\\ \ British Museum (Ratural bistory). This 1s No. 23. of 25 copies of the “ Descriptive Catalogue of the Marine Reptiles of the Oxford Clay,” Pi. 2, printed on special paper. = apes e aa, we, ‘STIMU WSED) SASS Oe) HOPIESILINOGH TL LMVd AVIO GaOsXO Lad ANIAVN TViLvVO (el / age% no | Ve aks wh { A DESCRIPTIVE CATALOGUE OF THE MARINE REPTILES OF PEE OXFORD CLAY. BASED ON THE LEEDS COLLECTION IN THE BRITISH MUSEUM (NATURAL HISTORY), LONDON. PART Il. BY : CHARLES WILLIAM ANDREWS, D.Sc, ERS. LONDON: PRINTED BY ORDER OF THE TRUSTEES OF THE BRITISH MUSEUM. SOLD BY LONGMANS, GREEN, & CO., 39 PATERNOSTER ROW, E.C.; B. QUARITCH, 11 GRAFTON STREET, NEW BOND STREET, W.; DULAU & CO., Liv., 37 SOHO SQUARE, W.; AND AT THE BRITISH MUSEUM (NATURAL HISTORY) CROMWELL ROAD, 8.W. 1913. ageonian Tnstingg (3 ‘e \ (All rights reserved.) Ro AA hs ~ON PRINTED BY TAYLOR AND FRANCIS, RED LION COURT, FLEET STREET, tl AC ae eeee Tue second and concluding part of the ‘Catalogue of the Marine Reptiles of the Oxford Clay’ begins with an account of the Pliosauride, which were known only by scattered fragments until the discoveries of Mr. Alfred N. Leeds. They are now exactly defined and described, and the gigantic species, Pliosaurus ferox, proves to be especially interesting. Among other features it will be noticed that in this reptile the bones of the young are comparatively dense, while in old individuals they are as light and spongy in texture as those of the larger existing whales. The marine crocodiles of the families Teleosauride and Geosauride, which are also described in a more exhaustive manner than has previously been possible, are represented by numerous skeletons and parts in an unusually good state of preser- vation. As the bones have been completely removed from the clay, they can be separately studied, and the collection thus adds in a remarkable degree to our knowledge of the Upper Jurassic genera hitherto depending mainly on the skeletons embedded in the hard Lithographic Stone of Germany and France. One of the finest of these skeletons, showing impressions of the skin, is preserved in the Museum and shown in the Frontispiece of the present volume. The value of the Catalogue is much enhanced by the careful drawings and diagrammatic sketches, which have been prepared by Miss Gertrude M. Woodward. A. SMITH WOODWARD. DEPARTMENT OF GrOLOGY, British Mvusrum (Natura Hrisrory), 4th February, 19138. a2 DVO bel vO.N: Ix the present volume the account of the Plesiosauria in the Leeds Collection is completed by the description of the Pliosauridie, represented by the genera Pliosaurus, Simolestes, and Peloneustes. The Crocodilia are also described and catalogued, this order being represented by several members of two families, the Teleosauride and the Geosauride. The Teleosauride include two genera, Steneosaurus and Mycterosuchus, the latter being now established for the reception of the species Wycterosuchus nasutus, which is in several respects less specialised for an aquatic life than the species of Steneosaurus. The Geosauride are all referred to the genus Metriorhynchus, the various species being, on the whole, closely similar to one another, and there being a fairly complete gradation of forms between the slender-snouted species like Jetrio- rhynchus leve and the broad-skulled and short-snouted I. durobrivense, which was formerly made the type of the genus Suchodus. The family Geosauride, as here understood, agrees exactly with the group Thalattosuchia of E. Fraas. The Plosauride differ in several respects from the Elasmosauride, described in Part I., the differences resulting for the most part from their greater adaptation to a pelagic life. As pointed out in the Introduction to Part I. (p. xv), the Elasmosaurs, with their long neck and small head, probably paddled about on the surface of the water of no great depth, the elongation of the neck being ill-adapted for rapid motion beneath the surface, but of great advantage in procuring food. In the Pliosaurs, on the other hand, the cervical vertebrae are not only fewer in number but possess relatively shorter centra than are found in the Elasmosaurs, At the same time, their head was proportionately larger, and in Pliosaurus and Peloneustes at least had a long v1 MARINE REPTILES OF THE OXFORD CLAY. pointed snout. Both the shortening of the neck and the elongation of the head seem to show that these reptiles could not merely paddle on the surface of the water, but swim through its depths at considerable speed. ‘The means of propulsion, also, in the Phosaurs differs somewhat from that of the Elasmosaurs, in which the fore paddle was the largest and most important organ of progression. In the Pliosaurs, on the other hand, the fore paddle, though still Jarge, is the smaller, and the shoulder-girdle is comparatively weak, while the pelvis and hind limb are enlarged and clearly played the chief part in swimming: there is no evidence that the tail bore any fin or took any part in the propulsion of the body in the members of this group. Although, from the contents of the stomach of Peloneustes (see Introduction to Part I. p. xvi), it is certain that these animals fed largely on Cephalopods, nevertheless the great size and strength of the teeth in the Pliosaurs generally seem to indicate that probably larger and more powerful animals were caught and killed by them. It is also likely that many of the deeply scored grooves often seen on bones from this horizon, were caused by the teeth of these animals while feeding on the carcases, and this use of the teeth may account for the considerable degree of wear often exhibited by the tooth-crowns, ¢.g., in the teeth of Peloneustes evans’, shown in text-fig. 28 (p. 73 