibial epiphysis made into a tarsal bone — and why other epiphyses, such as the proximal one of the tibia, or the distal one of the femur, should be differently treated is not obvious — but new bones by the score are added to the cranial series. ' Basitemporals,' ' prevomers,' ' antorbitals,' ' perpendicular ethmoids,' ' ali-ethmoids,' &c. &c., have been heaped up to obstruct the comprehension of the plain and intelligible nature of the bu'd's skull. The four unguiculate digits of the foot are of nearly equal length, but present a slight difference in their proportions in the Pterosauria. Cuvier having determined the Lacertian character of the phalangial formula of these digits, viz. 2, 3, 4, 5, adds that, apparently, the fifth digit was reduced to a slight vestige of two pieces in Pterodadylm longirostris? Subsequently discovered species have offered a like indication, to which Von Meyer alkides as a rudiment or stump (' stummel ') of the fifth toe.^ No other specimens, to my know- ledge, save the third of Dimorpliodon (PI. 16) and the Bhavqihorhynclms Meyeri (p. 502), have shown the condition of the fifth digit as of three pieces, viz. a metatarsal (w, v) and two phalanges (y, 1 and 2). The metatarsal of this toe shows an interesting affinity to that in the Crocodilia by its greater breadth and shortness in comparison to the other metatarsals. The two phalanges have proportions and forms which clearly show their adaptive relations as aids in sustaining the interfemoral or caudo-femoral parachute ('Restoration,' fig. 2, PI. 17). ^ Owen, "Lectures on the Comp. Anat. of Vertebrate Animals," 8vo, 1846, p. 38. - " II paroit qu'ici le cinquieme eloit reduit a im leger vestige de deux pieces." — ' Oss. Foss.,' vol. cit., p. 374. * "Cuvier, Wagler, und Goldfuss lassen den Fuss aus fiinf ausgebilteten Zehen bestehen ; in alien Pterodactyln liabe ichaber uie niehr alsvier solcherZelKii, unJbocbstens nocli einen Stummel vorgefunden."' ,— Op. cit., p. 20. LIASSIC PTERODACTYLES. 501 The crushed condition of many of tlie long bones in the specimens of Dimorpliodon shows the walls of the shaft to have been compact and thin, the cavity large. Although I have failed to detect such clear evidence of the foramen pneumaticum in these crushed bones as in some of the vertebrae, I cannot resist the inference from the structure of the long bones that they were filled with air in the living animal, as has been demonstrated in remains of the larger Plerosauria of the Cretaceous sei'ies.^ This general osteological character of the Pterosauria leads me to offer a few ren)arks on its relation to their peculiar power of locomotion among Beptilia, and to the affinity it may indicate to other groups of volant Vertebrates. Weight is, of course, indispensable to directed motion through the air ; but, given the weight requisite for the action against gravity resulting in flight, whatever structure tends to dispense with additional burthen enables the force to act with more avail — with less unnecessary resistance to overcome. Where provision is made for unusual flying force, as by the enormous pectoral muscles and concomitant shape of wing in the Swift, the required weight of body called for heavier bones ; hence the non-pneumaticity of the skeleton. Diminished flying force, especially with increased bulk of body, is attended with modifications of bony structure obviously adapted, and which have always been recognised in relation, to reduction of weight in the mass to be moved through the air. It is true that the mere quantity of air contained in bones would have an efiect inappreciable in aid of the force raising a weight of 5 lb. or 10 lb. from the ground ;" but the true view of the question is — given a bone of 1 foot in length and 3 inches in circumference, whether the restriction of bony matter to a thin- ness of ^ a line at the circumference, and a substitution of air for the rest of the diameter throughout the shaft, be not a provision for diminution of weight and conservation of strength which does relate to facilitate locomotion through air ? If the humerus of the Ostrich (No. 1373, Osteological Collection in the Museum of the College of Surgeons, London, ' Catalogue' of do., 4to, 1853, p. 265) be compared, as to weight, with the similarly sized humerus of the Argala Crane (No. 1107, ib., ' Catal.,' p. 214), the difference is striking and suggestive; the latter bone being "remarkable for its lightness, as compared with its bulk and seeming solidity" (ib., ' Catal.,' ib.). I demonstrated the cause of the difference by a longitudinal section of the two bones. In the Bird incapable of flight the humerus is solid ; in the Bird remark- able for the long-continued power of soaring in upper regions of the air, the shaft of the 1 Ante, p. 451, PI. xiii, fig. 2 p. ' A writer impugning the physiological inference of Hunter and Camper, tlie discoverers of the pneumaticity of the bird's skeleton, remarks : — "A living bird weighing 10 lb. weighs the same when dead, plus a very few grains ; and all know what effect a few grains of heated air would have in raising a weight of 10 lbs. from the ground. The quantity of air imprisoned is, to begin with, so infinitesimaily small, and the diiference in weight which it experiences by increase of temperature so inappreciable, that it ought not to be taken into account by any one endeavouring to solve the difficult and important problem of flight." — Pettigrew, "On the Mechanism of Flight," ' Linnean Transactions,' vol. xxvi, p. 218, 1868. 502 BRITISH FOSSIL REPTILES. bone is a ' thin shell of compact osseous tissue.' The relation of the weight of the volume of air occupying tlie capacious cavity of the Argala's wing-bone to the total weight of its body need not be taken into account in considering the problem of flight, but the relation of a hollow instead of a solid humerus is a legitimate element in the endeavour to solve that complex kind of animal locomotion. To say that a certain amount of weight in the bird is essential to the momentum of flight is no argument against the reduction to such requisite weight of the body to be upborne. Every structure so tending to lighten the body of a volant animal within the required limit is, and ought to be, recog- nisable as physiologically related to flight. By the pneumaticity of the bones of the Pterodactyle, it might be inferred, from a single bone or portion of bone, to have been an animal of flight. For, although certain volant Vertebrates, e.g. the Bat and the Swift, may not have air-bones, no Vertebrate save a volant kind has air admitted into the limb-bones. But the eff'ect of such admission, of such substitution of a lighter for a heavier material, is to diminish the weight without impairing the strength of the bone ; the legitimate, if not sole, inference, therefore, is that it contributes to perfect the mechanism of flight. It is a purely adaptive character, and the insignificant, barely appreciable, difference of weight due to difference of temperature in a given bulk of air makes the pneumaticity of the skeleton as available and advantageous to a cold-blooded as to a warm-blooded volant Vertebrate. A specimen of the pterodactylian genus Bampliorhynchus, discovered in the litho- graphic plate near Eichstiidt, Bavaria, with impressions of the wing-membranes, has been obtained by Professor O. C. Marsh for the Museum of Yale College, New Haven, United States. Of this rare specimen the accomplished Palaeontologist, by whom important additions to Pterosaurian organisation had been previously made, has recorded a description in the ' American Journal of Science,' vol. xxiii, with the subjoined figure of a restoration, in which the condition of the specimen leads to a conclusion that the volant membrane, after being continued from the hind-limbs upon the tail, is interrupted, and reappears as a special terminal caudal expansion, or ' rudder,' as in the subjoined cut, on which is .founded the specific name : — Ramphorhynchns phyl/urus, Marsh. WEALDEN DINOSAURS. IGUANODON. SUPPLEMENT (No. III). Bones of the Forearm and Paio (' Dinosauria,' Plates 46, 47, 48.) The additional elements towards a reconstruction of the Iguanodon, which form the subject of the present supplementary monograph, have been contributed by Samuel Husbands Becklks, Esq., F.R.S., F.G.S., and their acquisition is due to his persevering labour, liberal indifference to expense, and intelligence directing the quest, resulting in the successful exhumation of the parts in question. They were associated with the greater part of the skeleton, of which, besides the subjects of the present Monograph, Mr. Beckles secured a dentary element of the mandible, fifty vertebrae, a sternum, scapula, and coracoid, one humerus and fragments of the other, one femur, one tibia and parts of the other, a tarsal bone, the three metatarsals, and phalanges of one hind foot, and some bones of the other hind foot. Mr. Beckles was led to this excavation by a slight indication of l)one in a Wealden clay (Hastings Series), about two miles to the west of St. Leonard's-on-Sea, Sussex. The area worked up was 200 feet square, or 10 feet by 20 feet, and 4 feet deep. The bed was below high water, and could only be wrought at during one tide in the day. Neverthe- less the work of exposure was conducted with such energy that it was completed in a week. " The bones were imperfectly mineralized, and could only be secured by plaster of Paris, of which I used about thirty bags, each bag containing seven pounds. As a rule I applied the plaster with my own hands ; but as the weather was severe, the wind being high and cold, with occasional sleet and snow, I was compelled to leave the manipulation of more than one bone to my navvies, and consequently one femur was destroyed, one jaw, one humerus, and one tibia, nearly destroyed. Had I not made a digging expressly for these bones, the interesting specimens you have in hand could never have been obtained."^ 1 Extract from a letter by Mr. Beckles to the author, of the 25th September, 1871. 2« 504 BRITISH POSSIL REPTILES. The half or ramus of the lower jaw preserved is represented by the dentary element, containing many of the characteristic teeth of the great herbivorous reptile, and repeating the peculiar form of the fore part of the mandible which has been recognized in previously described and figured specimens of that bone.^ Though dislocated, displaced, and some- what scattered in the matrix, they impressed the discoverer with the conviction or certainty of their being parts of the skeleton of the same individual. A comparison of all the bones and fragments of bone submitted to me for determination give no indication of their having belonged to more than one animal, and all are referable to an individual of the same age and size. The left radius and ulna are in the best state of preservation ; the right radius and ulna are less entire ; an os cuneiforme is recognizable in the carpal series, and there are metacarpals and a few phalanges of both right and left paws. The radius is chiefly remarkable for its powerful spinous or spur-like appendage. The antibrachial bones in the present collection confirm the ascription to ' radius ' and ' ulna ' of the two bones imbedded near the upper corner, opposite the right hand, of the great slab of the ' Maidstone Iguanodon ;' " but Mr. Beckles' specimens having been worked out of the less intractable matrix — the Wealden clay — show the configuration and characters of the surface of the entire bone. In the following description the surface or aspect of the bone corresponding with the olecranon and ' back ' of the hand is termed ' ancoual ;' the opposite surface, or that answering to the ' palm ' of the hand, is termed ' thenal ;' the surface toward that side of the forearm where lies the radius is termed 'radial;' towards the opposite side ' ulnar.' ' Proximal ' and ' distal ' imply the ends of the bone respectively next to or farthest from the trunk of the animal. Ulna. Plate 46, 55. The ulna is 1 foot 5^ inches in length ; ' 4 inches 8 lines across the radio-humeral articulation (at a, h, fig. 1) ; 3 inches 8 lines across the distal end; 2 inches 10 lines being the greatest diameter of the middle of the shaft. The olecranon (c, fig. 1) extends 1 inch 9 lines above the humeral articular cavity {d, d') ; it is obtuse, about 2 inches thick at the base, thence gradually contracting, to be continued into the ridge {a, fig. 1) extending along or forming the ulnar border of the 1 More especially in the portion of the mandible of a young Iguanodon (' Binosauria,' PI. 16). - ' Dinbsauria,' Pis. 1 and 2. "The radius and ulna lie with their proximal ends ne.xt the right hand upper corner, the latter being distinguished by its prominent olecranon, which is rounded as in the Great Monitor," p. 266. ^ The length of the ulna in the Maidstone Iguanodon is estimated at 1 foot 6 inches, p. 268. r^ WEALDEN DINOSAURS. 505 bone, to beyond the middle of the shaft, which then becomes rounded, and finally broadens to near the distal expansion of the bone {k, Ic, fig. 1). The humeral articular surface (figs. 1 and 2, d, d') is oblong, and extends from above obliquely downward and forward to the strong anterior ridge (e), which, adding to its width, is then continued down to form (at e) part of tlie cavity for the radius. The humeral surface is concave lengthwise, and also, in less degree, transversely; but both ulnar and radial borders become convex in that direction, or are rounded off and thick. The sharpest or best defined border is that which divides the h)wer part of the humeral articular cavity (fig. 3, d',f, ' greater sigmoid' of Anthropotomy) from that {(/) presented to the radius (' lesser sigmoid cavity,' ib.). The length of the humeral cavity is 4^ inches; the breadth across the middle 2^ inches : the surface {d',f, g, fig. 2) for the head of the radius appears to be directly con- tinued over the well-defined lower part of the border {d,f) of the preceding cavity, directly downward, or with its plane in the longitudinal axis of the bone. This 'lesser sigmoid cavity' is semi-elliptical in shape, about 2 inches 8 lines in longest diameter, 1 inch 3 lines in the opposite direction ; the upper border is straight, the lower one curved. 'J^he exact extent in the direction transversely to the head of the ulna, or in the long axis of the semi-ellipse, has suffered by fracture of the antero-inferior end or angle of the combined humero-articular cavities. About half an inch below the radial surface the ridge (e, fig. 1), continued downward from the above broken angle, expands to a rough tuberosity, which was joined by syndes- mosis to a similar rough tuberosity {r, fig. 3) at the lower part of the anterior articular ridge of the radius. At the proximal end of the ulna a thick, rough, long tuberosity, or tuberous ridge (fig. 2, h, h), from the radial side of the huniero-radial articulation, is most prominent where it bounds or defines the radial division of that joint ; below which it contracts and sHghtly bends to its termination (//'). This projection augments the breadth of the back part of the ulna below the base of the olecranon. At this part the ulna is almost flat, and the surface is roughened by thick irregular ridges, which mostly affect a longitudinal direction. The general form of the bone at its upper three fourths is three-sided. The hinder side, continued from the above flat, rough expanse, maintains its character of flatness, gradually contracting to its termination 4^ inches above the distal end, where the shaft begins to l)e rounded. The ulnar surface of the olecranon is moderately convex, lengthwise and across, for 3J inches, or to below the middle of the humeral cavity. Then the surface begins rapidly to expand, by the development of the ulnar boundary (c) of the articulation for the radius, gaining a breadth of 4^ inches. The ulnar surface is here (fig. 1, i) moderately concave, both lengthwise and aci'oss ; half way down the bone the concavity is changed to a sur- face flattened lengthwise, and moderately convex transversely. 506 BRITISH FOSSIL REPTILES. The third or radial side of the shaft of the ulna has been somewhat crushed in, but seems to have been rather convex transversely, and is less sharply defined than are the other tvro surfaces. The thick rounded border between it and the hinder surface gradually subsides at the lower fourth of the shaft, and both blend into the somewhat flattened rough surface opposite the articular one at the distal expansion of the bone. The thick rounded border between the ulnar and radial sides of the shaft contracts about the lower fifth of the bone, inclines forward, and extends into the beginning of the rugous margin {k, k', fig. 1), which defines, by a convex curve, the lower or distal end of the bone. The non-articular surface of this expansion is smooth anteriorly, where the radial facet of the shaft terminates ; but is roughened by oblong tuberosities posteriorly, where the hinder facet of the shaft is lost upon it. The articular surface for the distal expansion of the radius is of a crescentic shape, with the anterior horn the longest. It is rough and irregular on the surface, indicative of the ligamentous nature of the union. The smooth ulnar surface of the shaft terminates ill the hollow of the crescent. The anterior horn extends 4 inches 3 lines above the distal end of the bone ; the posterior horn 2 niches 6 lines above the same end. The general breadth of the syndesmotic surface is about 2 inches, contracting at each end of the crescent. The compact bony wall of the ulnar shaft is from 6 to 9 lines in thickness ; the fine cancellous centre, of an oval form in transverse section (fig. 4), is 1 inch 3 lines by 10 lines in its diameters. In general shape, in the better definition of the joints for the humerus and radius, and in the development of the olecranon, the ulna of the Iguanodon resembles that of the larger living Lacertia more than that of the Crocodilia. From the idna of the Iguana and of the large Nilotic Monitor it differs in the greater relative strength and more trihe- dral figure, the shaft of the ulna being compressed and two-sided in the smaller recent Lizards. There is the same concavity at the proximal part of the ulnar surface of the bone ; but it seems relatively deeper in the Monitor. The chief diSerence in the Iguanodon is the thick tuberous extension on the radial side of the radial articulation, from which is continued that border which divides and defines the posterior and radial surfaces of tlie shaft. Radius. Plate 46, 54. The length of this bone is IG inches;^ the greatest diameter of the proximal end (fig. 3) is 4 inches ; of the distal end, from the upper border of the spur-surface (fig. 1, vi) I This appears to be its length in the Maidstone Iguanodon, but one end is covered by a crushed vertebra. WEALDEN DINOSAURS. 507 to the ulnar end of the distal articulation (ib. n) is 7 inches, 6 lines ; from the lower border of the spur-joint (o) to the same part {n) is 5^ inches. The proximal surface or 'head' (fig. \, p), for articulation with the humerus, is semi- elliptical. The long diameter gives the breadth above quoted ; the short diameter, at the middle of the ellipse, is 2 inches 4 hnes ; the truncate border or chord of the semi-ellipse is toward the ulna. From the posterior two thirds of this border the articular surface for the ulna (fig. 3, q) extends down, \\ inch, at right angles with the proximal surface. It is flat and rough, semi-elliptic in shape. The proximal surface is almost flat, feebly undulate, with a linear roughness for ligamentous union with the humerus ; it is continued at its fore part upon the ridge-like prominence of the bone (fig. 3, r, r), which bends toward the ulna as it descends, terminating 2j inches below the humeral surface ; this rough extension of the articular surface is separated from the flatter ulnar surface by a deep, smooth pit (ib. s), big enough to receive fiJie end of the thumb. Beneath this articular surface the radius contracts to a breadtli of 2 inches 5 lines, and a thickness of I inch 3 lines ; and this subcompressed form, flat or subconcave toward the ulna, convex on the opposite side, but irregularly so on both sides, continues two thirds down the length of the shaft ; which, then, gains in thickness and breadth, but especially and rapidly in the latter dimension by the extension of the distal end beneath that of the ulna. The distal surface for articulation with the ulna commences about 9 inches from the proximal end of the radius in a pointed form (fig. 1, t), which rapidly expands to a breadth of 2 J inches. This part of the distal ulnar surface is parallel, lengthwise, with the non- articular surface of the shaft of the radius, is almost flat or slightly convex and rough, and might be regarded as representing a partial interosseous syndesmosis; it is continued, however, at its lower broadest part into a smoother concavity upon the proximal side (ib. u, v) of the distal extension of the radius, and this concavity receives part of the distal convexity of the ulna (ib. 1-, /:'). The distal end of the radius is excavated by two con- cavities for the carpal bones ; that (ib. w) for the hemispherical part of the scaphoid is the deepest, and measures about an inch and a half in both transverse and fore and aft diameters ; the shallower concavity (ib. x) for the convex part of the cuneiforme is con- tinued into a slightly convex svu'face, extending to the apex of the distal extension ulnad (w) of the radius. On the shaft of the radius may be noticed a rough, slightly prominent tuberosity (y)^ about 15 lines by 12, at the hinder or anconal margin, commencing about 4 inches from the proximal end. The shaft is not quite straight ; the anconal surface below the tuberosity gains in thickness, and is slightly concave lengthwise; the thenal surface is thinner, and slightly convex lengthwise. The exceptional feature of this radius is an oblong, irregularly flattened, rough surface, as if caused Ijy fracture, occupying the radial aspect of the distal expansion {m, o) ; consequently, opposite the surface above described for articulation with the ulna. To 508 BRITISH FOSSIL REPTILES. this surface was joined, if not anchylosed, the base of a bone, corresponding with that which has been figured as the " horn " of the Iguanodon {zf ; the surface on the radius, like the co-adapted one on the base of the ' horn,' is 4 inches in long diameter, and 2 inches 4 lines in short diameter. The unsymmetrical character of this supposed ' horn' led me to infer that it was one of a pair of bones, which I conjectured to be ' phalangeal.'- The rough flattened base of the original specimen, on part of which the cellular osseous texture was exposed, I believed to be due to the articular surface " having been chiselled or scraped away."^ I now know that it was a natural surface due to separation from a close syndesmotic and partially anchylosed union with the distal end of the radius, as in the left antibrachial bones figured in PI. 46, fig. 1. In the right radius of the Iguanodon, which has afforded the subject of the present Monograph, this horn-like appendage is anchylosed, and stands out from the radial side of the distal end like a process of the bone (PL 47, fig. 1). The length of the detached radial spine in the left fore-limb is 0 inches ; the apex is not quite entire; the thenal surface (PI. 46, fig. 1, z) is less convex across and more convex lengthwise than the anconal surface (PI. 47, fig. '1, s). This surface is strongly convex transversely, slightly concave lengthwise, and is smooth along its distal half; it is roughened by thick and strong longitudinal ridges at its proximal third, and these are less developed at the corresponding part of the thenal surface. The vascular channels indicate, as in a claw-phalanx, the system of supply of horny matter sheathing the bone. The formidable spine, supported by this bony core, projected inward or from the radial side of the radius, with its distal border at right angles with the long axis of the bone, the proximal border (z) passing more obliquely to the apex of the spine-core. The right ulna shows an exostosis at the back part of the shaft, near the base of the olecranon. Such instances of disease in Mesozoic reptiles are rare. There is a slight difference in the shape of the proximal end of the right radius, which, nevertheless, belonged to the same individual Iguanodon, as the left one above described: the humeral surface, or 'head,' is 3 inches 5 fines by 2 inches 9 lines; the principal ulnar surface is 2 inches 3 lines by 1 inch 6 lines. The narrower surface for the ulna, extending upon the ridge-like process, with the digital depression dividing it from the broader ulnar surface, show the same characters, as at r, &; figure 3, Pi. 46. Fracture of the shaft of the right radius (fig. 5) shows a compact bony wall, 6 to 7 lines in thickness, surrounding a finely cancellous central tract : the shaft is sub-trihedral, approaching the cylindrical form prior to the distal expansion. 1 Mantell, ' Illustrations of the Geology of Sussex,' 4 to, 182", p. 7S, pi. xx, fig. S. - Ante, p. ,3'20. 3 lb., ib. WEALDEN DINOSAURS. 509 The radius of the Iguanodon resembles that of Lizards — Iguana tnherculata. Monitor niloticus, for example — in the larger and more definite extent of the proximal surface for the ulna, than exists in the Crocodilia. But no living reptile — crocodilian, chelonian, or lacertian — is armed like the extinct herbivorous Dinosaur. Of other examples in the animal kingdom of limbs with spinous weapons, the first that suggested itself was the monotrematous reptile-like Mammals. But in both Orni- Sexual spines of fore-limbs ; or 'Hand-spurs' (s, s), Male of large S. Amer. Toad {Cystignathus fuscus). thorhynchus and Echidna they are limited to the hind limbs, and are attached to the tarsus, not to the tibia. In the class of Birds are a few ' spur- winged ' species — Anser gamhensis, Parra jacana, Palamedea cornida, Hoplopteriis, e.g. — in which the weapons are attached to the radial side of the fore-limbs ; not, however, to the radius itself, but to the base of the metacarpus. My friend and colleague. Dr. Giinther, has kindly supplied me with the follovdng example of spines or spur-like weapons in an existing cold-blooded air-breather; but it is a member of the Batrachian order. In Cystlgnatlms fuscus a sharp, conical, horny spine, figure 1 , s,s, is supported by a bony core attached to the radial side of the meta- carpal of the innermost or radial digit. Many species of Fish support and wield with effect formidable spinous weapons, forming part of the pectoral fins, the homologues of the fore-limbs in Iguanodon and other terrestrial Vertebrates. 510 BRITISH FOSSIL REPTILES. The monotrematous and batrachian instances show the spinous limb-weapons to be related to sex, and to be present, or fully developed, only iu the males. In the class of Birds the carpal spurs are common to both sexes, but smaller in the female.^ The question remains — were the radial spines of Iguanodon common to both sexes, or developed only in one, most probably the male ? In the Maidstone specimen such appendage, with a concomitant considerable distal expansion of the radius, cannot be discerned. In the best preserved ends of the anti- brachial bones, those, viz., furthest from the humerus (as the separated fragments of the matrix, have been restored in the Maidstone specimen), the closest resemblance traceable to the more complete bones before me is at the proximal ends ; and especially, as originally determined by me, in the ulna, or lower placed bone. In this view the distal ends, espe- cially of the radius, are partly concealed by an overlying vertebra, yet not to the extent to obscure the beginning of the radial expansion if it had existed. The shafts of both radius and ulna seem to be more slender than in Mr. Beckles' Wealden specimen. It may be that this is of a male Iguanodon and the Maidstone specimen of a female one. A strange instrument truly in aid of the amorous embrace ; yet, as in the instance of Cystignathiis, and perhaps also the Ornithorhynclius and Echidna, not without a parallel ! If the radial spines, on the other hand, were developed in both sexes of the Igua- nodon, and wielded for purposes of defence by the otherwise weaponless herbivore, one cannot fad to discern in them a formidable means of transfixing an enemy — the carnivo- rous Megalosaur, e. (j. — in a close death-struggle. Mantjs. Plate 48. With the right and left anti-brachial bones and spinous appendages several bones of both the fore feet were exhumed, but not enough for a complete restoration of either foot. They give evidence that the fore-paw was peiitadactyle, and that the terminal phalanges, at least of some of the toes, were short, obtuse, rough, serving for the support of hornv matter in the shape of a hoof rather than of a claw. Such evidences of the carpal bones as were collected are more or less fragmentary ; and, where a satisfactory union of those belonging to one and the same bone could be made, the homology of but one bone can be safely or with probability be suggested, that, viz., which answers to the large os cuneiforiue in the carpus of Lizards. The proximal surface of this bone is divided into a convex and concave surface ; the former was apparently adapted to the concavity of the ulnar extension of the distal part of 1 The Secretary of the Zoological Society, P. L. Sclatkr, Esq., F.R.S., kindly informs me that this is the case in the pair (mule and feiiinle) of the spur-winged geese (Flectroptenis) now living in the Society's Gardens. WEALDEN DINOSAURS. 511 the radius ; the concavity was adapted to part of the distal end of the nhia, but leaving the ulnar end of the distal convexity of that bone (PI. 46, fig. 1, /c) for probable adaptation to an OS pisiforme. The distal surface of the unciforme shows the concavity for an os magnum, and a well-defined flatter surface for a small unciforme. The metacarpal of the pollex (PI. 4S, I, m) is 4 inches in length ; 2 inches 5 lines across the broadest part of the proximal end ; 2 inches across the corresponding part of the distal articulation. Both these dimensions are in the direction of the transverse breadth of the paw, the bone being subdepressed. The proximal articulation is a shallow, circular cavity continued radially upon a rough, angular production of that end of the bone. The opposite side of the articulation is produced into a broader roughened surface for syndesmotic union with the base of the next metacarpal. The anconal sui'face of the bone (shown in PI. Ill), for an inch or more in advance of the distal end, is roughened by longitudinal grooves and ridges : the surface then continues smoothly to the distal convexity ; but shows, on each side near that surface, evidence of the powerful lateral ligaments connecting this metacarpal with the first phalanx. On the radial side is a rough oval pit, an inch in long diameter, with the proximal border prominent and forming an angle in the radial outline of the bone. There is a similar projection on tlie ulnar side, but it forms the proximal end of a triangular tuberosity. The thenal surface of the bone is more or less rough, and is divided by a low medial prominence into two facets. The distal articulation is of an oval shape, convex in a greater degree than the proximal articulation is concave; it is 2 inches across transversely, IJ inch in the opposite direction, or from the anconal to the thenal surface. The plane of both proximal and distal articular surfaces is not quite transverse to the axis of the bone, but rather oblique from the ulnar forward to the radial end. The least transverse diameter, at the middle of the shaft of this metacarpal, is 1 inch 8 lines. The metacarpal of the pollex of both right and left fore-feet has been obtained. The first phalanx of the pollex (PI. 46, 1) is broader and more depressed, in proportion to its length than is the metacarpal which supports it. Its proximal concavity is smaller and more shallow than the convexity to which it is adapted, though this appearance may be in some degree due to the abrasion of the margins. That part which is preserved equally bespeaks the strength of the ligamentous attachment with the metacarpal ; it is most produced on the radial side of the bone {a), as if ossification had extended there along the lateral ligament toward the metacarpal. The opposite or ulnar roughened sur- face is broader, more tuberous, but less produced. The anconal surface of the bone is less regularly convex transversely than in the metacarpal ; the mid part being raised so as to divide it from the surface on each side, which is flatter transversely and shghtly concave lengthwise. The smooth surface on the radial side is continued along a notch at the radial border 2d 512 BRITISH FOSSIL REPTILES. of the phalanx, upon the pahnar surface of the shaft, two thh'cls across. All the rest of that surface is grooved and roughened for ligamentous attachment. The distal end of this phalanx is 2 inches in breadth ; of this, a feebly convex, semi- oval articular surface occupies a transverse extent of 1 inch 5 lines ; the breadth from the anconal to the thenal border of this surface gives that of the distal end of the phalanx, viz. 1 inch. The series of bones does not include any phalanx adapted to or agreeing in size with this surface. By the analogy of Sainia and Crocodilla, I conclude the missing phalanx would be the terminal one. Of the proximal phalanx of the ' poUex,' Mr. Beckles' series includes both right and left. The second metacarpal (PI. 48, 2, vi), or that of the index digit, is 6 inches in length. The proximal end is subquadrate, 2 inches in breadth, deviating from flatness by a slight convexity, most marked towards the ulnar side, where it probably projected into the cleft between the trapezoides and os magnum. There is no indication of a smooth synovial surface ; the union throughout, or nearly so, seems to have been ligamentous ; the longest diameter in the ancono-thenal direction is toward the ulnar side of the surface, and is 1 inch 8 lines. Near the radial side of the base is a rough surface of limited extent, apparently for ligamentous connection with the adapted surface of the first metacarpal. On the ulnar side of the second metacarpal a rough flattened tract projects, like an exostosis, from the whole length of that side of the bone. Its ancono-thenal breadth at the base of the metacarpal is 1 inch 6 lines ; it decreases to a breadth of 6 lines where it . passes into the rough surface for the lateral ligament on the ulnar side of the distal end. The anconal surface of the shaft is smooth, becoming roughened by linear striae as it bends upon the radial surface. The thenal surface of the shaft is ridged and grooved throughout ; it is nearly flat transversely, moderately concave lengthwise. The distal articular surface is moderately convex, 1 inch 4 lines in diameter ; there is a protuberance on each side of the thenal part of the distal end ; the ulnar side of the bone is slightly convex ; the radial one in a greater degree concave ; thus, the second metacarpal is slightly bent toward the radial side of the paw. The bone described belongs to the left foot. The proximal part of the same phalanx of the right foot is preserved. The proximal phalanx of the second toe (ib., ii, 1) is 2 inches G lines in length; 2 inches in breadth at the proximal end; 1 inch 9 lines at the distal end. The proximal articular surface has the smooth synovial character but slightly indicated. It is subcircular in form, about an inch in diameter, with a very feeble concavity ; the rough peripheral tract on nearly the same plane, from 4 to 6 lines in breadth, indicates how large a proportion of the joint had been syndesmotic : the protuberance for the lateral ligament on the radial side projects beyond the plane of the articulation ; that on the ulnar side has a more distal relation to the joint. The anconal and lateral surfaces of the shaft form a continuous WEALDEN DINOSAURS. 5ia convexity transversely. The tlienal surface is flattened, but irregular ; an oblique groove extends from the radial end of the proximal surface for about an inch onward toward the ulnar side ; this groove, 4 lines in breadth, seems to be natural ; the clay matrix could easily be picked out of it. Beyond the groove the short thenal surface is moderately smooth and slightly concave ; a pair of hemispherical tuberosities project near the distal articulation, and are continued into the tuberosities on each side of that surface. The form of the surface is trochlear, that is, concave transversely, convex ancono-thenally ; feebly defined in both directions. The breadth is 1 inch 3 lines ; in the opposite diameter 10 hnes. The well-defined anconal border projects a little above the level of the corresponding surface of the shaft ; the breadth of the shaft at its middle is 1 inch 3 lines. To the well-defined smooth trochlear surface of the above phalanx is adapted a surface of corresponding size, shape, and smoothness at the proximal end of a phalanx, 1 inch 3 lines in length, 1 inch 4^ lines across that end (PI. 48, ii, 2). The breadth of the distal articulation of this phalanx is 1 inch 2 lines ; its ancono-thenal diameter is G lines, that of the proximal surface being 9 lines. Thus, the shape of this phalanx is subquadrate and subsphenoid ; the apex of the wedge being cut off, so to speak, to form the distal joint. The upper surface of the short shaft is smooth, convex transversely, concave lengthwise. The under surface is flat, rough, and irregular, and is continued into rough prominences on each side of the shaft. To the distal articular surface of the above phalanx is adapted the proximal one of the present (ib., ii, 3, 3 a, 3 d), which is terminal, ending in a rough, obtuse, thickened border (3 d) ; the breadth exceeds the length in a greater degree in this than in the preceding phalanx ; it equals 1 inch 3 lines, the length of the bone being 10 lines. The greatest ancono-thenal diameter of the proximal end is 9 lines, while that of the articular surface is but 6 lines ; there is no trace of attachment for the claw. The non-articular surface of this obtusely wedge-shaped phalanx indicates by its roughness that it was imbedded in a callous sheath of the intesfument. Thus we have evidence that the second digit of the fore-foot of the Iguanodon had three phalanges supported by a metacarpal ; that it much exceeded in length the poUex or first digit, and that it was of less breadth, though with greater ancono-thenal thickness of the proximal phalanx. The entire lenoth of the four bones of the second dio'it is 10 inches 6 lines. The metacarpal of the third or ' niedius ' (ib., iii, ?«) digit is 6 inches 9 lines in length ; the ancono-thenal exceeds the transverse diameter, except at the distal articulation, where the two are equal ; the bone is most compressed laterally at the proximal end, which is strongly convex for being wedged or received into a groove-like cavity of the os magnum. The ancono-thenal diameter at this end of the bone is 2 inches ; the transverse diameter at the anconal part is 1 inch 3 lines, but narrowing towards the thenal end. The radial side of the bone has a roughened tract, narrowing forward, and of the same extent as that on the contiguous surface of the second metacarpal ; but it deviates from flatness at 514 BRITISH FOSSIL REPTILES. the parts, and in the degree in which that surface is convex in the attached bone. The two metacarpals were thus closely and ligamentously united, in a way and to an extent in which I have not observed the homologous bones in any recent Crocodilian or Lacertian. The anconal margin of the rough tract projects, ridge-like, along the proximal half of the bone. The anconal surface of the shaft begins, at an inch and a quarter from the proximal end, to be smooth, and is convex in both directions, but least so longitudinally. The ulnar surface of the shaft is roughened, but in a less degree than the radial one ; the distal articular surface, single at its anconal half, where it is feebly concave, feebly concave transversely at its mid part, and much more convex in the opposite direction, has that curvature continued upon two lateral portions toward the thenal aspect of the bone, divided by an intervening channel. The distal articular surface also inclines slightly to the radial side, where it projects beyond that surface of the shaft ; it does not extend beyond the ulnar surface. It thus repeats the tendency to the bend radiad noticed in the second metacarpal, but here limited to the distal end. The fourth metacarpal (PI. 48, iv, m) is 5 inches 6 lines in length ; it is more com- pressed than the third, especially at the anconal part ; the ulnar surface sloping anconad to meet the radial one, leaving the upper surface to be represented as a rounded border; thus, the shaft is trihedral, not quadrilateral. The proximal articular surface is 2 inches ancono- thenally by 1 inch 5 lines transversely. The chief part of tlie articular surface traverses that end of the bone in its long axis, with a strong convexity transversely, which passes into a flatter facet at the ulnar side ; this ridge-like disposition of the chief articular prominence was probably wedged between the os magnum and uiiciforme. The ulnar flatter surface would articulate with the latter bone ; in advance of this is a rougher tract, of small extent, for ligamentous articulation with a fifth metacarpal. The radial side of the fourth metacarpal is flattened and rough for junction ligamentously at its proximal part with the contiguous metacarpal ; with an interval in the rest of the extent left by the concave curve, which this surface describes lengthwise, and which interval was probably filled up by looser ligamentous tissue. The distal articulation, 1 inch G lines across, and the same in the opposite direction at the radial side, resembles in character that of the third metacarpal, but with an opposite obliquity tending to direct the toe which it supported more ulnad. The corresponding metacarpal is preserved of tlie right fore-foot. To either the third or the fourth digit belongs a proximal phalanx, 2 inches 6 lines m length, 1 inch 8 lines in transverse breadth of the proximal end, 1 inch 6 lines in the same breadth of the distal end, which supports a well-defined, smooth, shallow trochlear surface, 1 inch I line transversely by 10 lines ancono-thenally ; it closely resembles the proximal phalanx of the second digit, but is rather narrower in proportion to its length, and shows greater disparity of size between the two distal tuberosities on the thenal surface. It may belong to the right paw. WEALDEN DINOSAURS. 515 A distal phalanx (ib., iv, 4), of the same character as that of the second toe, is longer in proportion to its breadth, and deeper ancono-thenally. The rough, obtuse termination is bounded below by a transverse groove indicative of an ungual callosity of a more definite form. The fifth metacarpal of the right fore-foot (PI, 48, v, w, reversed) has been preserved. Its proximal surface is rather lozenge-shaped ; the transverse diameter is 2 inches 3 lines ; a circular, slightly concave, roughish articular surface is defined at the middle of the lozenge ; the rougher tuberosities, extending beyond it on each side, form the truncate angles of the lozenge in that direction ; a smaller extent of rough surface defines, in a feebler degree, the angles in the opposite direction. The length of this metacarpal is 1 inch 7 lines ; the breadth of the distal end is 1 inch 8 lines. The upper surface is smooth, broad, and almost flat. The radial surface is continued into the thenal one, which is strongly concave lengthwise, and these combined surfaces are roughened by longitudinal ridges and grooves. The ulnar surface slopes in that direction strongly from the upper one to meet the combined theno-radial surfaces ; the distal articular surface is trapezoid in form, convex vertically, slightly concave transversely at its middle part, and continued upon a pair of tuberosities thenally ; the toe which it supported would be directed obUquely to the ulnar side of the foot. The skeleton of the fore-paw of the Ignanodon, carpus inclusive, may be set down as about IG inches in length, and about 11 inches in extreme breadth, showing a like dis- proportion of size to the hind-foot which the humerus does to the femur. In the Supplement,^ No. 1 ('Restoration of the (Hind?) Eoot of the Ignanodon'), p. 3713, I remarked, in regard to its subject, "the resemblance to the hind-foot of the CrocodUia in the suppression of the fifth toe, and the resemblance of the third and fourth toes, in regard to their nearly equal length, to those toes in the Monitor, render it most probable that the tridactyle foot of the Ignanodon, here described, is a ' hind-foot ;' but it cannot be assumed that the fore-foot may not have been similarly modified" (ib., p. 375.) We have now the desired evidence, and know that the fore-foot was pentadactyle, and that its chief speciality is in the stunted character of the terminal phalanges, at least of the second and third digits. The entire length of the bony framework of the fore-foot, without the carpus, is 1 foot 1 inch ; its breadth across the proximal ends of the meta- carpals is 9 inches : the length of the bony framework of the hind-foot, without the tarsus, is 1 foot 8 inches ; its breadth across the proximal ends of the metatarsals is 9 inches. The fore-foot is smaller in proportion to the hind-foot in the Crocodile ; it is still smaller in the Iguana. The length of the bony framework of tlic hind-foot in a Crocodihis lijjorcatus, with a ' Vol. of the Palseontographical Society, 4to, for 1858, p. 3. 516 BRITISH FOSSIL REPTILES. vertebral column, fi'oni the first cervical to the last sacral inclusive, of the length of 3 feet 2 inches, is 8 inches, including the tarsus ; the length of the fore-foot, including the carpus, in the same skeleton, is 5 inches 4 lines. In the skeleton of an Iguana, with the same part of the vertebral column 9 inches 3 lines in length, the length of the hind-foot, including the tarsus, is 4 inches 5 lines ; that of the fore-foot, including the carpus, being 2 inches 3 lines. In most recent ReptUia the fore limbs are shorter than the hind ones ; in some of the tailless Batrachians the difference is extreme. But there is nothing in the proportions or structures, especially in the approach to the ungulate type of the unequal phalanges of the fore-foot of the Iguanodon, to justify, encourage, or even suggest that the fore limbs so terminated did not take their share, as in the Iguanas and Crocodiles, in terrestrial locomotion. The notion of the Iguanodon being a biped, and walking like a Ijird, would, were it true, lend countenance to the reptilian hypothesis of the Ornithicnites. But this notion would imply, not only ignorance of the structure of the fore limbs of the huge reptile, but also forgetfulness or disregard of the correlated conditions of avian bipedal progression on dry land. In proportion to the bulk and weight of the bird, and to its limitation to terrestrial locomotion, is the extent of the trunk-vertebrge grasped by the splints or side bones ('ilia'), which transfer the weight of the body upon the hind limbs. Thus, the ostrich has twenty coalesced sacral vertebras. We have no evidence that the Iguanodon had more than four sacral vertebra, and our knowledge of their characters is derived, as might be expected from the remains of a cold- blooded prone quadruped, from detached and unanchylosed sacral centrums. Observation of the genesis of the bird's sacrum showed,^ among other points, the alternating disposition of the central and neural elements ; and progressive research into the osteology of the extinct Bejjtilia led to the recognition of a correspondence in this par- ticular of the sacrum of the large Dinosaurs with that of Birds. But this afforded no ground to the Discoverer of the sacral structure for affirming or predicating a closer affinity of the Iguanodon or Megalosaur than of the Pterodactyle to the feathered class. In the strong ligament of the head of the femur in Birds — in the dejith of the socket for its reception — in the strength and close adjustment of the knee-joint, in which the fibula takes its share — in the well-turned trochlear form of the distal end of the tibia — in the rejection of any intermediate tarsus between it and the foot, and in the consolidation of the metatarsal bones for a firm and close articulation with the tibia, we may discern a perfect adaptation to the requirements of the single pair of limbs to which the functions of support, station, and progression on land, are exclusively confided. ' Owen, 'On the Archetype and Homologies of the Vertebrate Skeleton,' 8vo, 1848, p. 1.t9, fig. 27; ' Catalogue of the Osteological Series in the Museum of the Royal College of Surgeons,' 4to, 1853, p. 266. WEALDEN DINOSAURS. 