of the present volume). Of course, in many cases the tooth-marks may have been caused by some of the numerous Crocodiles. All the members of the Sauropterygia described in this Catalogue are too highly specialised for an aquatic life to supply any valuable information as to the early history and relationships of the order, but in the Trias there occur several genera which are of considerable importance from this point of view. The earliest remains are from the Lower ‘Trias, but it is in the Middle Trias (Muschelkalk) that they become abundant and sufficiently well-preserved to establish any conclusions. The best-known genus is Nothosaurus, of which the osteology of several species has been fairly completely worked out; some traces of a terrestrial ancestry are shown, é.g., in the comparative elongation of the propodial bones, but this animal had already attained a large size and was mainly, if not entirely, aquatic in its habits, so that it is of less importance from a phylogenetic point of view than the smaller forms, such as Lariosaurus and Neustico- saurus. ‘These are small lizard-like reptiles, which were probably amphibious, but certainly were capable of progression on land. A nearly complete skeleton of INTRODUCTION. Vii Lariosaurus balsami has been described by Boulenger*; this shows that the limbs were not paddle-like, the propodial bones being relatively long, and the manus and pes not having undergone any increase in the number of phalanges. In the shoulder- girdle the clavicular arch is strongly developed, but the scapule have no well-developed ventral ramus, and the coracoid is not expanded as in the later Plesiosauria. No ossified precoracoid has been found in any of the primitive Sauropterygians, but, as Seeley has shown fF, it is probable that a precoracoidal cartilage existed: the dis- appearance of this element is probably due to the great development of the clavicular arch, which is itself replaced functionally in many of the later Plesiosaurs by the ventral rami of the scapule. The pelvis in the Triassic Sauropterygia differs considerably from that of the later forms. Thus the ilium, ischium, and pubes meet in the acetabulum in a triradiate suture in the normal way (see Part I. text-fig. 64, p. 114), there is a pubic notch or foramen, and the pubes and ischia are not greatly expanded; the enormous plate-like pubes and ischia of forms like Pliosaurus have been secondarily acquired in correlation with the entirely aquatic mode of life—the enlarged pubes being mainly for the support and protection of the abdominal viscera, the ischia for the attachment of swimming-muscles. Concerning the relationships and origiu of the Sauropterygia many different opinions have been expressed. Many writers (e.g., Baur { and Fiirbringer§) have considered that there is close relationship with the Chelonia, but the many objections to this view which have been summed up by Williston || and Hay § render it untenable. Broom ** considers that the group sprang from a land ancestor somewhat resembling Sphenodon, but with the supratemporal fossa alone developed; Jaekel t{, on the other Ht Trans. Zool. Soe. vol. xiv. (1896) p. 1. Proe. Roy. Soc. vol. 54 (1893-4), p. 157. “The Phylogenetic Arrangement of the Sauropsida,” Journ. Morph. vol. i. (1887) p. 97. ++ sb § “Zur vergleichenden Anatomie des Brustschulterapparates und der Schultermuskeln,” Jenaische Zeitschr. vol. xxxiv. (1900) p. 335, || “The Skull of Brachauchenius, with Observaticns on the Relationships of the Plesiosaurs,” Proce. U.S. Nat. Mus. vol. xxxii. (1907) pp. 486-9. € ‘The Fossil Turtles of North America’ (1908), p. 30. ** « Observations on the Structure of Mesosaurus,” Trans. S. African Phil. Soe. vol. xy. (1904), p. 103. TT “ Ueber das System der Reptilien,” Zool. Auzeig., Jahrg. xxxv. (1910) p. 324. vill MARINE REPTILES OF THE OXFORD CLAY. hand, considers that both fossee were developed, but that the lower temporal bar had been lost. The present writer * also, chiefly on account of the structure of the palate, once regarded the Sauropterygia as descended from a primitive Rhynchocephalian reptile. Boulengerf considers, as Seeley{ did, that J/esosaurus is closely related to the Sauropterygia; but the skull in Mesosaurus is too imperfectly known to be certain of its relationships either to the Sauropterygia or any other order, though it has been referred by Osborn § to the Diaptosauria, a group including the primitive Rhynchosaurian types. A.S. Woodward and Williston, especially the last-named author, consider the group as nearly related to the ‘Theriodontia, a view which is here adopted, the arguments against the relationship of the two groups having been to some extent weakened by recent discoveries among the South African Therapsids. The primitive Sauropterygian may be regarded as probably possessing the following characters :— Skull with a single temporal fossa, the zygomatic bar being formed by the squamosal meeting the jugal or postorbital or both; large pineal foramen; fixed quadrate ; palate with vomers (prevomers) separating the internal nares and meeting the anterior ends of the pterygoids behind; a transpalatine and epipterygoid present; a well- developed parasphenoid (vomer) uniting posteriorly with the basisphenoid; postfrontal present and, in some cases, excluded from the temporal fossa; prefrontal and lachrymal present, at least in some, and a septo-maxillary (postnasal of Jaekel) occurring at least in Stmosaurus and Nothosaurus. Teeth on the edge of jaws thecodont; small teeth ‘on pterygoids (in Lariosaurus). The shoulder-girdle with strongly developed clavicular arch; probably a separate cartilaginous precoracoid ; coracoid not greatly expanded, and scapula