517 The reverse of all these conditions is seen in the bones of the hind limbs of the Iguanodon and other Dinosaurian reptiles. If one takes the pleasure of speculating on the genesis of Didtis or Dinomis, guiding or reining the roaming fancy by facts, the geographical limitation of such ornithicnitoid species, and their primitive association exclusively vpith creatures of which they could have no dread, suggest the more obvious and intelligible hypothesis of derivation from antecedent birds of flight, whose wings they still show more or less aborted, according to BufFon's principle of transmutation by degeneration, — with a progressive predominance of the legs over the wings, ultimately resulting in a maximization of the terrestrial and abortion of the aerial instruments of locomotion. Mandible and Mandibular Teeth (' Dinosauria,' Plates 49, 50). The dentary element of the right mandibular ramus of the young Iguanodon {Dinosauria, Plates 16, 17), discovered in the Wealden of Stammerhara, near Horsham, Sussex, by G. B. Holmes, Esq., demonstrated the fact that the sculptured surface of the crown in the teeth of the lower jaw was turned inward, the smooth surface outward, toward which aspect the entire tooth was moderately bent. Moreover, the alveoli in that jaw showed eighteen teeth to be the number supported in a close-set series and working position in the dentary element (««/e, p. 296). The portion of mandible obtained by S. H. Beckles, Esq., from the locality of the limb-bones above described, is also the dentary element of the right ramus, of which a figure of the inner side is given in Dinosauria, Plate 49. On this surface the crowns of seven teeth nearly risen into place are seen ; the worn crown and fang of a few of the preceding generation of teeth have been preserved, and the summits of the crown of a few teeth of a third set in succession is seen in the interspaces of the more developed teeth of the second set. The length of the portion of mandible here preserved is eighteen inches ; that of the corresponding part of the mandible of the Iguanodon discovered by Captain Brickenden in the Wealden of Filgate (Z)/»osa«n«, Plate 18) measures 20 inches. It is probable, therefore, that Mr. Beckles' specimen had nearly attained the full average size of the great herbivorous reptile. The antero-posterior breadth of the teeth rising into place averages 9 lines ; the largest mandibular teeth of I(^uanodon {Dinosauria, Plate 45) give 1 inch in the same dimen- sions. The crown-germs of the teeth in the Stammerham jaw {Dinosauria, Plate 10) average 6 lines ; we thus learn that each successive series of teeth had an increase of size corresponding in a general degree with the growth of the jaw. The subject of fig. 1, Plate 49, shows at its interior or symphysial end the abrupt slope downward of the short, edentulous, compressed part, which curves inward to meet the corresponding part of the opposite ramus at a short symphysis, extending along an hori- 518 BRITISH FOSSIL REPTILES. zontal surface, parallel with the straight lower border of the mandible. The smooth canal thus formed above the symphysis indicates a relation of facility in regard to the move- ments of protrusion and retraction of a long, cylindrical, muscular tongue, probably used, like that of the Giraffe and Megatherium, for the prehension of the vegetable substances selected by the Iguanodon for food. The commencement of the coronoid process, contributed by the dentary, is the same in extent as that shown in the younger Iguanodon's jaw {Din., Plate 16, a, /), and indicates the position of the suture of the dentary with the surangular element. The surface of the tooth-crowns here exposed show the subniedian pi-imary vertical ridge {a), which, in detached teeth, indicates the hinder border of the crown by its prox- imity thereto. The secondary ridge [b) is faintly marked, but is best shown in the two hindmost teeth. The anterior lamello-serrate border describes the usual convex curve ; the posterior border being almost straight or slightly concave along its chief extent. The dental characteristics of Iguanodon MantelU, as illustrated in previous plates {I)ui., Plates 23, 45), are well maintained. The secondary ridge is, however, less developed than in the larger teeth of older Iguanodous. The alveolar border here, as in the smaller jaw, describes a gentle sigmoid curve in the transverse direction, the convexity being inward in the hinder two thu'ds, then straight or slightly concave to the commencement of the symphysial slope. In the inwardly convex part of the alveolar tract the teeth are placed ' en echellon ;' the fore-and-aft plane of the anterior tooth {Bin., Plate 49, fig. \,d), if carried back, would pass outside the succeeding tooth (ib., b), and the crown of this stands in like relation to the next tooth behind (ib., c). Thus, when fully in place, the crowns slightly overlap in the lower as in the upper jaw {ante. Bin., Plate 45, fig. 2), and thus, eighteen teeth may range along an alveolar tract, which, if each tooth stood clear of the next, Avould not support more than fourteen. Room is also got for the full number along the working line by a certain alternation in the degree of attrition, as is well exemplified in the portion of mandible of a younger Iguanodon next to be described (Plate 50). I am indebted to A. J. Hogg, Esq., for the opportunity of examining and figuring this instructive specimen. It was discovered in the hard limestone, locally known as the "Under Peather," which is situated from four to five feet below the accumulation of shells of Ostrea dislorfa, called the " Cinder Bed," in the Middle Purbecks. A reference to p. 22, fig. 4, of my ' Monograph on the Fossil Mammalia of the Purbeck Formations, British Mesozoic Mammals' (Palseontographical Society, vol. xxiv, issued for 1870), will show the position in the Middle Purbeck series in which the present interesting evidence of the Iguanodon was entombed. It is the first example of that genus, to my knowledge, from the Purbeck series. WEALDEN DINOSAURS. 519 In making this statement I refer, of course, to the unequivocal evidence of Iguanodon afforded by the dentition. A large phalangeal bone is figured by Buckland in PI. XLI, ' Geological Transactions,' Second Series, as a " metacarpal " of Iguanodon. It was picked up " on the sea-shore, about half a mile north of the village of Swanwich " (ib., p. 428), and though "more or less injured by rolling on the sea-shore" has most claim to be referred to the hind-foot of the Iguanodon. It was most probably washed out of the cliffs of iron-sand and sandy clay described by Webster as dividing the Greensand of Ballard Down from the upper body of the Purbeck " limestone." The portion of jaw here exposed (PL 59, fig. 8), is the dentary element of a right mandibular ramus, al)Out the size of the Stammerham specimen (Plates 16 and 17), but is mutilated at both ends ; it includes, however, in an alveolar tract of four inches, ten teeth, alternately young and old. The foremost, b, is a lanceolate and acuminate crown-germ, least advanced in size and lowest in position in the jaw. The second, a, is fully in place with the upper third of the crown worn away and supported by a long, slender, tapering fang, occupying the interspace between the first and third teeth. The latter shows the crown fully formed, with the apex risen almost to the level of the worn surface of the antecedent tooth, between which and the fourth it accurately fills the interspace. The fourth tooth, a, rises to a higher level than the second and has rather more of the crown worn away ; much of its narrow fang is exposed. The crown of the fifth tooth — third of its series h — fills, like the third tooth — second of the series h — the interval between the fangs of the fourth and sixth teeth. The sixth tooth rises a little higher than the fourth, and is rather more worn. The seventh tooth — fourth of the series b — is more complete and rises higher than the fifth or third ; the apex of its crown is on a level with the worn surface of the sixth tooth : the outer part of the lower half of the crown and beginning of the fang of the seventh tooth has been broken away, showing the pulp-cavity in the latter. The eighth tooth— fourth of the series a — is worn down to the contracted base and beginning of the fang. The ninth tooth has risen above it, has come into service, and the crown is supported by a strong root. Beyond this is part of the crown of a successioual tooth of a third series, c. The close interlocked fitting of these teeth of different stages and periods of growth is most instructively shown in the present specimen ; former ones had given only a partial view of this arrangement, suggestive, however, of an Iguanodontal character of dentition, which is here demonstrated. The primary and secondary ridges are more equally developed, and the tertiary ridges less conspicuous, in these lower teeth of a Purbeck Iguanodon than is usual in the larger or older Wealden specimens. If any Palaeontologist should see in this a specific character he may, perhaps, accept the name of Iguanodon Hoggii. 3i 520 BRITISH FOSSIL REPTILES. Skull and Teeth of Iguanodon Foxii. (' Dinosauria,' Plate 59, figs. 9,9 a, 10; Plate 60, figs. 1, 5, 8— IS). This unique specimen, for the opportunity of describing which I am indebted to the discoverer, the Rev. W. Pox, M.A., throws much hght upon the cranial characters of the Iguanodon. The articular or condylar part of the basi-occipital {Dinosauria, PI. 60, fig. 1, i) is broken away, a portion of the broad basilar part of the bone (ib., fig. 5, i) remains in articulation with the basi-sphenoid (ib., ib., 5). This element shows a median contraction with lateral emarginations, bounded anteriorly by the pair of pterapophyses [f, t). The left of these abuts in its natural position against the corresponding pterygoid, the hinder branch of which, diverging obliquely backward, is broad and moderately concave on its postero-internal surface ; the end which would have abutted iq)on the inner and back part of the tympanic is broken off. There is no apparent " pre-sphenoid style " from the interspace of the pterapophyses. The left half of the foramen magnum [Din., PI. 60, fig. 1/) is entire, showing a vertical diameter of 4 lines, a transverse one of 5 lines ; the lower part shows the fractured surface from which the left exoccipital portion of the occipital condyle has been broken away : the basi-occipital part of the condyle is wanting. The super-occipital (ib., ib., 3) rises broadly and vertically from the upper half of the foramen,/, for an extent of 6 lines ; a tract of matrix of 3 lines extent intervenes between the super- occipital, which here shows a jagged upper margin, and the hind border of the parietal, 7. It may be, as in Varanus (ib., fig.. 2), that an unossified tract of the cranial walls has been left here ; or an angular ridge, as in the Crocodile (ib., fig. 4, 3), may have been broken away. The direction of the occipital surface is more vertical than in Lizards. The mid-tract of the super-occipital is moderately convex transversely, the lateral tracts as moderately concave to the lateral borders of the occiput, which borders gently converge as they rise [Din., PI. 60, fig. 1,3), The exoccipitals (2) extend, connately with the par- occipitals (4), outward, slightly downward and backward, for an extent of 9 lines from the foramen magnum, preserving a vertical breadth of 4 lines. In Iguana (lb., ib., fig. 3) the super-occipital (3) is a vertical crest, from which the sides slope forward and outward at an acute angle. In Varanus (ib., fig. 2) the super- occipital surface (3) is transversely convex and strongly inclined from the foramen magnum (/) upward and forward. The small Dinosaur, like Dicynodon, shows a crocodilian type of the occiput. The left tympanic (ib., fig. 1, 28) has been dislocated inward, and lies with its upper end beneath the par-occipital abutment (4). WEALDEN DINOSAURS. 521 The pterygo-palatine structures accord with the lacertian type. The proportions of the pterapophyses (ib., fig. 5, t) are more like those of Varanus (ib., fig. 6, t) than of Iguana (ib., fig. 7, i) ; but the pterygoid of the small Dinosaur resembles that bone in the herbivorous Lizard. The right pterygoid (fig. 5, 24) retains part of the tympanic process (J and of that (c) which abutted against the ectopterygoid (25) ; a portion of the right palatine (20) is preserved, of small size, showing an anterior and posterior emargi- nation, as in Varanus (ib., fig. 6, 20). The hind end of the right maxillary with the abutting part of the ectopterygoid are broken away in the fossil. The right malar bone has left its impression on the matrix (PI. 59, fig. 9, 26). The masto-postfrontal zygoma (ib., 8 — 12), in its breadth and relative position to the occiput and parietal, is crocodilian. The normal or lower (malo-squamosal) zygoma is indicated on the right side by the impression of the malar and a remnant of the squamosal; a larger proportion of which is preserved on the left side (PI. 60, fig. 1, 27) abutting against the tympanic (ib., 28). It is also shown in PI. 59, fig. 9 a, where the parts are drawn without reversing. The upper outlet of the temporal fossa is smaller than in Lacertians, larger than in existing Crocodiles ; its proportions are those of some Teleosaurs and Dicynodonts, and are approached by those of the small Crocodilian from the same Wealden locality (ib., fig. 24, t, t). The skull of Scelidosaurus, which gave the first considerable insight into the type of that part of the Dinosaurian skeleton, had, unfortunately, lost so much of the fore-end as prevented the application of the external narial test of its correspondence with one or other of the two existing divisions of Brongniart's Sauria. It could not, thereby, be determined, for example, whether the outer part or process of the fore-end of the nasal applied itself to the anterior edge of the ascending process of the maxillary, or to that of the premaxillary ; in other words, whether the maxillary entered into the formation of the outer nostril, as in Lacertilia, or was excluded therefrom, as in CrocodUia. The present Dinosaurian skull supplies this test and shows its correspondence with the Crocodiles ; there is, nevertheless, a touch of the Lizard. For the body or jaw-part of the premaxillary {Din., PI. 59, fig. 9, 22) sends upward not only the process from its hinder part (22'), applying itself to the outer border of the fore-part of the nasal (15) and excluding therefrom the maxillary (21), but it also sends upward a more slender process from the fore-part, which terminates in a point wedged between the ends of the nasals and dividing the right nostril (« ) from the left, after the lacertian type. Yet, again, the Crocodilian affinity is here manifested, for the premaxillaries are not confluent and the dividing process is not a single and symmetrical one, as in Iguana, Varanus, and most Lizards,^ but is bisected by the medial suture or cleft dividing the right from the left premaxillary. The premaxillary thus, in the main, adheres to the type of that of the Crocodile, circumscribing all that part of the nostril which is not due to the nasal ^ Hatteria {Rhynchocephalus) is an exception (' Phil. Trans.,' 1862, plate xxv, fig. 5, 22, p. 46"). 522 BRITISH FOSSIL REPTILES. bone itself, and excluding the maxillary from the boundary of the respiratory opening. The application of the outer process of the fore-end of the nasal to the anterior edge ot the ascending process of the maxillary could only be predicated by one mistaking a crack of the premaxillary fortliesutm-e. The ascending process (lb., ib., fig. 9, 22'') vvith which the nasal articulates at the outer part of its fore-end belongs to the premaxillary as well as does the inner process of the same end of the nasal bone. The premaxillo- maxillary suture extends from behind the sixth obvious premaxillary tooth for the extent of nearly an inch, with a slight curve convex forward, between the two main elements of the upper jaw. The maxillary and premaxillary have been slightly separated from each other along this suture by the force which has fractured both bones ; but the margins of the suture show its true nature and distinguish it from the fractures, especially those on the body of the premaxillary, one or other of which must be adopted for a suture on the hypothesis of the hinder ascending process (22") belonging to the maxillary bone. Of the six premaxillary teeth in place the foremost alone (lb., ib., fig. 9, i) has the crown entire ; its outer surface is convex across and lengthwise, most so along the middle, trans- versely, the main or mid-ridge of the Iguanodontal teeth being thus indicated. The margins are also slightly relieved {Bin., PI. ,C0, fig. 18, magn.) and converge at an acute angle to a sharp, slightly incurved, apex ; the enamel is minutely punctate. Neither in the right nor the left deflected part of the premaxillary, anterior to the pointed tooth, is there any trace of socket or fang. It would seem that this end of the premaxillaries was edentulous, like the corresponding slope of the symphysial part of the mandibular rami to which it was applied. The outer surface of the deflected ends of the premaxillaries is pitted and finely punctate or rugose. The fractured bases of the premaxillary teeth succeeeding the first show a transverse diameter nearly equal to the fore-and-aft one, and I can form no judgment as to the shape of their missing crowns, save on the analogy of the Iguanodon. They are close- set, and if those crowns extended antero-posteriorly they must have overlapped. This Iguanodontal arrangement is demonstrated in the undisturbed maxillary teeth, of which eight are recognisable ; the hind border of one crown overlaps the fore border of the tooth behind. The two anterior maxillary teeth have slipped in part from their sockets and do not show this arrangement. The fii'st is the smallest antero-posteriorly, but its crown has been worn to the fang, and when entire would be larger in that direction. The second tooth is less worn, and yields in size to the third. In the fifth the full size of the crown, antero-posteriorly, is shown, and this tooth is selected for the magnified view in PI. 59, fig. 10. The outer surface of the crown is bisected by a medial primary longitudinal ridge ; behind this ridge the surface is smooth and concave transversely ; in front of the ridge the similarly concave surface is accentuated l)y two low secondary longitudinal ridges. WEALDEN DINOSAURS. 523 The same characters appear, in tlie degree in which the crown is unworn, in the other luaxilkiry teeth. In upper or maxilhiry molars of Iguanodon Matitelli the following varieties have been recognised and figured. In tlie specimen figured in PI. 23 {Din.), fig. 2, the primary ridge is nearer the fore border of the crown than in fig. 10, PI. 59, of the present species; there is a feeble indication of a secondary ridge on the anterior transversely concave facet. There are two secondary ridges in the posterior facet, and the crown is so worn down as to show no trace of marginal serrations. In the upper tooth of lyuanodon ManteUi {Bin., PI. 23, fig. 2, vi), the crown is les8 worn than in lyuanodon Foxii, and the marginal serrations appear beyond the line of extreme breadth. The anterior facet shows no secondary ridge ; the two such ridges iu the posterior facet rnn together in the terminal part of the crown. In Din., PI. 45, fig. 2, three upper molars are shown in sitil with the Iguanodontal overlap, viz. the hind border of a fore-tooth (m) over the fore-border of the next tooth («) ; in these upper molars the primary ridge is sub-medial, and the front face smooth as in fig. 10, PI. 59 ; the two secondary ridges on the hind facet are feebly indicated. The marginal serrations are shown in the preserved terminal part of the crown, which is entire in the teeth marked n and o. Bisect the tooth n at the line at which it is worn away in figs. 9 and 10, PL 59, and no serrations would appear. In some upper molars of Iguanodon the margino-serrate character is continued in a minute form nearer to the base of the posterior margin. I have figured a left upper molar of this variety in figs. 2, 3, 4, of PI. 59 [Din.), and also to show the further variety of three secondary ridges on the hind facet of the crown. But the upper molars in the subject of fig. 9 show, as in the enlarged view (fig. 10), a continuation of the relieved or raised lateral borders across the base of the crown, in a curved course, convex toward the fang. This basal ridge does not project beyond the origin of the primary ridge, but falls into that origin. I have not observed this character, at least so definitely marked, in any upper tooth of Iguanodon ManteUi, and I regard it as indicative of a specific distinction of the smaller Iguanodon now under review, believing myself entitled to conclude as to its generic relationship fx-om the characters of the dentition of the upper jaw above defined and illustrated. It is true that one, at least, of the premaxillary teeth is canine-like. But no portion of the skull of Iguanodon ManteUi has yet been discovered which would supply the means of testing its resemblance to or difference from the smaller species, in regard to this dental character. Consequently, prior to our knowledge of the skull and dentition of the smaller species, the discovery of a tooth answering in size to the ordinary upper molars of Iguanodon ManteUi, but with a lanceolate and acuminate crown, would naturally suggest its reference to some other Dinosaurian genus of the Wealden, of the bulk of the 524 BRITISH FOSSIL REPTILES. Iguanodon. In giving a description of this tooth (pp. 420, 421, figs, a, h, c, p. 422) before the present discovery of the upper jaw and teeth of an Iguanodon was made, I suggested that it might belong either to Cetiosaurus or Pelorosaurus. I now, however, from its resemblance to the entire premaxillary tooth in the small Iguanodon — as close as is the resemblance in the maxillary teeth — deem it more probably to belong to the larger species and to be a premaxillary tooth of Iguanodon ManteUi ; and I now add two views of this tooth of half the natural size are given in Bin., PL 60, figs. 19 and 20, to facilitate comparison with the magnified view of the laniary of the smaller species (fig. 18). The surface of the crown (fig. 20) which answers to the outer one in fig. 18, and in i, fig. 9, PI. 59, is convex both lengthwise and transversely, and most so in the latter direction along the middle part ; the main or mid-ridge of the maxillary Iguanodoutal teeth being thus represented. On the opposite (inner) side of the crown (fig. 19, PI. 60) the surface is concave across the two thirds next the apex. One margin, the anterior according to the analogy of the small Iguanodon, is convex, the hinder margin along its terminal half is slightly concave. The crown expands antero-posteriorly above the root to nearly midway to the apex, towards which the borders then converge to a point with the different contours above noted. Both borders are trenchant, not serrate. Now that we know that a laniariform, or ' lanceolate and acuminate,' premaxillary tooth was associated with molars of the Iguanodoutal type, in a small exemplar of the genus, we may anticipate that the premaxillary part of the skull of Iguanodon ManteUi, when discovered, will show teeth, if they should be preserved there, of the laniary type exempli- fied in p. 422, a, b, c, and in PL 60, figs. 18, 19, and 20. The anterior mutilation of the skull of the Scelidosaurus, with maxillary teeth having the terminal and more expanded half of the crown serrate (PL 60, fig. 21), precludes, at present, the determination whether the iguanodontoid molars of this genus were similarly associated with anterior laniaries. But the dentition of the small Purbeck Dinosaur {Echinodon), with a corre- sponding type of maxillary dentition (PL 60, fig. 22), does include one or more laniaries in advance of molars of the serrate type, as in the small and large Iguanodons (' Monograph on the Eossil Reptilia of the Cretaceous and Purbeck Strata,' Pal. Soc. vol. for year 1858, p. 35, PL VIII, figs. 1, 1 a). I next proceed to determine how far the dentition in the small skull repeats the iguanodoutal character of overlapping arrangement of the crowns of the teeth. The right tympanic and mandibular ramus are wanting in the fossil. The left mandibular ramus has been pushed obliquely to the right side, and its fore end has partly displaced the first and second molars, beyond which the projecting end has been broken away. The crowns of those teeth, so driven out of line, are thereby partly withdrawn from their sockets, so as to expose the basal half of their fangs. From this I infer that the force has operated upon the recent animal: for, if it had acted subsequent to fossilisation, through movement of the matrix, it would WEALDEN DINOSAURS. 525 have broken the teeth, at that time cemented to their sockets. Howsoever that may be, displacement is obvious, and no inference can be drawn as to the original relative position of the crowns of these anterior teeth. As it is, the anterior edge of the crown of the third molar does not overlap in the slightest degree the posterior edge of the crown of the tooth before it ; the reverse is the case if any overlap at all can be predicated. In the undisturbed molars the hind edge of each tooth projects a little beyond the fore edge of the one behind it. This is the characteristic arrangement of the upper or maxillary teeth of Iguanodon. It is exemplified in the specimen figmed in Din., PI. 45, fig. 2, in the undisturbed upper teeth, there marked m, n, o. The overlap by the anterior edge of the crown in the anterior four maxillary teeth of the posterior edge of the tooth in front, and the reverse arrangement in the rest of the maxillary series, may be a character of Jlj/jjsilojj/iodo/i, Huxley, but is not one of the present nor of any previous evidences of Iguanodon. In the small species discovered by Mr. Fox, as in the large type of the genus, the maxillary grinders not merely seem to overlap, but do so, in the way and degree exemplified in fig. 9, PI. 59, and in fig. 2, PI. 45. Eour or five teeth may have occupied the alveolar interspace between the foremost of the series of ten maxillary teeth and the second tooth from the premaxillary one, i (PI. 59, fig. 9). Sixteen teeth of the pattern characteristic of the upper molars of Iguanodon would thus occupy the extent of the alveolar border of the upper jaw preserved behind the pointed tooth(j). The maxillary is broken away behind such sixteenth molar. The small Iguanodon may, therefore, have resembled the large one, in number or ' formula,' as in the characteristic and peculiar generic pattern, of its teeth. The arrow (lo) points to the tooth which is the subject of the magnified view (fig. 10). A comparison of this figure with a similar magnified view of an upper molar of Scelidosaurus {Din., PI. 46, fig. 3 ') shows the teeth of the two genera to be modifications of the same type. The exterior surface of the crown in Scelidosaurus (PI. 60, fig. 21) has a median and two marginal longitudinal elevations or ridges. The marginal ones diverge with the expansion of the crown, and end in points at its extreme breadth, rather more than half way between the base and apex of the crown. This apex and the points of the marginal ridges define a triangle, the converging sides of which are notched or serrate. The hollows between the medial and marginal ridges are smooth in Scelidosaurus, the anterior hollow is usually ridged in Iguanodon. In this genus the ' secondary ' ridges are more feeble than the primary ones, and are plainly the seat of variety, as in the instances above cited. The upper molars of the small Iguanodon (PI. 59, figs. 9, 10) exemplify the rule of the generic type : fig. 2, PI. 45, shows the variety more approaching the type of the geologically older Dinosaurian {Scelidosaurus). The molars of the Purbeck Dinosaur {Ecldnodon, PI. 60, fig. 22) repeat the pattern of those of Scelidosaurus, but the marginal serrations, being more numerous and relatively 1 Pal. Soc. vol. for year 1859. 526 BRITISH FOSSIL REPTILES. smaller, more resemble the serrations which the propounder of the genus Hi/psilophodon erroneously states " are so characteristic of the teeth of Iguanodon."^ The tooth, which I have referred, with prol)ahility, to the HyJceomurm, shows the shape of crown on which the Scelidosaurian and Iguanodoiital patterns have been superinduced ; it expands from the base to two lateral angles, whence the sides converge to a third apical angle. If the converging borders of the terminal half of the crown had originally been notched or serrate, those projections had been worn away by use, in the tooth figured (' Monograph on the Fossil Reptilia of the Wealden Formations : Genus HylcEosatirus in the Palfeontographical Society's volume for 1856^). I may remark, also, that this tooth is a mandibular one, and that a nearer approach to the serrident type may have been shown in the maxillary teeth of the Ilyloeosaurus. Howsoever this may prove to be, the conformity of cranial structure, as of fundamental tooth-type, between Scelidosaurus, Ecldnodon, and Iguanodon, now exemplified by the small skull (PI. 59, fig. 9), makes it convenient to associate the genera in a section of Dinosauria, which may be termed ' Prionodontia' i. e. serrident, or saw-toothed. In this family the skull exhibits a more generalised type of structure than in the existing Crocodiliu and Lacertilia. The short, square, massive character of the cranium, and the greater extent of ossification of the rest of its walls, are retained in modern Crocodilia ; but the majority of the characters, as the double or divided external nostrils, the divided frontals, the relatively large orbits, the pterygoids divaricated by intervening basi-sphenoidal pterapo- physes, and the separated palatines, are characters retained by modern Lizards. In the majority of existing Lacertian genera, however, the nasals form a single bone, and the premaxillaries are confluent anteriorly. These bones retain their parial condition in Crocodilia as in Prionodontia. The position of the portion of lower jaw — left mandibular ramus — preserved in the block of matrix with the skull, precludes the procedures of exploration requisite for detection of teeth or germs of teeth, with any regard for the safety of the rest of this unique specimen, although the temptation is great, in reference to the alleged absence of an Iguanodontal characteristic, namely, the serrations of the free edge in the teeth of this specimen. Not that the allegation has any real value as to the generic character of the Saurian so represented ; since it is plain that the renmants of the crowns of the upper molars are not such as could show the Iguanodontal serration if it had existed, the apical part being wanting where alone, as a rule, the crown is marginally serrate in the upper molars of Iguanodon Mantelli. In this species, moreover, the serrations are more numerous, and afiiect a relatively greater extent of the margins of the crown in the teeth of the lower jaw than in those of the upper. Hence it might be expected that the mandibular teeth of the small species from the Cowlease Wealden would apply a decisive 1 ' Quart. Journal Geol. Soc.,' vol. xxvi. 2 p 21. WEALDEN DINOSAURS. 527 test, on the assumption that the absence of marginal serrations — all other Iguanodontal characters present — was decisive against a generic relationship with Iguanodon. Mr. Fox has kindly transmitted to me the portion of the left mandibular ramus, 1 inch 7 lines in length, with a depth of 7 lines, where entire, which is the subject of figs. 8 — 11 in PI. 60. It includes the sockets and fangs of eight teeth, so closely set as to have necessitated the overlapping arrangement of the crowns, according to the Iguanodontal type, the hind margin of the anterior tooth covering the outer side of the fore margin of the tooth behind, in the lower as in the upper jaws. The proportion of transverse to fore-and-aft diameters of the fractnred bases of the mandibular teeth (fig. 8) in this specimen is also Iguanodontal, suggestive of a bruising function. These eight teeth occupy an alveolar extent of 1 inch 3 lines. The outer surface of the ramus (ib., fig. 9) is divided into an upper and lower facet by a low, obtuse, prominent angle or ridge extending horizontally, and giving the greatest thickness to that part of the jaw ; a series of five vascular or neuro-vascular foramina extends a little above this ridge. The structure of the outer surface of the ramus, exhibited by the larger jaw of a young Iguanodon, also discovered by Mr. Fox, in the same Wealden deposits of the south-west coast of the Isle of Wight, closely accords with that shown by the present specimen (compare Bin., PI. 24, fig. 4, with PI. 60, fig. 9). In like manner the inner surface of the smaller mandibular fragment (ib., fig. 10) shows a gentle convexity lengthwise and an almost level surface vertically, broken by a longi- tudinal groove near the lower border. Concluding that, as in Iguanodon, the germs of successional teeth would lie on this side of the roots of the broken ones which had been in use, and that such germs would have the ' lanceolate and acuminate ' portion of the crown, yielding the required test of con- formity or otherwise in regard to marginal serration, I removed the inner (splenial) plate at parts which exposed three such germs (PI. 60, fig. 11, «, j, d), each demonstrating the character in question. The inner side of the crown is traversed longitudinally by the submedial primary ridge, the coronal margin anterior to which shows four acute serrations, with grooves continued from their intervals some way down the surface. The extreme fragility of these precious evidences checked further attempts to expose more of that surface. My inter- pretation of the characters of the mandible and mandibular teeth, so far as they are exhibited by this specimen, is, that they demonstrate a reptile of the genus Iguanodon. If the specimen belong to a full-grown individual, the greater relative size and the smaller number of the coronal serrations show it to belong to a distinct species of Iguanodon, for which the name of its discoverer is deservedly to be retained. Still may remain the question whether, in the numerous successions of teeth which would ensue dm-ing the acquisition of the magnitude of Iguanodon ManteUi, the number of serrations might not be increased in greater proportion than the increase of the size of 4 b 528 BRITISH FOSSIL REPTILES. Fig. 1. such serrations. That would be the sole modification needed to make them specifically as well as generically the teeth of Jguanodoii Mcuitelli. Of the above-described mandibular fossil Mr. Fox writes: — "This jaw was found within a yard of the skull. They were both in a mass of mud that had slided down from the cliff, and was being gradually washed away by the sea." What is wanting in the exposed portions of the tooth-germs in the above specimen, viz. the continuation of the marginal serrations, of smaller size, upon the ridge bending from the margin at the broadest part of the crown upon the inner surface of the narrowing basal part of the crown, is fortu- nately supplied by an almost entire lower molar oi Iguanodon Foxii (PI. 60, figs. 12 — 17), which came from a slab of Wealden stone containing a portion of a right mandibular ramus (AV^oodcut, fig. 1), with the symphysis, «, confined to the lower border of the sloping end (as at 5', fig. 1, PI. 59) ; also a few ribs, a caudal vertebra of the pattern of those figured in PL 7 {Din.), and also " a distal phalanx of one of the toes." " I cannot tell," writes Mr. Fox, " where I have the bone itself, but its shape is exactly like that in Iguanodon Mantelli, very little curved in a downward direction, and rather broad.^ In the little paper box, along with the fragment of jaw, you will find one very small tooth, quite perfect," that came out of this slab in dressing."" This slab was found in the fallen cliff, about 150 yards east of " Barnes' High," directly fronting the den of my Polacantlms, which I dare say you will remember seeing. The skull and broken jaw were found about CO yards further eastward."* In the accompanying Woodcut, fig. 2, of the caudal vertebra, nat. size, of Iguanodon Foxii, are added letters of reference corre- sponding with those on the figure of a caudal vertebra of Igim- nodon Mantelli (PI. 14, fig. 1). The anterior or cervical vertebrae show the modification of the front ball and hind cup (PL 6, figs. 3, 4). If the sacral vertebrae should show the broad under surface, as in « 4, PL 8, a corresponding variability of vertebral shape in the same skeleton will characterise the present small kind of Iguanodon as it does the large kind. The tooth (PL 60, fig. 12) is 5 lines in length in a straight line ; it is moderately curved, with the convexity (as the teeth in situ above described show) towards the inner surface of •1 The shape and proportions of the ungual phalanges vary in the toes of the fore and hind feet in Iguanodon Mantelli. 2 Letter received 4th February, 1870. ^ lb. ib. * Letter above cited. Tlie skull and broken jaw are the subjects of figs. 9 and 9 a, of PI. L Fig. 2. WEALDEN DINOSAURS. 529 the jaw, the sculptured surface of the crowu having the same aspect. The length of the fang is 3 lines, that of the crown is 2 lines, but the apex of this has been broken off. The breadth of the crown is 2f lines ; the thickness of its base 1^ lines. The fang tapers to its implanted end, which is hollow and filled with matrix, subcircuku- in form, ^ a line in diameter ; the dentinal wall is here very thin. The fang expands towards the crown, chiefly in the antero-posterior direction, and is shorter on the outer concave than on the inner convex side, the coronal enamel descending rather lower on the outer side. The inner side of the fang is broader and less convex across than the outer side, towards which the fang seems to be, as it were, rather pinched in. The outer side of the crown (PI. 00, fig. 1 7, magn.) begins with a feeble rise of the enamel from the level of the fang, such rise describing a slight convexity downward ; this side of the crown is gently concave lengthwise, more strongly convex across ; it is relieved by low ridges continued down from the apices of the chief serrations, most of them subsiding before gaining the basal line. The finer serrations on each margin of the crown, where it bends in from its broadest part, are conspicuous. Minute, short, irregular, longi- tudinal, linear risings of the enamel may be seen with the pocket lens in part of the interspaces of the longer and plainer ridges. The crown expands to its extreme fore- and-aft breadth about one third of its length from the fang. The enamel on the inner side of the crown (ili. fig. 15, magn.) begins by a like definite rise from the level of the fang, but this runs straighter across before bending up to the margins of the expanding basal part of the crown. The continuation to the hinder border is more prominent and its termination is more abrupt, giving a slightly angular contour to that border, and making the surface of the crown between the border-ridge and the primary longitudinal ridge a little concave transversely. The basal rising subsides more quickly and completely upon the anterior border, which describes a gentle convex curve, and does not rise so as to render the inner surface of the crown between it and the primary ridge concave. Thus, the inner and outer sides of the crown being determinable by their difference of sculpturing, the fore and hind borders are shown by the above specified characters, and the detached tooth can be referred, as in the case of those of the larger I^ua- nodon, by like characters to its own ramus or side of the jaw ; this, in the present tooth, is the right one. The inner side of the crown of this tooth of lyuanodon Foxii, as in the lower teeth in situ, has one chief median primary longitudinal ridge, increasing in strength from its origin at the basal rising of the enamel to the apex of the crown. On the front facet a short secondary ridge begins, next the primary one, near the apex of the crown, and terminates in the point or ' serration ' next to that of the primary ridge. Another secondary ridge begins at the base of the crown, and runs nearly parallel with the primary one. The margin of the crown, anterior to this ridge, shows the usual smaller serrations. On the hind facet two secondary ridges commence at the up-bent part of the basal one, run parallel with the primary ridge, gaining in prominence and breadth, and terminate in the 530 BRITISH FOSSIL REPTILES. two stronger serrations behind the chief or apical one. Smaller serrations mark the hind border of the crown between the above and the end of the basal ridge. Thus, all the complexities giving the generic characters of the lower teeth of Igua- nodon are here manifested, as are those of the upper teeth in the skull (PI. 59, figs. 9, 10). The following differences from the larger teeth of Iguanodon Mantelli are of specific value : the defined rise of the basal border of the coronal enamel on both the outer and inner sides of the tooth, especially the latter ; the relatively larger size and smaller number of the marginal serrations ; the larger relative size and more definite median position of the primary longitudinal ridge. The latter character, however, is reached in the range of variety to which the teeth of Iguanodon Mantelli are subject, as may be seen in the anterior ' acuminate and lanceolate' tooth in the Purbeck Iguanodon (PI. 59, fig. 8 h), and in the figs. 10, 15, 17, PI. 45, exemplifying the characters of the upper and lower teeth of Iguanodon Mantelli and some of their varieties, due to age, wear, and position in the jaw. From the above facts I conclude that the fossils discovered by Mr. Fox, and figured in Pis. 59 and CO, afford the much-needed exemplification of the cranial structure in the genus Iguanodon, and that they contribute to supply characters of the serrident family of Dinosatiria which were not given in the fossil skull of Scelidosaurus Harrisonii, figured in Pis. 46 and 47. The importance of tliis addition to the knowledge of Dinosaurian structures induces me to recapitulate and enforce the passing remarks, offered in the course of my descriptions, on statements which, if true, would leave such addition still a desideratum. Serrations of the free edge of the crown, affirmed to be " so characteristic of the teeth of Iguanodon" (Huxley, ut supra, p. 5), are not in any degree characteristic of that genus. They are present in the teeth of older Dinosauria as of contemporary genera. The Liassic Scelidosaur and the Purbeck Echinodon alike manifest the modification. The true generic dental characteristic of Iguanodon is the superaddition to marginal serration of ridged and grooved sculpturing of one of the surfaces of the crown of the teeth ; to wit, the outer one in tlie upper teeth, the inner one in the lower, the sculpturing being in so broad and definite a style that the I'idges can be named. This character, comI)ined with marginal serration, in the molars of the small Dinosaur in question, and this other character of the overlap of the expanded crowns in the one direction above described, are now submitted to impartial Taxonomists as the ground of the reference of the subject of the present section to Conybeare's genus. So singular an anomaly in the arrangement of a molar series as the reversal of the order of overlapping at its two extremes might well support a generic distinction, but would need clear and indisputable demonstration for acceptance, Iguanodon Foaii affords no real ground for the ascription of such an anomaly. WEALDEN CROCODILES. 531 Genus — Hyl^ochampsa, Owen. The subject of figs. 23 — 25, PI. 60, was discovered by the Rev. W. Fox, M.A., in the Wealden of the south-west coast of the Isle of Wight. It is the hinder part of a skull of a small or young Crocodilian, showing the occipital surface (ib., fig. 23), the upper openings of the temporal fossae (ib., fig. 24 t) with the orbits (o) ; and so much of the palate (ib., fig. 25) as permits of histructive comparisons with that seat of divers modifications in other RepfUia. A few sockets of teeth are shown at the hind end of both right and left maxillary bones. These indicate the teeth to have been relatively as large as in GoniopJiolis ; and, although it is hazardous to conjecture the shape of the crown of a Crocodilian tooth from the cylindrical root, as indicated by its socket, yet it seems to me probable that the teeth of the present small Crocodilian resembled more those of Goniopholis {Crocodilia, PI. 7, fig. 2) than of Siichosaurirs (ib., PL 5, fig. 4) or of PoiJciJopleuron (ib., ib., fig. 5). The outer surface of the cranial bones shows a different pattern of sculpture from that in GoniopJiolis ; instead of small circular pits there are short irregular ridges, which, at some parts, the postfrontals, for example, have a tendency to diverge from a reticulate centre ; a number of short ridges and clefts radiate from the raised part of the border of the temporal outlet ; but all these accentuations of the surface are rather feeble. As I know of no con-esponding specimen of a skull of any Wealden Crocodilian like the present, and as it offers generic modifications of parts which are comparable with Crocodilians of older and newer formations, I propose to describe the specimen as representing a new genus and species under the name of " HylcBochampsa vectiana."^ The occipital surface (PI. 60, fig. 23), excluding therefrom the tympanies, 28, and pterygoids, 24, is of a triangular form, with the base upward ; the apex is pierced by the foramen, v. The breadth of this surface, taken at the mastoidean angles, 8, 8, is, to so much of the vertical diameter as includes the foramen,/ as three to one. The basioccipital, i, contributes the middle four fifths of the condyle, the upper angles of which hemispheroid tubercle, due to the exoccipitals, are broken off. The centre of the condyle is feebly impressed ; it projects, and is, as it were, sub-pedunculate. The basioccipital curves from the condyle forward and downward, then descends vertically to the foramen, ty and is ridged along the mid-line. The extent of the occiput below the foramen magnum,/, exceeds the part above the foramen. The exoccipitals, 2, are the largest elements of this cranial segment ; they meet above the foramen, excluding the superoccipital, 3, therefrom for an extent of nearly three lines. The suture appeal's to be continued upward through the superoccipital, 3 1 Gr. vXij, wood or weald ; ^nfii^ia, an Egyptian name of the crocodile. The specific name relates to the lociility of the fossil. 532 BRITISH FOSSIL REPTILES. but this may be due to fractiu-e. The superoccipital develops a tuberosity at each upper angle, near its junction with the mastoid, 8. Each exoccipital swells at its outer border into two tuberosities, representing the paroccipitals of Chehnia, and contribiiting to the articulation for the tympanic, 28. The direction of the bilobed paroccipital border, 4, is oblique from al)ove downward and inward. The tuberosity forming the angle of the mastoid, 8, projects distinct from the upper paroccipital one, 4. In the relative extent of the paroccipital tuberosities and in the direction of their border HylcBochampm resembles Teleosaurus, and differs from Crocodilns, in which the masto-paroccipital border extends from above downward and outward (ib. fig. 4), making the greatest breadth of the occipital surface to be at the paroccipitals, not at the mastoids. There is no vacuity between the mastoid and supei'occipital ; a linear suture, slightly concave upward, alone divides them on the occipital surface. The articular surface of the tympanic, 28, projects as usual, backward, beyond the plane of the occiput ; the medial half only of that surface is preserved in the present fossil ; it is almost vertical and very slightly convex. The upper platform of the cranium behind the orbits (PI. 60, fig. 24) is subquadrate, with the anterior angles rounded off. It is perforated by the pair of upper temporal openings, t, which are oblong-ovate, with the outer border almost straight, the inner one curved, and with the hinder or basal border slightly raised; the anterior border is depressed and continued upon the side of the cranium proper, forming the inner wall of the temporal fossa. A flat surface of bone (s, 12), equalling the breadth of the temporal opening, lies exterior to it; a narrower concave tract (11) divides the openings; the posterior surface (7) is broader than the lateral ones. In Teleosaurus and allied genera (e. g. MetriorJii/nchus, Teleidosaurus, Steneosaurus, Felagosaurus, &c.) the upper temporal openings are relatively larger and the surrounding flat tract of bone is of less extent than in Hyheoclumpsa, which herein more resembles the tertiary and modern CrocodUia, although the form of the openings is teleosauroid. The general form of the upper cranial surface posterior to the orbits resembles, in Hylceochamjisa, more that in Crocodilns, Metriorhi/nchus, and Pelayosaurus, than that in Teleosaurus cadomensis and in Gavialis, in which latter the breadth exceeds the length. The orbits in HylcBochampsa (PL GO, fig. 24, 0) are circular and better defined by the post-frontal (12) from the lateral outlets (<') of the temporal fossse than in Crocodilus, and herein they more resemble the orbits in Teleosaurus ; but they are less horizontal than in Tel. cadomensis, and incline less to the vertical position than in Tel. [Pelayosaurus) temporalis; their outline is obliquely upward and outward. The prefrontal (14) and lacrymal (73) swell out a little anterior to the orbit, whence the maxillary (21) and nasals (15) continue to form the upper jaw. This recalls the character of that part of the skull in the Gavial rather than in the Crocodile. These modern or procoelian representatives of the order CrocodUia differ from the Lacertilia in the greater extent or degree of ossification of the palate. WEALDEN CROCODILES. 533 Tlie ' pterygo-maxillary vacuity '^ is large, and is bounded, as in Lizards (PI. 60, figs. 6 and 7, y), by the pterygoid (24), the ectopterygoid (2.1), the palatine (20), and, in most genera, Ic/uana, e. g., by the maxillary (21). But the ' palato-maxillary ' vacuity" (figs. 6 and 7, «) between the vomer, maxillary, and palatine, does not exist in Crocodilia ; nor is there a trace in that order of an ' interpalatine vacuity.'^ The ' interpterygoid ' vacuity in Lacertilia * appears to be represented by the much smaller opening which serves as the ' palato-naris,' or hinder orifice of the nasal air-passages in modern Crocodilian genera.* \\\ his description of the Caen Gavial {TeJeosaurus cadomensis, Geof.) Cuvier indicates a large vacuity, more advanced in position than the hinder nostril of modern Crocodiles, and more resembling the interpterygoid vacuity' of Lizards (PI. 60, fig. 7, «). This he regarded in the Caen Gavial as the ' palato-naris.'" The smaller and more posterior orifice, resembling the ' palato-naris ' of Crocodiliis and Gavialis, and which De Blainville and Bronn affirmed to be the true hinder nostril in the Teleosaurs, Cuvier calls "le trou des arteres," and marks with the letter t in pi. vii, tom. cit. The real nature of this foramen in the Teleosaurs is pointed out in my paper " On the Eustachian Canals in Crocodiles,"'' and the accuracy of Cuvier's determination of the ' palato-nares ' in the Teleosaur, is now accepted.^ Li some Teleosaurians {Tel. temporalis, Bl., Felagosaurus typus, Bronn) the 'palato- naris,' instead of being broader than long, as in Tel. cadomensis, is narrower and is produced forward into a point, on the same transverse parallel as the pterygo-maxillary vacuities, which are thus reduced in size and, as it were, pushed aside. In Hylaochampsa (PI. 60, fig. 25) the vacuity (y) on each side of the bony palate is formed or bounded behind by the pterygoid (2-1) and ectopterygoid (25) and in front by the palatine (20), and probably by a small part of the maxillary (21), though here a portion of the antero-external part of the boundary is broken away. But sufficient remains to show that the vacuity is natural and is homologous with the " grand trou palatine " in 1 See my 'Anatomy of Vertebrates,' vol. i, p. 157, fig. 98, c, y; "grand trou palatin " of Cuvier, ' Ossemeiis Fossiles,' 4to, torn, v, pt. ii, p. 133, pi. vii, fig. 4 r; also " trou ovale assez grand," p. 259, pi. xvi, fig. 3, Varanus niloticus. 2 'Anat. of Vertebrates,' tom. cit., fig. 98, D, n. 3 lb., ib., fig. 98, D, m. * lb., ib., fig. 98, D, «. 5 lb., ib., fig. 98, c, n. ^ " La fosse nasale posterieure ;" described as " tres-grande," and marked with the letter s in fig. 4, plate vii, ' Ossemens Fossiles,' tom. cit. 1 ' Philosophical Transactions,' 1850, p. 521, pis. xl — xlii. * E. d'Alton and H. Burmeister, ' Ueber der Fossile Gavial von Boll in Wurtemburg,' &c., 8vo, plates in fol., Halle, 1854, in which the small hinder foramen is called "die vereiuigten Mundungen der Eusta- chischen Roiiren und gewisser Sinusse im Inuern der Ossis occipitis." 534 BRITISH FOSSIL REPTILES. Teleosaurus cadomensis, and with that called "grand vide palatine" or "trou palatine posterieur " by Eudes-Deslongchamps in Teleosaurus teiiqmralis [Felagosaurus typus) ; consequently with those which I have termed ' pterygo-maxillary ' and symbolised by the letter y in my ' Anatomy of Vertebrates/ loc. cit. The vacuities in the interspace between the two 'pterygo-maxillary' ones, bounded externally by the pterygoids and palatines, answer to the " fosse nasale posterieure " of Cuvier in Teleosaurus cadomensis} and to the " grande fosse pterygoidienne, qui limite en avant les arriere-narines " of Eudes- Deslongchamps in Teleosaurus temporalis f" consequently, also, to that which I have called ' interpterygoid ' and symbolised by the letter s in I(juana? It is plain that the palatal or posterior opening of the nasal passages offers no trustworthy homological character in Beptilia. It is anteriorly situated in Clielonia and Lacertilia, where those passages are vertical or nearly so; it is at the hindmost part of the bony palate in modern Crocodiles, and in a more advanced position, though still in the hinder half of the palate, in the mesozoic or ' amphicoelian ' Crocodiles. In each of these cases it has a distinct anatomical conformation. In Chelonia and most Lacertilia [Varanus, e.g.) its boundary includes parts of the vomer (13), palatine (20), and maxillary (21)/ in Iguana it includes, with the same bones, also a part of the premaxillary ; in Crocodilus proper it is wholly surrounded by the pterygoids ; in Teleosaurus the palatines combine with the pterygoids to complete it anteriorly. With regard to the opening answering to the hinder nostril in Teleosaurus, we find in Varanus that the halves of the divided vomer also contribute to boimd or form the pointed anterior prolongation of the vacuity,^ in the formation of which, as the pterygoids take the most constant and always the chief share in Lacertilia and Chelonia, and as the vacuity so bounded does not in these reptiles serve as the hinder or palatal opening of the nostrils, the term ' interpterygoid ' appeared to me to be most conveniently applicable. In the skull of the Varanus niloticus figured by Cuvier^ the presphenoid is prolonged so as to seem to divide the ' interpterygoid vacuity ' into a pair ; the point of the bone, however, in nature inclines upward, and does not join anteriorly either the palatine or vomerine bones. In the larger monitor {Varanus indicus) and in Iguana the presphenoid (PI. 60, figs. 6 and 7, 9) has a like relation to the interpterygoid vacuity (ib., «), but is not so far produced. Von Meyer, in his figure of the base of the skull of Belodon Kapffi"' represents the interpterygoid vacuity as divided by a longitudinal production, apparently, of the pterygoids, the lateral parts or plates of which form with the palatines the outer border 1 Tom. cit. ^ ' Notes Pal^ontologiques,' 8vo, 1S69, p. 146, pis. ix — xxiv, vi. 3 Op. cit., fig. 98, D. * Op. cit., fig. 98, B. 5 Cuvier, torn, cit., pi. xvi, fig. S, &c. &;c. '' lb., ib. 1 ' Palseontographica,' zehnter Baud, pi. xxxii, p. 227 (18C3). WEALDEN CROCODILES. 535 of such vacuity. The houiologues of the ' pterygo-maxillary vacuities ' are much reduced in size, are external and posterior to the ' interpterygoid ' openings, and are exclusively formed by the pterygoid and ectopterygoid, which, uniting externally to those openings as well as internally, are interposed between the maxillary and the ' pterygo-maxillary vacuity.' Von Meter, as usual, puts no figures or letters of reference upon the bones and orifices, nor refers thereto by means of such symbols in his text. Assuming, however, that the usually careful and accurate delineator of fossil specimens has correctly represented the palatal characters of his Bdodon Kapjji, it offers the nearest resemblance to the characters of that part of the skull of Hjjiaochampsa. In the proportion of this part of the skeleton of the Wealden Crocodile transmitted to me by Mr. Fox an extent of three inches of the hinder part of the bony palate is preserved (PL 60, fig. 25). In this extent four vacuities are more or less completely shown ; they are in two pairs. Of the medial pair (PI. CO, fig. 25, «, i) the left is entire, and the right lacks but a small part of its antcro-external border ; of the lateral pair (ib., y, y) the left wants a part of its antero-external border ; but of the right, only a small part of the inner and hinder border is preserved. The left pterygoid (24) is entire in its relations to the above vacuities, only the postero- lateral branch (answering to a, figs. 6 and 7) being broken off. The external branch (figs. 25, 6, 7, c), extends as usual, outward and forward to articulate with the ectopterygoid (ib., ib., 25) ; this abuts by its outer end against the hinder end of the maxillary (ib., ib., 21) and the contiguous part of the malar (ib., ib., 26), the fore part of the pterygoid (24) bounding with the ectopterygoid the hinder half of the pterygo-maxillary vacuity (y). The fore part of the pterygoid, continued along the inner border of that vacuity, articulates with the palatine (20), which, with the maxillary (21), completes the fore part of the boundary of y. We have thus the homologue of the 'great palatal opening ' of Cuvier,^ and of the ' posterior palatal opening ' of Eudes-Deslongchamps in the Teleosaurus cadomemis"" which answers to the vacuity y in the Lacerfians, figs. 6 and 7, PI. 60. The medial pair of openings (PI. 60, fig. 25, «, s), bounded externally by the palatines and pterygoids, and internally, as it seems, by medial processes of the same bones, answer to the 'fosse pterygoidienne' (vi) of Eudes-Deslongchamps in Teleosaurus temporalis^ and to the ' fosse nasale posterieure ' of Cuvier in the Teleosaurus cadomensis} But in H^laochawpsa this pterygoid fossa, or posterior nostril, is divided by so strong a longitudinal bony bar that the pair of vacuities might be taken at first sight to answer to the ' grands trous palatins ' in the Crooodilus rhombifer} 1 'Ossemen's Fossiles,' torn, cit., p. 133, pi. vii, fig. 4, r. " ' Notes Paleontologiques,' p. 139, pi. xi, fig. 3, vii. 3 lb., ib., pi. xii, fig. 10, vii. * Tom. cit., p. 133, pi. vii, fig. 4. 5 Marked ^ in fig. 2 of plate iii of the ' Ossemens Fossiles,' torn, cit., and marked y in 'Anat. of Vertebrates,' torn, cit., p. 15/, fig. 98, c. b6 536 BRITISH FOSSIL REPTILES. Such a determination is, however, incompatible with the coexistence of the vacuities (y, y) in Hi/lceochampsa and the concomitant recession of the maxillaries (21) from the outer boundaries of the openings («, «, PI. 60, fig. 25). We have thus another and most remarkable modification of the bony palate to add to those which have led that acute observer Eugene Eudes-Deslongchamps to remark, in reference to the extinct Crocodilia of the Caen Oolite and other Mesozoic localities, " chaque espece presente des modifications particulieres."^ But although it may be admitted that the pair of medial openings (fig. 25, *, «) answer to the single medial opening (Cuv., t. c., PI. VII, fig. 4, s) in Teleosaurus, it does not absolutely follow that they served in HylcBochampsa the office of palato-nares. It might be contended that the small sin2;le orifice at the mid-line of the extreme hind border of the bony palate (ib., e) fulfilled that function, as the similarly sized and situated orifice per- forms in recent Crocodilia. The still smaller orifice (fig. 23, «) placed at the hind surface of the skull might in that case be homologized with the median Eustachian outlet," and not with the vascular foramen,' in Crocodilm. It should, however, be borne in mind that the true hinder nostril in procoelian Crocodiles is divided by a pterygoid partition ; although Cuvier makes the absence of this division, or inconspicuousness of the septum, a character of the skull of procoelian Gavials.* Hi/laochampsa may show this partition in an exaggerated degree, and the orifices s, s, and not the orifice e, would be the hinder nostril. Whatever alternative may commend itself to competent Palaeontologists, the palatal characters which distinguish Hi/Iaochampsa from all other known Reptiles, recent or fossil, are unaffected. I have had no opportunity of studying the palatal characters in GoniophoHs, Suchosaurus, or any other Wealden Crocodile than the subject of the present Monograph. 1 Op. cit., p. 147. • " On the Communications between the Tympanum and Palate in the Crocodilia" ut siqjra, pi. xl, fig. 1, e. 3 lb., ib., V. * " La cloisou qui diviseles uarines ne se montre pas a leur ouverture posterieure." ' Oss. Foss,,' torn, cit., p. 106. WEALDEN PTERODACTYLES. 537 Order PTEBOSAUBIA. MESOZOIC PTERODACTYLES. Havtng in previous Sections on extinct volant Reptiles defined species (is Pterodadylus is the species which he calls longirostris. The chief generic character is the extreme length of the fourth digit of the fore-limb.^ The Pterodadylus longirostris, Cuv., is characterised, as the term implies, by long, slender, tapering jaws, armed along their anterior half by numerous long, slender, pointed, separated, and pretty equally distant teeth. In a general way the portions of mandible about to be described repeat these characters. The mandibular teeth appear to have been about the same in number. Nineteen are reckoned by Cuvier to have occupied the deutigerous part of each mandi- 1 " Un genre de Sauriens, caracteris6 par I'excessif allongement du quatrifeme doigt de devant, auquel nous avons donne le nom de Pterodactyle." — ' Ossemens Fossiles,' torn, v, pt. ii, 4to, 1S24, p. 358. WEALDEN PTERODACTYLES. 539 bular ramus in the type-species ;^ and about as many appear to have armed the same part as Pterodacfi/Ius saffittirosfris. There is as little trace of condyloid or coronoid processes in the present Wealden Pterodactyle as in the Oolitic loiigirostral species.^ The great and rapid addition to the number of extinct flying Reptiles having the characters of Cuvier's genus Pterodacti/lus has led to its subdivision into several groups or subgenera. If length of tail with number of caudal vertebrae be accepted as a generic character, those that have that appendage long, and supported by more than thirteen vertebra?, must go to a different group from that including the Pter. longiroslris? It is plain that Pter. sagittirostris has not the generic dental characters of Dimor- pJiodon. It is probable that the symphysial modification which supports the generic name Pampliorhynchis was not present. If the skull of the long- and sharp-jawed Wealden species, or of that from the Upper Chalk which I have described under the name of compressirostris, should ultimately be found to offer marked differences in the forms, sizes, and proportions of the narial, orbital, and intermediate vacuities, from those figured by Cuvier in pi. xxiii (op. cit.), it may be deemed requisite to refer them to a distinct pterosaurian group. At present it appears to be convenient to place the sagittirostral and compressirostral with the typal species in the Cuvierian genus Pterodactylus. The most striking characteristic difference from that species is the vastly superior size of the seemingly allied Flying Dragons from the British Chalk and Wealden. In the restoration of the skull of Plerodadylm compressirostris (pp. 234 — 252, Pis. 1 — 5) I ventured to assign to the mandible a length of 14 inches 9 lines {Pter., PI. 1, fig. 5). This species was represented by two portions of the upper jaw from the Middle Chalk of Kent, the longest portion being 4 inches in length. Of the nearly allied species, represented by three portions of the lower jaw, discovered by Samuel H. Beckles, Esq., F.R.S., F.G.S., in the Hastings series of the Wealden Formation, west of St. Leonard's-on-Sea, the restoration figured of half the natural size in PI. 18, fig. 8, gives a mandible of between 14 and 15 inches in length, and this on the most moderate estimate of the length of the symphysis. In a sketch of a restoration of the jaw, sent to me with the fossils by Mr. Beckles, the length of the symphysis, which he assigns on the basis or analogy of that in CoUins's or Cuvier's Plerodadyhm hngirostris, gives a total length of 18 inches to the mandible. The parts obtained by Mr. Beckles are of one and the same lower jaw ; and, as an extent of above 2 inches of both rami are maintained by a portion of matrix (ib. ib., 1 Cuvier, torn, cit., p. 3G4. 2 II)., ib. 3 In which Cuvier describes the tail as " trcs-courte, trfes-grele, et Ton n'y compte que iloiize ou treize vert^bres." — Tom. cit., p. 368. 540 BRITISH FOSSIL REPTILES. fig. 8, m) in their natural relative position, the angle of convergence is shown ; and this affords a ground for estimating the length of each ramus from the articular surface to the hind part or border of the symphysis at 13 inches, the extent beyond remaining conjectural. The specimen includes a portion of the left ramus, 9 inches 8 lines in length (of which the anterior 7 inches are given in PI. 18, fig. 1), and two portions of the right ramus, of which the dentary part measures 5 inches (ib., fig. 2) in length, the articular part 2 inches (ib., fig. 5). The portion of the left ramus includes the dentary element (ib., fig. 1, and fig. 4, 32) with the anterior part of the splenial element (fig. 4, 3i). The dentary includes ten of the hinder sockets (ib., fig. 1, i, 2, 3, 4, 0), of which the five foremost (ib., 6, 7, 8, 9, lo) retain more or less of their teeth. As the number of these which may have been present in the fore part of the jaw is unknown, I count those which are preserved from the hind end of the series forwards. Prolonging the alveolar border according to a moderate estimate of the symphysis, and supposing the teeth to maintain the same intervals, about eighteen may be assigned to each ramus. The border of the hindmost socket (fig. 1, 1) is not prominent as in the rest, and there is room for doubt whether the oval vacuity which indicates the hindmost tooth really contained one. There is none, however, with regard to the next socket (ib., 2), for tiiis, like the antecedent ones, rises at its outlet above the level of the surrounding part of the bone. It projects from the onter part of the thick, transversely convex, upper border of the dentary, and the course of the cavity shows that the tooth must have inclined some- what outward as well as forward from the perpendicular. The long diameter of the outlet is in the axis of the jaw, and is 1^ lines (3 m.m.). The short or transverse diameter is 1 line (2 m.m.). The interval between this socket and the one marked 3 is 5 lines (10 m.m.). The prominent outlet of the socket 3 gives 5 m.m. in long diameter and 3 m.m. in short diameter ; these dimensions with that of the interval are repeated to the socket 6, which retains its tooth. The exserted crown of this is 5 lines (10 m.m.) in length; it is conical, acute, gently curved, with the convexity outward and forward. The apex of the next tooth in advance is broken off", but the basal half is better cleared out of the matrix, giving an antero-posterior breadth of its issue from the socket of 5 m.m. The teeth in the sockets 8 and 9 are better preserved, and show well the characters of the mandibular ones in the present species. As in Pterodadylus longirostris, the teeth of Tter. sagittirosiris are subsimilar, divided by nearly equal intervals, these being somewhat wider than in Pter. longirostris} rela- tively shorter than in Ptcr. crassirostris," and more resembling in disposition the indica- 1 Pterosaurin, P\. l,fig. 1. 2 lb., lb., figs. 2 and 3. WEALDEN PTERODACTYLES. 541 tions given by the sockets in the portion of npper jaw of the Cretaceous Pterodacfylus compressirostris. The dentary bone supporting the above-numbered teeth is slender and subcompressed ; its depth is given in figs. 1, 2, and 4 (nat. size) ; its thickness is shown in fig. 3. This is the same at both upper and lower borders, which are similarly rounded off"; it is less half way down, owing to the concavity, vertically, of the inner surface of the ramus (ib., fig. 4). The outer surface (fig. 1) is nearly flat ; it is traversed lengthwise by a linear impression, which is 5 m.m. below the upper border at the hind end of the pro- portion of the ramus figured in fig. 1, and is 7 to 8 m.m. below the outlets of the sockets of the teeth 7 — 9. This linear impression does not indicate a suture. The ramus slightly increases in thickness, with a gain of convexity externally and a deeper concavity internally (both being in the vertical direction), at the fractured end (ib., fig. 1, 32) nearest the symphysis. At the opi)osite end the angular element (ib., fig. 4, 30) forms the inwardly prominent lower border ; the line between which and the thin flat splenial forms (ib., ib., 31) is clearly sutural. The portion of the right dentary preserved (PI. II, figs. 2, 3) answers to that containing the sockets of the teeth numbered 2 — 9 in fig. 1. There is the same obscurity or lack of demonstration of a socket or tooth behind the socket 2. The bases of the teeth are preserved in the sockets (numbered 2 — 6), and partly project from the sockets 2 and 3, but the sockets 7, S, 9, are vacant. The articular portion of the right ramus (figs. .5, 6, 7) lacks the prominent, backwardly directed, end of the subangular (30)- The articular concavity (fig. 6, a) is transversely extended, chiefly by the production of its inner wall (ib., h) ; its npper boundary is sinuous by a backward production of its mid part ; the upper surface in advance of the cavity is smooth and gently convex across ; it narrows to the ordinary thickness of the ramus about an inch and a half in advance of the articulation. In this extent it shows no trace of a coronoid rising. The inner surface is impressed with a deep longitudinal cavity (ib., fig. 7, c). According to the usual proportions of the upper and lower jaws of Pterodactyles, the premaxillary of the present species must have been twice, or nearly twice, the depth or vertical diameter of the portion of that bone of Pterodadylus compressirostris (figured in Pter., PI. 3, fig. 8). Both upper and lower jaws of PterodactyJus sayittirostris must have been broader, less compressed, than in the Cretaceous Ptcr. compressirostris. The value of a symphysis mandibuli, with its natural anterior termination, like that of the Gault species {Pterodactylus Daviesii), is its demonstration of a character determinative of the genus of Pterosaurian. Were it produced into a slender-pointed edentulous style, or ' rostrum,' it would lead to a reference of the species to Von Meyer's genus Rampho- rhyncJius and Family ' Sttdidirostres.'^ The opposite extreme is shown bj' the thick 1 ' Palaeontographica,' Heft i, 4to, 1846. 542 BRITISH FOSSIL REPTILES. obtusely tenninated snout, as if it had been cut short, giving the character of the Ptero- saurian family Truncirostres} The species of this family which have the foremost pair of teeth projecting forward in the upper jaw from the truncate surface at a higher level than the alveolar border form the genus Cohhorhynchus? B. — CololorJiyncJms cJavirostris, Owen [Pterosauria, Plate 19, figs. 1 — 4). In two species of these large Pterodactyles from the Cretaceous series, viz. Colobo- rliynchm Cuvieri, from the Middle Chalk of Kent,^ and Colohorhynclms Sedgwickii,^ from the Upper Greensand of Cambridge, the anterior pair of teeth of the upper jaw project, as in the present species, from the fore part or end of the premaxillary, and are dii-ected forward with a slight downward curve. In a still larger species {Criorhi/nchiis simug"), from the Upper Greensand of Cambridge, the foremost pair of teeth project from the under surface of the fore end of the premaxillary, and are directed downward like the following teeth. The fore end of the premaxillary was fortunately entire, showing a flattened or feebly concave tract corre- sponding to the part bored by the anterior alveoli in Colohorhynchus. Some reserve may be prudently entertained as to whether a pair of teeth so anomalously located as iu Colohorhynchus might not be shed without replacement by successors ; and the geiuis Criorhynchiis is to be accepted with this reserve, which future discoveries may dissipate. The manifestation by a ' truncirostral ' Pterodactyle of the Wealden, and by another from the 'Greensand,' of the produced and unopposed pair of teeth from the front surface of the muzzle, have dissipated the doubts as to its accidental and individual character which legitimately attached to the first specimen, from the Chalk, in which it was observed. Colohorhynchus clavirosfris is, at present, represented by the fore part of the upper jaw of a Pterodactyle {Pter., PI. 19, figs. 1 — 4) from the Wealden, of equal size with Crio- rhynchus simus, from the Upper Greensand, but in which the small anterior pair of premaxillary teeth project from the front surface of the bone, and at a greater elevation above the palate and the sockets of the second pair, than in Colohorhynchus Cuvieri or Coloh. Sedywickii. The flattened fore part of the premaxillary (ib., flg. 2) is broader and of less height in Colohorhynchus clavirosfris before the narrow upper surface [g) begins to slope backward to the upper contour of the cranium. The anterior median depression (h) is shorter 1 Mihi (Truncus, cut short). 2 KnXopus, stunted ; pvyx^os, snout. ^ Pterosauria, PI. 3, figs. 1 — 7. •• lb., PI. 7, figs. 1, a—(i. * Pterosauria, PI. 11, figs. 1—5. WEALDEN PTERODACTYLES. 543 vertically and deeper in Cohb. clavirostris, where it is below the alveoli of the teetli ( «, «). The convexities (/, /) on each side of this depression are the fore parts of the sockets of the second pair of teeth, not of the first pair, as in Criorhi/nchus shims {Pter., PI. 11, fig. 3, a). The sides of the fore part of the premaxillary in Coloborhyiichus clavirostris converge, with a slight vertical concavity, to the narrow but obtuse upper border of the skull; the same sides also converge as they recede in a slighter degree, but so that the breadth of the upper jaw behind the sixth pairs of teeth (ib., PI. 19, figs. 1 and 4,/,/) is less than two thirds the breadth behind the second pair of teeth (ib. ib., b, b, fig. 4), whence the name clavirostris (' club-snout ') proposed for the present formidable species of Wcalden Pterodactyle. The fore part of the bony palate, between the teeth of the second pair (ilj., ib., fig. 4, b,h), is transversely quadrate and flat (ib. ib., fig. 4, k). Behind this tract the mid third only of the palate retains its level, the two side thirds subsiding (as it seems when looked down upon) into shallow channels, which expand and arc continued into the slope rising to the sockets of the fifth («) and sixth (/) teeth, leaving the prominent narrow raid tract to represent, as it were, the bony palate ; this part has projected below the level shown between the fourth pair of teeth, behind which the thin compact wall is broken away, exposing the widely cellular structure. A similar abrasion affects the upper border of the skull (beyond i, fig. 1, PI. 19). The first or anterior pair of teeth (ib., «, «) bears the same relations of size to the second (5) and third («) pairs as in Criorhi/nchus sivms, and may be homologous with the first pair in that species (P/er., PI. 11, fig. 1, a) though differing so much in position and direction. In the present specimen of Colohorhynchns clavirostris the crown of the first, as of the second, tooth is broken off at the outlet of the socket. The shape of this outlet is a full ellipse (PI. 19, fig. 2, a, a) ; the long diameter, of 8 m.m., is vertical ; the short diameter, of 6^ m.m., is transverse. The size and shape of the five following teeth are shown in fig. 1 ; for, as is common in Pterodactyles, the sockets open obliquely upon the outer part of the alveolar border, and in the present species with a nearer approach to verticality than is usual (compare PI. 19, fig. 1, with PI. 11, fig. 1. The present unique evidence of one of the most extraordinary of the extinct order of volant Beptilia was discovered by S. H. Beckles, Esq., F.R.S., in the Hastings Series of the Wealden. The humerus of the Ftcrodactylus sylvestris, Ow.,' from the Tilgate Wealden, though larger than those next to be described, must have belonged to a smaller kind of Pterosaur than that represented by Mr. Beckles's fossil. ' 'Quarterly Journal of the Geological Society of London,' No. C, 184G, p. !)!), figs. 5, 6, 7. 6 b 544 BRITISH FOSSIL REPTILES. § 3. Pterosatjria of the Kimmeridge Clay. A. — Fierodactylus Manselii, Owen {Pterosauria, PI. 19, tigs. 10, 11, 12, 20, 21). Figures 10 and 11 of PI. 19 show front (thenal) and back (anconal) views of a mutilated proximal end of the left humerus of this rather small species of Pterodactyle. The reniform articular surface of the head of the humerus (fig. 12, o) is somewhat less extended transversely in proportion to its breadth than in a similarly sized species from the Lias {Pterodact'i/lus Marderi, ib., fig. 9) ; its anconal convex border has a bolder curve. There is no indication of a pneumatic orifice on this surface, as in Birds. The pectoral process {b, figs. 10 and 11) stand out more abruptly from a less extended base (compare with b, figs. 7 and 8, PI. 19). The proximal end of the first phalanx of the fourth or wing-finger, which is the subject of figs. 20, 21, 21^ corresponds in size with the portions of humerus above desci-ibed, near which they were discovered. The olecranoid process (ib., fig. 21, c) led observers of the first discovered specimens of this eminently pterosaurian bone to regard it as an ulna. Upon this process is extended part of both the outer and inner concave articular surfaces, so placed as to resemble the two divisions of the ' greater sigmoid cavity ' in the human ulna, the curve and depth of which surfaces is thus augmented, and therewith the security of the flexible joint on which the chief movements of the bat-like vnng take place. The outer surface, shown in fig. 20, is of less extent, in long diameter, than the inner articulation (ib., fig. 21, a) ; a larger proportion of it is supported by the olecranoid process ; and it is better defined along the margin next the longer concavity (a). Nevertheless, the smoothness of the surface of the ridge, dividing the concave articulations, suggests that they combined to fonn a single synovial hinge-joint or ' ginglymus,' limiting the movements of the bones so articulated to one plane, and combining freedom and extent of motion in that plane with great strength of joint. The summit of the olecranoid process in the present specimen shows a rough flattened surface, not a fracture, suggestive of the contact of a sesamoid, probably lodged in the tendon inserted into the phalanx (ib., fig. 2P). B.—Pterodadylus PleydelUi, Owen {Pterosauria, Plate 19, figs. 15, 16, 22, 23, 23==). The portion of the fossil skeleton of the small species of Kimmeridgian Pterodactyle here figured is the distal half of the left humerus. It shows the generic obliquity and superiority of size of the articular convexity for the head of the radius (ib., fig. 15, a,) ; that for the ulna has suffered fracture, and part of it is lost with the ulnar tuberous ridge ; KIMMERIDGIAN PTERODACTYLES. 545 but sufficient remains to show its liemispheroid form, and the mere chink dividing it from the radial condyle instead of the groove which is here seen in Birds. The flexor (?) ridge, leading to the broken tuberosity, extends more forward than in Pterodacti/lus Duncani (ib., fig. 13), and contributes to a deeper concavity above the condyles on the thenal aspect of the distal expansion of the humerus. The transverse ridge behind the condyles is confluent therewith at its extremities, the defining groove not being developed (ib. ib., 16')- The broad shallow canal for the ' triceps' tendon marks the anconal surface of this expansion (ib., fig. 16). To the same species of Pterodactyle may probably belong the proximal end of the smaller example of the first phalanx of the fourth or wing-finger, of which I have given two views in Plate 19, figs. 22, 23, and 23^ to contrast with those of the same bone and part of Pterodactylus Manselii. The olecranoid process in Pterodadylus Pleydellii is relatively longer and more incurved ; its apex is not truncate ; it is more compressed ; has a smaller and lower posterior tuberosity, and a smaller basal tuberosity. The longer concave articulation is similarly extended upon the anterior angle. From the tuberosity at the corresponding or lower end of the shorter concavity a ridge is continued down the bone, giving a triedral form to the shaft as far as it is preserved in this and the previously described specimen (figs. 20, 21). The bony wall of the shaft is thin and compact, the air-cavity large, and in one specimen occupied by crystallised calcite. The two narrower sides are concave or flat transversely ; the broader side is gently convex ; it shows, in both species (figs. 21, 23), a longitudinal linear impression, which may indicate a confluent rudiment of a fifth digit. To the above-described, well-defined, trochlear or ginglymoid joint were adapted the two obliquely disposed condyles of the distal end of the metacarpal of the fourth or wing-finger. I have pleasure in contributing this mite of testimony to the unremitting attention to the fossil evidences of Kimmeridgian Vertebrates, discovered from time to time on his estates by John C. Mansel-Pleydell, Esq., F.G.S., of Longthorns, Blandford, and to the wise liberality by which they have uniformly been deposited in the National Collection, where inferences and conclusions from their study can be tested by Palseontologists. C. — Pterodadylus, sp. incert. Two specimens of the carjjal bone, provisionally referred in a preceding Section to a Pterosaurian ' midforme' are figured in Plate 19, figs. 24 — 27. They were both obtained from the " Kimmeridge Clay," at Weymouth, Dorsetshire. -t The distal surface of the smaller specimen is given in figure 24 ; they show the larger concavity (a), and the smaller one (6), adapted to the two proximal condyles of the 546 BRITISH FOSSIL REPTILES. metacarpal of the wing-fiiiger. The thenal border of the bone is the thinnest, and is produced at each end into a short |)rocess ; the anconal border of the bone is thicker, especially where it supports the smaller and outer articular metacarpal concavity. The proximal surface (ib., fig. 25) is also divided into two principal articulations, but the larger one (c) is subdivided into a concave and a flattened facet. The smaller concave surface (rf) is next the outer and thickest end of the bone. The subject of figs. 26 and 27 is the homologous bone, and from the forelimb of the same side, but it shows modifications that plainly bespeak its having come from a distinct species of Pterodactyle. The outer subhemispheric concavity of the proximal surface (ib., fig. 27 d) is relatively larger, as is likewise the flat facet at the inner part of the larger surface (c). The two condylar concavities (« and i) on the distal facet are more equal than in the larger unciforme. Both bones exemplify the definite, well-marked, or finished character of the articular surfaces which characterise the l)ones, especially those of the wing, of the volant Reptile. I would still be understood to be guided by considerations, not beyond probability, in referring this well-marked bone to the distal row of the carpal series ; for I have not yet had the opportunity of studying a Pterosaurian carpus or tarsus in so well-preserved and undisturbed a condition as would enable me, with certainty, to determine the homologies of its constituent bones. § 4. Pterosauria of the Great Oolite. A. — Pterodaclylus Kiddii, Owen {Pterosauria, Plate 19, fig. 17). The first phalanx of the wing-tinger (fig. 17), referable to this species is somewhat stouter, but about one eighth shorter, than that bone in the Pterodacfi/las saevicits, Quensted,^ from the Lithographic Slate of Wirtemberg. It indicates a species with a more powerful, though, perhaps, less elongate, wing. The groove for the flexor tendon of the fourth digit, bounded Ijy the prominent thenal extensions of the two articular grooves, is well marked. The extensor process (ib., c) has a relatively longer basis than in the Kimmeridge specimens. A rough groove or Imear depression beginning about an inch beyond the proximal articulation, and extending as far down the fore or thenal surface of the shaft of the bone, indicates the extensive attachment or insertion of that tendon. The shaft is subtriedral, the anconal side being the broadest; it becomes flattened towards the distal end, which expands unequally towards the ulnar side, and ^ " Ueber Pterodactylas suevicus," 4to, Tubingen, 1855. OOLITIC PTERODACTYLES. 547 affords an oblong, moderately developed, concavo-convex surface for the second phalanx of the wing-finger. This bone, from the Stonesficld Oolite, is sHghtlv crushed. B. — Pterodaciylus Duncani, Owen (ib., Plate 19, fig. 18). The first phalanx of the vifing-finger, referred to the alwve species, is of the left wing, and is imbedded with the anconal surface exposed in a slab of Stonesfield Slate. It is from a larger Pterodactyle than the preceding. The extensor process is thicker but springs from a less extended base, relatively to the length of the bone. C. — Pterodacti/lus Aclandi, Owen (ib., Plate 19, fig. 19^ This species is represented by a still larger specimen of the characteristic wing-bone (fig. 19) in Pterosauria. The olecranoid process (e) is shorter in proportion to the breadth and thickness of the proximal end, and the free termination of the pricess is more definitely marked by a smooth and shallow groove, over which it seems that the tendon of the " extensor alfe " may have glided before its insertion into the strong rough process («"). The second phalanx of the wing-finger (Plate 19, fig. 28) may have belonged to a Pterodactyle of the same species or size as the proximal phalanx of the Fferodnctijlan Kiddii. On this hypothesis its proportion of length would resemble that in the Pterodaciylus {Dimorphodoii) macronyw {Pterosauria, Plate 17). The distal end of the present " Stonesfield " bone becomes triedral by the rise of a ridge from the thenal aspect, extending longitudinally, and enlarging, to near the outer end of the distal oblong articular surface ; this is more convex transversely than is the proximal surface. The longitudinal ridge in question afforded insertion to a strong fiexor tendon. § 5. Pterosauria from the Lias. I have not yet received any evidence of a Pterosaurian froui the " Alum Shales " of Whitby, or any other member of the Upper Lias of our North-Eastern Coast, which represents, by the sum of its palajontological evidence, the " Posidonomyen-Schiefer " of Bavaria. There, however, in the locality of Banz, have been discovered instructive 548 BRITISH FOSSIL REPTILES. remains of a Pterosaurian, which Professor Quensted refers to my Lower-Liassic genus under the name of Dimorphodon Banthensis. The specimen about to be described, from the Lower Lias of Lyme Regis, is insufhcient to give subgeneric characters, and is provisionally registered under the wider generic name. A. — Pterodactylus Marderi, Owen {Pterosauria, Plate 19, figs. 7, 8, 9). Of this species is here figured the upper or proximal half of the right humerus (figs. 7 and 8). The head or articular surface (fig. 9) is a narrow, bent, or reniform convexity, with the concave margin toward the thenal side of the bone (fig. 7). The inner and more obtuse end of the articulation, with the tuberosity of that side, is broken away ; the outer, narrower, and, in this species, pointed end is lost upon the ridge or upper border of the "pectoral process" [b). The expanded part of the shaft, beyond the articulation, is concave transversely' on the thenal aspect (fig. 7), convex on the opposite or anconal side (fig. 8), which shows, as usual, no trace of the fossa and foramen characterising that part of the humerus in Birds of flight. The antero-posterior thickness of this part of the bone is less than that of the contracted cylindrical part of the shaft lower down, the section of which is circular. This humerus, besides being smaller than that of Dimorphodo7i macronyx,^ has a more straight and slender shaft, which in transverse section is more nearly cylindrical. B. — Dimorphodon macronyx, Owen {Pterosaiiria, Plate 19, figs. 13, 14). The other Pterosaurian fossil, obtained by Mr. Marder, from the same foi'mation and locality, might well, by its superior size, and more ellipsoid section of the shaft , have formed part of the first long-bone of the wing of the species restored in Pter., Plate 17. The articular surfaces of the humerus in both specimens of this Pterosaurian figured (ib., Plates 15, 16, 53, 53^) were too much crushed and mutilated for profitable descrip- tion. The present specimen shows instructively the distal articulation. The surface for the radius presents one uniform convexity, a, oblong in shape, and obliquely disposed, extending from the lower part of the radial ridge (c), upward, forward, and ulnad; it is almost wholly developed from the thenal aspect (fig. 13), only the lower border of the convexity being visible from the anconal side (at a, fig. 14). It is longer and more prominent than the ulnar convexity or condyle. This (ib., j) is subhemisphei-ical ; 1 ' Monograph of Liassic Pterosauria,' Pal. vol. for year 1869, pi. xviii, figs. .53, 53 a. LIASSIC PTERODACTYLES. 549 its diameter equals the shorter diameter of the radial condyle. The intercondylar fissure is a mere cleft; and tuberous ridges, extending from the condyles, augment the breadth of the distal end of the humerus. The outer or radial one (c) is produced forward, bounding there, and in part forming the anterior concavity. The inner or ulnar ridge (d) is more distally placed, projecting to a lower level than the condyle (6) ; it is continued upwards with a convex curve, but is not pi'oduced forward like the radial ridge. Both ridges are connected l)y a narrower one, extending transversely behind the two condyles, from which it is divided by a fossa (fig. d, c). There is a broad and shallow depression on the back part of the distal end of the humerus for a large " triceps " tendon : there is no ancoual depression. In my description of the articular end of a long-bone of a Pterosaur (figured in Pter., PI. 10, figs. 1, 2, 3), I remarked that, " guided by considerations of size, the fragment might form the opposite end of the bone, indicated by the articular ends (PI. 9, figs. 7 and 8), which were referred to the head of the humerus. But I proceeded to remark, ' I am not acquainted with the precise configm-ation of the distal end of the humerus in any Ptero- dactyle. From general analogy, however, one should scarcely be prepared to find so feeble an indication of divisions into condyles, an absence of a general convexity, and a presence of a well-defined concavity in one condyle, and as well defined a flattened or feebly concave facet in the other condyle, of the distal end of a humerus." The demonstration of the true characters of this end of the humerus, given in Plate 19, figs. 13, 14, and d, c, have justified the refusal to regard the articular end of the bone of the large Cretaceous Pterosaur as part of the humerus. There is no part of the skeleton of the Bird that more resembles the answerable bone in a Pterosaur than the humerus. But the following, with other differences pointed out in previous Sections of this work, are well marked and, as far as my observation goes, constant. The pectoral process from the radial side of the proximal expansion of the humerus is relatively longer from base to apex, with a broader, more truncate, or less pointed termi- nation in the flying Reptile : it usually forms a low angle in the Bird. At the distal end of the humerus of the Bird the oblong radial condyle is usually more pointed anteriorly ; the ulnar one is more extended transversely, and the inter- condylar cleft is widened to a groove. The outer and inner ridges are not connected by a post-condylar transverse ridge. The olecranial surface is more depressed, and the tricipital tendinal grooves are better marked ; but the transverse expansion of the distal end is less in proportion to the breadth of the shaft of the humerus in the Bird than in the Pterosaur. Other differences in the Pterosaui'ian humerus, notwithstanding its adaptive develop- ment to flight, showing departure from the avian, and approach to the crocodilian, type have been previously pointed out. The largest vertebra in a swan, an albatross, a condor, or a lammergeyer, scarcely 550 BRITISH FOSSIL REPTILES. equals the largest known vertebra of an unquestionable Pterodactyle (corap. Pter., PL S, figs. 7, 11, and Pter., PI. 12, figs. 1 and '2). But tiiese pterosaurian vertebrae are from the region of the neck, and served to sustain a head which, from the proportions of that in Dimorphodon mucronyx {Pter., PL 17), and most probably also in CriorhyndiuH >iiiuu>i {Pter., PL 11, figs. 1 — 3) and Coloborhi/nchtis dmirostris {Pter., PL 19, figs. 1 — 4), was considerably larger in relation to the trunk and wings than in the largest examples of ])irds capable of flight. We may with I'eason, therefore, assume that the total magnitude or weight capable of being raised and sustained in air was not greater in the cold-blooded, naked, volant reptile than in the warm-blooded, feathered bird. The instruments of flight were, however, relatively longer in Pterosauria. In illustration of this pi-oposition 1 subjoin admeasurements of the chief parts of the skeleton in the best-restored specimen of a flying dragon, viz. that of Di)norphodon macronyx. cngth of head neck trunk tail femur tibia foot humerus antibrachium „ fourth or wing-finger ,, bones of a wing, from head of humerus to end of wing-finger Breadth of trunk between articular ends of right and left scapulae Span of outstretched wings, including breadth of trunk ft. in. lines n 8 0 0 3 G 0 6 8 1 9 0 0 3 6 0 5 0 0 3 6 0 3 7 0 4 3 1 5 10 s 2 i. « 3 fi t 0 t 3 0 t 4 10 0 Now, the largest neck-vertebra of Criorhynclms simus {Pter., PL 12, fig. 1) is rather more than two such vertebra? in Bimorpliodon macrony.v. Other things being equal, therefore, we may assign to Criorhynchus simus a span of outstretched wing of nine or ten feet. Birds, like the cassowary, ostrich, and moa, which have attained a bulk superior to that of the albatross, obey the law of gravitation, and lose the faculty of soaring above the surface of the earth. We may with reason, therefore, conclude that we have in Criorhynclms simus and Coloborhynchus davirostris the extremes of magnitude in the volant Reptilia. KIMMERIDGIAN DINOSAURS. 