without largely developed ventral ramus. ‘The pubes and ischia not greatly expanded, and joining the ilium in the acetabulum in a triradiate suture; there may be a pubic foramen or notch. ‘The limbs ambulatory, not modified to form paddles, there being no * «On the Structure of the Plesiosaurian Skull,” Quart. Journ. Geol. Soc. vol. lii. (1896) p. 246. Tr “On a Nothosaurian Reptile from the Trias of Lombardy, apparently referable to Lariosaurus,” Trans. Zool. Soe. vol. xiv. (1896) p. 1. = “The Mesosanria of S. Africa,” Quart. Journ. Geol. Soe. vol. xlviii. (1892) p. 586. § “The Reptilian Classes Diapsida and Synapsida, and the Early History of the Diaptosauria,’ Mem. Amer. Mus. Nat. Hist. vol. i. (1903) p. 451. INTRODUCTION. ix hyperphalangy. Plastron consisting of ventral ribs arranged in rows, each consisting of a median element and two or more lateral pairs. The primitive Therapsids seem to possess many of the above characters. Thus in the skull of the Therocephalia we find a single temporal fossa (the zygomatic arch being formed by the postorbital and squamosal), a large pineal foramen, a fixed quadrate; a postfrontal excluded from the temporal fossa, a prefrontal, a lachrymal, and a septo-maxillary. The palate also is very similarly constituted, and there is a parasphenoid (vomer) which in the later Theriodonts becomes large. The teeth in the premaxille and maxilla are thecodont, but are here differentiated into incisors, canines, and cheek-teeth, a-character which shows that this group is too highly specialised to be the actual ancestor of the Sauropterygia. In some forms there are small teeth on the pterygoids. In the shoulder-girdle the precoracoid is ossified, but the reduction of this element to cartilage in the early Sauropterygia is probably due to their beginning to be adapted to an aquatic life, and to the development of their clavicular arch. The pubes and ischia, though plate-like in the Therocephalia, become modified in the Cynodonts, and a similar modification leading to the development of a Jarge obturator foramen might have given rise to the form seen in Nothosaurus. The large plate-like pubes and ischia in the later Sauropterygia are, no doubt, as already noted, secondarily acquired. The phalangeal formula in Lariosaurus (2,3, 4,4, 3 in the manus, 2, 3,4, 5,4 in the pes) might easily be derived from the Therocephalian 2, 3, 4, 5, 3 and 2, 3, 4, 5, 4. The great development of the ventral ribs in the Sauropterygia might be regarded a difficulty in the way of regarding them as related to the Therocephalian stock, but this is discounted by the fact that in the Dromasauria (Galepus and Galechirus) ventral ribs occur. This group, though in many ways specialised, is clearly closely related to the primitive stock of the Therocephalians, in which, no doubt, ventral ribs and an undifferentiated dentition existed. It is from some such early type as this, rather than from any of the known Therocephalia, that the Sauropterygia may have arisen. The Crocodilia of the Oxford Clay were probably all aquatic toa much greater degree than the modern representatives of the order, but the various groups differ considerably among themselves as to the extent to which the skeleton has become modified for pelagic life. The Teleosauride, represented by the genera Steneosaurus and PART II. b Xs MARINE REPTILES OF THE OXFORD CLAY Mycterosuchus, are much less specialised in this direction than the Geosauride, especially in the following points:—(1) the premaxillary region of the snout is expanded, not pointed as in Metriorhynchus, and the prefrontals do not overhang the orbits; (2) the neck is relatively rather longer; (3) the fore limbs, thongh reduced in size, are not paddle-like; (4) the end of the tail is not deflected to form the support of a large terminal caudal fin, although there probably was a narrow dorsal fin, at least on the terminal portion of the tail; (5) the dorsal and ventral armour is retained. Of the Teleosauride, Mycterosuchus is somewhat less specialised than Stencosaurus, the fore limb being considerably larger in proportion to the hind limb. Probably these reptiles were capable of dragging themselves out of the water on to mud-banks, but it seems impossible that they can ever have moved any distance from the water, as sometimes happens in the case of the modern Crocodiles. The Geosauride, represented in the Oxford Clay by various species of Metrio- rhynchus, have undergone extreme modification for a purely aquatic life. ‘Thus the head has a pointed snout, the prefrontals form a protective projection above the orbits, the neck is shortened, the fore limb is paddle-like and very small compared with the large hind limb, the terminal section of the tail is deflected and carried a large vertical fin which, no doubt, was the chief means of propulsion. The dermal armour has disappeared, but there is a well-developed sclerotic ring on the eye. Some of the more slender forms (e.g., JZ. leve) show a complete loss of the cranial sculpture, probably an advantage to an animal rapidly moving through the water. E. Fraas *, Abel, Arthaber {, and Auer § have described and discussed at great length the various modifications undergone by the skeleton in this family, which Fraas separated from the rest of the Crocodilia as a distinct group, the Thalatto- suchia. He, for the most part, drew his descriptions and conclusions from Geosaurus, * “Die Meer-Crocodilier (Thalattosuchia) des Oberen Jura,” Palxontographica, vol. xlix. (1902) p.1; “ Reptilien und Siiugethiere in ihren Anpassungserscheinungen an das marine Leben,’ Wirttemberg. Naturwiss. Jahreshefte, vol. !xi. (1905) p. 347. + “Der Anpassungstypus von Metriorhynchus,’ Ceutralb]. f. Min. ete. 1907, p. 225. See also this author’s volume ‘ Paleobiologie’ (1912), p. 105 et seq. + “ Beitrige zur Kenntnis der Organisation und der Aupassungserscheinungen des Genus Jfetrio- rhynchus,” Beitriige Paliont. Oester.-Ungarns, vol. xix. (1906) p. 287 ; also “ Ueber den Anpassungstypus von Metriorhynchus,” Centralbl. f. Min. 1907, p- 385. § “Die Extremitiiten von Ietriorhynchus,’ Centralbl. f. Min. 1907, p. 536; “* Weitere Beitrige zur Kenntnis des Genus Metriorhynchus,” tom. cit. p. 353. INTRODUCTION. xi while Abel, Auer, and Arthaber discussed more or less imperfect skeletons of Metriorhynchus, sometimes incorrectly restored, from the Oxford Clay of Peter- borough. A beautiful skeleton of a young individual of Geosaurus gracilis from the Kimmeridgian Lithographic Limestone of Eichstatt has lately been acquired by the British Museum, This specimen, which has been described by Dr. L. v. Ammon *, is figured in the Frontispiece and gives a good idea of the general appearance of these sea-crocodiles. It is especially remarkable, because, to some extent, it shows the outline of the body, and the form of the caudal fin (text-fig. A, p. xii) is beautifully shown. Dr. Ammon believes that portions of the muscles are preserved in phosphate, but it seems possible that these are fragments of wrinkled skin. The skull, which in the original block was thrust back over the cervical vertebre and tilted up, has been freed from the matrix and placed in its natural position. The skeleton lies in a curved position on the left side, the dorsal surface being turned to the concave side of the curve: one result of this is that the downwardly flexed part of the tail is partly straightened out, so that the exact form of the caudal fin is somewhat distorted. The total length of the skeleton along the curve is about 114 cm. (38 ft. 8} in.), of which the skull occupies about 21 cm., the tail 51 cm. The skull and mandible are in close contact in their natural position. The former is in the shape of an elongated triangle, the base of which is between a quarter and a fifth of its height (7. e., length of skull to tip of snout). The skull- roof in the neighbourhood of the orbits is incomplete and consequently does not show the form characteristic of the group, the overhanging prefrontals being lost. The occipital and the antorbital regions of the skull are fairly well preserved. ‘The palatal region is much crushed and its structure obscure. The snout is relatively longer and more slender than in any species of Metriorhynchus and none of the bones preserved show more than a trace of sculpture. ‘The form of the supratemporal fossee is doubtful, the openings, as shown in the figure, being probably too small. The external narial opening is elongated and without a median division. The teeth are small and numerous, but their exact form and number cannot be determined. The anterior cervical vertebree are incomplete, only three at the posterior end being preserved, though much crushed. Behind the last, the slab has been broken across * “ Ueber jurassische Krokodile aus Bayern,” Geognostische Jahreshefte, Jahrg. xviii. (1905) p. 62. b2 xli MARINE REPTILES OF THE OXFORD CLAY. and there is a space large enough for one centrum, probably the last cervical. The next vertebra has the parapophysis almost entirely on the arch and is here regarded as the first dorsal—if rightly so, there are nineteen dorsals altogether. In all, the transverse processes are broken away, but the neural spines, which are broad, low, and sloping a little backwards, are well preserved. ‘The two sacrals are much obscured by the crushing that has taken place, the right ilium having apparently been forced down upon them and destroyed; the neural spines are similar to those of the dorsal region. The caudal vertebrae (text-fig. A) are about fifty in number, and of these twenty-seven are in front of the downward flexure of the tail. E. Fraas states that in Text-fig. A. Terminal portion of tail of Geosaurus gracilis, showing the outline of the fin. (R. 3948, } nat. size.) Geosaurus suevicus there are forty-four caudals, but possibly some of the very small terminal centra, here preserved, may be wanting in his specimen. Candal ribs seem to have been present on the first fourteen vertebra, but on the last two of these they merely form slight prominences. The neural spines are not well preserved in the first few caudals, but further back it can be seen that they are composed of a larger back- wardly sloping portion separated by a notch from a small anterior pointed process (the “Vorreiter” of Fraas). From the sixteenth to the twenty-fifth the neural spines are not well preserved, but on the twenty-sixth and twenty-seventh (the two immediately anterior to the downward bend) they are seen to slope sharply backwards and are INTRODUCTION. xii thickened at their upper end. The twenty-eighth vertebra (at the bend) has a high neural spine thickened at its upper end and upright or a little inclined forwards. The spines of the succeeding five vertebre are inclined forwards and gradually become shorter. On the next the short spine slopes backwards, and the same is the case with the next two. Behind this to the end of the tail—that is, in about the last fifteen vertebree—no spines can be seen, and probably in some of the terminal vertebrz no neural arch was present. The chevrons begin on the second or third caudal vertebra; at first they are long Y-shaped bones, but from the fourteenth to the twenty-fifth vertebre they are not clearly seen. Behind this they have very short pedicles and a much expanded median ventral portion, consisting of a smaller anterior and a longer posterior lobe. The ends of these lobes