551 Order. DINOSAJJRIA. Genus — Bothriospondylus. Species — Bothriospondi/Ius suffossus, Owen (' Dinosauria,' Plates 61 — 63). The subjects of the present section might be deemed to have more interest for the Anatomist, by reason of the singular modilication of vertebral structure which they exhibit, than for the Palseontologist, as affording evidence of an additional specific or generic form to the already known numerous extinct Saurian Re[)tiles of the Mesozoic formations. The yertebra, for example (Pi. 61), which, by the presence of pre-(p) and post-(;j') parapophyses with expanded rough syndesmotic articular surfaces, is a sacral one of the Dinosaurian type, presents so singular a degree of depression, or horizontal flattening, of the centrum, as to suggest artificial and posthumous pressure as its cause ; and it is true that some of the lumbar or dorsal vertebrae therewith associated show unmistakable marks of such violence. But, as the side view of the present vertebra, ib., fig. 4, shows, at c, e', there is no such evidence of fracture of the peripheral compact layer of the bone with distortion, causing more or less departure from symmetry in the centrum, as accom- panies every instance of crushing out of shape in the present series of vertebrae (compare figs. 1 and 4, e.g., with fig. 5, in PI. 63). There is also evidence of a transitional assumption of the depressed form of centrum, in another sacral one (PI. 62, figs. 4, 5, 6), which, from having the syndesmosal surface on a single parapophysis {p) on each side, was part of a terminal vertebra of the sacral series. Four views (PI. 61, figs. 1 — 4) are given of the vertebral centrum M'hich appears to correspond vpith that marked 5 in ' Dinosauria,' PL 38. In the sacrum of the Hglceo- saurus there figured the vertebra No. 5 offers the greatest breadth and flattening of the under surface, which is also notable for the absence of the longitudinal ridges, parial or single, marking the under surface of the succeeding or preceding centrums. The under surface of the present sacral (PI. 61, fig. 1) is less accentuated than the Hylseosaurian one compared with it, and the venous canals are relatively smaller than in it : they also issue irregvdarly, instead of being symmetrically disposed as are the large pair in Ilylcsomurus. The under surface, as shown in the side view (ib., fig. 4, c), is feebly undulate lengthwise, the concave curves being mainly due to the expansion of the articular ends (ib., fig. 3). The under surface of the centrum is as moderately convex across, becoming flat near the free portions of the side of the centrum (ib., figs. 1, 2, 4, c'), and very slightly concave th.'ough the distal expansion of the parapophyses (ib., fig. 1, pp'). But the distinctive peculiarity of the present centrum from the known sacral ones lb 552 BRITISH FOSSIL REPTILES. of other Dinosaurs is the continuation of the free surface, over the side of the centrum (fig. 2, c') between the origins of the parapophyses {p, p') into a long, low and deep cavity (ib., figs. 2 and 4,/,/), overarched by the part of the side of the centrum supporting the neurapophyses (ib., figs. 2 and 4, np), which appear to have been confluent therewith, and to have been removed, with the rest of the neural arch, by fracture. This displacement exposes the floor of the neural canal (ib., fig. 2, «)> the breadth of which indicates a sacral enlargement of the myelon, and consequent development of the pair of limbs deriving their nerve-supply therefrom. The issue of a large pair of these nerves is indicated by the continuation of the neural surface outward at o, o, behind tlie broken bases of the neurapophyses {np) whicli have not extended so near to the end d, as to the opposite end, a, of the centrum.* Owing to the abrupt continuation of the lateral surface of the centrum into the depressions,/,/, characteristic of the present genus of Dinosaur, the free surface of the side of the centrum presents the form of a smoothly rounded, longitudinally concave, ridge (ib., figs. 2 &4, c'). It may be that the approximation of the roof and tloor of the lateral fossae has been increased by pressure. Yet the horizontal surface, y; could hardly have been bent from the vertical side-surface of the centrum, c', without some fracture of the compact outer layer of bone ; and, farther, if the flat form of the centrum had been due to such cause, the seemingly natural undulate configuration of the under surface, with its expansion at the two ends, would not have been unobliterated and unmodified in the degree exhibited by the fossil specimen. The outward production of the fore part of each side of the centrum (fore parapo- physis, p) has a longitudinal extent of an inch and a half, a vertical one at the articular surface of seven to eight lines. The surface is rough and slightly concave ; it may have contributed less than one half of the vertical extent of the sacro-iliac joint at this part. The fractured or roughened surface above this parapophysis indicates a corresponding diapophysial production of the neural arch for extension of the joint. Longitudinally the pre-parapophysial surface slightly inclines toward the front articular siirface, a, of the centrum. This surfiice is flat, very rough, and irregular, indicative of having been broken away from a partial confluence with the opposed surface of a contiguous sacral clement ; the lower part showing here and there a smoothness as of the original free sur- face of this end of the centrum. Above this surface large unossified vacuities are shown in the cancellous texture of the bone. The vertical diameter of the articular end of the centrum is one inch three lines ; the transverse diameter is three inches six lines. The lower margin is not entire, but has been eroded or worn away for an equable extent of about four lines ; along the transverse curve it has not been broken ofl' that end of the centrum. The post-parapophyses (p') are shorter antero-posteriorly, thicker vertically ; and the articular surfaces of tliis pair converge at a greater angle to the posterior surface, b, of the * Compare the figure of the sacral vertebra of lyiuinoilun, PI. 12, fig. 4, o, o, p, 288. KIMMERIDGIAN DINOSAURS. 553 centrum (ib., fig. 3) than in the anterior pair. The iij)per rough or fractured surface (fig. 3, n, n) may have coalesced with the fore part of the neural arch of the succeeding sacral vertebra, if such arch, as in other Dinosaurs, has crossed the interval between its own centrum and that of the next sacral. A greater extent of the hinder surface of the present centrum (fig. 3, c), at its lower half, shows freedom from anchylosis than on the fore surface. The Reptile indicated by the portion of the vertebra above described is referable by the characters Avhich such fossil shows to the Dinosaurian group. In the Crocodiiia the confluent outstanding parts of centrum and neurapophyses, affording attachment to the pelvic arch, are single on each side of the sacral vertebra, and the neural arch retains its normal position in connection with its centrum.* In MegaJosaurus the lateral abutments for iliac attachments have diapophysial bases, or spring exclusively from the neural arch.f Pre- and post-parapophyses are indi- cated in the sacral vertebrae of Iguanodon by the slightly produced or outstanding parts of the side of the centrum articulating with the two displaced neural arches (compare figs. 1 and 2 of PL 61, with figs. 3 and 4, ' Dinosauria,' PI. 12). In the sacral vertebra of the Hglaosaurifs, above referred to, the duplex parapophyses have about the same develop- ment as in BothriosponJglus. Not any of these earlier described Dinosauria have the flattened form and lateral cavities characteristic of the sacral vertebra; of the present genus ; whence I infer, from the different relative expanse of the neural canal, as shown in the figures of the vertebrae above compared, that the hind limbs were relatively less in Bothriospondglus than in Iguanodon. They, probably, came nearer to Crocodilian proportions. A second more mutilated sacral centrum of Bothriosjjondglus (PI. 62, figs. 4, 5, 6) shows the modification of that marked 4 in the sacrum of Hglaosaurus (' Dinosauria,' PI. 38, figs. 1 and 2), in having the parapophysial expansion limited to one (?) on each side of the centrum. In the present genus its base occupies the anterior half of the lateral surface, instead of the smaller proportion shown in TlyJtsosaurus ; it is also more depressed, and the entire centrum is flatter, though not in so great a degree as in the subject of PI. 62 above described. Both ends of the present centrum are flat, and show a greater proportion of the smooth unconfliient condition than in the subject of PI. 62, fig. 3. The supporting parts of the neural arch forming the roofs of each lateral cavity (PL 62,flgs. 4 and 5,/) are broken off together with the arch itself, and but a small part of the neural surface (ib., flgs. 4 and 5, w) is preserved. This mutilation exposes the whole depth of the lateral excavations (ib., fig. 4,/,/) of the centrum, undermining, as it were, the base of the neural arch ; and these show that the breadth of the centrum beneath that arch is reduced, about midway between the two ends, a and i, to half an inch, the breadth of the centrum at the fore end, a, being, when * See ' Crocodiiia, PI. Id, fig. (5, sacral vertebra of Crocodilus Haslingsice. f See 'Dinosauria,' PI. 25. 554 BRITISH FOSSIL REPTILES. entire, 3 inches 3 lines. At the opposite or hinder end the breadth was less, and the height ajjparently greater, whence it may be inferred that this vertebra was near to the hinder end of the sacrum. The right half of the anterior, flat, smooth but irregularly indented, articular surface of the centrum is nearly entire. Extending, as far as the origin of the pre-parapophysis, ;;, which is preserved, and wanting only part of its upper surface, the entire transverse extent can be estimated, as above noted. The under surface of the centrum (PI. 62, fig. G) is more convex across than in the subject of fig. 1, PI. 61, concomitantly with its greater extent in the present vertebra. The longitudinal contour of the luider surface (PI. 62, fig. 5) is more uniformly concave. The margin of both articular ends is eroded. The aperture of the lateral excavation (ib., fig. 4, c') is 1 inch 5 lines in longitudinal extent; but the cavity is continued 10 lines further above the pre-parapophysis (ib.,jy) ; the depth of the excavation at the middle of the vertebra is 1 inch 3 lines. The smooth compact crust of the centrum passes, without fracture, over the free lateral tract (ib., fig. 5, c). The vertically convex border of the floor of the cavity is somewhat thicker than in first-described sacral vertebra, but similarly shows a natural condition and contour. The upper surface of the floor of the cavity shows a fine crack (outside the letter / in fig. 4) as if the inner half of that floor, with the adjoining part of the centrum [p) supporting the base of the neural arch had been slightly depressed. The proportion broken away from the left side of the present vertebra is indicated in outhne in figs. 4 and C. The subject of figs. 1, 2, 3, PI. 02, transmitted at the same time with the vertebrae above described, and from the same locality, I refer, from the superficial characters of the vmder surface and of one of the terminal surfaces of the centrum, to the same genus and species of Dinosaur, and it probably formed part of the same individual. The flattened surface of the centrum, at «, fig. 2, in the irregular impressions of its otherwise smooth surface closely accords with the one, *. of the subject of fig. 5, to which it adapts itself sufficiently closely to suggest that it may have been liga- nientously articulated thereto. The opposite surface (ib., fig. 1 and fig. 2, 6) is not so impressed, is slightly convex and smoother, and indicates a joint with the succeeding vertebra admitting of more movement. I infer, therefore, that the present specimen is the centrum of the last sacral vertebra, and that the end articulating with the first caudal vertebra had resumed more of the usual vertical proportions of the centrum. The para- pophysis (p), with the irregular syndesmosal surface, has a greater extent, both vertically and lengthwise. Abo've it extends the narrow fractured surface of the broken off base of the neurapophysis. The floor of the neural canal (fig. 1, n) is preserved, which is concave lengthwise as well as across, sinking somewhat into the substance of the centrum. Its diameter midway between the two ends is 7 lines. The lateral excavations of the centrum appear to have ceased at this vertebra, and KIMMERIDGIAN DINOSAURS. 555 probably were not resumed in the caudal series. It has been fractured and somewhat distorted by posthumous violence : but this has not affected the contour of the under surface of the centrum (ib., fig. 3), or the vertical proportions of this element, any more than in the case of the two previously described sacrals. In four centrums of dorsal or dorso-lumbar vertebras of Bothriospondylus stiffossus, forming part of the same series transmitted from the Kimmeridge Clay of Swindon, the characteristic excavations are conspicuous and with longer apertures than in the sacral vertebrae, where these are interrupted by the broad articular parapophyses. No trace of the latter processes are present in the trunk vertebrae of which the type is selected for the subjects of Plate 03. The centrum is subconipressed (fig. 2) ; its sides moderately concave lengthwise (fig. 1), with one end feebly convex, a, the opposite end rather more concave, b. I regard the latter as the hinder one, and the trunk-vertebrae to be, as in Streptospondylus, of the opisthoccelian type. The free surface of the centrum is smooth, save near the articular ends, where there are low longitudinal risings and shallow channels. The under surface (ib., fig. 4) is perforated by two or more small vascular (venous) canals near the articular ends. The fore end (ib., fig. 2) has a somewhat irregular surface. The hind one, which has suffered less from compression (ib., fig. 3), shows a similar coarse pitting and rising at the central part of its surface, the peripheral part being smoother than that at the middle, which has yielded to pressure, the large cancelli there having been crushed in. The bases of the neurapophyses (PI. 63, np), commencing about three lines from the anterior end of the centrum, are continued to the posterior end. They have been anchylosed to the centrum and broken away. Posthumous pressure has crushed this specimen laterally and oblicpiely. Part of the floor of the neural canal is exposed (at n, 11, fig. 5), and is continued outward, at o, where the spinal nerve has had issue. The narrowness of the tract of the centrum, between the lateral excavations, /, /, giving support to the coextensive parts supporting the neural arch, is a singular characteristic of the present genus, and made it difficult to conceive that a mere jjlate of bone like that between / and n^ in fig. 1, PL 63, would relate to the support of a neural arch. It recalled the structure of that part of the vertebrae in the thoracic-abdominal region of a Chelonian. What the character of such arch may have been we have yet to learn, in the present species, from better preserved specimens. Not a fragment recognisable as belonging to such portion of the vertebra could be found among the fossils ijcnt up from the Kimmeridge locality at Swindon. Two rather more crushed and distorted centrums show, nevertheless, an increase of transverse diameter indicative of their having come from a region of the spine near the sacrum. The centrum shows the same opisthoccelian type, the same wide and deep lateral excavations, undermining, as it were, the neural arch, an absence of transverse processes, and the fractured bases of anchylosed neurapophyses. 556 BRITISH FOSSIL REPTILES. The " Swindon Brick and Tile Company's Works/' whence, through the kindness of the managing director, James K. Shopland, Esq., the above-described fossils were obtained, are situated on land adjoining the Wilts and Berks Canal. The vertebrae were found, associated with remains of Pllosaurus brachi/deiriis, in the Kimmeridge clay, at a depth of fifteen feet. The clay here is of a deep black-blue ; and a mass of lignite, seemingly derived from a crushed trunk of a tree, and burning like ordinary coal, was here discovered. Order. DIN08AUB1A. Genus — Omosaurus, Species — Omosaurus armatus, Owen ('Dinosauria/ Plates 64 — 75). Shortly after the foregoing pages on Bothriospondylus had been penned I was favoured with the subjoined note,* announcing further discovery of larger bones in their Kimmeridge Clay works, followed by a liberal offer on the part of the Company t of such of these fossils as might be found worthy of being added to the Geological Collection in the British Museum. Mr. William Davies, of that Department, was thereupon instructed to inspect the diggings, and, on his ' Report ' of the appearances, was authorised to take the requisite steps to remove and transmit to the British Museum as much of the matrix as gave evidence or promise of containing organic remains. This operation * " Swindon Brick and Tile Company, " Swindon, Wilts ; 2'ird May, 1874. "Dear Sir, " I last year had the pleasure of sending you some Saurian Remains discovered in this Company's Kimmeridge Clay Pits, and I beg to inform you that we have just laid open other remains considered to be unusually large and fine, which are left in situ, carefully covered over. " As exposure to light and air will, I fear, cause the remains to split and crumble, I should suggest your coming or sending some one to inspect them at once ; the clay adjoining I will leave unworked until Wednesday next. "I am, &c., "James K. Shopland. " Professor Owen, British Museum." t It is due to their enlightened liberality and prompt co-operation in applying to the advance of science whatever, in the course of the works, might aid therein, to subjoin the names of the Directors of the Company: — J. C. Townsend, Esq., Thomas K. Shopland, Esq., Henry Kixneir, Esq., Richard Rowley, Esq, KIMMERIDGIAN DINOSAURS. 557 was carried out with Mr. Davies' experienced skill and judgment.* Some tons weight of matrix was transmitted to the British Museum, and occupied, during the remainder of the year, the practised chisel of Mr. Barlow, the mason -sculptor of the Geological Department, under the guidance and supervision of Mr. Waterhouse, Mr. Davies, and myself. The result was the extrication from these masses of the bones of one and the same individual dragon, or Saurian, and these form the subject of the present section. They were found at a depth of ten feet from the surface soil covering the clay deposit, which deposit, where it surrounded the bones, presented rmusual density and almost intractable hardness, and was traversed by fissures or cavities occupied by infiltrated spar, presenting in parts a septarian character. This condition of the matrix suggested that it might, in some degree, be due to the decomposition and exudation of the soft parts of the large reptile when buried in the clay sea-bed into which it had sunk ; gaseous emanations might give rise to fissures or vacuities in the surrounding tenacious mass, into which the stalagmitic spar might subsequently infiltrate during the long ages of the condensation, petrifaction, and upheaval of the deposit; but cracks and cavities, from whatever cause, do become so occupied, as in the present local accumulation, and have received the name of ' septarian doggers.' In the borings lately carried on at Netherfield, near Battle, Sussex, 660 feet of ' Kimmeridge Clay ' were traversed before the ' Oxford Clay ' was reached, without inter- position of ' Coral Rag ' or ' Coralline Oolite.'f This testimony to the time during which Kiunneridgian strata had been accumulated to such vertical extent gives free scope for surmise and speculation as to the long ages during which Pliosaurs, Cetiosaurs, Bothriospondylian and other enormous reptiles, lived and died in a world of which they seem to have been masters, as far as grades of organic life and power, acting at that epoch, have been determined. Other lines of variation and modification of the dragon type, besides the new one about to be defined, probably remain to be determined by ulterior research, and to reward the labour, skill, and science of investigators and collectors of Kimmeridgian remains. Of the Dinosaurian genus and species, for which the name Oinosannis armatuii\ is proposed, parts of the vertebral column, the pelvis, a femur, and tibia, and almost all the bones of the left fore limb, have been worked out. The scapular arch, sternum, skull and teeth, and bones of the hind feet, are still desiderata. That not a single tooth * See tlie processes described by liini in bis instructive ' Catalogue of Pleistocene Vertebrata in the Collection of Sir Antonio Brady,' 4to., 187-1, p. 71. t A thickness or vertical extent of 10.50 feet is assigned to tbe combined 'upper' and 'lower' divisions of the Kimmeridge Clay, by tbe Rev. J. F. Bbilthey meet and coalesce about one inch and nine lines above the centrum, whence their compact coalesced mass rises above the crown of the arch, expanding to a height of five inches (posteriorly, PI. 66, fig. I) before giving off the neural spine (ib., 71 s)- At three inches above the base the outer surface of the neurapophysis is excavated by a smooth oval cavity (ib., fig. 2, p), 1 inch 9 lines in vertical, 1 inch 0 lines in transverse, diameter, and about y lines in depth. To this cavity was adapted the ' head of the rib :' for this part there is no parapophysis, or outstanding process. Below the capitular cavity the outer surface of the neurapophysis is divided from the hinder surface by a low obtuse ridge or angle (ib., ib., e) ; a broader ridge (ib., ib., a), also low and obtuse, rises along the middle of the outer surface of the neurapophysis, and expands to form the lower margin of the costal pit. In advance of this jut the 8d 560 BRITISH FOSSIL REPTILES. neurapopliysis extends forward to form the prezygapophysis {ib., and PI. Go, fig. 1, r). The ridge {e), rising to the costal pit, forms or e.Ktends its hind border and is thence continued, expanding or thickening, into the ridge which forms the diapophysial buttress,/. The ridge (Pi. 66, fig. 3, a) does not, in this vertebra, combine with the ridge, e, to form the buttress, as in the Iguanodon (' Dinosauria,' PL 3), but appears as a shorter inde- pendent ridge. A median ridge (PI. 65, fig. 1, r) rises from above the interspace of the prezygapophyses to the neural spine, n s. Another median ridge (PL 66, fig. 1, «) extends along the back of the neural arch and rises to the interspace of the postzygapo- physes, /, /, The chief expanse of the summit of the neural arch in the antero- posterior direction is a zygapophysial one (PL 66, fig. 2, z, /) ; in the transverse direction it is a diapophysial expansion (ib., fig. 1, d, d). Each diapophysis is three-sided; the broadest facet is on the upper side, forming with the zygapophyses the neural platform. External to the zygapophyses this surface is 2\ inches from before backward ; it is flat. The postinferior surface (PL 66, fig. 1, /, d) is in that direction concave, most so below the postzygapophyses, z', and growing shallower to the tumid extremity, d, of the transverse process. The least fore-and-aft diameter of this surface of the diapophysis is 2 inches 3 lines, that of the antero-inferior surface is 1 inch 5 lines ; this is feebly concave across, and is divided lengthwise for part of its extent by the zygapophysial ridge (PL 65, fig. 1, t). The free end of the diapophysis is swollen and tuberous ; a well-marked facet (PL 65, fig. 1, d, and PL 66, fig. 2, d) cuts the lower part obliquely ; it is of a rhomboid shape, nearly flat, and is roughened for the ligamentous attachment of the ' tubercle of the rib ;' it measures 2^ inches by 1 inch 9 lines. The postzygapophjses (PL 66, fig. 1, z -') are formed by an expansion backward of tlie neural platform, the pair of processes being indicated by a medial notch ; they are more clearly defined by their fiat articular surfaces, which are subtriangular in shape, the angles being rounded off"; their longest diameter is 2 inches : they look outward and downward. The prezygapophyses (PL 65, fig. 1, :, ;) have been mutilated in the present vertebra, but the extent of their basal origin, 2 inches, may be traced ; they are more distinct productions of the neural platform, which abruptly sinks to the level of their medial borders. The anterior basal ridge (ib., r) of the neural spine begins at this lovA^er part of the pLitform, which it divides into a pair of hollows. The spine rises fi-eely from the broader upper level of the platform. Its base here has a fore-and-aft extent of 3 inches 8 lines. The hind border of the spine is rather sharp ; the thickest part of the body of the spine is 9 lines ; its free termination was probably, from the analogy of a caudal vertebra subsequently to be described, swollen and tuberous. A vertebral centrum and a portion of the neural arch, from the same region of the spinal column, repeat the characters, so far as they are shown, of the less fragmentary KIMMERIDGIAN DINOSAURS. 561 vertebra above described and figured. Two vievifs of the centrum, of half the nataral size, are given in Plate 65, figs. 2 and 3. The capacity of the neural canal (fig. 2, n) is worthy of note ; it is rather Mammalian than Saurian, and implies a great development and vigour of the muscular system. Lumbar Vertebra. — The last lumbar vertebra (' Dinosauria,' PI. 72, /) appears to be confluent with the first sacral (ib., s 1). Its centrum is 3 inches in longitudinal extent ; the side is slightly depressed below the base of the neural arch, from which extends a lumbar rib (ib., I,p I) 9 inches in length; this is 1^ inches in breadth at three inches distance from its free extremity. This lumbar rib, and also that of the antecedent lumbar vertebra, are straight and extend transversely to the axis of the vertebral column. The distance in a straight line from the hasnial surface of the lumbar centrum to the end of the last lumbar rib is 1 foot 3 inches. Sacral Vertebra. — These are five in number (ib., «i— «5), coalesced together, and seemingly with their pleurapophyses. The antero-posterior extent of the five sacral centrums is 1 foot 4^ inches, each centrum averaging 3^ inches in length. After the first they increase in breadth and decrease in the transverse convexity of the haemal surface, the middle ones showing traces there of a shallow longitudinal hccmal channel with thick low convex borders. The interspace between the heads of the third pair of sacral ribs (ib., pi 3) is 7 inches, between the fifth pair it is 6 inches. Fractures of the mass of matrix enveloping the pelvis exposed the close cetiosaurian texture of these vertebrae and the shape, in some degree, of the neural canal in a portion of the sacrum. One (fifth) sacral vertebra was thus divided lengthwise through the centrum, neural arch, and spine, and yielded the following dimensions : — Vertical extent 1 foot 5 inches ; il)., length of neural spine, 6 inches ; antero-posterior diameter of do., 3 inches 0 lines. This spine for a great pai't of its length was not in contact with the ante- cedent neural spine. The neural canal partially depresses the upper surface of the centnun of each sacral vertebra, probably in relation to venous sinuses rather than to ganglionic enlargements of the myclon. The vertical diameter of the neural canal where it dips down into the centrum is 2 inches 3 lines ; in the ordinary course of the canal, it is I inch 2 lines : but, as the fracture affording this view was not exactly along the middle of the vertebra, the canal might gain more de|3th at that part. The central part of the sacral centrum shows a rather coarser cancellous texture than the rest, or than is seen in any part of the centrum of an anterior caudal vertebra (PI. 75, fig. 1). What appears to be the first sacral rib (PL 72, pi. 1) is slightly dislocated hgemad, and probably, at the same time, bent forward obliquely from above downward and backward in a greater degree than natural, the haemal end of the articular surface 562 BRITISH FOSSIL REPTILES. projecting a cbuple of inches in advance of the second sacral rib (ib., pi- 2). The Ion" or vertical diameter of the head or articular end of this rib-plate is 6 inches ; at 3 inches of its outward course it expands to a breadth of 1\ inches by a convex extension of the fore border, which appears to have articulated like a rib-tubercle with the neural arch, and to have been underlapped by part of the ilium (PI. 72, a). Beyond this point the rib- plate, as it approaches the acetabulum, diminishes in breadth but increases in thickness and seems to develop from its haemal side a broad, transversely convex ridge or buttress (ib., pi. 1) 5 inches long by 2^ broad at the distal end, which abuts upon the fore and haemal angle of the acetabulum, e. A process of the antacetabular part of the ilium (ib., a) is continued inward and hseniad to articulate with the upper border of this first broad, sacral rib ; an oblong vacuity, 4 inches by 2 inches, intervenes between this process of the ilium and the acetabulum. The second sacral rib (ib., pi. 2) is indicated by the part of the plate posterior to pi- i- The ])roximal portion of this seemingly single broad and bifid pleurapophysis is applied to the greater part of the sides of the two anterior sacral centrums (it)., s \, s 2), showing it to be the confiuence of two pleurapophyses, the part described as the convex side or buttress being the distal articular end of the anterior of these. On this view the next independent sacral rib would be the third (ib., pi. 3) ; its proximal end is expanded and applied by a similar, but not so great, obliquity to the side of the third sacral centrunj (ib., « 3), having a breadth of 3 inches with a thickness of nearly 2 inches, but contracting to a narrow rounded haemal border, retaining above this part a thickness of 1 inch, then expanding to a breadth of 3 inches to abut upon the htemal border of the acetabular part of the ilium, filhng the interval between the like extremities of the second and fourth sacial ribs. The direction of the third pair is nearly trans- versely outward. The length of the interspace between the second and third ribs is , 0 inches ; the fore-and-aft breadth is 3^ inches ; it narrows towards the acetabulum, where the distal expansions of these ribbed buttresses come into contact and seemingly coalesce with each other, and similarly narrows to their })roxinial expansions, thus showing an elliptical shape. The head of the fourth sacral rib (ib., pi. 4) is applied to the whole side of the corresponding centrum (« 4), and is S^ inches in fore-and-aft diameter; from this the rib contracts to the form of a subvertical thick ])late, and then expands to a breadth of 4 inches applied to, and confluent with, the lower border of the acetabulum and a considei'able extent of the medial surface of the ilium rising tiierefrom. The fifth sacral rib, with the head reduced to 2^ inches in fore-and-aft extent, is applied to the side of the last sacral centrum (« 5). This rib, contracting at first like the previous ones, then expands as it extends outwards and slightly backwards, chiefly in the vertical direction, to be applied for an extent of 5 inches to the part of the acetabulum to which the ischium is articulated. A considerable part of the right ischium (ib. 63) is retained, dislocated a few inches from the articular facets (ib., b, c), KIMMERIDGIAN DINOSAURS. 563 and thrust a little mesiad and forward. This bone will be subsequently described showing the proportion of the acetabular cavity contributed by it. Anterior to the pelvis is a dislocated group of eight hinder trunk-vertebrae, each retaining more or less of its neural arch and processes. On the right side of the pelvis a complete dorsal vertebra is exposed, measuring 1 foot 5 inches in length and 13 inches in breadth, between the diapophyses. The centrum is 3 inches 9 lines in length, 5 inches in breadth, 4^ inches in height, to the base of the neural canal ; the hinder outlet of this is pyriform, the apex about 2^ inches in vertical, and 1^ incehe in transverse, diameters. Trom the floor of the neural canal to the base of the spine is 8 inches ; the length of the spine is 5 inches. Beyond this dorsal vertebra is the body of a caudal one, showing a greater degree of concavity of the fore surface of the centrum, which has a breadth of G inches. Behind the sacrum is a dislocated group of four caudal vertebrae, mainly agreeing in character with the subject of Pis. 67 and 68. Caudal Vertebrae. — The vertebra of Omosaurus which has been most perfectly wrought out of the matrix is one from the base of the tail ; it was in the same block with the sacrum, not far from the hind part of the pelvis. This anterior caudal vertebra forms the subject of ' Dinosauria,' Pis. 67 and 68, of the natural size ; and I here subjoin, also, the following admeasurements : Height or vertical extent of the entire vertebr Breadth of ditto Length at the zygapophyses, giving extreme Centrum, length, lower surface „ „ upper surface „ breadth, anterior surface „ ,, posterior surface „ height, anterior surface „ ,, posterior surface Neural canal, vertical diameter „ transverse diameter, least Neural arch, breadth at upper level of centra „ „ across prezygapophyses „ postzygapophyses Pleurapophysis, length from base to apex „ depth from tubercle to under „ thickness, extreme, at base „ „ at tubercle „ „ below tubercle length of neural arch n surface In. Lines . 14 9 . 14 6 . 4 2 . 2 10 . 2 5 . 5 8 . 6 0 . 4 5 . 4 6 . 2 0 . 1 4 5 8 . 4 5 . 2 2 . 4 0 0 3 . 1 6 . 0 10 . 0 8 504 BRITISH FOSSIL REPTILES. In. Lines. Neural spine, length from fore part of base . . .71 „ ,, hind part of base . . .56 „ fore-and-aft breadth at mid-length . .18 „ transverse breadth, at mid-length . .10 „ „ at tuberous end . .25 A comparison of such of the above admeasurements as have been recorded of trunk- vertebrae shows that the caudal ones become shortened, at least, at the basal part of the tail. As the length of this appendage would depend upon the number of vertebrae, and especially of those reduced nearly to the centrum, which might again gain in length, it would be premature, on present evidence, to hazard an opinion on this dimension in Omosaurus armatus. But the size of the outstanding parts for muscular attachments indicates great power in the tail, which would probably be exercised, as in the largest living Saurians, in delivering deadly strokes on land, as well as in cleaving a rapid course through the watery element. The centrum is transversely elliptical, with both upper and under surfaces sloping from before downward and backward from the terminal articular planes, these being vertical. Of them the anterior (PI. 67, fig. 1, a) is flat, with a slight convexity toward the periphery and a shallow transverse groove at the centre; the posterior surface (PI. 68, fig. 1, h) is more decidedly, though but slightly concave ; the deepest part here, being along a central transverse groove, with a slight upward bend, like that on the opposite surface. A rugged border for the attachment of a capsular ligament projects from two to five lines beyond the articular tract. This, though smoother than any part of the free surface of the centrum, has evidently, by its inequalities or sculpturing, related to a syndesmosal joint, as in the Chelone and Mammalia, not to a synovial one as in Crocodilia. Between the fore and hind borders of the centrum the lower surface is antero-posteriorly concave (PI. 68, fig. 2), the concavity narrowing as it approaches the line of confluence of the pleurapophysis (ib., ih., pi). This line begins below, half way between the under and upper surfaces of the centrum, and extends upward, approaching obliquely the fore surface (ib., a) to overlap and be lost (by anchylosis) in the base of the neurapophysis ; a feeble trace of the primitive separation of this element may be discerned at the hinder outlet of the neural canal (ib., fig. 1, npl). The pleurapophysial line of confluence is more distinctly traceable ; the base of the pleurapophysis, representing the head of the caudal nblet, is broadest below, and there extends nearer the posterior than the anterior surface of the centrum ; but, as it rises, it narrows and leaves a larger pi-oportion of the post- lateral surface of the centrum free. The ' tubercle ' (0 of the rib is a well-marked rough prominence at which the upper border of the rib descends at an open angle with the ' neck ' to its obtuse apex. The under border of the riblet is gently concave lengthwise. No diapophysis has been developed, in this vertebra, to afford abutment to the tubercle. KIMMERIDGIAN DINOSAURS. 565 Each neurapophysis at its confluence with tlie ceiitnmi gives a triangular horizontal section (PI. 67, fig. 3, np)^ the base of the triangle, 1 inch 5 lines, being anterior, the obtuse apex behind. The inner, shorter side, next the neural canal, is parallel with its fellow and the trunk's axis, the outer side, 2 inches 9 lines in extent, slopes from the broad fore part backward and mesiad to the hind margin of the neural arch. From the upper and anterior forwardly sloping part of each neurapophysis the prezygapophysis (~) is developed ; it is short, thick, obtuse, with a flat articular surface, looking upward, inward, and slightly forward ; subcircular, an inch in diameter. From the narrower hind part of the neural arch the common base of the pair of postzyg- apophyses {:', ^') rises, expanding to form their articular surfaces, which look in directions opposite to those in front. The hind surface of the common base of these articular expan- sions has a wide and deep vertical channel.* The neural spine (««) is subquadrate at its base, with the lateral angles broadly rounded off (PI. G8, fig. 2, ns)- The line of attachment of the base of the spine rises from before backward (ib., fig. 3). A median anterior ridge (PI. 67, fig. 1, x) strengthens the lower half of that surface, as a similar but thicker ridge (PI. 68, figs. 1 and 3, «) does the posterior corresponding tract. Where these ridges cease the spine begins to expand into its rough obtuse summit, chiefly transversely, so as to give it an elliptical contour extended in that direction (PI. 67, fig. 2). The foremost of the caudal vertebrae remains in the block of matrix with the sacrum. The present I take to be the second of the series. There is no trace of hypapophysis for a hsenial arch in either of these caudals (the under surface of the centrum of the second is figured in PI. 67, fig. 4). In Scelidosaurus the first or foremost caudal alone is devoid of haemal arch ; in the second caudal the lower part of the hind border is touched by the smaller anterior facet on the base of the haemapophysis. In the few succeeding caudal vertebrae, with diminution of general size, the vertical extent and the length of the plenrapophyses decrease in a greater ratio. A larger proportion of the side of the centrum is left free below the rib's confluence therewith ; and this free surface of the centrum shows, as in the specimen selected for PI. 69, an upper C^) and a lower (<■') depression. The transverse extent of the centrum decreases without corresponding loss of vertical extent. The hind surface of the centrum (ib., fig. 2) becomes more concave, without corresponding increase of convexity of the fore surface. The contour of the hind surface approaches the subhexagonal. The anterior and posterior ridges of the neural spine subside ; the fore ridge is longest retained, but shrinks toward the base of the spine, as at r, fig. 1. In the subject of this Plate, as in three other caudals extracted from the matrix, the neural spine has been bent to one side, as shown in PI. 69, fig. 2. This distortion I conceive to be due to movements of the matrix after the fossil had been inclosed thereby and become petrified therewith. For, * It is possible that a similar facet may have been ligamentously attached to tiie rough surface exteuded from tlie lower margin of the terminal surface. 566 BRITISH FOSSIL REPTILES. being thus supported at every point by the matrix, during the slow and continuous partial pressure, the spine has yielded and bent without breaking. In one instance the sustaining neural arcli has suffered partial fracture at the side (ib., fig. 1), toward which the spine has been bent. A thickening at the outer side of the neurapophysis, feebly indicated in the larger anterior caudals (PI, 68, fig. 2, np), becomes more prominent near the base of the prezy- gapophysis, as at np, figs. 1 and 2, PI. 69, in the succeeding smaller vertebrae, in which the hypapophyses are more distinctly marked. These articular protuberances (ib., figs. 1 — 3, %) form a pair at the hind border of the inferior surface of the centrum ; the articular tracts at the fore border of that surface are barely defined, or may be indicated by an extension backward of the rough marginal syndesmosal tract. The caudal vertebra in PI. 69 is figured a little more than half the natural size. The answerable caudals in the great Monitor Lizard {Faranus niloticus) are given, of the natural size, in figs. 4 and 5. The haemal arch in the caudal vertebra, with a centrum 5^ inches in vertical extent, has the same length. The haemapophyses (ib., fig. 2, A) are 2f rd inches in length before coalescing to form the spine (ib. ib., A«), which is 2^rd inches in length in the subject of the Plate ; it was probably longer when quite entire. But the length of the arch and spine was plainly less in proportion to the vertical extent of the rest of the vertebra than in Cetiosaurus lonr/us. The hypapophyses are accordingly relatively smaller, and are limited to a narrower transverse extent of the inferior surface of the centrum (ib., fig. 3, hy) than in Celiosaurus, or in the recent Varanus (PI. 69, fig. 4, hj). In Cetiosaurus brevis the hypapophysial facets [h, h) are broader and wider apart than in Cetiosaurus longus. In Iguanodon the reverse conditions prevail. These surfaces have become confluent, and present a single bilobed facet to the similarly confluent surfaces on the bases of the rio'ht and left haemapophyses {' Dinosauria,' V\. 13). Both neural and haemal spines are relatively longer in Iguanodon ; and the neural spine springs from a smaller pro- portion of the hind part of the neural arch at a nuich greater distance behind the prezygapophyses than in Omosaurus. The caudal vertebrae differ less from each other in Omosaurus and Cetiosaurus than they do in either of these genera as compared with Iguanodon. As in the case of Cetiosaurus longus and other previously described Dinosaurian sub- jects, I have selected the best preserved specimen of an average-sized vertebra for figures of the natural size, the requisite comparisons being much facilitated, and accurate results ensured, by such life-size figures. Humerus. — Of the skull, teeth, or scapular arch of Omosaurus I have not as yet received evidence. The humerus and some other bones of the left fore limb (' Dinosauria' PI. 70) have been relieved from the matrix in a more or less complete state. KLAIMERIDGIAN DINOSAURS. 567 The humerus (ib., figs. 1 — 5) is remarkable for its breadth, especially at the proximal half, compared with the length. The articular surfaces at both ends have been more or less abraded. That at the proximal end (figs. 1 and 2, a and fig. 3, a) shows the elongate oval form, with the larger end, c, toward the ulnar aspect, narrowing to the beginning of the great radial crest, b', b', as in Crocodilus, Varanus, and most existing Saurians ; as in these, also, the head projects somewhat toward the anconal surface (as at a, fig. 2) ; but the prominent part of the shalt continued therefrom is less marked than in Cetiosaurun longus (p. 585, fig. 4). The radial tuberosity (PL 70, figs. 1 and 2, j) is not developed distinctly as such, but, as in Crocodilus and Varanus (il)., fig. 6, b), is the beginning of a plate or crest of bone, answering apparently to both the deltoid and pectoral in Mammals, which plate extends considerably radiad, but with less inflection palmad, than in Crocodilus or Varanus, so that more of its breadth is seen in a direct palmar view, as in fig. 1, than in the Ptero- dactyle or the above existing Reptiles. It has a certain forward or palmar bend, and subsides a little below the middle of the shaft. From the proximal beginning, b, of this great crest, a broad tuberous rising (ib., fig. 2, a) projects anconad, and is continued, narrowing obliquely distad, to terminate or subside at the radial side of the shaft, close to the termination of the crest ;/. The tuberosity and ridge, d, a , niight be regarded as ' deltoidean,' as distinct from the ' pectoral ' h, b' , save that its position is anconal instead of palmar. There is a rudiment or indication of this 'anconal ridge' in the humerus of the Crocodile, and a shorter one in Varanus. In the latter existing Saurian it gives origin to a muscle answering to the external ' head ' or portion of the ' triceps extensor cubiti' in Mammals. The ulnar tuberosity extends ulnad and distad as a thick tuberous ridge, which terminates more abruptly than the ladial crest, at e, figs. 1 and 2, al)out seven inches beyond the proximal end. The broad surface of the hiunerus between the crests is rather concave across on the palmar surface, somewhat more convex on the anconal surface, which is interrupted by the ' anconal or tricipital tuberosity and ridge.' The shaft at its narrowest part presents in section the form given in fig. 5, PL 70, being almost flat, palmad and convex, anconad, transversely. It soon begins to expand into the distal end of the bone. The crest, e, simulates the ' supinator ' one in Mammals, and is not perforated, as is the answerable disto-radial crest in some existing Saurians. Such perforation is very small in Varanus (ib., fig. 0, e). There is no indication of this vascular or nervous canal in Omosaurus, and tiie crest is i-elatively shorter than in Varanus. The ulnar expansion, f, of the distal end is thick and tuberous. Sulficlent of the radial condyle, g, remains to sliow its Saurian extension palmad, and its convexity in Omosaurus (ib., fig. 4) ; the precise form and extent of the less prominent ulnar condyle or trochlea is not definable. The texture of the shaft of this humerus, as exi)osed by tlie fracture across its middle 9^ Ft. In. Lines. 2 9 0 1 6 0 0 11 0 0 5 6 1 6 0 1 4 0 0 S 0 568 BRITISH FOSSIL REPTILES. narrowest part, is compactly dense ; there is a small medullary cavity (fig. 5) which seems to have but a short longitudinal extent. A deep anconal depression (ib., fig. 2, i), marks that aspect of the distal expansion in a greater degree than in any Crocodilian, Lacertian, Dinosaurian, or Pterosaurian humerus that, as yet, has come under my notice ; it gives to this part of the humerus of Omosaurus something of a Mammalian character. The following are admeasurements of the humerus : Length ..... Breadth across radial or pectoral crest „ ,, distal end „ middle of shaft Girth of „ , . . Length of base of radial or pectoral crest ulnar crest The figures of tliis bone on PL 70 are reduced to one fourth of the natural size. Although I should have hesitated to found a genus or generic term on a solitary limb-bone if sucli distinction had not been supported by the vertebral characters, yet the features were so much more strongly marked in the present than in previously described or figured humeri as to have afforded a better excuse for such taxonomic deduction, which ought to rest, and, as a rule, can only safely do so, on characters afforded by associated parts of the skeleton or teeth. Mutilated as are the humeri discovered with unquestionable vertebrae of Cctiosaurus longus in the Geological Museum of Oxford, justifying the conclusion that they belonged to the same individual, they are unmistakably distinct in character from that bone in Omosaurus. Although the radial or pectoral ridge be broken away in the subjects of figs. 4 and 5, p. 585 {Cctiosaurus), its base has a minor relative extent than in Omosaurus ; the shaft beyond that ridge expands more gradually into the distal end ; the entire length of the bone — 4 feet 4 inches in Cetiosaurus longus — is greater in proportion to the breadth or thickness of the shaft. The slender character of the humerus is more marked in that bone which chiefiy represents Mantell's genus Pelorosaurus (' Dinosauria,' PI. 49), in which the radial or pectoral crest (ib., fig. 2, d) subsides above the middle of the shaft, encroaching, as in the Crocodile, Varanus, and Pterodactyle, upon the palmar surface of the bone. The humerus of lyuanodon {' Di/iosauria' PI. 19) is still less robust in proportion to its length, not to mention its inferior size as compared with associated dorsal vertebrae, than in Omosaurus. KIMMERIDGIAN DINOSAURS. 569 111 Hylaosaurus we find the nearest approach to Omosaurus in the proportion of the length of the humerus giving attachment to the great tuberous crests from the radial and ulnar sides of its proximal part. But in the Isle of Wight specimens referred, with doubt, to that Dinosaur, the radial crest is more strongly, and, in reference to its Saurian nature, more typically twisted palmad than in the huger Kimmeridgian genus. It shows a tuberous thickening anconad of its distal end, in the place of the ridge, d', fig- 2, PI. 70, in Omosaurus. Radius. — This antibrachial bone in Omosaurus (ib., figs. 7 — 11) has a subcom- pressed shaft, expanding moderately and almost equally into the two articular ends, as far as their degree of conservation shows; but it is probable that the more mutilated distal end (fig. 10) when entire would give a somewhat greater breadth than the proximal one or ' head.' This (ib., fig. 9) is of a narrow subelliptic shape. A small part of the concave articular surface, a, for the radial condyle of the humerus, is preserved. The anconal surface of the shaft (fig. 7) is feebly divided at its distal two thirds into two facets by a low rising, hardly to be called a ridge, beginning at the middle of that surface at its proximal third and inclining as it descends toward the radial border of the distal end. The concavity of both borders, and especially of the ulnar one, narrows transversely the shaft, but this preserves more equably its ancono-palmar thickness (see the section of the middle of the shaft in fig. 11). The lateral facet (fig. 8, h) at the proximal end for articulation with the ulna is more convex than is usual in Bcpiilia. The surface (ib., fig. 8, e) for the insertion of the biceps tendon is well defined. The thenal prominence (ib., figs. 8 and 10, /) extending or deepening the cup, y, for the scaphoid, is strongly developed, and is thicker than usual, as far as it is preserved. Its outer surface is roughened, as if for the ligamentous attachment of some bone, such sur- face extending to the angle, y (fig. 8), at the broadest part of the distal end of the radius. Ulna. — The proximal extension of the articular cup (PI. 70, fig. 13, „) upon an anconal or olecranal production marks this bone as sti'ongly as in Varanus (ib., fig. 15, a) but the excavation (p) of the shaft below the proximal end is differently situated. It Avould seem as if the ulnar or outer border of that depression in Varanus (ib., fig. 15) had been moved or extended palmad, in Omosaurus, toward the narrower, palmar, surface of the bone ; and to such an extent that part of this excavation comes into view from the ulnar side, as at c, fig. 14. This excavation is continiied distad for more than half the length of the bone {c,c'). Below this part the shaft assumes a subtriedral form; and its anconal border bends toward that aspect as it approaches the carpus. The articular surface for this segment of the fore limb is wholly destroyed. Manus. — Of the carpal bones have been extracted a left scaphoid, left cuneiform, and left unciform. Of these three large wrist-bones the scaphoid is the smallest, as in 570 BRITISH FOSSIL REPTILES. Varanus, not tlie larijest, as iu Crocodilas, in which it is connate with the trapezium and trapezoides. The proximal surface for the radius is more uniformly and less boldly convex ; the opposite articular surfaces for the trapezium and luuare is more deeply concave. The outer (ulnar) surface is elongate, narrow, and is the smallest on the bone ; it seems barely to have touched the cuneiform, which is here, as in Varanus, the largest of the carpals. The free broader radial surface of the scaphoid is flattened and roughened, and seems to have continued, distad, the corresponding surface of the radius itself, which is on the radial side of the distal end of that antibrachial bone (PI. 70, fig. 8, 9). The length (transverse extent) of the scaphoid is 5 inches ; the extreme (ancono- palmar) breadth is 3 inches ; the extreme proximo-distal extent (on the rough flat surface) is 1 inch 1 0 lines. The cuneiform is a massive cuboidal bone, with a proximal surface less concave for the ulna than in Varanus, but with as deep an opposite (distal) concavity for the division of the unciforuie which supports the fourth digit. There is an approach to the croco- dilian character of the bone in the increase of the distal part or surface. The transverse extent of the bone there is 4 inches 9 lines ; that of the proximal surface being 4 inches ; the ancono-palniar diameter of the bone is 3 inches 9 lines ; the proximo- distal diameter is 3 inches 10 lines. The unciform seems, as in the Crocodile, to have supported both fourth and fifth metacarpals, not to have been divided to afford articulations for these bones on separate portions. Its transverse extent in Omosaurus is G inches 4 lines ; the other dimensions closely correspond with those of tlie cuneiform carpal. The digits of a hind foot are longer, as a general rule, than those of a fore foot in existing Saurian Reptiles, and the same proportion has been demonstrated in the fore and liind feet of some extinct Dinosauria.* The proportions, at least, of the metatarsals in HylcEosaurus and Scelidosaurus support a belief that tiiose of the metacarpals would be as in the homologous bones of Itjuanodon. Of the five metapodial bones of Omomiints which have been wrought clear out of the matrix not any show a length as compared with the breadth which exceeds that of the metacarpal of the first digit in the fore-foot of Jgitanodon (' Dinosauria' PI. 48, fig. 1, »«) ; and the homologues of the intermediate metacarpals are shorter in proportion to their l)readth than in Iguanodun. I conclude, therefore, that the above metapodials of Omosaurus are metacarpals, that the digits were less unequal in length, and the whole fore-foot was more massive and elephantine in its proportions, in Omosaurus than in Iguanodon. A metacarpal {' .Dinosauria,' PI. 71, figs. 3 — 6) has a flattened proximal surface (ib., fig. 5) of a subtriangular shape, slightly convex near its radial [r) and anconal [a) peri- * Jymmodon, ' Dinosauria,' PI. 45 ; Ilijheosaurus, ' Dinosauria,' PI. 44 ; Scelidosaurus, &c. KIMMERIDGIAN DINOSAURS. 571 phery slightly concave toward the palmar border {/>), which is broken away, the articular surface being continued a short way upon the ulnar {u) side of the shaft for junction with the second metacarpal. The articvilar surface is pitted with small deepish depressions, as in most great Saurians, where the joint surfaces seem to have been more syndesraosal than synovial. The transverse and ancono-thenal diameters of the proximal surface are equal, each being 3 inches G lines ; but, had the ulnar border been entire, the transverse diameter would have somewhat exceeded the other. The short thick shaft of this bone is three-sided ; one side extends obliquely from the ancono-ulnar (fig. 3, an) angle to the radio-palmar (rp) angle, with a transverse convexity ; the second, or palmar, side (fig. 4, p) is less convex across ; the third, or ulnar side, is flat across at the middle part, and somewhat concave near the two expanded ends of the bone. All these surfaces are concave lengthwise, the palmar one least so ; but the proximal half of this (fig. 4, P> l>') has been crushed. The distal articular expansion (fig. 6), almost flat transversely at its anconal part (a), begins to be concave at the middle of the distal surface (J), and this deepening to the palmar one [p) divides the joint there into a pair of convex trochlear condyles. The radial (,-, fig. G) of these, when entire, would have been the most prominent of the two. The metacarpal (PI. 71, figs. 1 and 2) which supported the fourth digit has a proximal articular surface of a more definite triangular figure (PI. G7, fig. 5) ; the anconal border (a) being the longest, and the angle between the radial [r) and ulnar {u) borders being rounded off". The articular surface is continued upon both these sides of the shaft, but fui'ther for the articulation with the mid-metacarpal than for that with the fifth. The anconal surface (PI. 71, fig. 1) of the shaft is almost flat and lies more on the plane of that surface of the entire metacarpus than in the marginal metacarpal above described (fig. 3). The radial and ulnar surfaces of fig. 1 converge palmadtothe narrow convex palmar surface whicl) forms the rounded angle of the proximal triangular tract (ib., fig. G, ur,p). Both radial and ulnar surfaces of the shaft are concave lengthwise and across (ib., fig. 2, r). The transverse concavity of the distal articular surface is feebly indicated, and the bifid character of the joint is scarcely marked, though fractured surfaces suggest that a pair of low palmar prominences may have been broken away ; but the joint is much less trochlear than in the first metacarpal (ib., fig. G). A metacarpal of similar type to the preceding has suffered too great mutilation of both ends to serve for profitable description ; it is not a corresponding metacarpal of the right fore-foot, but may be either a second or third, thougii from the slight su[)eriority of length I should judge it to have been the second metacarpal of the same left fore-foot as the subjects of PI. 71 belonged to. A metacarpal with a subtriedral shaft, aiul an oblique twist at its basal half through an extension radiad of the radial angle, upon which angle the flat proximal articular surface has extended for the metacarpal on that side, is evidently a fifth metacarpal bone. 572 BRITISH FOSSIL REPTILES. The distal surface (PI. 67, fig. 6) is oblong and almost flat save where it becomes convex on being continued from the basal upon the radial surface ; it is feebly concave trans- versely at its middle half, but this is not continued, deepening, so as to divide the palmar part of the joint into a pair of trochlear condyles. The length of this metacarpal is 5 inches 9 lines ; the breadth of the proximal end is 4 inches ; of the distal end 3 inches 2 lines ; the breadth of the middle of the shaft is 2 inches 3 lines. The largest of the proximal phalanges extracted gives a length of 5 inches 5 lines ; with a breadth of the proximal end of 4 inches, and a breadth of the distal end of 3 inches 7 lines. The breadth of the middle of the shaft is 3 inches ; and this seems not to have been more than 1 inch 7 lines in ancono-thenal diameter, but the thenal surface is partially crushed in. The anconal surface is smooth and flat save toward the expanded articular ends. The proximal surface, moderately concave, appears to have been adapted to a distal articular surface of the simple character of the metacarpal last described (PI. 67, fig. 6). The distal surface of the phalanx is moderately trochlear, i.e., with a feeble transverse concavity along its middle half ; it is strongly convex throughout in the opposite (anconothenal) direction. The size of this proximal phalanx indicates it to have belonged to one of the larger middle digits. Of the instructive terminal phalanges, the most entire forms the subject of figs. 4 and 5 of PI. 6S. The small proportion preserved of the thin, smooth, punctate, articular surface shows a partial depression at i, fig. 4 ; but the bone is so slightly abraded where that smooth crust is wanting as to aff'ord a fairly true figure of its general shape, which is almost flat, with a feeble sinuosity. The anconal border («) is most produced ; conse- (juently that surface of the phalanx is longest ; but it is little more than half as long as it is broad. The thenal surface is made concave lengthwise by the thenal production of the terminal lobes of the distal end (PI. 68, fig. 5). There is no appearance of these being articular. I regard them as the free termination of a last or ungual phalanx, and to show a modification of that end like the terminal phalanx of the second toe in Iguanodon {' Dinosaicria,' PI. 48, a, 3). Not any of the fragments of phalanges suggested a structure for supporting a terminal claw, such as exists in Ilegalosanrus. The fore-foot of Oinosaurus, as represented by the bones above described, was a short, broad, massive member, relating chiefly to progressive motion, and suggests the huge species, if not, like Iguanodon, phytophagous, to have been a mixed feeder. Ilium.— The mass of matrix with the portion of the skeleton of Omosauriis figured in PI. 72, reduced to one ninth of the natural size, includes, with the sacrum, both the iliac bones and a large portion of the right ischium. The left ischium and both pubic bones, one of which was almost entire (PI. 73, figs. 4 and 5), were wrought out of the block in the course of exposing the rest of the pelvis upon which they were lying dislocated. The length of the ilium is 3 feet 5 inches ; that of the antacetabular portion is 1 foot KIMMERIDGIAN DINOSAURS. 573 9 inches ; that of the postacetabular portion is 9 inches, but the end of this is broken off on both sides ; the breadth of the superacetabular portion is 7 inches ; the length of the acetabidum is 1 foot 1 inch ; the breadth of ditto is 9 inches ; the extent of the unwalled part of the cavity is 7 inches. Besides the pelvis and the detached vertebrae above noted the right femur and probably the shaft of the fibula were left in the mass in the relative positions exposed in PI. 72, in which the pelvis is seen from the haemal (ventral or lower) aspect. The ilium (ib., 62—62") is an oblong, broad, and thick bone, anchylosed by a neu- romedial tract, two feet in length, to the expanded ends of the five sacral ribs (ib., pi. i_v). The haemal surface is divided into an acetabular tract (62) , an antacetabular production (62') of greater antero-posterior extent, and a shorter postacetabular production (62")- The lateral or external surface, or superacetabular tract, extends neurad and outward to terminate in a thick rugged convex border (;•), which is continued forward, subsiding as a ridge upon the outer or neural surface of the antacetabular prolongation, (62') ; the ridge is lost about nine inches from the fore-end of the antacetabular plate, and gives a triedral form to this part of the ischium. The ridge, continued from ?■, answers to that in the ilium of the Igucmodon noted at p. 287.* But the proportions of the antacetabular and postacetabular productions are reversed in the Kimmeridgian as compared with the Wealden Dinosaiir.f The length of the antacetabidar part of the ilium in Scelidosaurus more resembles that in Omosaurus, but it is narrower and extended more in the axis of the trunk, or is less inclined outward. The corresponding part of the ilium in Cetiosaurus resembles in breadth that of Omosaurus. In this the acetabular cavity (62) is thirteen inches in longi- tudinal, nine inches in transverse extent. Its outer and hinder boi*der subsides at e, and the cavity is continued upon the superacetabular surface of r, the break in the boundary being somewhat analogous to the cleft in the more developed border of the Mammalian acetabulum for the passage of vessels to the intra-acetabular synovial mass. The lower or haemal part of the cavity is completed by the ischium (ib., 63), which articulates syndesmotically with the surface (6, e)- There is no surface for the articulation of a pubis with the ilium, the Omosaurus in this respect corresponding with the Crocodilia. In the breadth also of the ilium as compared with the length that bone of Omosaurus comes nearer to the Crocodilian than to the Lacertian type. And, again, in the extent to which the ilium is prolonged in front of the acetabulum the Crocodiles^ depart less from the Dinosaurs than do the Lizards. In Lacerta * "The outer surface is divided into two facets by a strong longitudinal ridge, for the attachment of some of the powerful muscles of the hind limb." t Compare ' Bmosauria,' PI. 10, fig. 1, 62' and 62", with PI. 72. X Cuvier, ' Ossemens Fossiles,' 4to, 182-1, vol. v, pi. iv, fig. 15, a. 574 BRITISH FOSSIL REPTILES. nilotica, e.rj., the ilium is prolonged in front of the acetabulum to an extent equalling only that of the acetabular excavation of the same bone. Ischium. — This bone (PI. 72, 63, and PI. 73, figs. 1 — 3) offers the structural type of that in Chelonia and certain Lacertilia {TJromastyx, e.g., PI. 73, figs. 8 and 9, 63), in its ' tuberosity ' or })osterior process (c) ; l)ut, in its slenderness or relation of breadth to length, it exceeds that in any Lacertian or otlier (to me) known forms of existing Reptile. Of the iliac articular end of the right ischium but little is exhibited, the bone (63, PI. 72) having been pressed forward and behind the part of the acetabulum from which it has been dislocated. The process (c) answering to that so marked in TJromastyx, in the more perfect left ischium (PI. 73, fig. 8), comes off nearer the articular end than in the Lizard. The rest of the bone is simply styliform and straight, having no process crossing, as in Birds, the obturator interspace between ischium and pubis. The smooth concavity on the under or haemal surface of the expanded end, articulating with the ilium, contributes about a fourth part of the cavity for the head of the femur. The end of the process (e) is rough, thickened, of an elongate subtriedral form, 2^ inches by 1 inch ; the opposite or fore-end of the expansion has a rough syndesmotic surface for the attachment of a similarly roughened end of the pubis. The breadth of the ischium, including these processes, is 13 inches; from this part the bone quickly contracts to a narrow plate. The hind margin of this plate (ib., fig. 1, e) is moderately thick and rounded, whence the bone thins off to an edge in front (ib., /). The haemal surface is flat or feebly concave, transversely, and is smooth (PI. 73, fig. 1). The upper or neural surface is, transversly, rather convex, save where it extends upon the acetabular part (a, ,i), and here it is rather concave. The body of the Ijone gradually contracts to a breadth of 2^ inches; it then slightly expands to its symphysial end (ib., 9, and fig. 3), which has a breadth of 4 inches, with a thickness of 2 inches. Restoring a part wanting between the preserved body of the ischium and the symphysial end, to the extent indicated by the dotted lines in PI. 73, fig. 1, the total length of this pelvic bone in Omosaurus would be 2 feet 6 inches. Pubis. — This bone (PI. 73, figs. 4 — 7) presents the type of the pubis in Lacertians (ib., figs. 8 and 9) in the pectineal process (c), and the perforation (rf), but adheres to the Crocodilian type in presenting one articular surface only at the proximal end (a) for the ischium, and (seemingly") contributing no share to the acetabular cavity. AChelonian character is shown in the length of the bone between the head (a) and the process (e). The articular end {a) has been better preserved than the coriesponding one of the left ischium (ib., fig. 1). It presents a narrow, elongate, synchondrosal, roughish facet, C inches in length, 1 inch 7 lines in breadth, with a moderate convexity in the long axis (ib., fig. 6). The posthumous abrasion of the articular surface checks an absolute state- ment as to the precise configuration of this ischio-pubic joint in the recent Omosaur, but KIMMERIDGIAN DINOSAURS. 575 the proportion, if any, contributed by the pubis to the acetabulum must have been very small, for no trace of such appears. The pubis as it recedes from this joint gradually narrows to a breadth of 3 inches 4 lines, then more rapidly expands to form the perforated pectineal plate (c). This plate or process becomes, as in Lizards and Tortoises, thickened and tuberous at its free prominent border, which describes a bold convexity before subsiding into the slender continuation of the pubis (e,/). The margin of e continued thereto by the dotted line, in figs. 4 and 5, is a fractured one ; and the angle of the border (e) to which the dotted line is continued shows also fracture ; the extension of bone along that line is inferential. Proximad of such fracture the anterior border of the pubis is entire and sharp, a continua- tion of that which partly circumscribes the oblique pectineal hole or channel ('^). From the pectineal expansion the pubis contracts to a breadth of 2 inches, then expands to its symphysial end {ff), which, when entire, must have had a breadth of from 5 to 6 inches. The abraded surface (ib., fig. 7) gives a fuller ellipse than that of the ischium (ib., fig. 3), but, as in that bone, indicates a symphysial junction with the opposite pubis. The hind border of the pubis (/) is rounded and thicker than the fore border {e). The neural surface (ib., fig. 5) is feebly canaliculate lengthwise in part of its extent, and this character is shown, though still more feebly, in the pubis of TJromastyx (fig. 9, 64). But the accentuation of this surface in the broader half of the pubis of Omosaurus, as shown in fig. 5, is due to crushing and fracture seemingly in relation to the original prominence of the part of the pectineal process (c, fig. 5), which has been pressed to flatness with slight concavity. I conclude from the length of both ischium and pubis that they diverged from each other, viz., from their outer to their inner or symphysial ends, at an angle nearer that iu Crocodihans than in Lacertians. There is no evidence or indication that these hseniapo- physes were disposed otherwise than in the rest of the Reptilian class, meeting, each pair, at the medial line, with a space between ischia and pubes, answering to a common and uninterrupted obturatorial vacuity. This space, in Bicynodon, is obliterated by continuous ossification. The length of the pubis in Omosaurus is 3 feet 6 inches, the extreme breadth is 9 inches ; the least breadth of the pre-pectineal part (*) is 3 inches 6 lines ; the extreme thickness of this part is 1 inch 3 lines. Femur. — To the right of the pelvis lies the femur of the same side, with the hinder surface exposed (PI. 73, 65). The head (a) of the bone is at a distance of 1 foot S inches from its socket («) and a little posterior to it. The distal end lies exterior to and a few inches in advance of the right ilium. The terminal articular surfaces of the shaft are, to some extent, worn away, but sufficient remains to show that the chief convexity or head (,,) projected some inches within the inner longitudinal border of the shaft, the proximal surface sloping slightly distad to the rough convex angle, 10^ 576 BRITISH FOSSIL REPTILES. representing a trochanter [b], from which a thick rough ridge is continued, graflually subsiding upon the shaft. The breadth of the proxunal end of the bone is 1 foot 1 inch ; at I foot distance from that end the shaft is contracted to a breadth of 8 inches, and at its middle part to one of 0 inches. Notwithstanding the posthumous pressure which has shattered this part of the crust of the femur, one may infer that tlie shaft was naturally subcompressed from before backward. At three fourths of the distance from the head of the bone the shaft again begins to expand, attaining at the distal end a breadth of 13^ inches. There is a distinct oblong protuberance ( ) at the inner and back part of the shaft, 1 foot 6 inches beyond the head, corresponding to that more developed prominence which has received the name of ' third trochanter ' in lyuanodon and Scelkhmurm. There is also evidence of a longitudinal ridge id) continued from the back part of the trochanter, about 9 inches down the shaft, inclining toward the middle of the hinder surface. The popliteal cavity [e] is moderately concave, chiefly transversely through the l)ackward production of the outer condyle {g). This is of less breadth posteriorly than the inner condyle (/) but is more convex as well as more prominent. The outward extension of the femur (/,) beyond this prominence is somewhat umisual. Tibia. — This bone is represented by its proximal end and three fourths of the shaft (PI. 74, figs. 3 — 6). The shaft is more slender in proportion to the head than in Ihjlceo- or Scelido- saurus, and yields a full subelliptic section (ib,, fig. 6). Part of the articular surface for the inner femoral condyle may be recognised at a, and that for the outer condyle at h, fig. 3, PI. 74. A ])rocnemial plate (c), ^Yith a base of 7 inches in extent, projects forward 4 inches beyond the articular part of the head of the bone. As wrought out of the matrix this plate shows a sharper free border than probably was natural ; its obtusely rounded summit, ,i, has retained its condition as an epiphysis. The diameter of the head of the tibia in the direction of the procnemial prominence («. <", fig. 5) is 11 inches. The preserved longitudinal extent of the tibia is 2 feet. Tiie two diameters of the fracture (/, fig. 3) are 4 inches 6 lines and 3 inches 6 lines. The indication of a medullary cavity at the fracture (/) are hardly so definite as in fig. G, and such as it is, the cavity was short ; for at the fracture («) the corresponding central portion of the shaft shows an open osseous tissue with wide chondrosal interspaces. In the obliquely fractured and partly crushed end of the shaft the trace of medullary cavity has disappeared. The osseous tissue of the rest of the shaft is compact. Not- withstanding the degree of crushing, the beginning expansion in the tibio-fibular direction and of contraction or flattening in the rotulo-popliteal direction is unmistak- able, and has led me to conclude that the distal, more flattened end of the bone is that which is wanting in the present specimen. KIMMERIDGIAN DINOSAURS. 577 Other parts of Hind Limb. — Exterior to the right femur and overlain by it is the shaft or slender part of a bone, 1 6 inches in length and 3 inches in breadth ; it bears the proportion of a fil)ula to the tibia above described. -p^^ j No recognisable tarsal, or other bone of the hind-foot, has been detected in the indurated matrix forming the bed of the Omosaur. But Professor Phillips, in his instructive ' Geology of Oxford,' states,* " Three metatarsals in the Oxford Museum, apparently of Megalosaurus, lying in their original apposition, have been obtained from the Kimmeridge Clay of Swindon and seem to indicate a tridactyle foot (diagram Ixviii)." I subjoin a copy of the cut of these bones (Fig. 1), deeming it more probable that they belonged to the genus of Dinosaur now known to have left remains in that formation and locality, than to the Mer/alosaurus, of which no indubitable evidence has yet been obtained from Kimmeridge Clay, either at Swindon or elsewhere, a is an outline of the proximal, b of the di.stal, ends. These bones exemplify the ' leptopodal ' character of the Dinosaurian foot, due to the reduction of thickness or breadth by suppression of two of the toes, and a consequent departure from the shol-t, thick, or broad ' pachypodal' character of the pentadactyle hind foot of the existing and extinct terrestrial Cheionia and of some Lacertia. Metatarsals of Omosaurus ? Dermal Spine. — One osseous spine {' Dinosaur ia,' PI, 74, figs. 1 and 2; PI. 75, figs. 2 and 3) has been successfully wrought out of the matrix ; but though a close search was made for other evidences of a dernio-skeleton none have been found. The spine in question is 1 foot 6| inches in length, and not more of the tip seems to be wanting than might extend this dimension to 1 foot 7 inches, or, at most, 1 foot 8 inches ; the long diameter of its base (PI. 75, fig. 2) is 5 inches ; the shaft gradually tapers to a point. The spine is rounded and slightly compressed ; the narrower diameter is shown in Plate 74, fig. 1, the greater breadth in ib., fig. 2. The surface, smoothest toward the base, becomes slightly broken by fine longitudinal, quasi fibrous, markings ; and this sculpturing becomes coarser as the spine contracts. At every part may be seen small orifices, apparently vascular ; few in number along the basal two thirds, but more frequent near the point. These indicate a periosteum in relation to the supply of a horny sheath, of which we have here the petrified bony core. The texture of the osseous substance is dense (PL 75, fig. 3). The base is obliquely truncate, with a boldly sculptured border, broadly and deeply notched as if for strong ligamentous attachments, the whole basal surface being coarsely roughened ; it is also channelled, seemingly, by two vessels entering the substance of the * 8vo, 1871, p. 21,-). 578 BRITISH FOSSIL REPTILES. spine, one, perhaps, an-artery, the other a vein (PL 75, fig. 2). The spine is traversed by a central medullary or chondrosal canal, in diameter one third that of the smaller diameter of the spine (ib., fig. 3). The rough imperforate part of the base, like its coarse periphery, suggests adaptation to syndesmotic junction with some other bone. But with what part of the frame? There is a want of symmetry at the obliquely truncate base, which suggests this spine to have been one of a pair. In Scelidosaurus the dermo-neural spines at the neck and fore-part of the back are similarly ' somewhat unsymmetrical in form,' showing a parial arrangement along that part of the trunk, but they are succeeded by symmetrical dermo-neural spines having a medial position along the rest of the trunk and tail. The osseous spines, probably dermo-neural, of Hylceosaurus, show a length in propor- tion to the adjacent vertebral centrums somewhat exceeding the present spine of Omosaurus ; they are, likewise, obliquely truncate at the base, and misymmetrical in shape, but in a greater degree ; and they are much more compressed (' Dinosauria,' PI. 37, d). In the Hylseosaurian specimen in the British Museum, which turned the scale in favour of the dermo-neural hypothesis, an irregular angular depression is described and figured at the base ; and this repeats, though single, the i)air of depressions or canals above noted, and reputed vascular, in the base of the spine of Omosaurus. The low, obtuse, thick ridge girting the base of the spine in Hylceosaurus is, however, simple, unnotched ; the provision for attachment of the spine, in Omosaurus, betokens a greater power of resistance against displacement. The superior strength of the spine, due to its full elliptical sha[)e in transverse section, suggests its application as a weapon to be wielded for attack rather than as one of a merely defensive palisade of spines. Considering the number of vertebrae — dorsal, sacral, caudal — which have been recovered in more or less completeness from the intractable mass of some tons weight, including the rest of the above described recovered parts of the skeleton of the Omosaur, it might reasonably be expected that, had the trunk and tail been defended by dermal spines, as in Scelidosaurus and Hylaosaurus, especially by spines similar in number and arrangement to the dermal ridged scutes in the more Crocodilian Dinosaur of the Lias, evidences of such appendages to the trunk-skeleton should have been found in the grave of the great Kimmeridgian dragon. But we are, now, not limited to the head, the trunk, or the tail in quest of positions of armour afforded by dermal bones to extinct members of the Reptilian class. In the great Mantellian Iguanodon, or at least in the male of that species, a pair of spines supported by unsymmetrical conical bony cores were wielded for offensive action by the fore-limbs (p. 508, Pis. 46, 47). The form and proportions of the Iguanodontal carpal spine, especially in its degree of compression, are more like those of the spine in Omosaurus than are any of the dorsal spines in Hylceosaurus. True, the conical spine- OOLITIC DINOSAURS. 577 core in Iguanodon is shorter in proportion to its basal breadth than is the problematical spine in Omosaurus. It is significant of the nature of this one unsymmetrical osseous spine that the bones of one of the fore limbs, the left, and that limb only, should have been preserved, and in a more complete state than any other part or limb of the present remarkable Dinosaurian framework ; the spine in question lay not far from the radius and carpus. Two spines of similar form to that of Omosaurus, but of larger size, were discovered near each other in a pit of Kimmeridge clay at Wootton Bassett, Wiltshire, and formed part of the well-known collection of William Cunnington, Esq., F.G.S., now in the British Museum. Whatever contiguous bones may have been dug out of the same part of the pit were not preserved. These two spines form a pair, and resemble each other as much as would the right and left radius, or the right and left ulna, of the same Dinosaur? They differ from the (carpal ?) spines of Omosaurus in having a sharp edge, which in a transverse section, like that of fig. 4, PI. 77, would terminate one end of the long diameter of the ellipse. The lethal power of the weapon was augmented by this character of the sword added to that of the pike. The degree of obliquity, the coarse marginal notching, and vascular perforations of the base, are as in Omosaurus ; but the expansion is greater, yielding dimensions of 8 inches and Q\ inches in long and short diameters ; thei'e is a slight submedial ridge dividing the basal articular surface into two shallow channels. The long diameter of the shaft, four inches beyond the least produced part of the base, is 3^ inches, being nearly the same as in Omosaurus. The edge of the spine is along the same line as the most produced part of the base. The shaft has a central cavity, as in Omosaurus. Should these prove to be a pair of carpal spines they indicate a species of Dinosaur distinct from Omosaurus armatus. They will be further described and figured in a subsequent part of the present work. Order DINOSAURIA. Genus — Cetiosaurus.* Species — Cetiosaurus loiir/us, Ow. (Plate 76, and Woodcuts 3 — 11). Until a comparatively recent period the generic or family characters of the great extinct Cetiosauroid Reptiles were founded on a few scattered bones of the trunk and limbs. t The texture of these fossils mainly differentiated them from the corresponding vertebrae and limb-bones of previously determined genera or species of Saurians. No * Gr. K»)reios, cetaceous ; aaiipos, Lizard ; " Report on British Fossil Reptiles," Part ii, in ' Reports of the British Association,' &c., for the year 1841 ; also ' Proceedings of the Geological Society of London' or June, 1841 (vol. iii, p. 4,57). t Ante, p. 40.V ; provisionally referred to the order Crocodilia. 580 BRITISH FOSSIL REPTILES. portion of the skull, not one tooth, had been discovered so associated with Cetiosaurian bones, at the date of my " Reports on British Fossil Reptiles,"* as to throw any additional light on the ordinal affinities of the new genus. I had not, then, grounds for dissociating it from the Crocodilian group or order. The grand accession of evidences of the osseous framework of one of the speciesf added to the original Collection of Buckland, preserved ill his Museum at Oxford, by his eminent successor. Professor Phillips, F.R.S., by whom they have been instructively elucidated in his excellent work on the ' Geology of Oxford,'! lias proportionally advanced the means of determining the ordinal relations and affinities of the genus. The inferences which may be drawn in favour of the Dinosaurian characters of the sacrum will be subsequently discussed. But the demonstration of the sacral characters of the more recently discovered Cetiosauroid genus Omosaurus adds to the grounds for referring the type-species of Cetiosaur to the Dinosaurian group of Reptilia. It is characteristic of the accidents that attend the quest and acquisition of the remains of extinct Vertebrates, that skull, jaws, and teeth should have escaped the careful operations to which we are indebted for the present means of restoring both Cetiosaurus hngus and Omosaurus armatus. Of the former reptile a single doubtful and mutilated tooth was all that Prof. Phillips could refer with any degree of probability to that species. That the side-pits of saurian vertebrae have no essential relation to largely cancellated, pseudo-pneumatic structure of the bones is shown by their presence in the anterior trunk-vertebra3 of the genus for which the uniformly close though coarse osseous textm-e, as in the whale tribe, suggested the generic name Cetiosaurus. The first indication of this type of Saurian was, however, afforded by an inspection of a limb-bone, submitted to me by Dr. Buckland in 1838, when I was engaged in collecting materials for my ' Report ' to the British Association " On the Fossil Reptilia of Great Britain." Buckland had referred to this fossil in his ' Bridgewater Treatise,' 1st edit., 1836, in the following terms: — "There is in the Oxford Museum an ulna from the Great Oolite of Enstone " (Enslow probably meant), " near Woodstock, Oxon., which was examined by Cuvier and pronounced to be cetaceous ; and also a portion of a very large rib, apparently of a whale, from the same locality." This limb-bone I could not match with any then known to me in the Cetaceous order. Yet, save a thin compact outer crust, the osseous structure was, where exposed, like that in the humerus of a "Whale or Grampus ; there was no medullary cavity. In shape the resemblance, though remote, seemed nearest to that of the outer metatarsal of a Monitor Lizard. § * ' Reports of the British Association for the Advancement ofScience ' for the years 1839 and 1841. t " Cetiosaurus longus," lb., ' Report ' of 1841, p. 101 ; ante, p. 413. X 8vo, 1871. § Prof. Phillips, who had obtained, in 18"0, from the Great Oolite at Enslow, the three metatarsals OOLITIC DINOSAURS. 581 Shortly after I was able to differentiate certain saurian vertebrae from those ascribed to the genera Iguanodon, Hylceosaurus, Megahsaurus, and Poikilopleuron, not only by superiority of size, but by differences in form, proportions, and structure.* The latter character applied, more especially, to these huge unknown fossil bones in the comparison with PoikilojiIeHron , in the vertebrae of which four-footed reptile ossification is incom- plete and large chondrosal vacuities are left in the substance of the centrum, which, in the fossils, become filled with spar.f From the similarity of texture of the vertebrae of the new genus of Saurian so indicated to that in the limb-bone from " Blechingdon,'' Enslow, I suggested that it might belong to Cetiosaurus.X The cetaceous hypothesis of the huge Oolitic Vertebrate was thereupon abandoned, and my determination was adopted in the second edition of the ' Bridgewater Treatise,' and also by Lyell, who gives a reduced cut of the fossil in his ' Manual of Geology,' ch. xx. In 1848 Dr. Buckland informed me of the discovery of a femur, 4 feet 3 inches in length, which, from the correspondence of its texture with that of the metatarsal from Blechingdon, and also with that of some fragmentary long bones from Blisworth, Northamptonshire, I referred to the genus Cefiosaiirus, and to the species from the Great Oolite called Cetiosaurus longus. % More recently (1868 — 70) a considerable proportion of the skeleton was discovered in the quarries of the Great Oolite of Enslow Rocks at Kirtlington Station, eight miles north of Oxford, the bones of which more nearly approached in size to the type specimen of Cetiosaurus longus.\ I, therefore, visited Oxford for the purpose of studying these remains. Such of the trunk-vertebrae as were sufficiently entire appeared to have come from the fore part of that region, and showed the opisthocoelian character of those vertebrae as in certain Dinosaurs. In the best preserved anterior dorsal vertebra the parapophysis, short but large in vertical extent, shows remains of the articular surface for the head of the rib. The diapophysis, supported by a strong buttress-like ridge, is directed upward and outward at an angle of 45° with the neural spine. The distance between the articular surface for of each bind foot of a Cetiusaurus, wherewitb he was able to compare the above fossil long bone, "incom- plete at both extremities," considers the determiualiou of it as a metatarsal of large size to be 'probably true.'—' Geology of Oxford,' &c., 8vo, 1871, p. 285. * ' Proceedings of the Geological Society of London,' June, 1811, loc. cit. t The chief of these cavities, being in the centre of the vertebrse, was termed 'medullary' (loc. cit., p. 4.'39) ; but I have since had reason to conclude that it was occupied in the living Saurian by unossified chondrine. X 'Report,' ut supra, p. 101. § lb., ib. Also a?ite, p. 413. II "Vertebrse 8, 9, and 11 inches in diameter," " monstrous ribs," " femora upwards of 5 feet iu length." — 'Athenaum,' April 2nd, 1870. 582 BRITISH FOSSIL REPTILES. the ' tubercle ' and that for the ' head ' of the rib is ten inches, which indicates the extent of the ' neck ' of the rib at this fore part of the thorax. The neural spine is strengthened by lateral buttress-like ridges rising from the neural platform ; it is of a massive quadrate form and seems to have terminated obtusely. The zygapophyses are supported by buttress-like vertical ridges.* All the characters of this massive vertebra bespeak the great strength of the back-bone of the enormous saurian. The total vertical extent of the above vertebra, which is incomplete at the wider part of the centrum, is 2 feet 4 inches ; the breadth at the diapophyses is 1 foot 6 inches. The vertebra which is the subject of ' Binosauria,' PI. 76, from a hinder position of the trunk than the above-described, exemplifies the cetiosaurian characters of texture (fig. 2, p) also of a contracted antero-posterior extent of the neural arch as it rises from the centrum,! and of a partial subsidence of the anterior ball. This vertebra has been crushed and fractured; the right side is pressed obliquely backward for an inch or so beyond the left side, so that the length of the centrum, measured as it has been squeezed out of shape, exaggerates its original or natural longitudinal diameter. This would not exceed, according to my estimate eight inches. The vertical diameter of the centrum has also been pressed down beyond its original extent. I estimate the ball or fore part at 6^ inches, the cup behind at 7 inches, in height. The neural arch, as in the type-vertebrse of Cetiosaurus lonc/iis,X is retained in anchylosed union with the centrum to the extent shown in Plate 76, viz., eight inches. A vertically grooved median ridge appears to commence at the back part of the base of the spine. This process is wanting ; it probably would have added a foot to the present vertical extent of the vertebra, which is sixteen inches. Minor projecting parts have been equally broken away, and, as usual, lost in the quarrying or extricating operations. Such fractures occur on both sides of the prominent rim of the hinder cup of the centrum (as at p, fig. 2, Pi. 76). The singularly naturally compressed upper and middle part of the centrum (ib. /) imderlying the neural canal and forming a vertical plate or medial wall of bone, three to four inches in height, and but six lines to eight lines in thickness, has been in part broken away, exposing that canal. The fore and hind outlets of the neural canal are squeezed into a narrow, vertically lengthened, oval shape (ib., fig. 2, «). The neurapophysis rises by two buttress-like columns (ib., fig. \, n n, n) which converge as they ascend and overarch the lateral depression / . The base of the neural arch is coextensive with the centrum, save in so far as the anterior ball may have projected * "On Cetiosaurus from Oolitic Formations," ' Proc. Geol. Soc.,' 1841, 1. c, p. 459. Cetiosaurus lonyus is defined as in the ' Report,' and distinguished from the Cetiosaurus brevis of the Wealden Forma- tions, pp. 101, 102, which will probably prove to be referable to a distinct cetiosauroid genus. t In the account, illustrated by woodcuts, given by Phillips in his excellent ' Geology of Oxford,' pp. 246 — 294, a vertebra, supposed to be lumbar, the subject of the diagram Isxsviii, p. 257, has assigned to it the following admeasurement: — "Greatest length from front to back (crushed) 46 in." I have found no trunk-vertebrae of the Cetiosaurus from the Kirtlington Oolite sn short as this. X " In all these vertebrae the neurapophyses are anchylosed to the centrum," Ac— ' Report,' p. 102. OOLITIC DINOSAURS. 