in the successive chevrons are in contact, forming a continuous chain Fore paddle of Geosaurus gracilis. (R. 3948, nat. size.) a., radius; b., ulna; ¢., radiale; d., ulnare; mc.1, first metacarpal; me.4, fourth metacarpal. as far back as the thirty-seventh vertebra: this arrangement probably greatly strengthened the basal portion of the tail-fin. The structure of the shoulder-girdle and fore limb can, to a great extent, be made out from their impressions on the matrix. The fan-shaped upper end of a coracoid with a coracoid foramen is well shown, and there is a mass of bone crushed beneath the vertebral column, which may be the lower part of a scapula, but the state of preservation is such that this is uncertain. The humerus is wanting, but the form of the paddle-like distal part of the limb is well shown; this is figured above (text-fig. B). It will be seen that it consists proximally of two pairs of subequal disc-like bones, the nature of which is not quite clear. Ammon, in his description, regards the proximal pair (a., 4.) as the radius and ulna, the distal (¢.,d@.) as the radiale and ulnare. XIV MARINE REPTILES OF THE OXFORD CLAY. Fraas, in his account of the fore limb of Geosaurus suevicus, adopts this interpretation : in that species the preaxial bone of the distal row is large and quadrate, the postaxial very much smaller and roughly triangular (see ‘ Paleeontographica,’ vol. xlix. (1902) pl. viii. fig. 3). If Fraas and Ammon are right, as they probably are, then the distal row of carpals has entirely disappeared and the metacarpals articulate directly with the radiale and ulnare. It is not, however, possible to be quite certain that the four bones figured may not represent the two rows of carpals, the radius and ulna being lost. Fiven in the specimen upon which Fraas’ figure is founded, the displacement of the bones is considerable and does not appear entirely to exclude this interpretation. Of the metacarpals the first is large and plate-like, with a convex anterior and slightly concave posterior border. ‘The second, third, and fourth metacarpals are much more slender, probably flattened, rods of bone, somewhat constricted in the middle; the second is the longest and most slender. Ammon figures a fragment of the fifth metacarpal, but this I cannot see. ‘The first phalanges of the first, second, and third digits are preserved; they are small and seem to have been much flattened. The whole limb must have formed a paddle-like organ, the digits being separated at their tips only, if at all. Though so much altered from the form of the fore limb of ordinary Crocodiles, the paddle is not very greatly reduced in proportion to the size of the body, its apparent smallness being partly the result of contrast with the enlarged hind limb; probably it was not used for propulsion, but rather in maintaining the balance of the body. The pelvis is for the most part destroyed, but portions of the ilium and ischium, together with an impression of the rather slightly expanded distal end of the pubis, can be made out; unfortunately, the upper end of this bone is not sufficiently well preserved to show its relations to the ium and ischium. The hind limbs are very well preserved, that on the right side being almost completely shown, though the tibia and astragalus are represented by impressions only. ‘The tarsus in the left foot is complete and is very closely similar to that of Metriorhynchus leve, shown on Pl. X. fig. 3 of the present volume. In fact, the whole limb is very similar in the two species, the only notable difference being, that while in Metriorhynchus lave the tibia is more than a third of the length of the femur, in the present specimen it is less. The numbers of the phalanges preserved in the digits are 2, 2, 4, 4, but the terminal one is probably wanting in the second; the phalanges are much flattened. INTRODUCTION. XV The ventral ribs seem to have been strongly developed and a number cof widely open V-shaped elements of the middle row can be seen; they are fairly stout and well ossified. There was probably at least one pair of lateral elements in the form of short rods. The outline of the soft parts of the body seems to be indicated by a yellow stain, best seen in the caudal region. ‘The terminal caudal fin, however, is not only outlined in this way, but also stands in slight relief as a natural cast, the anterior border being especially clear (see text-fig. A, p. xil). The exact form of this region is, however, somewhat obscured by the circumstance that the downwardly flexed portion of the vertebral column has been somewhat straightened out into line with the anterior part of the tail, in consequence of the curved position in which the animal is lying. In a few places on the ventral side the surface is covered by some patches of a thin layer of a peculiar fibrous-looking substance. ‘This has been examined in detail by v. Ammon, who regards it as phosphatized muscle. The possibility that muscle may be preserved in this way has been demonstrated by Reis * in several papers, but at the same time the uniform thinness of the substance rather suggests that it may be fossilized remnants of the skin which had fallen more or less into longitudinal wrinkles. So long ago as 1860 von Meyer noticed the presence of what he con- sidered to be skin in a specimen of the present species, also from the Solenhofen Lithographic Limestone. On the question of the origin of the Crocodilia, the Oxford Clay specimens throw no light. ‘The Steneosaurs are no doubt derived from the various species of Mystrio- saurus found in the Lias, but beyond that their descent cannot be traced. In the case of the Geosauride the early history is still more obscure. ‘The