583 beyond ; but the neurapophysis soon shows, as it rises, the ' short antero-posterior extent/ which is among the characteristics of the genus. One advantage of the fractures, which must otherwise have been got by sections, is the demonstration of the cetiosaurian texture of the bone (PI. 76, fig. 2, p). The resemblance of this close but somewhat coarse osseous tissue to that of cetaceous bone, especially in the larger Whales, and which seems to characterise the whole skeleton of the present genus of gigantic saurians, might well excuse the idea that the huge long bone first observed was cetaceous. The unbroken surface of the vertebra has a fine fibroid character ; the interrupted lines affecting a longitudinal course on the centrum and a vertical one on the neurapopliysis. How far any exposure of the arch at the base of the spine may have formed a part answering to the ' platform ' in the antecedent vertebra, and as in most Dinosaurs, the broken state of the specimens does not allow of determination. Near the borders of the articular ends of the centrum, which are more or less rubbed away, stronger sculpturing is indicated, as if in relatiou to ligamentous attachments. The lower border of the lateral depression, /, is more obtuse, less definite, than in BotJiriospondj/lus (PL 03, fig. 1) ; the vertical convexity of the side of the centrum changes in Cetiosaurus more gradually into the concavity of the depression. The sternum of Cetiosaurus hngus is a transversely elliptical plate with an almost fiat, slightly undulate upper or inner smface (fig. 2); 19 inches broad, 15 inches long, 1 inch 10 \\ inch thick, increasing to 2^ inches at the coracoid articular surfaces, though, probably, the entire expanse of the border here is not preserved. The hind border shows prominences for the attachment of three pairs of sternal ribs, r, r, the hindmost pair in contact, as in Monitor niloticus. In this Lizard the sternum has a rhom- boidal form, with a low median ridge on the outer or under surface, a deep hollow on the opposite surface, and considerable thickening of the articulations for the cora- coids. Were these bones fully ossified in that Lizard they would correspond in breadth with those of Cetiosaurus ; there are, however, two tracts retaining the primitive sclerous state, and an antero-medial part which has not gone beyond that of gristle, in the coracoid of the recent saurian. AVe have, therefore, in Cetiosaurus, as in some other ancient 11/^ Fig. 2. Sternum, Cetiosaurus longus, \^i^ nat. size. (Phps., ' Geol. of Oxford,' part of diagr. xcviii, p. 208.) 684 BRITISH FOSSIL REPTILES. Fjg. 3. Right. Left. Scapula, Cetiosaurus longus, ^'^th nat. size. (Phps., diagr. xcix, p. 270.) saurians, notably of the order Dinosauria, a degree of lacertian structure combined with a crocodihan advance of vertebral and concomitant cardiac and pulmonic structures. The scapula of Cetiosaurus (fig. 3) is more crocodilian than lacertian in its proportions. It is an elongate plate, expanded at both ends, but most so and most abruptly at the articulations for the coracoid, <', and humerus, h, h. The more gradual OOLITIC DINOSAURS. 585 Fig. 4. Fio. 5. Right. Right. Humerus, Celiosaurus longiis, x'jth nat. size. (Phps., diagr. c, p. 272.) expansion of the ba.se or free extremity is chiefly due to the hinder border, and this describes a concavity, while the fore border is nearly straight. The outer surface (left) is slightly depressed lengthwise behind a longitudinal ridge near to and parallel with the anterior border. The inner surface (right) has a longitudinal rise near the middle. 586 BRITISH FOSSIL REPTILES. which bifurcates to strengthen tlie humeral and coracoid surfaces, and to add to the thickening of the articular end of the bone. Phillips notes the modification of structure of tiie basal three inches of the blade, indicative of coarse or partial ossification of an original cartilaginous superscapuha, the proportions of whicli element would thus be more crocodilian than lacertian. The resemblance of the blade-bone of Cetiosaurus to that of Scelldoi f^nc^ retain longer that con- dition in the Reptile (Pig. 16, Varanus, p ^ and Scelidosaurus, p t). Tlie attachment of the distal epiphysis with the shaft of the tibia [t) is made firmer in the biped [Dinornis, p t) than in the quadruped (Pig. 10, Ruminant, ;) t) ; and the extent of the attachment is greater, is more irregular or interlocking in the warm-blooded quadruped than in the cold-blooded one; it is still greater in the Bird, in which a process, longer than that in the Ruminant, ascends upon the front of the diaphysis, closely fitting to a groove there, and clamping, as it were, the articular epiphysis to the main shaft of the leg bone. The bigger the Bird the greater the shai-e of locomotion allotted to the hind pair of limbs in standing, walking, or running, the longer is the clamping process and the later is the period of the coalescence of the epiphysis with the shaft. The Ostrich among existing Cursores, and the Dinornis amongst 612 BRITISH FOSSIL REPTILES. extinct ones exemplify this relation. In the metatarsus of the Bird the shafts of the ento-,. raeso-, and ecto-metatarsi are severally ossified from separate centres, but the proximal epiphyses of the three bones are ossified from one centre, and form a single cap of bone where the shafts are still distinct.* Such cap (Eig. 10, Dlnornis, p m) may be arbitrarily homologised with one or more bones of the distal tarsal series in Reptiles (Eig. IG, ScelidO' satcrus, b, e ; in Varanm, h, e) and in Mammals (Eig. 16, Mitminant, b, n, e). It seems more natural to regard it as answering to the epiphysial cap, covering the ends of the two chief metatarsals, of the Ruminant (ib. ib., 2m, Hi, iv), and I associate such instances of complex osteogeny of the metatarsus with the high conditions of organisation differentiating the warm-blooded classes, Aves and Mammalia, from the cold-blooded licpUUa. In the Ruminant, as in the Bird, the single epiphysis and multiple diaphyses coalesce into one so-called ' cannon bone.' In the Dinosaiu'ia the hind limbs are not adapted, as in the Birds, for transference of the entire Aveight of trunk, neck, head, and fore limbs, from the leg upon the foot by due development and modifications of the main leg-bone, the tibia ; but the fibula is continued to the ankle-joint, and takes a larger share in its formation than is usual in Mannnals. Both leg-bones have their distal epiphyses (Fig. 16,^/,;, t. Scelidosaurus, Varanus). The tarsal segment is represented, usually by four ossicles : one, a, answers, by its connections, to the astragalus, naviculare, and entocuneiform bones of the Mammal ; a second, I, repre- sents the calcaneum with the lever process slightly if at all developed ; there are, also, a cuboid, I, and an ectocuneiform, e- The metatarsals, whether they be three or four in number, never coalesce, but retain their primitive distinctness throughout life. The sole ground taken to bridge over this significant difference in the structure of leg and foot in the Bird and Dinosaur is to affirm that the distal epiphysis, pf, of the tibia in the Bird, is the homologue of the astragalus in the Mammal and Reptile (Fig. 16, a).t " If the whole hind-quarters, from the ilium to the toes, of a half-hatched Chicken could be suddenly enlarged, ossified, and fossilised as they are," | the ilium would be distinguished from that of a Dinosaur by the major number of its sacrovertebral attach- ments and by their greater extent, by the absence of the ridge continued from the super- acetabular plate upon the antacetabular one ; the pelvis would be distinguished by the presence in the ischium of an obturator process wanting in the Dinosaur (Eig. 12, is), and by the absence of a pectineal process of the pubis present in the Dinosaur (ib., pi), by the parallelism of the ischium and pubis, and by the backward extension of both bones (compare Eigs. 12 and 14). The differences grow and multiply as the comparison proceeds ; as, e.(/., by the non-extension, in the Chick, of the fibula (Eig. 14,/i) to the ankle-joint and by the larger and more complex distal epiphysis of its tibia (Eig. 16, Binornis), by the * 'Transactions of the Zoological Society of London,' 4to, vol. iv (1856), p. 149, pi. xlv {Dinornis elephantop^is, puUus ; Binornis crassvs, pullus). t Prof. Huxley, ' Quarterly Journal Geol. Soc.,' vol. .xxvi, p. 29. ; X lb., loc. cit., p. 30. LIFE . AND KINSHIP OF DINOSAURS. C13 absence of a tarsus, by the backward direction of the innermost or first toe (Fig. 16,0, as con- trasted with the parallel position of that toe with the second toe in the reptilian foot (Fig. IG, Scelidosaurus, Varanus). If the entire skeleton of an immature Chick, Ostrich, or Moa were enlarged, whether suddenly or gradually, to the dimensions of that of a Cetiosaiu", and were so ossified and fossilised, the characters of the dorsal vertebrije, of the cervical ver- tebrae, of the skull, and the absence of an anterior pair of limbs with fore-paws organized to be applied to the soil and take their share in the support and progression of a long and bulky trunk and massive head as in the Dinosauria, would be decisive against the reference of such imaginary gigantic Chick to any known representative of the Dinosaurian order of Reptiles. But, to the Biologist who rejects the principle of adaptation of struc- ture to function, the foregoing facts and conclusions will have no significance. By a modification of the hind-limbs the Bear, and by addition of a longer sacrum to plantigrade feet the Ground-sloth, may assume a crouching bent-kneed attitude and hold the fore-limbs free to grapple with a foe or a tree. Such is tlie plasticity of some mammalian structures that, by due training, a Bear, a Dog, or a Monkey may be taught to dance and walk erect for a brief space. It may be doubted whether a cold-blooded, small-brained Reptile could by any training be brought to exemplify the mode of motion conceived in the quotation at p. 609, note t- But that, like the Chlamydosaur with its long-toed, wide-spread, hind feet, the huge Dinosaurs might assume the fighting posture of the Bear, when occasion called them to wield their carpal weapons, is conceivable without commission of physiological or anatomical solecism. The woodcuts, p. 603, Figs. 12, 13, 14,* give the pelvis and hind limb of a Moa [Dinornis) and of a Crocodile {Crocodiliis) for comparison with the corresponding parts of a Dinosaur {Omosaurus) : the position, proportions, and structure of the foot of which are guaranteed by those of Ir/iianodon and Scelidosaurus. In the Crocodile the foot may be applied flat to the ground and the thigh turned out nearly at right angles to the body ; but, in some phases of progressive motion, the limb can assume the position delineated: the same may be predicated of the Dinosaurian Reptile. The Bird occasionally rests on the foot, with the metatarsus flat to the ground : but the thigh cannot be turned outward at the angle, which is possible in the Dinosaur and Crocodile. When an accessory trochanter is present in the femur of a Dinosaur {Iguanodon, Scelidosaurus), it projects from the inner border of the shaft, not from the outer one, as in the restoration given in Fig. 3, p. 27, 'Quart. Journal Geo). Sec.,' vol. xxvi, 1S70. * The letters have the same signification throughout ; U, ilium ; a, antacetabular plate ; I, post- acetabular plate ; ib (in the Dinosaur) marks the superacelabular plate ; is, ischium ; pb, pubis ; /, femur (of this only the lower part of the bone is given, so as not to conceal parts of the pelvis important in the comparison); ;, tibia ; 6 or /J, fibula ; as, astragalus ; ca, calcaneum ; ci, cuboides ; ;", inner or first toe; !i, second toe ; Hi, third toe ; iv, fourth toe ; v, rudiment of fifth toe. 614 BRITISH FOSSIL REPTILES. When the question as to tlie power of predicating homologies both special and genera], as in the case of the bones of the vertebrate skeleton,* became finally accepted, the hypothesis of the successive incoming of specific forms or modifi- cations of the vertebrate archetype through the operation of secondary causes was the only one which could adapt itself intelligibly to the facts. In enunciating my conviction that ' nomogeny,' i. e. natural laws, or secondary causes, had so operated " in the orderly succession and progression of such organic phenomena," I laid myself open to comments from opposite quarters. On the one hand, the admitted ignorance of the nature and mode of operation of such secondary cause or causes led to the rebuke by a Successor in the chair of the Hunterian Professorship, to wit, that, as to the secondary origin of species, my ' trumpet gave an uncertain sound.' On the other hand, an able, theological critic blew the following note of alarm : — "It is not German naturalists alone who are contributing to diffuse scientific Pantheism. We have in England an anatomist, Richard Owen. To call him an atheist because of his scientific conclusions would be an imper- tinence ; nevertheless, in a lecture on ' The Nature of Limbs ' which was delivered at the Royal Institution of Great Britain in February last, and has since been published, he brings all his scientific knowledge and demonstrative skill in support of what is called the Theory of Development, and which has become popularly known by its introduction into the book called the ' Vestiges of Creation.' This theory of development, as our readers may know, assumes that God did not interpose to create one class of creatures after another as the consequence of each geological revolution ; but that, through the long course of ages, one class of creatures was deveIoj}cd from another. Now, Richard Owen midertakes to demonstrate scientificaUy (and his demonstration is very rigorous) that the arms and legs of the human race are the later and higher developments of the ruder wings and fins of the vertebrated animals— that is, those which have a true back- bone ; and he shows in the splint bones of the foot of ahorse, bones analogous to those of the fingers of the human hand. Therefore he concludes that God has not peopled the globe by successive creations, but by the operation of general laws." t The sole ground for Professor Flower's depreciatory remark is my acknowledgment of being " as yet ignorant "% of the nature or way of operation of such general or secondary laws; and I regret to say that after all that has been advanced since 1849 in the endeavoiu' to elucidate the Avay in Avhich one species may be transmuted into another, I am still in need of lio;ht. Assuming that the ornithic modification of the vertebrate archetype was one of those under which the ' vertebrate idea ' became embodied in the course of progression from * ' Hunterian Lectures,' Royal College of Surgeous, 1844; 'Reports of the British Association for the Advancement of Science,' " On the Archetype and Homologies of the Vertebrate Skeleton," 8vo, 1846;. and ' Discourse on the Nature of Limbs,' 8vo, 1849. t ' Little Lectures ou Great Topics,' 12mo, 1849. X 'On the Nature of Limbs,' p. 80. LIFE AND KINSHIP OF DINOSAURS. 615 " its old Iclithyic vestment,"* two questions present themselves : — Out of what antecedent vertebrate modification was the avian one evolved ? How, or under what conditions or secondary influences, was such evolution efiected? The hypothesis of the bipedal locomotion of the Dinosauria, the advocated homology of their OS pubis with the ischium of the bird, and the alleged restriction of the avian antacetabular production of the iliac bone to the Binomuria among Reptiles, have been superadded to the proved fact of a correspondence of structure between the shortei sacrum of the Dinosaurs and the longer sacrum of Birds as grounds for the conclusion that Birds are transmuted Dinosaurs, and that the feathered class made their first step in advance under the low form of Sfruthiones or Cursores, incapable, as yet, of flight. The kind and amount of modification required to evolve an Ostrich out of an Iguanodon may be appreciated by the osteological comparisons already submitted in the present section of this work. To revert only to the structure of the fore-limb. In losing its power of aiding in the quadrupedal progression, and of grasping or otherwise applying the hand, it has as yet, in the hypothetical first form of Birds, gained no other faculty. At best it may help in the swift course of the ostrich by flapping motions similar to those of better birds during their flight; or the more minute moiiodactyle hand may just serve to scratch the back of the head, as in the New Zealand Kivi. In their larger extinct relatives, the ]\Ioas, it is still doubtful whether more of the framework of a fore-limb existed than the supporting scapular arch, and that of the simplest character. In all these gradations of structure of a limb unavailable for flight or any other mode of locomotion we see no approach in the scapula to the Dinosaurian types of that bone ; it retains in all Cursorials the strictly avian sabre-like shape and pointed free extremity, without expansion and truncation there such as obtains in the alleged ancestral Reptilia.\ The coracoid still further departs from any well-determined Dinosaurian type of the bone, and as closely adheres to that of the Birds of flight, save such decrease of breadth and of relative size as accords with its necessity to bear upon the sternum in the mechanical mode of inspiration peculiar to Birds with Pterodactyles. What could be the conceivable conditions of the life of an Iguanodon or Megalosaur which rendered a fore-limb useless or cumbersome, and concomitantly called for lengthened and strengthened hind-limbs and a more vigorous and exclusive exercise of these in the acts of locomotion ? The abettors and acceptors of the exposition of the operation of the secondary mode of origin of species by way of ' natural selection ' are amenable to the call for an explanation of such conditions, especially if such mode of origin be hypothetically applied to the kinds of Birds deprived of the power of flight. But such explanation would have to square with the fact that a loss of one pair of limbs had been associated, on the assumption of the Dinosaurian ancestry, with an advance of the mechanical structure * ' Ou the Nature of Limbs,' p. 86. f Compare, tor example, the scapula of the Apteryx, 'Transactions of the Zoological Society,' vol. ii, pi. XXX, fig. 2, g, and figs. 3 and A, with Cut, fig. 3, p. olsG. 15 b 616 BRITISH FOSSIL REPTILES. of the organs of circulation, and a progress in the extent and perfection of the lungs, together resulting in the higher temperature, with more numerous and minute coloured discs, of the blood. For these conditions of the vital organs characterise alike both winged and wingless Birds, and the resultant unvarying warmth of the body is accompanied by a clothing of down and feathers, the most exquisite and complex of all tegumentary coverings, common to the Kivi and Ostrich with the Eagle and Swift. But there are other hypotheses of the way of operation of secondary genesis of species anterior in date to that of Darwin. The influence, viz., of exercise and of disuse in altering the proportions of parts mooted by Lamarck ;* the hypothesis of ' degeneration ' pro- pounded by Buffon ; f and the effects of congenital changes in parts of the body, mainly depended upon by the author of ' Vestiges,' in his endeavour to explain the way of operation of the secondary law of the origin of species. The comparative ease is so refreshing, aft^r the labours of induction and dry descrip- tion, in supposing a case, that I may be forgiven for indulging in a suggestion of a possibility of the few still extant wingless or flightless birds having originated, not from any lower cold-blooded vertebrate form, but from higher active volant members of their own warm-blooded feathered class. Consideration of extinct kinds, in the restoration of which I have been occupied, has strengthened the supposition. Here, in yielding to this indulgence, I own to finding more help from the Lamarckian hypothesis than the Darwinian one, and I am ultimately led to propound the SfruthionidcB as exemplifications of Buffon's belief in the origin of species by way of degeneration ; on other grounds than those on M'hich my anonymous Critic, above cited (p. 614, t), views the Papuan and Boschisman in relation to an antecedent higlier, indeed perfect, form of man. Let us suppose, for example, an island affording abundant subsistence to vegetarian birds, and, Jinppily for them, to be destitute of creatures able or desirous to destroy such birds. If the food was wholly, or chiefly, on the surface the power of traversing such surface would be of as much advantage to the bird as to the herbivorous quadruped. As flight calls for more effort than course; so cursorial progression would be more commonly practised in such a happy island for obtaining the daily food. The advent or proximity of a known element of danger might excite the quicker mode of motion ; the bird would then betake itself by a hurried flight to a safer locality. If, however, certain insular birds had never known a foe, the stimulus to the use of the wings would be wanting in species needing only to traverse the ground in quest of food. In the case of New Zealand, for example, the roots of wide-spread ferns, being rich in farinaceous and amylaceous princi- ples, the habit of scratching them out of the ground would lead to full development of the muscles of the leg and foot. So, such daily habitual exercise of legs and feet by unscared Rasorials would lead in successive generations to strange developments of hind-limbs ; * ' Philosopliie Zoologique,' 2 vols., toni. i, chaps, iii, vi, vii, 8vo, 1803. j- ' Histoire Naturelle,' torn, xiv, p. 311, 4to, 1/66. LIFE AND KINSHIP OF DINOSAURS. 617 whilst the disuse of the wings during the pre-Maori aeons would lead to their atrophy. The Laniarckian hypothesis has, in fact, this advantage over others of like kidney, that pliysi- ology testifies to the relation of growth to exercise, and of waste to disuse, and so far votes in favour of the conditions evoked by Lamarck as vera causae in transmutation. We recog- nise in the stunted wings of the Dodo evidences of its affinity ; as, for example, by their close conformity, save in size, and in the prominence of their processes for muscular attachments, to the scapula, coracoid, brachial and antibrachial bones, carpus, metacarpus, &c., of the perfect instrument of flight in truly winged birds, and such conformity of structure is agree- able with the hypothesis of the origin of the Mauritian species of ground-pigeon through descent or degeneration. The differences which the wing-bones of the Dodo present when compared with their homologues in the Ic/uanodon is in the same degree adverse to the hypothesis of its evolution from any such reptile, in the direction of ascent and improve- ment. The same course of argument applies to the impennate Awk, the Cassowary, Rhea, Ostrich, &c., as to the wingless birds of the Mascarene, Polynesian, or Melanesian Islands. Confidence in the impartial exercise by Biologists of the logical faculty leads to the conclusion that their science will accept the view of the Dodo as a degenerate Dove rather than as an advanced Dinothere. But whence the dove .- Are we then, I will not say driven, but rather guided, to the old belief that the winged bird was " created " in the sense of being .miraculously made, at once, out of dust, agreeably with the alternative hypothesis conceived by my critic ? Or, is a belief in a Dove's coming to be through the operation of a secondary law still legitimate and germain to our truth-seeking faculties ? Not necessarily relegating an honest inquirer to the bottomless pit of Atheism, if he should happen to ask : — AVere there no volant vertebrates of earlier date and lower grade than the " Fowls of the Air" ? Without knowing or pretending to know the way of operation of the secondary cause, the vast increase of knowledge-stores of biological phenomena makes it as impossible to com- prehend them intelligibly in any degree, on the assumption of primary or direct creation of species, as it was impossible for Copernicus to understand and explain the vast accession of astronomical facts in his day, on the belief of the subservient relation of sun to earth, of the posteriority of the creation of the luminary to that of the light-receiver, and of their respec- tive relations of motion, as received in his day. To the objection, how, on his assumption of the diurnal rotation of the earth, loose things remained on its surface, Copernicus could offer no explanation. Neither has the Biologist been able, as yet, to explain how the Ramphorhynchus became transmuted into the Archeopteryx. It is open, of course, for any one to deny such change. What seems to me to be legitimate, in giving an account of the labours that have resulted in a certain accession to the know-ledge of extinct forms of cold-blooded, oviparous, air-breathing Vertebrates, is the indication of the respective vicinity of certain groups of such now much reduced class to the warm-blooded oviparous Vertebrate air-breathers which in our times so greatly prevail in life's theatre. 618 BRITISH FOSSIL REPTILES. Every bone in the Bird was antecedently present in the framework of the Pterodactyle j the resemblance of that portion directly subservient to flight is closer in the naked flyer to that in the feathered flyer than it is to the fore-limb of the terrestrial or aquatic Reptile. No Dinosaur has the caudal vertebrae reduced as in Birds ; many Pterodactyles manifist that significant resemblance. But some Pterodactyles had long tails and all had toothed jaws. A bird of the oolitic period * combined a long tail of many vertebrae with true avian wings, and it may have had teeth in its mandibles. It is certain that a later extinct bird.f though of an early tertiary period, far back in time beyond the present reign of birds, had tooth- like processes of the alveolar borders of both upper and lower jaws. Fact by fact, as they slowly and successively drop in, testify in favour of the coming in of species by ' nomogeny,' and speak as strongly against ' thaumatogeny ' J or the multiplication of miracle on the alternative hypothesis of the writer of ' Little Lectures on Great Things.' He and his school invoke a cataclysm to extinguish the Palgeothere, and an inconceivable operation to convert dust into the Hippothere ; yet a slight disproportion of the outer and inner of the three hoofed toes of each foot of these quadrupeds is their main diff'erence. jMy critic again invokes a cataclysm to extinguish the race of Hippotherian species and again requires the miracle to create the Horse. Yet the loss of the small side-hoofs that dangled behind the main mid-hoof in the Hippothere is the chief organic distinction between liippotherium and Hippos. Every bone, every tooth, present in the eocene and miocene predecessors of modern Horses is retained in them, with slight changes of shape and proportion. The second and fourth metacarpals which bore hoofed dioits of moderate size in eocene davs, bore them of diminutive size in miocene days ; and now, when such dangling spurious hoofs are gone, their metacarpal and meta- tarsal suspensories still remain, hidden beneath the skin, and ending in a point where, of old, was a well-turned joint. It has become as impossible to square the hypothesis of " the peopling of the globe during the long reign of life thereon, by successive and s])ecial creations " with the known vital phenomena, as it was impossible to explain the sum of astronomical facts, accumulated in the fourteenth century, by the cumbrous machinery of cycles and epicycles, necessitated under the assumption of the globe as the fixed, central, and largest body of the Universe. Biology seems now to be at the Copernicau stage ; and if the rejection of the incoming of species by primary creative acts should exercise an influence on the pro- gress of that science akin to that of astronomy after the abandonment of the faith in the earth's fixity, Biologists may confidently look for as rapid a progress through acceptance of Nomogeny. What, then, may be the meaning of the reduction of bulk in the fore-limbs of certain Dinosaurs ? Does that reduction indicate a step in the conversion of such Reptiles into * Archeopteryx, ' Pliilosopliical Transactions,' 18fi3. t Odou/opferi/.r, ' Quarterly Journal of the Geological Society,' 1873. X 'Anatomy of Vertebrates,' 8vo, vol. iii, p. 81-1. LIFE AND KINSHIP OF DINOSAURS. 619 Birds ? Do we get an explanation of the small fore-limbs by the picture which Professor Phillips, under Huxleyan guidance, vividly presents to us " of the grand and free march on land chiefly, if not solely, on the hind-limbs ?" Or, is the fact of the disproportion of size between the arms and legs in the Megalosaur and Iguanodon susceptible of other than the Oxfordian hypothesis ? As a matter of fact, such disproportion is shown by Crocodilian Reptiles still in existence ; whilst extinct Crocodiles of more aquatic habits and marine sphere of life had the fore-limbs as much reduced in size as in any known Dinosaiu'.* Of this Teleosaurian character the physiological explanation which has been advanced is, that the com-se of such Crocodile through water, due to the action of the long, laterally flattened tail, would be facilitated, or less impeded, by such reduction of size of the fore-Hmbs ; those limbs taking no share in the forward dash of the piscivorous reptile in pursuit of its prey, and, if of any use in the water, being limited in natatory evolutions to assist in a change of direction ; the fore-limbs, in fact, being mainly if not wholly required to help in the progress of the amphibious beast upon dry land, or to scratch out the nest in the sand. Actual obser- vation of a swimming Crocodile or Lizard testifies to the fore-limbs being then laid flat and motionless upon the sides of the chest. All known Dinosaurs have the Crocodilian swimming organ ; the Iguanodon exemplifies the compressed vertically broadened tail in an eminent degree. And just as such appendage was essential to the proportion of the active life of these huge cold-blooded amphibians which was spent in the watery element, so such far-produced caudal fin must have been a cumbrous impediment to the way of walking upon dry land pictured in the Work and Paper above cited.f In the ratio in which the fore-limbs approach the hind ones in size may be inferred the proportion of time spent by the huge reptile on land, and the importance of the share taken by these Hmbs in such quadrupedal mode of progression : when the Dinosaur betook itself to water its fore-limbs would be, most probably, disposed as in the Crocodiles. If, then, the hypothesis that the reduced fore-limbs of Dinosauria receive the most intelligible, and therefore acceptable, explanation, admitting the principle of adaptation of structures to functions and reciprocally, agreeably with the analogy of such living animals as are most nearly allied to them in organization ; the notion that Birds, under their wingless conditions, were derived from Dinosaurs may be safely left to the judgment of whomsoever may be disposed to bring unprepossessed and impartial judgment to the consideration of the hypothesis. * ' Crocodilia,' Plate 1, of the present "Work, and "Monograph on the Fossil Reptilia of the London Clay," part ii, in the Volume of the Palreontographical Society for 1849, p. 24, t. xi. t Phillips, ' Geol. of Oxford,' p. 19G; and Huxley, ' Quarterly Journal of the Geological Society,' 16^ 620 BRITISH FOSSIL REPTILES. Qenus — Omosaurus. [Continued.) Species — Omosaurus hasti(jer, Owen. (' Dinosauria,' Plates 77 and 78.) If the gi'ouncls assigned in a former part of this worlv (p. 577) for the probable homology of the unsymmetrical spine figured in Plates 74 and 75, which spine was found with the bones of the fore-limb of Omosaurus armatus, should be deemed to warrant such conclusion, a similar one may be provisionally accepted as applicable to the pair of spines of similar size and character discovered in the same division of the Kimmeridge Clay, in the Great Western Railway Cutting at Wootton Bassett, Wiltshire, briefly referred to at p. 577. Many large Saurian fossils were collected from the sections of Kimmeridge Clay at that time exposed ; but none have reached me save the subjects of the present Mono- graph, which were there obtained by William Cunniugton, Esq., F.G.S., and have passed with the rest of his collection into the possession of the British Museum. The apical portion of each spine has been broken away, but the degree of decrease from the base affords satisfactory grounds for the restoration given in Plate 78, the ratio of decrease being less in the present species than in the almost perfect spine of Omosaurus armatus (Plate 74). The base of the spine (Plate 78, h) expands from the body, «, more suddenly and in a greater degree in Omosaurus hastiger. It is suboval in form and, as in Omos. armatus, its plane is oblique to the axis of the spine. The long diameter of the base is 9 inches, the short diameter is 7 inches. The articular surface is divided into two unequal facets by a low ridge of the base (Plate 77, fig. 1, r, r) parallel with the long diameter of the base; each facet is feebly convex lengthwise, less feebly concave transversely. The surface for attachment is roughened by low short ridges diverging from the long ridge, r, and is irregularly pierced by vascular canals ; the borders are thick and irregularly notched. The body of the spine is continued more directly from one end (Plate 78, figs. 1, 2, 3) of the oval base, a, fig. 2, sloping and expanding more gradually to the opposite end of the base, b, fig. 2. The body of the spine is a full oval in transverse section (ib., fig. 4), pointed at each end, where the two opposite edges, d, e, are cut. The anterior edge (fig. 1, d), begins about G inches beyond the anterior produced part of the base; the posterior edge (fig. 3, e) begins about 2 inches from that end of the base. Both edges extend along the presei'ved portions of each spine, and were probably continued to, or near to, the pointed OOLITIC DINOSAURS. 621 end. An additional advantage as a lethal or piercing weapon must have been derived from this two-edged structure. In the right spine (fig. 1) the length preserved is 14 inches; in the left spine (fig. 3) the length preserved is 10 inches. Each spine may be estimated to have been upwards of 20 inches in length when entire. The transverse section taken from the broken end of the left spine (fig. 4) gives 4 inches and 3^ inches in the two diameters -. the broken end of the better preserved spine gives 3 inches and 2f inches in the two diameters ; the spine approaches to a circular section as it nears the pointed end. The texture of the outer inch is a compact bone susceptible of a high polish ; it becomes finely cancellous within a few lines of the central cavity, the section of which at the part cut, viz. 8^ inches from the base of the spine, gives 1 inch 6 lines, and 1 inch 3 lines, in the long and short diameters. The close correspondence of the present fossil in general form, in basal modifications for attachment, and in texture, with the spine, probably left carpal, of Omosaurus armatus, will be obvious on comparison of Plates 77 and 78 with Plates 74 and 75 of a former part of this work, treating of that species ; and such correspondence may be deemed to support the provisional reference of the carpal (?) spines from the Kimmeridge Clay of Wootton Bassett to the same genns as that from the Kimmeridge Clay of Swindon ; they manifestly indicate a distinct species on the above hypothesis of their nature. The osseous core of the carpal spine in Ic^uanodon (p. 508, Plates 46, 47) difi'ers chiefly in its relative shortness or speedier diminution from the base to the apex. After a comparison of these fossils with all the examples of carpal and tarsal spines in existing vertebrates, I found the nearest resemblance to the basal expansion, by which the spine of Omosaurus has been attached, in the tarsal spine of the Platypus {Ornitho- rliynchm ]jaradoxus,Y\d\jQ 77, fig. 2, twice natural size). There was the same pro- portion of breadth to the body of the spine ; the same sudden expansion to form the base ; the same medial rising in the long axis of the base, and furrows extending therefrom to the margin. But these radiating furrows are more numerous, and the spine, though it is hollow as in Omosaurus, has that cavity converted by terminal apertures into a canal, and this canal is traversed, as in the poison-fang of certain Ophidian Reptiles, by the duct of a gland. The atfinity shown by the Monotrematous Mannnals to the Reptilia in certain parts of the .skeleton is well known, and is closer in the structure of sternum, coracoids, and clavicles, than in any Bird. 622 BRITISH FOSSIL REPTILES. Order. DINOSAURIA. Genus — Chondrosteosaurus. Species — Chondrosteosaurus (jigas, Owen. (' Dinosauria,' Plates 79 — 82.) The flatness of the under surface of the vertebra figured in Plates 79 — 82 recalled the character of that of Boihriospondylus snffossus (p. 551, Plate 61), and, with the pre- dominance of the transverse over the vertical diameter, suggested that it also might have come from the sacral series. The hemispheroid convexity, however, of the anterior end, notwithstanding abrasion of the articular surface itself, and the proof of its truly indicating such form given by the more perfect preservation of that surface in the opposite concave articular end (Plate 80), too plainly pointed to a much more forward position of this remarkable vertebra in the backbone series of the huge Reptile which it represents. That the vertebra is from the fore part of the trunk may be inferred from the presence, on each side, of both a parapophysis (PL 79, ;j) and a diapophysis (ib., d), indicative of the bifurcation of the proximal end of the rib into a capitular and a tubercular articulating process. The portion of neural canal preserved (Plates 80 and 81, «) gives the vertical diameter of the centrum. There is no indication in the concave articular surface of that diameter having been diminished by posthumous pressure. The gentle transverse con- cavity of so much of the broad under surface as is preserved (Plate 79) is evidently natural. The deep depression (Plate 82, fig. 1,/) on each side of the centrum betvpeen the par- and di-apophyses recalls a vertebral character of the genus Bothriospondylus. The parapophysis (Plate 79, fig. 1, p) projects from the level of the under surface: it commences behind, four inches from that end of the vertebra, as an extension of the lower border of the centrum, curving outward and gaining vertical thickness as the process advances (Plate 82, fig. 1, p), the fore part of the base of the process occupying the lower vertical half of the centrum, and terminating very near to the beginning of the anterior articular ball. The neurapophysis (Plates 80, 81, 82, w«), which has coalesced with the centrum, begins to rise about two inches in advance of the hinder cup. The part of the broken base there preserved yields a transverse thickness of 3^ inches. Anterior to this the upper surface of the centrum has been abraded to the level of the neural canal, but sufficient is preserved to show that the neurapophysis loses thickness at the middle of the vertebra, and appears to regain it as it approaches the anterior ball (Plate 81, fig. 1). The base of the diapophysis (Plate 81, fig. 1, rf), at the part of the neurapophysis pre- OOLITIC DINOSAURS. Cy2^ served, gives a fore-and-aft extent of ;3j inches, and a vertical dianaeter of 2 inches, from -which the size of the tubercle of the rib may be inferred. Restoring the margin of the posterior concavity and the articular surface of the anterior convexity, the length of the centrum of this vertebra would be 1 foot 3 inches. The whole of the side of the centrum is occupied by a deep oblong depression which, probably, lodged a corresponding saccular process of the lung. On one side this depres- sion was partially divided by a thin oblique plate (Plate S,C, tig. 1,/, /). I deem it much more probable that the large cancelli obvious at every fractured surface of this vertebra (ib., fig, 2) were occupied in the living reptile by iniossified cartilage, or chondrine, than by air from the lungs, and consequently have no ground for inferring that the whale-like Saurian, of which the present vertebra equals in length the largest one of any Cetacean recent or fossil, had the power of flight, or belonged to either Pterosauria or Aves. The neural canal (Plate 81, «) indicates a centre of origin of motory nerves subservient to less energetic, more sluggish, movements than in the volant groups ; movements probably exercised more commonly in the aqueovis than the gaseous atmo- ■spheres ; and it leads to the inference that, when emerging, the huge frame was sustained by the solid earth on limbs of dinosaurian proportions. The neural canal at the middle of the vertebra yields 1 inch, 3 lines in diameter, and expands to that of 2 inches at its hinder outlet ; it is here, therefore, one fourth the transverse diameter of the vertebral centrum. In a corresponding vertebra of an Eagle (Plate 81, fig. 2) the posterior outlet of the nem-al canal, n, is 4 lines in diameter, that of the end of the centrum, there, being 6 lines in diameter : the relative size of the myelon, here indicated, harmonises with the rapid and powerful exercise of muscles of flight deriving their motive energy from an adequate nervous source. The contrast in the relative size of the myelon and vertebra between the Eagle and the Chondrosteosaur is shown by figs. 1 and 3, n, in Plate 81. The specimen here described and figured was obtained from the submerged Wealden deposit on the south coast of the Isle of Wight, and was purchased for the British Museum . The extreme modification of structure in the vertebrae of Cliotidrosfeosaurus contrasted with that of the subjects of Plates Gl — 73 leads me to refer them to a distinct genus from BotJiriospondi/lus ; but it is a nearly allied one. I had a vertical longitudinal section made of a rolled and worn centrum, of smaller size than the type of Chondrosteosaurus gi(jas, but of similar proportions. It is figured three fourths of the natural size in Plate 82, fig. 2. The black tint indicates the ossified proportion of the vertebral substance ; the lighter tint the chondrosal proportion, filled in the fossil by Wealden marl. 624 BRITISH FOSSIL REPTILES. Species — Chondrosteosaurus magnm. (' Dinosauria,' Plates S3 — 85.) In the subject of Plate 84 sufficient of the concave articular surface is preserved to show its correspondence in size with that of the subject of Plate 80, but its pro- portions are reversed, the vertical diameter plainly appearing to surpass the trans- verse one. The present vertebra, it is true, has come from a more posterior part of the column. The parapophysis has disappeared, at least from the position from which it projects in the subject of Plate 79 : if such process was present its origin has risen to near the base of the neural arch. So much of the free surface of the centrum as remains is concave lengthwise ; all trace of flattening of the inferior surface has disappeared. The curve of the free surface toward the fore end of the centrum indicates that vertebral element to have been shorter absolutely, and much more so relatively to the hinder cup, than in Cliondrosteosaurm (/igas. It is hard to suppose that so extreme a degree of modification of shape and proportion should be present in an anterior and a middle dorsal vertebra of the same spine or in the same species, as is exemplified by the subjects of Plates 80 and 84 ; I therefore refer them to distinct species. The present vertebra agrees more closely in proportions with that of which a side view is given in Plate 83. The centrum is shorter in proportion to both breadth and height than in Chondro- steosaurus gigas. The rise in the position of the parapophysis shows the vertebra (Plate 83) to have come from a more posterior part of the spinal column than the subjects of Plate 79, and of fig. 1, Plate 82. The outlet of the side-pit is shorter and deeper (vertically) ; yet the long diameter of the aperture is about one third that of the centrum ; its compact lining layer of bone is entire. The fore end of the centrum shows the con- vexity, the hind end the concavity, characteristic, with the chondrosal texture of the bone (Plate 85), of the present remarkable genus. The neurapophysial bases extend to within an inch and a half of the hind margin of the centrum ; they rise at the beginning of the convexity of the fore end. This convexity has suffered abrasion, and the widely cancellous structure is exposed, as shown in Plate 85. It seems not needless to remark, in reference to such fossils, that the primal basis of the vertebrate skeleton may be converted into sclerine or chondriue, and that ossification may begin in either ' membrane ' or ' cartilage.' In some vertebrates, chiefly if not exclusively cold-blooded, more or less of the bone may remain unossified, retaining the antecedent stage, with some slight modification of tissue, to which, as in selachian vertebrae, the term ' chondrine ' has been applied. Such partially ossified bones, when petrified, show corresponding cavities, usually filled with matrix or spar. But this condition of fossil bones may depend on other osteogenetic changes. After substitution of bone-earth for gristle, or the conversion of the entire cartilaginous mould OOLITIC DINOSAURS. 625 into bone, the central part may be alisorbed and marrow be substituted for bone. Then, in the course of fossihsation matrix or spar may be substituted for marrow. Or the absorption of previous solid bone, such as that of a chelonian humerus or femur, may go further ; the marrow may also be absorbed, the wall of the bone may be perforated, or ' tapped,' and air be admitted from a contiguous portion of lung. But in the course of fossilisation the non-ossified parts of the substance of the bone become filled by the same mineral infiltration whether the cavities in the recent state contained chondrine, marrow, or air. The inconsiderate conclusion that fossil bones with large vacuities and thin compact osseous walls and partitions must have been bones of volant vertebrates led to the sup- position that certain fossil eggs belonged either to Pterodactyles or Birds, because the bones of the unexcluded embryo showed the hollow or tubular character. Such eggs in a portion of stone from a quarry in the Island of Ascension were submitted under this impression by Lyell, in 1834, to my examination. The characteristic scapula and coracoid of a chelonian embryo were detected in the petrified contents of the fossil egg. To the objection, based on the hollowness of those limb-bones, against the reference of those bones to the reptilian genus, I showed, by dissection of a newly hatched Chelone preserved in spirits in the Hunterian Museum, that the cavity of such bones was filled with chondrine, not with air, and I explained to my friend that the thin outer shell of bone was a transitory embryonal character, and that the femora, humeri, and other bones became massive and solid in the adult turtle.