only form anterior to the Oxford Clay which appears to be nearly related is Teletdosaurus, of which Deslongchamps { has described two species (7. calvadosi and T. joberti) and Collot § * See especially: “‘ Untersuchungen iiber die Petrificirung der Muskulatur,”’ Archiv f. Mikros. Anatomie, vol. xli. (1893) p. 492; and “ Neues iiber petrificirte Muskulatur ete.” op. ct. vol. lii. (1898) p. 262. E. Fraas has also written on the subject: see ‘“‘ Ueber die Finne von Jchthyosaurus,” Jahreshefte Ver. Vaterliand. Naturkunde in Wiirttemberg, vol. xliv. (1888) p. 293; and “Die Hautbedeckung yon Ichthyosaurus,” op. cit. yol, 1. (1894) p. 493. + “Fauna der Vorwelt,” Rept. Lith. Schiefer, p. 96, pl. xv. + ‘Notes Paléontologiques,’ p. 274. § “Reptile Jurassique (Leleidosaurus yaudryi) trouve & Sainte-Seine l’Abbaye (Cote-d’Or),” Mem. Académie Dijon, [4] vol. x. (1906) p. 41. XVi MARINE REPTILES OF THE OXFORD CLAY. one (2. gaudryi), from about the horizon of the Fuller's Earth (L. Bathonian) in Northern France. In this Crocodile the prefrontals form slight projections over the orbits, apparently the commencement of the large overhanging prominences seen in Metriorhynchus. The snout is pointed and the surface sculpture, particularly of the frontal, is not unlike that of some species of Metriorhynchus. Deslongchamps regards this genus as transitional between the Steneosaurs and Metriorhynchs; but the structure of the base of the skull and palate is not well known, so that it is uncertain whether or not there was a large vomer (parasphenoid) as in the latter group. In fact, the presence of this structure in the Geosauride suggests that they have probably been derived from a stock widely different from that of the Steneosaurs, in which, so far as is known, it is absent; and if Teleidosaurus should be found to possess this character, it is the earliest-known member of the family of which the origin and relationships to the other Crocodiles are quite uncertain. CHARLES W. ANDREWS. Department of Geology, December 1912. List ORLPUBLICALLONS REFERRING TO THE MARINE REPTILES OF THE OXFORD CLAY OF PETERBOROUGH, COLLECTED BY Messrs. CHARLES EDWARD ayp ALFRED NICHOLSON LEEDS. 1. ABEL, O. Der Anpassungstypus von Metriorhynchus. Centralbl. f. Min. ete. (1907) p. 225. 2. AnpREws, C. W. On the Development of the Shoulder-Girdle of a Plesiosaur (Cryptoclidus oxoniensis, Phillips, sp.) from the Oxford Clay. Ann. Mag. Nat. Hist. [6] vol. xv. (1895) p. 333. 3. ——. On the Structure of the Skull in Peloneustes philarchus,a Pliosaur from the Oxford Clay. Ann. Mag. Nat. Hist. [6] vol. xvi. (1895) p. 242. 4. ——. The Pectoral and Pelvie Girdles of Murenosaurus plicatus. Ann. Mag. Nat. Hist. [6] vol. xvi. (1895) p. 429. 5. ——. Note on the Skeleton of a Young Plesiosaur from the Oxford Clay of Peterborough. Geol. Mag. [4] vol. ii. (1895) p. 241. 6. ——. Note on the Pelvis of Cryptoclidus owoniensis (Phillips). Geol. Mag. [4] vol. iii. (1896) p. 145. 7. ——. On the Structure of the Skull of a Pliosaur. Quart. Journ. Geol. Soe. vol. lili. (1897) p. 177. 8. ——. Notes on the Osteology of Ophthalmosaurus icenicus, Seeley, an Ichthyosaurian Reptile from the Oxford Clay of Peterborough. Geol. Mag. [5] vol. iv. (1907) p- 202. 9. ——-.- Onsome new Steneosaurs from the Oxferd Clay of Peterborough. Ann. Mag. Nat. Hist. [8] vol. iii. (1909) p. 299, pls. viii. & ix. 10. ——. On some New Plesiosauria from the Oxford Clay of Peterborough. Ann. Mag. Nat. Hist. [8] vol. iv. (1909) p. 418. 11, ——. On the Mounted Skeleton of a small Pliosaur (Peloneustes philarchus, Seeley, sp.). Geol. Mag. [5] vol. vii. (1910) p. 110, pl. xii. 12. ——. On the Structure of the Roof of the Skull and of the Mandible of Peloneustes, with some Remarks on the Plesiosaurian Mandible generally. Geol. Mag. [5] vol. viii. (1911) p. 160. PART II, C XVili MARINE REPTILES OF THE OXFORD CLAY. 13. 14, 15. 16. V7 18. 19. 20. PMG 22. ARTHABER, Gustav von. Beitrige zur Kenntnis der Organisation und der Anpassungs- erscheinungen des Genus Metriorhynchus. Beitriige Paliiont. Oester.-Ungarns, vol. xix. (1906) p. 287. ——. Ueber den Anpassungstypus von Metriorhynchus. Centralbl.f. Min. etc. (1907) p. 385. —. Ueber die Hinterextremitit von Metriorhynchus. Centralbl. f. Min. ete. (1907) p. 502. Aver, Ei. Weitere Beitriige zur Kenntnis des Genus Metriorhynchus. Centralbl. f. Min. (1907) p. 353. ——. Die Extremitiiten von Metriorhynchus. Centralbl. f. Min. etc. (1907) p. 536. ——. Ueber einige Krokodile der Juraformation. Palzontographica, vol. lv. (1909) p. 217, pls. xxii-xxvi. Bauer, Fr. Osteologische Notizen iiber Ichthyosaurier. Anat. Anzeig. vol, xviii. (1900) p. 074. Baur, G. On the Morphology of the Vertebrate Skull. Journ. Morphol. vol. iii, (1889) p- 467. Dotxo, L. L’audition chez les Ichthyosauriens. Bull. Soc. belge Géol., Brux. vol. xxi. (1907) Proe.-verb. p. 157. Fraas, E. Die Meer-Crocodilier (Thalattosuchia) des Oberen Jura. Paleeontographica, vol. xlix. (1902) p. 1. 23. Hurxr, J. W. Contribution to the Skeletal Anatomy of the Mesosuchia, based on Fossil Remains from the Clays near Peterborough in the Collection of A. Leeds, Esq. Proc. Zool. Soc. 1888, p, 417, pls. xviii—xix. 24. ——. On the Shoulder-Girdle in Ichthyosauria and Sauropterygia. Proc. Roy. Soe. vol. lii. (1892) p. 233. 25. JaccarD, F. Notes sur le Peloneustes philarchus, Seeley, du Musée paléontologique de Lausanne. Bull. Soc. vaud. Sci. nat. [5] vol. xliii. (1908) p. 395, pls. xxvi.—xxxii. 26. ——. Notes sur le Peloneustes philarchus, Seeley, du Musée paléontologique de Lausanne. Bull. des Laboratoires de Géologie ete. de ? Université de Lausanne, Bull. 10 (1908). 27. JAEKEL, O. Ueber die Bildung der ersten Halswirbel und die Wirbelbildung im allgemeinen. Zeitschr. deutsch. geol. Gesellsch. Protokolle, vol. lvi. (1904) p. 109. 