* Now, the earlier chondrosal stage in the existing genus was not overpassed but retained as the normal adult osteal character of the extinct huge and heavy reptiles of the genus Chondrosfeosaurus. It is a relief to banish the marvellous and awful vision of flying Dragons with vertebrae of the size of those of Chondr. giffcis and Chondr. mat/nus ! Order. DINOSAUR I A (?). Genus — Cardiodon. Species — Cardiodon ruyulosus. In the Wealden and Upper Oolitic, as in other mesozoic formations, the evidences studied in the process of restoring the Reptiles of those periods come to hand, for the most part, fragmentarily. Bones without skull, jaws, or teeth may indicate genera before unknown, such as Omosaurus and Chondrosfeosaurus ; or scattered teeth unasso- ciated therewith may suggest reptiles as huge but be generically distinct from the known * See note in Lyell's 'Principles of Geology,' vol. ii, p. 292, ed. 1835. 626 BRITISH FOSSIL REPTILES. teeth of Iffuanodon, HylaEomurus, or Mcyalosaurus. A happy accident may one day bring to light the connection of the subjects of the present subsection with those of the foregoing of which the dental characters are unknown. In this state of doubt it is convenient to indicate the new fossil by a distinct generic term, and such has been suggested, for the subjects of figs. 2 — 5 of Plate 85, by the heart-shaped form of the crown of the fossil tooth. The crown, being 1 inch in length, 8 lines in breadth, and 5 lines in thickness, might well have come, according to the proportions of the teeth of Hylaosaiirus (Plate 39), and Scelidosaurus (Plate 40), from a Dinosaur with trunk-vertebrse of the size of those of species of Chondrosteosaurus. In the teeth of Cardiodon the ' crown ' suddenly expands above the ' neck,' and thins off to the fore and hind borders (Plate 85, fig. 3), and contracts to a subacute apex (ib., fig. 2). The enamel rises into wavy longitudinal ridges with widish intervals, where it is minutely rugous. The fang is cylindrical, coated with smooth cement. The original or typical specimens of Cardiodon rugidosus were from the ' forest marble ' of Wiltshire.* * See my ' Odontography,' 4to, p. 291, pi. Ixxv a. WEALDEN CROCODILES. 627 Order. CEO COD ILIA. Family. CCELOSPONDILIA.* Ge7ius — PoiKiLOPLEURON. Eucles-DeslongcliampsA (' Crocodilia,' Plate 39.) This genus was established on fossils discovered in the Oolitic building-stone at Caen, Nornaandy, and the characters which have led to the recognition of evidences of the genus in our own Wealden deposits are the shape and texture of the vertebrae, and more especially the latter. By these were determined a caudal vertebra from the Wealden of Tilgate, in the Mantelhan collection, now in the British Museum : which vertebra differed from the type-specimens on which the genus was founded, only by a shght inferiority of size. M. Deslongchamps assigns the length of a ' decimetre,' or thereabouts, to his vertebrae, say 3 inches, 10 lines. The Wealden specimen, which has been fractured across the middle of the centrum, gives a length of that element of 3 inches, 8 lines ; or about 9 centimeters. The vertical diameter of the articular end is 2 inches, 3 lines (58 mm.), the transverse diameter is 2 inches, 2 lines (55 mm.) ; the transverse diameter of the middle, contracted part of the centrum is 1 inch, 4 lines (30 mm.). The external free surface of the vertebra is marked with faint striae, otherwise it is almost smooth. Both terminal surfaces are of a full elliptical form, with the long diameter vertical; they deviate from flatness by a slight concavity. The centrum gradually contracts from the two extremities toward the middle : a diapophysis extends from the upper and hinder part of the side, below which there is a shallow groove, slightly bent with the convexity downward. The neural arch has coalesced with the centrum, and the base of the diapophysis extends from the hinder upper half of the centrum upon the base of the arch. A longitudinal sulcus traverses the anterior half of the under surface of the centrum. The hypapopbysial surface is a single obliquely bevelled plane indicative of the confluent bases of the hasmapophyses, and this is the character of the haemal arch preserved in the Caen specimen. In my 'Report on British Fossil Reptiles'! I did not recognise grounds for specifically difl'erentiating the Wealden Poikilojjleuron from the Poik. Bucldandi of the * This terra refers to the large vacuity in the centre of each vertebral body, simulating a medullary cavity ; ossification is here arrested at the middle, not, as in the Amphica-lia, at the two ends of the centrum. t 'Memoires de la Societe Linueenne de Normandie,' vol. vi, 1838, p. 37. X ' Reports of the British Association,' 1841, p. 84. in 628 BRITISH FOSSIL REPTILES. Caen Oolite. Besides the Tilgate locality I was able to note, after examination of a series of fossils belonging to S. H. Christie, Esq., from the siibmergecl AVealden Beds, Isle of Wight, the " half of a dorsal vertebra from Brook Bay, which agrees in size, in the form of the articular extremity, in the degree of median constriction, and especially in the large size of the medullary" (chondrosal) " cavity at the middle of the bone, with the vertebral characters of Poikilopleuron."* Species. Poikilo2)leuron pusillus, Ow. (' Crocodilia,' Plate 39.) This species is, to me at present, represented by eight vertebras, an ungual phalanx of the rapacious type, and part of a medial symmetrical bone to which are articulated portions of a pair of rib-like bones, as to the nature of which the nearest guess I can make is that they represent part of the series of abdominal ribs with their sternum. All these bones show a compact osseous texture with a smooth or polished exterior, and a section of one of the dorsal centrums exposed, what a fractured caudal one indicated, viz. a large central chondrosal vacuity, such as characterises the centrum of the Oolitic crocodilian genus Poikilopleiiron of Eudes-Dcslongchamps. The reptile, of which the present are fossilised remains, was discovered by the Rev. W. Eox, M.A,, in the south-west Wealden of the Isle of Wight ; it is much smaller than the type of the genus Foikilopleurou from the Caen Oolite, or the Wealden \ertebr3e above referred to Poik. Bucklandi. It may be objected that the present specimens are from a young individual of the same species ; but they show no signs of immaturity, and the caudal hypapophyscs indicate the bases of the piers of the haemal arch not to have been confluent as in the Poikilopleuron Bucklandi, and as in Igiianodon. The vertebral centrums are long in proportion, to their breadth and depth, and the non-articular surface is so concave lengthwise as to give the appearance of the centrum being constricted between the terminal articular surfaces. These arc almost flat. In one trunk-vertebra, the sides of the centrum converge to a carinate inferior surface. In another (Plate 39, flgs. 1 — 3) that surface is less narrow (ib., fig. 2). In both the suture of the neural arch is traceable, but the arch has remained attached : it shows a small facet (fig. 1, p) for the head of the rib at the fore part of the base of the neur- apophysis. A horizontal (diapophysial) ridge (ib. d) extends from the prezygapophysis to the upper surface of the postzygapophysis, broadening as it recedes. The neural spine is compressed, but rises from nearly the entire length of the neural arch. The outer surface of the centrum is compact, smooth, and glistening; and on making a vertical longitudinal section the more definite generic character of the large chondrosal vacuity was exposed, as in fig. 3, ch, 3. * ' Reports of t!ie British Association,' 1841, p. 84. .WEALDEN CROCODILES. " 629 In the series of five vertebrae, including the three hinder lumbars and the sacrum (ib., fig. 4), the costal surface has been transferred to the diapophysial ridge, d, which now extends outward from a contracted base midway between the zygapophyses, the terminal articular surface being supported by a lower buttress-like ridge,/. The under surface of the centrum is here broader than in the preceding vertelira, and is transversely rounded : the carinate character in the dorsal vertebrae, giving space to the abdominal cavity, has here disappeared. In some of the present series the deeply concave side of the centrum has yielded to pressure, and the compact outer wall has been fractured and pressed in upon the chondrosal or quasi medullary cavity. In the last lumbar vertebra the diapophysis, depressed and subelongate, shows a narrow costal surface, d', for a small or short ' false rib.' The two hindmost vertebrae in this series of five are sacral (.? i , « 2) . They have the crocodilian character of limited number, and the non-dinosaurian character of retaining their neural arch in normal junction with the centrum. The doubt expressed as to the ordinal affinities of Poilcilopleuroji,* in my ' Report,' is here dispelled. The diapophysis, short, but broad and deep {s 1, d), terminates in a large flattened semi-oval surface for the sacral rib. The corresponding surface upon an equally large diapophysis in the second sacral has rather less vertical extent(s 2, d)- The centrums appear to have coalesced, but the primitive line of separation of the terminal expanded surfaces is traceable. The neural spines are broken aw^ay in all this series of vertebrae, but their narrow elongate bases indicate the same character as in the detached more anterior vertebra from a smaller individual (figs. 1 and 3, ns). The two caudal vertebrae (figs. .5 — 8) are from the terminal part of the tail where both transverse and spinous processes have disappeared. The low neural arch has coalesced with the centrum, and this, retaining its length, as in the sacral and lumbar region has diminished by loss of transverse and vertical extent. The under surface is canaliculate (fig. 7), and both the anterior and posterior expanded ends of the boundary ridges of the lower groove have articular surfaces, h, h, for a haemal arch. In Plate 39, fig. 9, the compressed subtriangular portion of an abdominal sternum (?) is marked hs ; the pair of abdominal ribs which articulate by expanded thinned-off ends to the sides of hs are marked h, h. The ungual phalanx (ib., figs. 12, 13) is remarkable for its degree of curvature, its strong lever-process, and the deep lateral grooves. The value of this little specimen and fruit of Mr. Fox's persevering researches in the Wealden deposits of his vicinity is its demonstration of the limited crocodilian number of trunk-vertebrae deprived of reciprocal motion upon each other, and with transverse processes thickened and terminally expanded for junction with the pelvis. * " Subsequent discoveries may prove it to belong, like the Megalosaums, to the Binosaurian order ; but, as the Poi/ciloplein-on is, at present, known, it seems to have most claim to be received into the crelor spondjlian family of the Crocodilian order," ' Kep. Brit. Assoc.,' 1S41, p. 85. 630 BRITISH FOSSIL REPTILES. I repeat, with some stress, this character because the experienced and accomplished palaeontologist of the United States, Joseph Leidy, ]\I.D., while rightly recognising the " half of a vertebral body " from a Cretaceous formation at Middle Park, Colorado, as of a Poikilo2}leuron, remarks : — " Poicilophuron was probably a semi-aqnatic Dino- saurian, an animal equally capable of living on land or in water, and perhaps spending^ most of its time on shores or in marshes."* But the cited capacity is enjoyed by Crocodilia equally with Dinosauria ; and Toilcilophuron may well have spent, like its neighbour and contemporary the Telcosaurus, least of its time on shores or in marshes, if the latter were accessible to it in its Oolitic or' Cretaceous localities. The fossil described and figured by Leidy adds nothing to the evidence previously- extant of the affinities of Poikilopleuron ; and if I plead for the retention of the orthography of the estimable discoverer of the genus, I more strongly protest against the addition of a new generic term for which Leidy's fossil yields not a single character.f The geological conditions under which Dcslongchamps discovered his Poikilopleuron; led him to remark : " aussi dut-il passer ime grande partie de sa vie dans les eaux et probablement dans les eaux marines : puisque ses os sont restus dans un calcaire qui doit evidemment sa formation a des debris marins." j Amongst the rounded pebbles discovered in a position suggestive of their having been in the stomach of the Poilcilopleuron, as such pebbles are commonly found in the stomach of a Crocodile or Alligator, Deslongchamps detected the tooth of a Cestraciont Fi3h,§ very significative of the element whence the Poikilopleuron derived its food. Our actual knowledge of the skeleton of Poikilopleuron is sufficiently complete to give the answer to the question, " Whether the cavernous structure of its skeleton was related to pneumatic functions, as in Birds, flying Reptiles, and some others ?'' || The central cavity is completely closed ; no pneumatic orifice or canal penetrates thereto : it had no communication with pulmonary or other air-cells. Nor is the alternative limited to marrow.^ Primitive " chondrine," to which ossification had not extended, most probably filled the vacuity in the vertebral body shown at d, fig. 2, plate ii, of the ' Memoires de la Societe Linneenne de Normandie,' sixieme volume, -ito, 1S38; as in figures of Plate 39, and in fig. 16 of Leidy's plate xv, op. cit. * ' Contributions to the Extinct Vertebrate Fauna of the Western Territories,' p. 268, 4to, 18/3. t Ibid., pi. XV, figs. 16 — IS, " Antrodemus." \ Op. cit., p. 51. § Mem. cit., p. 65, " elle provient tres-probablement d'uue des deruiers proies qu'il avait avalees." II Id., p. 279. \ " Dans les deux series, le corps des vertebres est creuse d'une grande cavite meduUaire (fig. 2 d, et V. 6) ; le tissu spongieux n'existe qu'aux deux bouts ; il y a de chaque cote, dans la gouttiere laterale un trou pour le passage des vaisseaux nourriciers," p. 78 ; " ces vertfebres presentent a I'interieure une grande cavite meduUaire analogue a celle des os longs." Mem. cit., p. 83. WEALDEN CROCODILES. 631 Family.— STEREOSPONDILIA. Genus — Goniopholis. Species — Goniopholis simus, Ow. Crocodilia, PI. 40. This species is founded upon the entire skull, minus the lower jaw, imbedded in the limestone of the Swanage quarry, of which skull a reduced view of the upper surface is given in PI. 40, fig. 1 ; and of so much of the under surface (ib., fig. 2) as could be brought to light by exploratory operation on that part of the imbedding slab. The skull in its general shape corresponds with the broad-faced species of the Procoelian Crocodiles;^ and in the festooned contour of the alveolar borders, with those having teeth of unequal size, and with a crown of mainly the proportions of the teeth in the present Amphicoelian genus. The conclusion conveyed by the latter expression is not, indeed, based upon the discovery of vertebrae in such contiguity with the present skull as to support an inference as to their having formed part of the same skeleton ; but it is a probable one from the association of such vertebrce with the nearly allied species Goniojjholis crassidens {ante, p. 427) ; and such probability is strengthened by the nature of the cranial modifications by which the skull under review differs from those of the Procoelian species most nearly resembling it in shape. The temporal vacuities (ib., fig. 1, t) are relatively larger than in Crocodilus proper, or other broad-faced Procoelians, and are subquadrate in form. The palatonaris (ib., fig. 2, n) is not only larger, but is more advanced in position, so as to come wholly into view on the bony palate, and on the same plane therewith ; and here, moreover, they receive, for completion of their anterior contour, the hinder ends of the proper palatine bones (ib., ib. 20), three fourths only of the border being contributed by the pterygoids (ib., ib. 24). The Eustachian aperture (ib., ib., e) is likewise on the palatal, not the occipital, plane.^ In these characters is manifested the nearer aifinity of the Purbeck Crocodilian to the Amphicoelian Teleosaurs^ than any Tertiary or modern genus presents. The following are amongst the modifications of minor import in the skull of the present species of Goniopholis. The external nostril (PI. 40, fig. 1, «), horizontal in position, is more nearly terminal than in modern Crocodiles, or than in Goniopholis crassidens (?\. 11, fig. 1). It is formed by the premaxillaries exclusively; the nasal bones terminating about an inch behind the nostril. In Procoelian Crocodiles a graduated series of developments of the nasal bones can be traced. They may be short, * Cuvier, ' Ossera. Foss.,' torn, v, part ii, pi. i, figs. 4 and 5. 2 See ' Phil. Trans.,' mdcccl, pi. xi, fig. 1 e. 3 lb., p. 522. 18 5 632 BRITISH FOSSIL REPTILES. as ill Gavialit gongeticus, or extend to nenr tlie nostril, as in Crocodilus catapJiracfus, rathei- nearer in Crocodilus intermedius, still nearer in Crocodilus Hastingsia, be produced close to the aperture as in Crocodilus cJiampso'idcs, penetrate a short way into the aperture, as in Crocodilus sucJius, or, by continuous ossification of the septum in old individuals of Crocodilus niger and Alligator lucius, extend seemingly across the nostril. These characters, barely of specific value, have been used in the fabrication of genera of existing Crocodiles and Alligators,^ in all of which the orbits are larger than the upper temporal apertures. In Goniopholis simus the orbits (PI. 40, fig. 1, o) are rather smaller than those apertures (ib., ib., t). When p. 536 of the description of the Wealdon HglaocJiampsa was printed off I had not materials for studying the palatal characters of Goniopholis. By excavating the under surface of the block of Purbeck stone on the opposite side of which the subject of Plate 40, fig. 1, was exposed, the characters in question were brought to light. A narrow medial tract, ib., fig. 2, w, contributed by both pterygoids and palatines divided the vacuity answering to Cuvier's ' Posse nasal posterieure ' in Teleosaurus cadomensis. An increase in the breadth of this pterygo-palatine septum gives the character of the '' 2^rxlalonares ' {Biiiosauria, PI. 60, fig. 25, «, «) in Hgla>ochamj)sa, and removes any doubt as to the homology of those vacuities with the palatonares in Goniopholis. The pterygo-maxillary vacuities (PI. 40, y, y) are relatively larger than in Hylceochampsa. Each pterygoid (fig. 2, 24), articulating by a crenate suture with the narrow hind end of the palatine (ib. 2o), which diverges from its fellow to form the fore part of the palatonaris, loses vertical thickness and gains in breadth as it extends backward. It there articulates by a tract of an inch in length with the basisphenoid. The Eustachian canal (ib., e) at the midspace between the basisphenoid and basioccipital. The latter arches down in advance of the condyle, and the venus foramen is conspicuous on this tract. As the pterygoids are relatively less than in the Procoelians, so the palatines are relatively larger, especially in anterior breadth. After contributing their share to the palatonaris they come into contact, and the medial sutiu'e is continued forward to an extent of 3 inches 5 lines. The anterior breadth of the pair is 3 inches 4 lines. The medial suture of the palatal plates of the maxillaries was traced forward two inches or more in advance of the palatines, and laterally the plates were exposed to the same breadth as the palatines proper. The palato-maxillary suture, 20'— 21', is strongly sigmoid, describing as it leaves the midline a convexity forward and then a concavity. It was not thought expedient to endanger the unique specimen by further excavation in reference to the comparatively unimportant preraaxillo-maxillary palatal suture. The bony palate, as far as it was exposed, is smooth ; the upper surface of the skull is rugose and pitted. The pits are circular or subcircular, from 1 to 1\ hnes in diameter, situated chiefly on the swollen sides of the maxillaries and on the cranial part of the skull, including the expanded upper and outer surface of the squamosals ; and 1 'Trans. Zool. Soc.,' vol. vi, p. 125. WEALDEN CROCODILES. 633 the tympanic pedicles are smootli, and terminate iu the usual transversely extended concavo-convex articular surface. The tooth called "anterior canine" (ib., fig. 3, ?> c) is preserved, somewhat mutilated, in each premaxillary. Sockets of smaller premaxillary teeth are faintly traceable. The tooth termed "posterior canine'' (ib., >«, c) projects from the anterior part of the out- swollen and convex border of the maxillary. From portions or traces of the other teeth or sockets I estimate that there were from sixteen to eighteen teeth on each side of the upper jaw. In the largest and least mutilated crowns of these teeeth the dental characters of the genus Goniopholis are shown. In the ' Catalogue of the Osteological Series, Mus. Coll. Surgeons,' 4to, 1853, p. 164, is described the specimen No. 75.:2, as "The skull of a Crocodile from Bengal wanting the lower jaw, of a species {Crocodilus palustris ?) which is frequently found inhabiting the larger ponds. It differs from the Cr. biporcatus of the Ganges in having shorter maxillary and premaxillary bones in proportion to its length, and in having much less developed prefrontal ridges ; the palatal suture between the maxillary and pre- maxillary bones is transverse, not curved. The anterior extremities of the palatine bones are narrower and more pointed. The number of alveoli is — premaxillary 5 — 5, maxillary J) 14—14. The doubt indicated (?) arose from the inadequate characterisation by Lesson, of the species described by him in the 'Zoologie' of the ' Voyage aux Indes Orientales de Belanger;' but there is no reference of the specimen. No. 752, to the Crocodilns rhombifer, as is affirmed by the author of the " Synopsis of the Species of Recent Crocodiles," ' Trans. Zool. Soc.,' vol. vi, p. 140. I did not regard my doubt as justifying the sinking of Lesson's " paliisiris " into a synonym, and of imposing a new specific, much less generic name. But the osteological character of the palatal region of the skull, pointed out in my ' Catalogue,' appears to be the chief of those relied upon by the author of that * Synopsis ' for his genus Bomhifrons, of which the first character is : — " The premaxillary suture straight, or rather convex forwards" (loc. cit., p. 139). The other characters are not of specific value. The sutures of the premaxillary bones, I may remark, are of three kinds; one is medial and unites the pair ; it is the " interpremaxillary suture :" the second is lateral, uniting the outer or dental plate of the premaxillary with that of the maxillary ; it is the " premaxillo-maxillary suture :" the third is transverse, more or less, and unites the palatal plate of the premaxillary with that of the maxillary ; it is the " premaxillo- maxillary palatal suture." Its modifications, added to other ditferences, when determined to be constant, may aid in differentiating the species of Crocodilus proper, of Alligator, and of Guvialis} ^ Prof. Marsh, in his 'Introduction and Succession of Vertebrate Life in America,' 8vo, 1877, writes (p. 21) : "The beds of the Rocky-Mountain Wealden have just furnished us with a genuine "missing link," a G34 BRITISH FOSSIL REPTILES. The convenience of these three genera of ProcccHan Crocoflilia, although they agree in palatonarial and vertebral characters, will probably ensure their retention; but Tomistoma, Oopholis, Ilalcrosia, Palceomchus, Rhjnchosuclms, Jiamjjhosfoma, Mecistops. Boiiihifrons, Palinia, Moliuia, Caiman, Jacare, &c., into which they have been subdivided, exemplify the evil of " encumbering the science with a multitude of names " (loc. cit., p. 128), — an evil which, if the " names " do not represent " generic distinctions," cannot be laid to the charge of the " Palaeontologist." At least, the "small fragments of the fossil skeleton" (ib., p. 128) on which the genus GomojjhoUs was originally founded have subsequently been proved, by acquisition of other parts, to have indicated accurately that well-marked and interesting addition to the recorded modifications of the Crocodilian type. Those of the vertebral and cranial structures have, indeed, proved to be not only of generic, but of family value. Genus — Petrosuchus, Owen} Species — Petrosuchus levidens. Crocodilia, Plate 41. This genus and species of Crocodile is founded on the portion of skull and mandible, figured in Plate 41. The skull is imbedded in the same limestone of the Middle Purbecks, now quarried at Swanage. It was discovered in a block with the upper surface (ib., fig. 1) exposed. This surface is partially weathered, but shows here and there a faintly wrinkled natural sculpturing. The upper temporal apertures are larger than the orbits. In front of these the skull contracts more rapidly tliau in GoniojilwUs, and presents, as far as it is preserved, a slender form of face approaching to the propor- tions of that in the modern Crocodilus cataphractus^ and in the Tertiary Crocodilus champ- so'ides (p, 115) ; but the more rapid contraction in front of the orbits is gavial-like, and there are other characters indicative of a nearer affinity than in Goniopholis to the Teleosaurian group. This affinity is decisively marked by the larger relative size and more advanced position of the palatouaris (ib., fig. 2, »), into the formation of which the diverging hind ends of the palatines (ib., fig. 2, 20) enter in a larger proportion than in Goniojj/iolis. The basisphenoid (ib., ib., .5) is more produced, and the pterygoid (ib., ib., 24) contracts Saurian (Diplosaurus) with essentially the skull and teeth of a modern Crocodile, and the vertebrae of its predecessor from the Trias." When the cranial characters of this Crocodilian are made known it will be of moment to compare the temporal apertures on the upper surface and the palato-narial apertures on the under surface of the skull. When the dental characters of the same fossil are described and figured we may be able to determine whether they are those of the broad-faced procoelian Crocodiles and Alligators or those of Goniopholis. 1 Gr. ■nerpos, rock, and 1r)v-)(^vi, an Egyptian name of the Crocodile. ^ Cuvier, 'Ossem. Foss.,' 4to, tom. v, part ii, pi. v, figs. 1 and 2; Gray, 'Trans. Zool. Soc.,' vol. vi, pi. xxxii, fig. 2. WEALDEN CROCODILES. 635 a more extensive sutural uiiioii therewith. Each palatine bone (ib., ib., 20), where they divei'ge at the palatonaris, shows a protuberance on its under surface. Tlie Eustachian outlet is seen at «. The portion of the left mandibular ramus (PL 41, fig. 3) includes the dentary element (32), nine inches in length, with portions of the angular (30) and surangular (29) ; that of the angular including six inches of its extent. Of this element two inches extend forward in advance of the hindmost point of the dentary ; and, guided by the proportions of the Crocodihts champsoides, I estimate the total length of the mandible of Pefrosuchus levidens to be 16 inches, or thereabouts, indicating that from four to five inches are wanting at the fore part of the upper jaw, the subject of fig. 1. The vertical extent of the ramus behind the mandibidar vacuity (ib., fig. 3, v) is 1 inch 9 lines ; the vacuity itself is 1 inch 6 lines in long diameter, 6 lines in short diameter ; its long axis is nearly parallel with that of the ranms. The lower, like the upper jaw, appears to have been long exposed on its imbedding block of stone. Little of the outer layer of the bone is preserved, and this is limited to parts of the angular and surangular. It here shows a more decided reticidate sculpture, the meshes being in the form of subcircular pits of from 1 to 3 lines in diameter. The vertical breadth of the dentary at the terminal point of the angular is 1 inch 3 lines ; it loses, as usual, in this diameter as it advances, but irregularly, owing to a gentle undulation of the alveolar border. This is convex where it supports the anterior group of teeth opposed to the premaxillary and foremost upper canine teeth ; it is then slightly concave to the mid-third part, where the border is more feebly convex ; beyond this, after a feeble concavity, it gradually rises to the surangular piece (29). Of the foremost group of teeth seven are preserved ; the third counting from the fore- most being the longest and broadest, with the crown curving upward and a little back- w^ard ; the length of this tooth is 1 inch 4 lines, its extreme breadth is 3 lines, about half of the total length forms the exserted crown, but the point is not entire. The first and fifth of this series are the next in size, but do not exceed an inch in length, the intermediate teeth are smaller ; two or three sockets of still smaller teeth may be traced in the concave part of the border. In the following convex part, seven teeth are preserved, with shorter and relatively thicker crowns than in the foremost group; but none of them showing the robust proportions of the teeth of Goniop/iolis. Behind this group the indications of teeth and sockets are faint. I estimate the number of teeth in the present ramus at about twenty ; which is the number in the mandibular ramus of Cfocodilus champadides : a margin of two or three more or less being allowed for a perpetually changing set of teeth. The inequality of the size of the teeth and concomitant festooned course of their alveolar series is Crocodilian, as contrasted with the Gavialian and Teleosaurian types. But the temporal and palatonarial openings indicate the generic distinction of Pdro- suchus, with its transitional character between the Teleosaurian and Tertiary Crocodiles. 636 BRITISH FOSSIL REPTILES. Portions of dermal scutes, with the pitting as on the mandible, but with wider intervals, are preserved on the slab in which the above-described fossil is imbedded. A few Wealden vertebrae, not associated with characteristic parts of any of the fore- going (pp. 431, 631, 634) CrococUlia, differ from those in Plate 10 by the carinate under surface of the centrum. They are figured in CrocodUia, Plate 14, under the provisional name of Goniopholis carinatus. Of the known species of mesozoic Crocodiles, including the Purbeck and Wealden kinds now added, the following are common characters. A greater development, than in Tertiary Crocodiles, of the dermal bony armour, which consists, without exception, of both dorsal and ventral scutes, the scutes in each series well connected with each other, and in Goniopholis exceptionally so. A less development of the osseous surface for the origin of the muscles of the mandible indicated at the upper surface of the cranium by the larger ' temporal vacuities,' and at the under surface by the smaller pterygoid plates. The horizontal plane, larger size, advanced position and palato-pterygoid formation of the palatonares. Relatively small fore-limbs ; Amphicoelian vertebrae in most, in none Proccelian. These common characters of mesozoic CrocodUia suggest considerations of their relation to the prey of such CrocodUia and also to the coexistent marine reptiles of which those CrocodUia themselves became the prey. Similarly, if the common characters of the tertiary and existing CrocodUia be summed up they become suggestive of analogous considerations. They are : — cup-and-ball vertebrae, the cup in front ; fewer dermal scutes, not co-articulated suturally or by peg- and-socket joints ; posterior aspect and position of small and exclusively pterygoid ' palatonares ;' upper temporal apertures, when present, less than the orbits; fore-limbs relatively larger than in Amphicoelians ; with one exception jaws stronger with larger and more varied teeth. The Proccelian articulation of the trunk-vertebrae better adapts that part of the body to be sustained and moved in air than the Amphicoelian articulation which characterises the vertebral column of the more aquatic and probably marine Crocodiles of the Mesozoic period. The presence of prey not in existence at those periods, but which in later, tertiary and modern times, might tempt a Crocodile to rush on shore in pursuit of a Mammalian quadruped, is a phenomenon contemporary at least with the acquisition of the Proccelian structure in the axial skeleton of such Crocodile. The extent, the density, the closer fitting articulation of the bony scutal armature of the Mesozoic Crocodilians, suggests its use and need in waters tenanted at the same epoch by larger carnivorous marine reptiles, as, for example, the Ichthyosaurs, Plesio- WEALDEN CROCODILES. 637 saurs, Polyptychodonts, and Mosasaurs. The oolitic species of Crocodile (' Crocodile de Caen.'') is signalized by Cuvier as " I'espece la luieu.x cuirassee de tout le genre." But the Goniopholis of the Wealden and Purbeck formations surpassed even the Teleosaiirus Cadoiiiensis and its congeners in this part of its organization. The great quadrangular dorsal scutes of Gouiop/iolis are distinguished by the presence of a conical obtuse process continued from one of the angles transversely to the long axis of the scute, like the peg or tooth of a tile, which fits into a depression on the under surface of the opposite angle of the adjoining scute, thus serving to bind together the plates of the imbricated bony armour and repeating a structure which is characteristic of the large bony and enamelled scales of many extinct ganoid fishes." The hexagonal ventral scutes of Gonio2jJioIis were firmly joined together by broad sutural borders. No knight of old was encased in jointed mail of better proof than these Crocodiles of an older world. But the inimical contemporaries of those Crocodiles have passed away. No repre- sentative of Mosasaurian, Plesiosaurian, or Ichthyosaurian families lived after the secondary epoch. Crocodiles alone of the larger aquatic saurians continued on to the present times more fortunate than their predecessors in respect to possible hostile fellow denizens of the deep. Certain it is that the defensive armour of Procoelian Crocodiles has degenerated. Bony ventral scutes are exceptional in them,' and the dorsal ones are fewer, thinner, less closely arranged and less firmly connected with one another. And if this change can be connected with the disappearance of Beptilia against the attacks of which a better coat of mail may have advantaged the contemporary Mesozoic Crocodilia, it may further be remarked that diminution of weight would favour Crocodilian movements in air, and that a loosely-jointed armour would less impede the evolutions required to catch a prey on land. In this relation, also, arising out of the introduction in tertiary times of many species of warm-blooded Mammals frequenting the banks of lakes and rivers tenanted by carnivorous Alligators and Crocodiles, I have been led to ponder upon the well-marked difference in the relative position of the ' palatonares ' (internal or posterior nostrils) which exists between the secondary and tertiary Crocodiles. The physiologist discerns in the palatal and gular structures concomitant with the back- ward position and small size of the ' palatonares ' in the existing Crocodiles and Alligators of Asia, Africa, and America, the power of holding submerged a powerful Mammiferous (luadruped without the streams of water traversing the great cavity of the mouth during the struggle getting access to the posterior nostrils and windpipe of the amphibious assailant. The valvular mechanism applicable to, or, I may say, possible with, the ^ Cuv., Teleosaiirus cadomensis, Geoffr. 2 " Report on British Fossil Reptiles," ' Reports of Biitisli Association,' 8vo, 18-11, p. 70. 3 Observed by Natterer in certain Saiuh-American Alligators, ' Beitrag fur iiiihareu kenntniss der Siid-Amerikanischeu AUigatoseu Ann. Mus. Wien,' ii (18-10), p. 313. 638 BRITISH FOSSIL REPTILES. peculiar position of the posterior nostrils of Procoelian Crocodiles, opening vertically behind the bony palate, not horizontally upon that plane, could hardly be adjusted to the relatively larger post-palatine apertures, upon a horizontal plane at some distance from the occiput, with the inner nostrils opening at a more advanced position in the mouth, an arrangement which characterises all Amphiccelians. No doubt there were sphincteric structures which would exclude water from the glottis in all the aquatic air-breatliing reptiles, but the peculiar and well-developed valvular contrivances to that end in existing Crocodiles are conditions of the relative size and position of the posterior nostrils in them ; and the repetition of that character in the palatonares of all known tertiary Crocodiles justifies an inference as to the concomitant valvular structures of the soft parts in those extinct Procoelian species, and their con- formity with those in existing Crocodiles. Tliese considerations stimulated or augmented the desire to determine the palatal characters of the fossil skulls of those Crocodilia of the newer Mesozoic formations which, in the massive proportions of their jaws, made the nearest approach to the tertiary and modern kinds. Such demonstration of the struc- ture of the bony palate is accordingly given in the specimens of the Purbeck Crocodiles in the British Museum, described at pp. 632, 634, and figured in Plates 40 and 41. Although the jaws of Goniopholis crassidens and GoniophoHs simus have proportions adapted to grapple with large and active Mammals, the evidence of any such warm- blooded air-breathers co-existent with those Crocodilia is not yet acquired. And the probability of such co-existence is, in my opinion, very small, from the circumstance of the palatonares being relatively larger and more advanced than in the Crocodiles con- temporary with great Mammals. The palatonares in Goniojiholis open likewise upon a horizontal plane, look directly downward, not obliquely backward, and, moreover, have a different conformation. With this anatomical character, which I am disposed to asso- ciate with a fish diet, are combined in both Goniopholis and Petrosuchus upper temporal apertures larger than the orbits, and Amphiccelian or Amphiplatyan vertebrae. Now all known tertiary and existing Crocodilia combine with small, posterior, pterygoid palatonares, upper temporal apertures less than the orbits, and in some broad-faced kinds, the upper temporal apertures are almost obliterated by the progressive increase of the osseous roof of the temporal vacuities. These vacuities in the recent reptile are occupied by the temporal muscles, and the power of these biting and holding muscles is in the ratio of the extent of their bony origins. In the Amphiccelian fish-eating Crocodilia, the upper temporal apertures are larger and usually much larger than the orbits ; and they are, for the most part, associated with slender jaws and with numerous small uniformly-sized teeth. With the palatine modifications, which relate to the drowning of air-breathing prey, and with the cranial developments which relate to the grip of such prey, we find, as a rule, in Procoelian Crocodiles, concomitant modifications in the breadth and strength of the jaws, and in the size of the teeth. There is also inequality of size, favouring hold- WEALDEN CROCODILES. 639 fast, as in Mammalian Carnivora, and certain teeth of the dental series have accordingly- received the name of canines in the Crocodiles with such analogous dentition. Partial developments of the alveolar borders concomitant with the modified dentition give a festooned course or contour to those borders. In Mesozoic Crocodiles this character is exceptional and begins to appear at the Wealden period. The oolitic and older Amphicoelians have more numerous, smaller, and sharper teeth, occupying straight, or nearly straight, alveolar borders of the jaws. One genus, Gavialis, still exists, which exceptionally exemplifies the old dental fish- catching character. Finally, in reference to the limb-character as distinguishing the AmphicwUa from the Proccelia. This character, at least, is exemplified in all the Mesozoic Crocodilia, of which the skeleton of the same individual has been sufficiently restored. It is then manifested by the shorter and smaller proportions of the fore pair of limbs as compared with the hind pair than we find in existing Crocodiles, and in the similarly restored skeletons of extinct Neozoic species {Crocodilia, PI. 11). The diff'erence in question I take to relate to the more strictly or uniformly aquatic life of the Teleosauroids. When the nilotic Crocodile darts under water after a prey, or swims off swiftly to escape a danger, the fore-limbs take no part in the action, but are closely applied prone to the trunk. The same motionless and unobstructive disposition of the fure-limbs has been observed in the still-surviving marine lizards of the genus Amhlp-hpichus. But the resistance to rapid swimming of fore-limbs so disposed is calculable accord- ing to the degree in which they break the uniformity of the curve and project beyond the surface of the fore part of the body to which they may be applied. The smaller, there- fore, such limbs may be and the less will they obstruct the forward course of the Crocodile. Thus, the Mesozoic Amphicoelians in their rush after fishes, or retreat from attacking larger Reptilia, would be favoured by their limb-character. On the other hand, their progress on dry land would be more difiicult, unless, as has been suggested in regard to some kinds of Dinosaur with similarly stunted fore-limbs, the Teleosaurs were able to run upright on their hind-legs. But dismissing such interpretation of the dwarfed fore-limbs of Mesozoic Crocodilia, to what conditions, it may be asked, do the augmented size and strength of the§e limbs in Neozoic Crocodiles relate ? The advent in tertiary times of large Mammalian quadrupeds browsing or prowling along the banks of estuaries and rivers haunted by such Crocodiles might, and does, tempt them to make a rush on the dry land to seize such passing prey. In such rushes the fore-limbs come into strenuous action. A Lamarckian might say that this temptation to terrestrial locomotion would, by the repeated increased exertion and exercise of the fore-limbs lead, in the course of genera- 196 640 BRITISH FOSSIL REPTILES. tions, to their augmentation of size, and he would set it down as one of the factors in the progressive transmutation of a Teleosaur into an AHigator. His opponent would ask, of course, for the transitional forms. The subjects of the foregoing pages (631 — 636) in some degree represent such. Those which I next proceed to describe also suggest relations of adjustment of characters to associated, probable, prey. Before entering on the descriptive details I may revert to the topic last discussed. A large and powerful modern Crocodile having seized and submerged a tiger or bufiido, admits the water of the river it haunts into its wide lipless mouth by the spaces to which the thickness of the part of the prey gripped keeps asunder the upper and the lower jaws. Thus, the part of the mouth not occupied by the prey is filled with the fluid in which the mammal is being dragged and drowned. " The closure of the exterior nostrils "^ would not prevent the water entering the ' glottis.' A special arrangement is requisite for this purpose, and such arrangement, as it exists in Neozoic Crocodiles, is incompatible with the relative position of " the posterior nares" and the glottis in the Mesozoic Crocodiles. The question is, with a closure of the external nostrils and the exclusion of water admitted by the mouth into the nasal passage, how is the water to be prevented from getting into the windpipe? We know how this is eflfected in the Cetaceans ; and modern Crocodiles have as efficient a mechanism to the same end though on a different plan, but requiring a size and position of the palatonares which, as shown in previous pages, constitutes one of the best marked cranial characters differentiating the Mesozoic and Neozoic CrococUlia. In all the Crocodiles contemporary with "large and active mammals "^ there is a double valvular structure at the back of the mouth, which prevents the water having access to the mouth, from entering either the hinder nostril or the glottis. A mem- branous and fleshy fold hangs, like a curtain, from the hind border of the I'oof of the mouth, and answers to our ' velum palati :' the other valve is peculiarly crocodilian ; it is a broad, gristly plate, which rises from the root of the tongue, carrying with it a covering of the lingual integument ; and, when the palatal valve is applied to it, they form together a complete partition wall, closing the back of the mouth, between which and " the posterior nares " it is situated, shutting off both the latter aperture and the glottis from the mouth. To make this mechanism available, the hind nostril is reduced in size, and such reduction is shown in the skull. The palatonaris is also placed far back, and its plane instead of being horizontal is tilted up at the angle which makes the operation of the two parts or folding doors of the partition most effective in closing the oral chamber posteriorly.^ If the submergence of the Crocodile, with its large mammalian prey, I 'Quart. Joiirn. of Geol. Soc.,' May, 1S78, p. 429. - Loc. cit., p. 425. 3 ' Proceedings of the Zool. Soc.,' October 2.5th, 1S31, p. 139. PURBECK CROCODILES. 