28. Lerps, E. Taurtow. Notes on Mletriorhynchus superciliosus, Desl. Geol. Mag. [5] vol. iv. (1907) p. 314. .—. On Metriorhynchus brachyrhynchus (Deslong.) from the Oxford Clay of Peterborough. Quart. Journ. Geol. Soe. vol. Ixiy. (1908) p. 345. . LypexKerR, R. Notes on the Sauropterygia of the Oxford and Kimmeridge Clays, mainly based on the Collection of Mr. Leeds at Eyebury. Geol. Mag. [3] vol. v. (1888) p- 350. .—. Catalogue of Fossil Reptilia and Amphibia in the British Museum (Nat. Hist.). Pis, iiv. (1888-1890). . ——. On the Remains and Affinities of five Genera of Mesozoic Reptiles. Quart. Journ. Geol. Soc. vol. xlv. (1889) p. 41. . —. Contributions to our Knowledge of the Dinosaurs of the Wealden and the Sauro- pterygians of the Purbeck and Oxford Clay. Quart. Journ. Geol. Soc. vol. xlvi. (1890) p- 36. LIST OF PUBLICATIONS. xix 34. Lypexker,R. Ona Crocodilian Jaw from the Oxford Clay of Peterborough. Quart. Journ. Geol. Soe. vol. xlvi. (1896) p. 284. 35. Puruuirs, J. Geology of Oxford. Oxford, 1871. 36. Scumipt, W. E. Ueber Metriorhynchus jaekeli, nov. sp. Zeitschr. deutsch. geol. Gesellsch. Protokolle, vol. lvi. (1904) p. 97. 37. Snetty, H.G. On Murenosaurus leedsi,a Plesiosaurian from the Oxford Clay. Quart. Journ. Geol. Soc. vol. xxx. (1874) p. 197, pl. xxi. 38. ——. Note on some of the Generic Modifications of the Plesiosaurian Pectoral Arch. Quart. Journ. Geol. Soc. vel. xxx. (1874) p. 436. 39. ——. On the Pectoral Arch and Fore Limb of Ophthalmosaurus, a new Ichthyosaurian Genus from the Oxford Clay. Quart. Journ. Geol. Soc. vol. xxx. (1874) p. 696. 40. ——. The Nature of the Sheulder-Girdle and Clavicular Arch in Sauropterygia. Proc. Roy. Soe. vol. li. (1892) p. 119. 41. ——. Further Observations on the Shoulder-Girdle and Clavicular Arch in the Ichthyosauria and Sauropterygia. Proc. Roy. Soc. vol. liv. (1893-4) p. 149. 42. ——. On the Extremity of the Tail in Ichthyosauria. Ann. Mag. Nat. Hist. [8] vol. i. (1908) p. 436. 43. ——. On the Interlocking of the Neural Arches in Ichthyosauria. Ann. Mag. Nat. Hist. [8] vol. i. (1908) p. 441. c2 Tee ee Oc ee Lk Acemeaiianill MUU Wier Ter ad ee Piste | Py PRIA rhe UR aR aang hte nD ly Aen, ee: dis a i ee tas ve of ee eS sect ti SSE MATIC INDEX: Order SAUROPTERYGIA (cont.) . Suborder PLESTOSAURIA Family PriosavRIpz . Genus Pliosaurus a ferox Genus Simolestes . . 35 VOPA Ky ay etn, Cutten Genus Peloneustes . , is philarchus 35 eyansi . Order CROCODILIA Suborder MESOSUCHTA Family TELnosavrip® Genus Steneosaurus 53 leedsi. $5 hulkei durobrivensis . ” obtusidens . Genus Mycterosuchus . SS nasutus Family GrosavRip@ Genus Metriorhynchus 5 superciliosum . moreli % lave . i leedsi np cultridens . 5 brachyrhynchus . 2 durobrivense . FRONTISPIECE. THE photograph represents a nearly complete skeleton (R, 3948) of Geosaurus gracilis, v. Meyer, sp., in which the outline of the soft parts, especially of the caudal fin, is preserved. The fore and hind paddles are well shown, but the skull, which was imperfect, has been restored. The total length of the skeleton along the curve is about 3 ft. 84 ins. (114 cm.). This specimen was described and figured by Dr. L. v. Ammon in ‘ Geognostische Jahreshefte,’ vol. xviii. (1905) p. 62. A brief description, with figures of the fore paddle and tail, is also given in the Introduction to this volume (p. xi). From the Lithographic Stone (Lower Kimmeridgian) of Eichstadt, Bavaria. LIST OF ILLUSTRATIONS IN THE TEXT. Fig. 1, Pliosaurus ferox; palatal surface of skull 2. - 3 cervical vertebra ay “ os caudal vertebra. . . . . 4, ue ee cervical ribs . 5. 5 a left coracoid . , 6. a ‘ fore and hind paddles ie ie re pubes and ischia 8. Simolestes vorax: shoulder-girdle . oh. 5 ss fore and hind paddles 10. . 5 pelvis . AM 11. Peloneustes philurchus: occipital region of skull . 12, + 3 bones of the auditory region of skull Hey, 4 5 inner side of skull-roof 14. Peloneustes and Murenosaurus : mandible 15, Peloneustes philarchus: atlas and axis 16, Be ‘ atlas and axis 3 Mfc is 3 anterior cervical vertebrae 18. a a middle cervical vertebre . 119: es y posterior cervical vertebre . 20. >, Hs cervical ribs. Dike as Me shoulder-girdle . 22. = 33 interclavicle . : 23. ; es fore and hind paddles 24. a pelvis os 2 55 ilium 26. 53 3 restored skeleton 27. Peloneustes philarchus and P. evansi: mandible 28. Peloneustes evanst: teeth 29. ms * sacral ribs . 30 Pr rs coracoids CS bat ib aT ST ST ST io) XXIV MARINE REPTILES OF THE OXFORD CLAY. Fio Page ePSteneoscurus aurovrivensis;: Upper sutiaceiofskull ~ 9 . . . s « « + | se & je ae 6 CO 32. Be 3 palatal surface of skull . . . . ‘ ome tc) Lees hoy’ lots) Oo. 3. posterior portion of ventral face of skull 6S) oo an OO. 34. - leedst and St. durobrivensis: atlasand axis . . . . +6 « «© «© «© «© « « « « 92 35. ; = middlescervical’vertebrei:; < = 7 es ee eeOO. 36, + leedsaa-edorsalavertebrae’ ia th cee, tis ok ee. 8. | a Fey te a OLED 37 “4 CLUPODTZUENSIS|2 9G OTSAleVELLGDI2e- ae) ach ies eh wb ee. er te) el ees) ee 38 : rf andi Sti leedsa:) caudalivertebree s< f4 Sori Sa he ee won a) es eel 39. i GUurobrivensiser TIDS ea Oe ee a Te Ss) aa Nee eee, he or eae ee TSS 40. i Leedsreh CHOVEOT Site: (is B vecedeenesiiee's,. cok ta, ia,, pei ocaey “WoL. Yo aah el BL evs ee Ae error () 5) 41. * durobrivensis and St. leedsi: coracoidand scapula. . . . . . . .. .. . 106 42, = 3 boneszot fore limb! 4. «2: ss “a. a. ees Ge ae eee eee OS 43. is Ucedsoiielvis; DIDS) s)fstine Je) is) he eee) ee OCS 68. ss a chevrons). "43059 24 shy go ee nt ke 2 ORE ee eC) 69. ¥ 3 and Jf. leve: shoulder-girdle and humerus. . . . . . . . . 17/1 70. = oa shoulder-pirdle and forelimb. “2 22 2 7. 