641 should last so long as to render it needful for the reptile to take a fresh breath, it can protrude its prominent snout from the surface of the river, and inhale a current of air which will traverse the long meatus and enter the glottis by the chamber common to nose and windpipe, which is shut off from the mouth by the above-described structures. We have no ground for inferring this faculty and mechanism of soft parts from the bony palate in amphicoelian Crocodiles ; the difference in its size and position are such as to have deceived both Bronn and De Blainville as to the position and homology of the palatonares in Teleosaurus) The subjects of the following sections bear unexpectedly, and in an interesting degree, on another objection, raised during the discussion at the Geological Society of London, on the topics treated of in pp 636 — 640. The objection was, that " warm- blooded animals did actually exist contemporaneously with the Mesosuchian Cro- codiles." ° As the only examples of the Mammalian class of which I was cognisant were the subjects of the undercited Monograph,' and a few other species of like dimi- nutive size, it did not seem to me to affect a question exclusively bearing upon large Mammalian quadrupeds. It seems, however, that the Crocodiles which most abounded, if we may judge from the proportion of their fossil remains in the fresh-water deposits of the ' feather-bed ' subdivision of the Purbeck series, were related in size to their con- temporary diminutive ]\Iammals. The Spalacotheres, Peralestes, Stylodons, Triconodons, &c., may well have been the prey of the dwarf Crocodiles of the locality. For these were reduced to dimensions which forbade them to disdain such succulent morsels, and at the same time they were suitably armed and limbed for the capture of the little Marsupials. At the first aspect, detecting in the scattered groups of scutes in the Purbeck shales submitted to my inspection, specimens showing the peg (PI. 45, fig. 3, d) and groove (ib., fig. 4, 6), it seemed as if remains of some young specimens of Goniopholis were so exposed. The condition, however, of two of the skulls (PI. 44, figs. 1 and 3) enabled a comparison to be made which determined their specific and, by their den- tition, generic distinctions from both Goniopholis and PefrosucJius. The number of maxillary and mandibular specimens, of which several are figured in PI. 44, exem- plified a degree of constancy in size which begat a conviction that such was a character of the species; and, diminutive as were the Reptilia which have supplied the subjects of both plates, their characters were indisputably those of the Order Crocodilia. One of them, by the size and shape of certain teeth, came nearer to Goniopholis, another by the same character resembled Petrosuchus, but the differential characters were such as could not have been obliterated by growth or age. A third form of Crocodilian made a nearer approach in one of the species (PI. 42, fig. 2) to the average size of the broad-faced genera. A fourth (ib., fig. 1) * ' Abhandlungen iiber die Gavial-artigen Reptilien der Lias-formation,' fol., 1841, pp. 12, 16, 24, 2 Hulke, J. W., ' Quarterly Journal of the Geological Society,' May, 1878, p. 428. ^ " Ou the Fossil Mammalia of tlie Mesozoic Formations," Palaeontographical Soc. Volume for 1871. 642 BRITISH FOSSIL REPTILES. corresponded in size with the subject of fig. 2, bui offered no character by which it could be legitimately removed from the genus Goniopkolis. I commence with the description of this small but well-marked species. Genus — Goniopholis, Owen} Species — Goniopholis tenuidens, Ow. Crocodilia, Plate 42, fig. 1. The dental character of the Amphicoelian genus Goniopliolls consists of the numerous close-set, fine, longitudinal ridges of the enamel, two of which, larger and sharper tlian the rest, traverse opposite sides of the tooth from the base to the apex of the crown, midway between the convex and concave lines of the curvature of the tooth, that is, at the fore and back parts of the crown.^ The general shape and proportions of the tooth-crowns indicate distinctions of species of Goniopholis. The type of the genus is characterised by the thickness and subcircular section of the crown, and the obtuseness of that in the posterior teeth. In Goniojjholis simus^ the proportion of breadth to length of crown is less than in G. crassidens, and this difference is more marked in the specimen from the Feather- bed of Purbeck which forms the subject of fig. 1, PI. 42. This specimen consists of the chief part of the dentary and co-articulated splenial elements of both rami of the same mandible, partially dislocated at the symphysis. The alveolar tract includes the incisive (?) and molary {■>») convexities, without an intervening laniary rising. The incisive convexity includes five sockets, a tooth being retained in the first, third, and fourth on the right, and in the first and third sockets on the left dentary. The foremost tooth has a crown of 6 mm. length and barely 2 mm. of basal breath ; each has partially emerged from a socket larger than itself, and exhibits a portion of a tooth in succession to one which has been lost or shed. The socket is separated by an interval of 2 mm. from the second. This shows a subcircular aperture of 5 mm. in diameter. The third socket opens at 2 mm. distance from the second. The tooth [h) in the right dentary shows the inner, longitudinally concave side of the crown, with a basal breadth of G mm. and a total length of 16 mm. One may count about a dozen fine longitudinal linetir ridges between the fore and hind stronger ones (ib., fig. 1 b and b', magn.). The corre- sponding tooth (ib.jfig. 1 a, magn.)in the left dentaryshows the outer longitudinally convex side of the crown, with about sixteen fine ridges. These teeth answer to, or interlock with, the premaxillary or anterior canines of the upper jaw. The fourth tooth (ib. c) is less than the third; its crown projects 10 mm. from the right dentary; the fractured base of 1 'Reports of the British Association,' 8vo., 18-11, "On British Fossil Reptiles," part ii, IS4I, p. C90. 2 Loc. cit., pp. 69, 70. 2 Ib. ib., p. 7, pi. V. PURBECK CROCODILES. 643 the corresponding tooth in the left dentary is 4 mm. in diameter. Seven close-set sockets follow along the feebly concave part of the alveolar tract. The tooth of the twelfth socket at the beginning of the second convexity is preserved in both rami ; its crown is 8 mm. in length, 4 mm. in basal breadth, with an obtuse summit, showing the feeblest indication of an apical point. This point is rather better seen in the crown of the next tooth, which has not wholly emerged. The total number of teeth is sixteen in each of the dentary elements here preserved, and by analogy to the Goniopholis shnus^ the whole, or nearly the whole, of the dental series or sockets, in one dentary element is here exhibited. The outer surface of the dentary is pitted by small subcircular, not close-set, impressions, except on the outer alveolar plate of the molary rising, where a few longitudinal pits indent the otherwise smooth surface of the bone. The length of the symphysis is 25 mm., the depth 10 mm. The extreme breadth of the incisive part of the mandible is 32 mm. The length of the preserved alveolar part of the dentary is 85 mm. (3 inches, 3 lines) ; the length of the entire mandible might have been between 5 and G inches. Fragmentary evidences of the Goniopholis tenuidens in other slabs of matrix do not indicate any individual of a larger size than is exemplified by the above-described portion of lower jaw. The mandible of Goniopholis crassidens, with an extreme depth of 4 inches, attained the length of 2 feet. Of this length the alveolar part of the dentary element occupied, as in most broad-faced Crocodiles, one half. The length of the alveolar part of the mandible of Goniopholis tenuidens being 3 inches, the total length of the jaw may be set down at one fourth of that of the type species of the genus. Genus — Brachydectes, Owen} Species — Brachydectes major, Ow. Crocodilia, Plate 42, fig. 2. In this genus and species a left mandibular ramus, 9 inches 6 lines in length, shows an alveolar tract of but 3 inches 9 lines in length. In the proportion of the jaw, there- fore, appropriated to the lodgment of the teeth this Crocodile differs from the rest of the family. The ramus has a less relative depth than in Brachydectes minor, fig. 3 ; it measures in extreme vertical extent, taken at about one fourth of the length from the angle, 1 inch 9 lines, or little more than one sixth the entire length of the ramus, whilst in Br. minor the extreme depth of the mandible, which is about midway between the two ends, is nearly one fifth of the entire length of the ramus. This proportion might, however, be deemed an immature character of the smaller specimen, but there are 1 Gr. ^jin-^vs, short ; Sj/kd/s, biter. 644 BRITISH FOSSIL REPTILES. other diflferences in tlie jaw of Brachydedes major not attributable to age and conse- quent growth. There is no longitudinal ridge on the angular element. The angle itself is more produced. This process repeats, indeed, the low position characteristic of the genus Brachydedes, but the Hne descending thereto from the articular element is straight, not concave, as in Br. minor, and the curve from the angle to the convex border of the angular element (fig. 1, 30) is deeply concave. Moreover, the outer surface of the deep hinder part of the ramus is sculptured with close-set deep pits, giving a strongly reticular character to that part of the bone. The alveolar tract shows, as in Brachydedes minor, a laniary convexity {J) as well as an incisive one (i) ; both, however, are slight. In the latter the crown of the third or fourth incisor is preserved ; it is 20 mm. in length, 6 mm. in basal breadth. The enamel of the exposed outer side is smooth ; the fore part of the crown is obtuse, the hind part trenchant, with a faint appearance of minute denticulation. This is the only tooth preserved in the present jaw. There are faint indications of ten or twelve alveoli behind the tooth ; two of these in the laniary curve (') indicate teeth proportionally as large as the canine in Brachydedes vnnor. The outer surface of the laniary convexity is smooth. The rugged irregularly and minutely pitted character is continued to the alveolar border of the incisive convexity. The sutures between the dentary and hinder elements of the mandible are not clearly definable. Certain parts of the outer surface which were wanting made it doubtful whether any vacuity between the surangular, angular, and dentary elements existed ; and the condition of the jaw of the smaller species weighs in favour of assigning an uninterrupted outer wall of the mandible as an additional differential character of the genus. The proportion of the incisor tooth approaches that of the third in Petrosuchus} but the latter is longer in proportion to the basal breadth. The dental series, and conse- quently the dentary element, are relatively longer in Petrosuchus than in Brachydedes. A second specimen of the left dentary bone repeats closely the same size and characters of the corresponding part of the mandibular ramus above described. The teeth are wanting. Behind the alveolus of the ' anterior canine ' are indications of seven or eight following alveoli, not more. The better preserved outer plate of the bone demonstrates the absence of the vacuity which is present in Petrosuchus, Gonio^holis, and Crocodilia generally. Species — Brachydedes minor, Ow. Crocodilia, Plate 42, fig. 3. This species first indicated the genus in the exploratory operations ; it is represented by the left mandibular ramus (Plate 42, fig. 3), which is remarkable, as in the larger species, for the small proportion which the alveolar tract bears to the entire length of the 1 P. 634, PI. 41, fig. 3. PUKBECK CROCODILES. 645 hone, and for the entireness of the outer wall. The alveolar tract is undulated, showing an iucisive and a laniary convexity with intervening and hinder concavities. The incisive convexity holds five teeth, close set, the two hindmost rather larger than the rest ; but no single tooth is so much larger as to suggest the name of ' canine.' The laniary convexity shows one large canine with a broad, straight, laterally compressed crown. It is preceded by a smaller tooth, rather less than the hindmost incisor, and separated therefrom by a space which may have held two or three small teeth. The alveolar tract behind the canine seems to have lodged three or four teeth, the crowns of which are lost. The whole length of the alveolar tract is 23 mm. (1 inch) ; that of the entire ramus is 85 mm. (3 inches 2 lines). The dentary element bifurcates behind as usual; the upper prong joining the surangular, the lower and longer one the angular, but without defining or leaving any vacuity ; the union where such vacuity would have been left in ordinary Crocodiles is situated well within the anterior half of the ramus. The posterior elements are correspondingly of unusual length; their breadth is also proportionally greater than in previously known Crocodilian mandibles. The length of the surangular element (29') is 48 mm. (1 inch 10 lines) ; its depth (vertical breadth) is 13 mm. (6 Hnes). The upper border describes a feeble convexity ; beneath the articular surface of 29 the surangular curves downward and backward, meeting the lower border at a point wedged between the articular and angular elements. The articular exposes the outer antero-posterior concave border of the joint. From this it descends obliquely backward and joins the angular in forming the process (30'), which here projects directly backward, its termination being much below the joint, and nearly on the level of the lowest part of the lower border of the jaw. The angular element extends forward from the angle, with its lower border at first straight or feebly concave, and then moderately convex to its junction with the dentary ; a ridge projects along the greater part of this course a little way above the lower border. A portion of the splenial element shows above the fore part of the surangular, and supple- ments the inner alveolar wall at the hind part of the dentary. From the lower jaw of Theriosuchus (Plate 44, figs. 5, 14, 16) the present differs in the shortness of the dentary element and alveolar series, in the greater depth and verticality of the outer surface of the ramus, and the narrower inferior border. It also offers a generic distinction in the number and shape of the teeth. The proportional length and slenderness of the dentary and the absence of any laniary convexity succeeding the incisive one, together with greater number and the shape of the teeth of Nannosuclms (PI. 43, figs. 8 and 9) offer a more striking contrast with the mandible and teeth of Bracliydects. No specimens have been brought to light which show characters of Brachi/dcctes minor on a larger scale than is represented by the mandibular ramus above described. 646 BRITISH FOSSIL REPTILES. Genus — Nannosdchus,^ Oioen. Species — Nannosuchus gracilidens, Ow. Crocodilia, Plate 43, figs. 1 — 10 ; Plate 44, figs. 1 and 2. ■»■' In this genus the teeth have long, slender, sharp-pointed crowns, slightly recurved, mostly sub-circular in transverse section, impressed by a few linear or narrow and shallow grooves. The dental series is pretty uniform as to size and shape of crown, but less so than in the Teleosaur and Gavial ; the teeth are also less numerous and wider apart. The claim to generic distinction indicated by the armature of both upper and lower jaws was established by an additional dental character revealed in the following specimen. The fore part of the mandible (Plate 43, fig. 1) exhibited a tooth in situ (fig. 1 c and fig. 2 enlarged), answering to that termed the 'anterior canine' in Crocodilia, but presenting characters which I had not before observed in those or other BeptiUa. The crown is long in proportion to the basal breadth, conical, recurved, and pointed. It is traversed along the middle of the outer surface by a ridge, or rather a low angle of the enamel, simulating a ridge ; between this and the trenchant hind border is included one third of the outer surface of the crown. This tract is smooth, and, transversely, is feebly depressed or concave, giving a trenchant character to the hinder longitudinally concave edge of the crown. The two thirds of the outer, transversely convex, surface of the crown is traversed by close-set linear grooves, and intervening ridges, which mostly subside at the apical half of the crown, leaving about one third of the apex smooth. This tooth appears to be the fourth counting backward ; the length of the crown is 10 mm., the basal breadth 3 min. An enlarged view is given of the outer side of the crown in fig. 2. The foremost tooth, also preserved (fig. 1,;), shows a coronal length of 5 mm., a basal breadth of 1 mm. The crown of a fifth tooth rises close behind that of the fourth, with a basal breadth of 2 mm , and a length of 5 mm. ; it is conical, but is straight. The outer side, uniformly convex, is traversed along the basal half by fine ridges and intervening grooves ; it may be that the whole of this crown has not emerged. The portions of mandible, the subject of fig. 1, consist of the right and left dentary elements, of which the major part is preserved, the rest indicated by impressions on the matrix. The presei'ved parts include the symphysial expansion, the joint being slightly dislocated through pressure, which has acted obliquely. The right dentary shows its outer side, the left dentary its lower border, and beyond the symphysis a small proportion of the outer surface, while the inner one is partly covered by the smooth splenial element (31). ' vHvi'os, dwarfish, 5!oii^i;s, an Egyptian name of the Crocodile. PURBECK CROCODILES. 647 The breadth of the symphysial part of the right dentary is 15 mm. ; the length of the under part of the symphysis is IS mm. At 33 mm. from the fore end the (vertical) breadth of the ramus diminishes to 10 mm., beyond which it gradually increases to 15 mm., where the bifnrcation of the bone begins. The entire length of the part preserved is 114 mm. (nearly 4^ inches). The exterior of the symphysial part of the dentary is pitted by numerous minute subcircular depressions. As the bone contracts the depressions enlarge and elongate, then take the form of longitudinal grooves of irregular depth ; but these become limited to the lower half of the outer side of the dentary, the part above, which forms the outer alveolar plate, being smooth, with a few faint, short, longitudinal linear impressions. The symphysial expanse of the right dentary shows iive sockets, of which, as above stated, the first, fourth, and fifth retain their teeth. The implantation of these teeth in complete sockets confirms the indication by the sculpturing of the bone that the jaw has belonged to a member of the Crocodilian order. The first tooth was the smallest ; the second and third, judging from the sockets, gained in size ; the fourth is the largest, and represents, as above remarked, the tooth opposing or interlocking with the premaxillary canine above ; the fifth abruptly loses size. Of the succeeding teeth little more can be divined from the present specimen than that they were small or, at least, slender. The convex curve, lengthwise, of the outer alveolar border is very feeble, and seems to have helped to lodge the hinder teeth ; it is divided by a long feeble concavity from the symphysial or incisive convexity. There is no laniary rising. Two smooth bones {3\, x) contribute to the inner wall of the ramus, as exposed on the left side. If the lower one (a^) represents the splenial, the upper one (31) would be an unusually developed inner plate of the dentary. If this, however, should be, as its posterior expansion indicates, according to the analogy of the modern Crocodiles, the splenial element (31), then the lower bone (x), would represent an angular clement unusually produced forward. The longitudinal line of demarcation between these smooth inner questionable elements is not an accidental crack. The Crocodilian character of the present jaw is supported by the scutes (PI. 43, fig. 4) and impressions (fig. 5) of scutes, by a vertebra (fig. 3), by portions of ribs with a bifurcate proximal end, and by a metacarpal bone, all on the same slab of matrix. The vertebra is Amphicoelian ; the neurapophysial suture is unobliterated ; it is from the part of the trunk where the rib articulation has risen wholly above the centrum. This element is 13 ram. in length ; the non-articular surface is smooth and entire, gradually and slightly expanding to the articular ends ; the one exposed being subcircular, 10 mm. in diameter. Of the scutes preserved the largest are oblong, quadrangular, with a tooth-like process from the anterior and outer angle, from the base of which is continued a raised 20 6 648 BRITISH FOSSIL REPTILES. smooth tract along the anterior border, from 4 to 3 Dim. in breadth. The breadth of the entire scute is 17 mm. ; the length is 35 mm. Some smaller scutes are pentagonal. We have here, therefore, evidence of an Amphicoelian Crocodile, with the dermal armour after the type of that of GoiiiophoUs, but generically distinct by the characters of the mandibular dentition. If the dentary bone constituted three fourths the leiigth of the mandible this may be reckoned to have been about 6 inches in length, and the entire Crocodile may have been 6 feet in length. The portion of mandible of which the under surface of the dentary and splenial elements are exposed, forming the subject of fig. 6, Plate 43, is shown by certain teeth in place and others scattered near in th& same slab, to belong to the same genus and species as that represented by fig. 1, and to have come from an individual of similar size. Both are the largest evidences of Nannostichm shown in the numerous series of Reptilian fossils from the portions of the ' Feather-bed ' formation now under review. The symphysis, 21 mm. in longitudinal extent, forms a fifth part of the preserved extent of the dentary ; the breadth of this part of the jaw is 30 mm. ; that behind the symphysis is 27 mm. The rami, as far as they are preserved, diverge to a breadth of 70 mm. The alveolar part of the symphysis describes an incisive convexity, and the sockets indicate one or two teeth of larger size and thicker proportions than those of the rest of the dental series. The crowns of two of these teeth, which had become detached, are fortunately preserved, near the fore part of the jaw. The largest (fig. 7, magn.) represents the ' anterior canine,' and is the homologue of fig. 1 c and fig. 2, magn. It shows the well- marked characteristics of that tooth in Nannosuchits, and, besides the difi'erence of sculptur- ing, the crown is more strongly curved than in Goniopholls or Petrosuchus. The second detached tooth near the incisive alveoli shows both I'oot and crown. The latter is but half the length of that of the ' canine ;' more of the convex side is exposed than in fig. 2 ; it is traversed by fine longitudinal ridges. The teeth which are in place show a smaller size and more slender pointed crown. There is no evidence of any tooth equalhng in size the largest of the symphysial or incisive series. The numerous minute circular pits sculpturing the sym])hysial expansion change, as in the specimen (fig. 1), to coarser and larger longitudinal impressions as the rami recede and pass backward ; and the surface near the alveolar border showing the feeble molary convex curve is smooth. The dental character of Nannosuchus is more fully exemplified by smaller specimens, of which two, forming parts of the lower jaw, will be first noticed. The subject of fig. 8, PL 43, includes the dentary and angular elements, partially dislocated, of the right mandibular ramus. Two of the molary series of teeth are in siltl, showing long, slendei', feebly recurved crowns, each 5 mm. in length ; other teeth of similar shape and with finely striate enamel are on the same slab. In a smaller dentary (PI. 43, fig. 9) the sockets of eighteen teeth are visible. The proportions and outer markings agree with those of the larger specimen. PURBECK CROCODILES. 649 The Immerus (fig. 10), preserved near the jaw, shows the usual Crocodilian characters, with more slender proportions than in Crocodilus niger ; it rather resembles that of the Gavial.i The characters of Nannosuchus yielded by the foregoing specimens are supplemented by those of the skull represented of the natural size in PL 44, fig. 1. The teeth preserved in situ and detached, but in contiguity with the alveolar border, are generically those to which they would be opposed assuming the skull to be that of a Nannosuchus. The inferiority of size is not shown by any other distinctive character to indicate a species other than that founded on the lower jaws above described. As in those, the teeth of the upper jaw are divided by intervals usually greater than their basal breadth. Each premaxillary (fig. 1, 22) had four teeth at least; the maxillary had not fewer than ten teeth. The characters of length and slenderness of crown in the teeth of this small Crocodile suggested a comparison of its skull with that of Petrosuchus, but the differential characters exceed in importance those of size. The upper jaw of Nannosuchus does not contract so rapidly, or in so great a degree in advance of the orbits, as in Petro- suchus (PI. 41) ; it is also shorter as well as broader; no amount of growth could have converted it into the slender elongate shape which approximates Petrosuchus to the gavial-like Crocodilus catcqjhr actus. The hind border of the parieto-mastoid platform is undulate ; gently convex at the middle, where it is formed by the parietal (ib., 7), concave on each side, where it is carried out by the mastoids (ib., 8). In Crocodilus niger this border is straight; in Croc. palusfris it is undulate, but the middle parietal convexity is much less than the lateral, concave, mastoidean curves, owing to the relatively narrower extent of the parietal bone. The lateral borders of the supra-cranial platform, due to the mastoids (ib., 8) and post-frontals (ib., li), present, in Nannosuchus, a gentle sigmoid curve. In most modern Crocodilia these borders are straight, running parallel in Croc, niger, slightly convergent forwards in Croc, cafa- phr actus and Croc, intermedius. The breadth of the platform is to that of the skull, taken across and including the zygomatic arches, as 8 to 10 in Nannosuchus ; in Croc, niger the platform is little more than half the breadth of the skull taken across the hind part of the parieto-mastoid or upper temporal apertures ; in Croc, jjalustris the platform occupies half the breadth of the skull taken at the same part. The upper temporal apertures (t) have the same relative size as in Petrosuchus, but they differ in shape, being less circular, the longer diameter being longitudinal, or in the skull's axis. As far as the orbits are preserved these do not exceed in size the upper temporal apertures. This character of the Mesozoic Crocodile is retained in the present dwarf species. A super-orbital bone strengthened the upper eyelid ; it retains 1 'Catalogue of Osteology, Mus. Coll. Chir.,' 4to, 1853, p. 153, No. 691. 650 BRITISH FOSSIL REPTILES. its connections with the frontal (n), post-frontal (12), and pre-frontal (n) in the left orbit (0); but has become slightly detached in the right orbit (o'). The nasal bones (15) terminate in a point distant from the external noscril by rather more than the diameter of that aperture, which accordingly is single and exclusively bounded by the preniaxillaries. In this character Crocodilius cataphractus and Croc, intermedius resemble Nannosuchus ; but the upper jaw is longer and more slender in proportion in both these existing Crocodiles than in the Purbeck species ; in both, also, the upper temporal apertures are relatively smaller than in Nannosuchua. In the character of the nasal bones and conformation of the external nostril Nanno- suchus resembles GoniophoHs (PI. 40), but the supra-temporal apertures are more oblong and the maxillaries are not so out-swollen as they approach the premaxillaries. The facial part of the skull, from the front border of the orbit forwards, equals the extent of the skull from the same part to the occiput in Nannosuchus ; in Goniopholis the facial part of the skull, so defined, is one third longer than the extent behind. The mutilated state of the unique skull of Petrosuchus prevents a similar comparison being made. The sculpturing of the upper surfaces of the exposed parts of the skull in Nannosuchus presents the common Crocodilian character of minute subcircular pits, leaving a reticulate disposition of the intervening bone. Genus — Theriosuchus,^ Owen. Species — Theriosuchus pusillus, Ow. Crocodilia, Plate 44, figs. 3—18 ; Plate 45. This Crocodile, somewhat smaller in size than the preceding species, approaches nearer to the type of the broad-faced Alligators in the proportion of the antorbital part of the skull. The dentition is more modified than in any other known Crocodile, recent or extinct, and approaches that which characterises the Theriodont order of Triassic Reptilia. The premaxillary teeth are five in number in each bone; the three middle ones subequal, the first and fifth smaller. The maxillary teeth are divisible into laniaries and carnassials or trenchant molars. The first maxillary tooth is small (PI. 44, fig. 5) ; the second and third gain quickly in size, the latter (a) assuming the character of a canine ; the fourth tooth {b) is a still larger canine ; the fifth (c) and sixth [d) decrease in size somewhat suddenly, but in length rather than brcadtli of crown, and terminate the series projecting from the convex part of the alveolar border of the maxillary. The tooth c ox d may be said to terminate the laniary series. Beyond d the teeth lose length and slightly gain in breadth ; the crown assumes a triangular, laterally corn- er, dtjpwv, wild beast ; a-uv)(^oi, crocodile. PURBECK CROCODILES. C51 pressed, or lamellate form, and the enamel is transversed on the outside by fine but distinct lines (ib., fig. 6, e). Of these sectorial or carnassial molars some of the detached specimens of maxillary (figs. 7 and 11) indicate as many as eight or nine. The broad base or root of each tooth is not inserted into a separate and complete socket, but is lodged in a recess of the outer alveolar wall ; moreover, the partitions between these recesses are low or partial, and the teeth appear to have been applied thereto, without being so completely confluent therewith, as in the pleurodont mode of fixation of the teeth in certain Lizards. Hence, in some of the specimens of the maxillary bone the incisors and canines only are retained, being rooted each in its own complete socket ; while the molars have fallen out, and their partially separated recesses are shown, as in figures 7 and 11. In the lower jaw the foremost tooth is rather larger than those which interlock with the ttiiddle premaxillary or ' incisor ' teeth above ; but not any of the succeeding laniary teeth attain the size of the upper canines. The twelfth tooth, counting back- wards, assumes the lamellate, triangular shape of striate crown characteristic of the superior sectorials ; and the inferior ones wer& lodged, like those above, in a common depression of an outer alveolar wall, developing the ridges dividing such depression into the dental recesses, as shown in fig. 16, PI. 44. This approximation to a Lacertian dental character might seem ground for something more than a family section of the order Crocodilia ; but the quasi-})leurodont attachment of the hinder teeth in Theriostichus is only an extension of the character affecting some of the teeth in existing species of Crocodile.^ In the cranial platform of Theriosuchus the medial parietal part of the hind border is less convex and the two outer parts are more concave by reason of the further backward production of the mastoids than in Nannosuchus. The lateral borders of the sculptured part of the platform are more convex than in that genus. This is owing to the greater proportion of the outer and posterior angles of the platform which is abruptly depressed below the level of the sculptured surface of the mastoid, and which becomes smooth like the contiguous and lower-placed tympanic. This character, shown in the subject of fig. 3, PL 44, usefully indicated fragmentary parts of the skull of other individuals of the species, such as are figured in fig. 1, 12', PI. 45. The supra-temporal vacuities are relatively larger than in Naimosuchus. The intervening tract of the parietal, rather more canaliculate than in Nannosuchus, is divided by a mid ridge in two of the cranial specimens, and partially so in the more complete skull. No palpebral ossicle is preserved in the orbit (o). The pointed ends of the nasals are produced so as to divide the outer nostril into two, as in some specimens of Crocodilus ' It is noted in the Alligator niyer. "No. 7G5. The right ramus of the lower jaw, from which the posterior part of the inner alveolar wall has been removed, showing the five posterior teeth lodged in a common alveolar groove." ' Osteological Catalogue, Museum of the Eoyal College of Surgeons,' 4to, vol. i, p. IC; (1853). 652 BRITISH FOSSIL REPTILES. vifjer ; were this a character of generic value, it might unite T/ieriosuchus with Ilalcrosia, Gray.i The alveolar part of the maxillary in which the canines are developed make a corresponding convex extension of its outer border, as in Goniopholis. The extent of the 'symphysis mandibulae ' and the angle of divarication of the rami are shown in fig. 4, PI. 44. The matrix was removed as far as practicable from the palatal surface of the skull (fig. 4) and exposed a portion of the basisphenoid (.i), of the pterygoids (24), of the palatines (20), and palatal plates of the maxillary (21) ; the pterygo-maxillary vacuities {y) and the hind portion of the palatonares (w) were brought into view. What seems to be a portion of the hind part of a mandibular ramus was so wedged down upon a part of the palatal surface that, in regard to the fragile character of this unique skull, it was deemed unadvisable to attempt its removal. In PI. 45 a portion of the skeleton of Theriosuchus prmllus is figured. It is of one individual. In the slab of matrix in which it is imbedded the fore part, marked a, a, is continued on from the hind part with an interval of the extent marked b. At this interval the slab has been broken across, but the parts appear to have been naturally readjusted before the specimen was fixed in its present frame. The position in which the two portions of the skeleton are figured relates to the convenience of size of the Plate. 'j'he skull has been displaced and fractured, but tlie contiguity of the preserved portion ■with the vertebral column supports the conclusion that it formed part of the skeleton of the same individual. It thus serves to determine the species to which the subject of Plate 45 belonged . The part of the skull includes the parieto-mastoid platform (7, 12') with the tympanic (28) and the squamosal (27). The articular surface of the tympanic for the mandible shows the Crocodilian character. The median or sagittal ridge of the parietal is well marked, and is continued along the raid-frontal. This character is partially effaced by mutilation in the more entire skull (PI. 44, fig. 3). It is well shown in the frontal bone indicating the largest of the specimens of Theriosuchus (ib., fig. 8). The vertebral centrums of the trunk show the shallow Araphicrolian character of those of the Goniopholis and Teleosaurians. The smooth under or dermal surface of part of the two median rows of the dorsal scutes are shown in the fore half of the skeleton. In the hind half the upper or epidermal surface of the scutes is exposed, showing in most the submedial longitudinal ridge. This is wanting in certain, probably lateral, scutes, of which a group is exposed at the fore part of the anterior portion of the skeleton. One of these unridged, but toothed, scutes is figured at fig. 3, PL 45. Of the limb-bones preserved may be recognised the right scapula (,51) and humerus (53), the left humerus (53) with the radius (54) and ulna (55), followed by some dislocated 1 'Trans. Zool. Soc.,' vol. vi, p. 135. PURBECK CROCODILES. 653 metacarpals and phalanges of the fore-foot. In the hind portion of the skeleton (fig. 2) the right femur (fjs), tibia (66), fibula (e;), vvith the four metatarsals and scattered phalanges, are preserved. All the limb-bones show the ordinal Crocodilian characters, but the proportion of the fore to the hind limb is that of the Procoelian division, not that of the Teleosaurs.^ In this respect, as in the proportions of the maxillary bones and teeth, the advance to Tertiary types of Crocodilia is manifested. As in these the Theriosuchus was better adapted for locomotion on dry land than were the Teleosaurs. In Theriosuchus the breadth and shortness of the antorbital part of the skull in proportion to the part behind exceeds that in any modern broad-snouted Crocodile. Even in the young ' Crocodile a deux arretes,' figured in PL I of Cuvier's ' Ossemens Fossiles,'^ a transverse line across the fore part of the orbits equally bisects the skull, omitting the mandible. In Theriosuchus the same line leaves in advance six thirteenth parts of the length of the skull. This proportion suggested at first view the immature state of the individual to which the subject of fig. 3, PI. 44, had belonged; but of the numerous evidences of Theriosuchus pusillus none were larger than those figured in PI. 45, and in figs. 3, 4, 8, 14, 16, of PI. 44 : several other fragmentary evidences had come from smaller individuals. I conclude, therefore, that, as in the case of most species notable for their diminutive size, immature characters of the larger species of the genus are associated with such dwarfishness of the adults. The only known mammals of the Purbeck period charac- teristic, moreover, like the dwarf Crocodiles, of the fresh-water ' Feather-bed ' deposits, are of diminutive size, and the carnivorous Saurians seem to have been thus adapted in dimensions and force to their prey. I estimate the average length of a mature Theriosuchus at 18 inches. The length of the skull, taken as that of the mandible, is 3 inches 6 lines. In the articulated skeleton of a modern Crocodile the angle of the lower jaw extends to the third cervical vertebra. In Alligator lucius the trunk from the third cervical to the last sacral vertebra inclusive is nearly equal to two lengths of the skull ; the length of the tail is 2^ lengths of the skull. The trunk oi Theriosuchus so defined includes two lengths of the skull. The tail, as indicated by fig. 2, PI. 45, equalled 2^ lengths of the skull. In the long-jawed Gavials and Teleosaurs the trunk includes about 1| length of the skull ; but the tail is proportionally longer than in the short- and thick-jawed Crocodiles. ^ Crocodilia, PI. 11. 2 Quarto, torn, v, 2de partie. 654 BRITISH FOSSIL REPTILES. Crocodilian Vertebrae. Plate 42, figs. 4 — 12. Of the mimerous scattered vertebrae in the different slabs of the Purbeck matrix those specimens have been selected for figuring which exemplify the CrocodiHan characters of different portions of the vertebral column. The subject of fig. 4, PI. 42, is from the neck or fore part of the trunk, in which the hypapophysis {hy) has not subsided on the under surface of the centrum ; the processes for the head (' parapophysis,' p) and tubercle (' diapophysis,' d) of the proxi- mally bifurcate rib are well developed. The pre- (i) and post- (z') zygapophyses, together with the neural spine (».«.), complete the series of developments of this complex type of Crocodilian vertebrae.^ Figs. 5 and 6 are two consecutive, but slightly dislocated, vertebrae from the hinder part of the trunk. The long and broad diapophyses show the notch {d) where the simple and short hinder ribs were articulated, each by a single joint, with the rest of their osseous ' segment ' or vertebra." Figs. 7 and 8 are side views of mutilated hinder trunk vertebrae. Fig. 9 gives a back view of one of the sacral vertebrae, showing the robust processes represented by coalesced pleurapophyses. The suture is traceable by which the latter articulate with both centrum and neural arch.^ Fig. 10 is a caudal vertebra, with the haemal arch and spine (a) ; a front view of the latter is given in fig. 11 ; the vertebra is from that part of the tail where the pleura- pophyses cease to be developed.* Fig. 12 shows the completely ossified substance in a section of a dorsal centrum. Fig. 13 probably belonged to Brachydedes minor. All these and other detached vertebrae indicate the dwarfed proportions of the Crocodilia characteristic of the fresh-water deposits of the ' Feather-bed.' Many correspond in size and shape with those shown iri sitd in T/ieriosucJius, PI. 45. The subjects of figures 4 — 10 I am disposed to refer to NannosucJtus. Crocodilian Scutes. PI. 43, figs. 4, 5, 11, 12. In almost every slab containing Crocodilian remains are scutes, or portions or impressions of scutes. They include the ' peg-and-groove ' type, the hexagonal with I No. 687, ' Catalogue of Osteology,' 4to. ut supra. - No. 689, op. cit., p. 153. ' It accords with the character of the sixth cervical vertebra in Gavialis gangeticus (' Catal. of Osteology, Mils. Coll. Chir.,' 4to, vol. i, p. 152, No. 684), save in the minor development of the hypapophysis, which indicates a position in the vertebral column somewhat further back. * See No. G8C of the same series and 'Catalogue.' PURBECK CROCODILES. 655 SLitural margins, and the ordinary quadrate with bevelled edges, either plain or single- ridged. All show the Crocodilian pitted or reticular sculpturing on one side, the smooth surface on the opposite. The scutes exemplified in Plate 43, figs. 4 and 5, partly by portions, partly by impressions, may be referred both by contiguity and proportional size to the larger examples of NannosucJius gracilidens. Some scutes of this type, of rather larger size, and with the smooth, overlapped, anterior border relatively broader and more elevated than in GoniopJiolis crassidens^ may belong to the smaller species of Goniopholis {G. tenuide?is) or to the larger kind of Brachydedes. A smaller-sized peg-and-groove scute would fit Brachydedes minor ; the smallest and most numerous of all are commonly associated with evidences of Theriosuchus pusillus. The most instructive scutal fossils are those which exemphfy the relative position and mode of interlocking of the articular mechanism. Of these are figured two groups, one showing the outer (ib., fig. 11), the other the inner (ib., fig. 12) surfaces. These specimens afford grounds for additions to the original description of the peg- and-groove modification of CrocodiUan armature. To the " process continued from one of the angles vertically to the long axis of the scute "' may be added " from the anterior and external angle ;" and for " the depression on the opposite angle of the adjoining scute " may be written " on the under surface of the posterior and external angle of the scute in advance." When the medial dorsal series of scutes are seen in natural connection from the outer surface the articulating peg is concealed, as in the two hinder pairs of the three shown in fig. 11, PI. 43. When the inner surface of a similar series is exposed, as in fig. 12, the mode of application of the pegs and grooves comes into view. The scutes of the two medial rows along the back of these Purbeck Crocodiles join each other at the medial line by a close contact of the inner borders — a kind of ' harmonia ' or toothless suture. Ventral scutes usually show thicker, more sutural, margins. The dorsal scutes upon the tail lose the peg and groove, are longest in longitudinal diameter, and mostly support a longitudinal submedial ridge on the outer surface ; at least in Theriosuchus pusillus (PI. 45, fig. 2). Genus — Nuthetes, Owen, Species— iVtfif/ze^es destructor, Ow. PL 43, figs. 13—16 and 17—23? In a former ' Monograph on the Fossil Lacertian Reptiles of the Purbeck Limestones ' the above genus and species were founded on portions of jaw and teeth, kindly trans- mitted to me by Charles Wilcox, Esq., of Swauage, Dorsetshire. 1 Pis. 7 and 8. 2 'Report on British Fossil Reptiles,' 1841, p. 70. 21 b 656 BRITISH FOSSIL REPTILES. In Mr. Beckles' collection further evidence of Nuihetes destrncior is afforded by the portions of jaw (PI. 43, figs. 13 and 14) and by numerous detaclied teeth, ranging in size from a length of enamelled crown of 5 mm. to 20 mm. (fig. 15, c), and with variations in the proportion of length to basal breadth (comp. fig. 15, d, e, with a, h). The teeth in the mandibular fragment accord in size and shape with those of the original or type specimen -^ they are laterally compressed, strongly recurved, and combine a basal fore-and-aft breadth of 3 mm. with the length of 5 mm. (straight). They likewise show the " excavation or longitudinal depression on the side of the base." The coronal enamel does not extend over this depression, but is continued along its margins, and to a greater extent on that next the convex border of the crown than on the opposite side. In the portion of jaw, originally figured, with seven more or less perfect tooth-crowns, two of these indicate a longer and more slender shape than the rest- Several detached teeth of this type have been exposed in portions of the ' Feather-bed Marl ' in the Becklesian series. Some of these, exemplifying difference of size, are figured in Plate 43, fig. 14. In all these tooth-crowns the characteristic fore and hind finely denticulate ridges are discernible, as shown in the magnified view (fig. 16) ; the rest of the enamel is smooth and even, as in the type of Nuihetes destructor. Of this species I am disposed to regard the specimens above described as indicative of the range of size according to growth of individuals rather than as exemplifying specific modifications of the genus. Dermal Bones (' granicones '). In many portions of the matrix of the ' Feather-bed ' are ossicles of a conical shape, the cone showing various degrees of elevation, with a granulate surface, the base being flat and smooth, or faintly and minutely pitted. These ' granicones ' I regard as dermal bones. In PI. 43, fig. 18, is represented a 'granicone' with a basal breadth of 8 mm. and a length or height of cone of 14 mm. In fig. 19 the base is oblique, reducing the shortest side of the cone to a height of 8 mm. In this, as in some of the similarly shaped ' granicones,' part of the basal margin is raised or prominent, sometimes formed by a single series of close-set granules, as in fig. 20. Those on the surface of the cone are less regularly disposed, but at some parts affect a longitudinal arrangement (fig. 21.) The apex shows various degrees of obtuseness, which finally reduces the granulate or exterior surface of the cone to a moderate convexity, but the conical shape is the rule. The smallest of such ' granicones ' has a basal breadth of 3 mm., a length of 5 mm. Slices of these enigmatical fossils prepared for the microscope (figs. 22, 23) demon- strated the absence of the structures characteristic of piscine dermal bony cones and spines. 1 'Quarterly Journal of the Geological Society,' 1854, p. 120. PURBECK LIZARDS. 657 Moreover, the geological deposit (a subdivision of the Parbeck series) containing the grani- cones is a fresh-water one, and their structure was equally distinct from the ganoid dermal defences of the Sturionidce or other fishes habitually frequenting lakes or rivers. The dermal scutes of Theriosuchus are notable for the greater number of the canaliculi, and the more regular ' lay,' or disposition, of the ' lacunas ' or bone cells, than in Lacertians ; also by the wider ' sinuses ' or unossified tracts. In the dimensions, size, shape, and number of the ' canaliculi ; ' in the minor regularity of the ' lay ' of the lacunae, and in the less proportion in both number and dimensions of the sinuses, the bony tissue of the granicones resembled that in Lacertians ; and in this conclusion from microscopical characters,* combined with the evidence of the association, and the contiguity of the granicones, with the unquestionable fossil remains of Nuthetes destructor, I derive the grounds for referring them to that extinct genus and species. Among modern Lizards the singular ' Moloch horridus ' of Australia exemplifies dermal scutes most nearly resembling these ' granicones ' in shape ; but the horny exterior is supported by dense fibrous tissue, not bone. It may be that we have in them a formal exemplification of the dermal armour of Nuthetes destructor. If so, the association of a Lizard of such forbidding physiognomy with small Marsupials having their nearest of kin in Australia would be worthy of note. 1 See ' Journal of the Royal Microscopical Society,' vol. i. No. 5, p. 233, pis. xii and xiii. w\^ U^i l.:t