0 72 a - morely:, pelvis, outerside! 2) 274.9 298. ys Ge ee be eee ae 72. % = pelvis, inner side . . . . ogee Gale pt fois ASP ae 5 EN as ea 175 73. Upper surface of skull of the various species of Metsiorh ynchus: > 3% Tee ten ee eee nae 178- 9 A DESCRIPTIVE CATALOGUE OF THE Mie Ancien eI eioniokev dle lp bus OES) THE OXFORD CLAY. PART Il. Order SAUROPTERYGIA (continued). Suborder PLESTIOSAURIA (continued). Family PLIOSAURIDZ. Head relatively large, neck short ; cervical ribs for the most part with double heads. Scapule not forming an extensive median ventral symphysis; clavicular arch not well known, but including, in some genera at least, a triangular interclavicle interposed between the inner ends of the ventral rami of the scapula. Fore paddles smaller than the hind paddles; pelvis very large. Range: Lower Jurassic to Upper Cretaceous of Europe. If, as seems probable, the large Rhomaleosaurus (t Thaumatosaurus) cramptoni is referable to this family, then its range in time was from the Upper Lias to the Chalk, where it is represented by Polyptychodon. The family seems to have flourished especially during the period of the deposition of the Oxford and Kimmeridge Clays. In the Oxford Clay of Peterborough it is represented by three genera: Pliosaurus, Simolestes, and Peloneustes. ‘The genus Thaumatosaurus is very imperfectly known, but if the species Thaumatosaurus victor, recently described by Fraas*, from the Upper Lias of Holzmaden, actually belongs to that genus, it is probably very nearly * Paleontographica, vol. lvii. (1910) p. 123. PART II, B 2 MARINE REPTILES OF THE OXFORD CLAY. allied to the other members of this family, but is excluded from it by the possession of single-headed cervical ribs. Williston * has attempted a definition of this family on the assumption that the genus Brachauchenius from the Cretaceous cf Kansas is closely allied to Pliosaurus. His definition is :—‘ Skull depressed, no parietal crest ; palatines broadly contiguous on the middle line; pterygoids with a prominent ridge and abutting mandibular process. Neck short, cervical ribs single- or double-headed, all vertebre without infracentral vascular foramina.” Such a definition would exclude the type genus from the family. Probably the North-American reptiles corresponding to the Pliosaurs of Europe will be found to constitute a distinct family, in which the characteristics common to the two groups are the consequence of parallel modifications. Genus PLIOSAURUS, Owen. [ Odontography, pt. ii. (1841) p. 282.] 1873. Liopleurodon, Sauvage, Bull. Soc. Géol. France, [3] vol. i. p. 377. Skull relatively large, with an elongated rostrum; mandibular symphysis moderately long, extending back to about the level of the seventh tooth. Teeth sharp-pointed, with numerous longitudinal ridges of enamel of varying length, usually absent or only slightly developed on the outer side, which in the later (Kimmeridgian) forms may be flattened, so that the crown is roughly trihedral in section. Neck short, consisting of twenty-two or twenty-three vertebre, with short centra and high neural spines. Cervical ribs with double heads, except, perhaps, the last. Dorsal and sacral vertebre at least twenty-four in number; caudals at least fifteen, the posterior three or four diminishing in size very rapidly. Stull (Pl. 1.; text-fig. 1).—The skull in this genus has already been described in some detail in the Quarterly Journal of the Geological Society, 1897, p. 177, and although other specimens have been obtained since that description was written, none are better preserved or add much to our knowledge of this important part of the skeleton. The specimen (R. 2680) there described and figured is, therefore, now taken as the basis for a somewhat more detailed account, and is figured on Pl. I. It is unfortunate that this skull was not associated with the mandible or any other part of the skeleton. A second and more imperfect skull (R. 3536) is also referred to—this specimen being of especial importance, because it is associated not only with the mandible, but also with a considerable portion of the rest of the skeleton. In its general outline the skull is a greatly elongated triangle, its length being about 23 times its width at the quadrates. The temporal fosse are very large and are separated by a narrow and high sagittal crest. ‘The orbits seem to have been rather * Science, n. s. vol. xvii. (1903) p. 989. PLIOSAURUS. 3 smaller than in some other members of the group. The premaxillary region of the snout is very slightly expanded. The basioccipital (b.oc.) is a very large and massive bone, bearing the whole of the large occipital condyle ; this is almost hemispherical, its transverse diameter being a little longer than the vertical. In the middle of the condyle there is a slight flattening with a dimple-like depression, probably marking the former position of the notochord. Laterally and superiorly the surface of the condyle passes without interruption into the sides and top of the bone, but ventrally it is marked off by a deep groove which forms a sort of short neck to the condyle in this region. In the middle ventral line there is a rounded ridge which, beyond the region of the neck of the condyle, turns sharply down at right angles and terminates in the ventral face of the bone which is completely overlapped by the pterygoids. The lateral (pterygoid) processes are very short and stout; they arise about one centimetre in front of the rim of the condyle; their outer ends are deeply concave and seem to have been covered by the pterygoids in the uncrushed skull. The surfaces for union with the exoccipital-opisthotics are very large and separated by a narrow interval only. The exoccipital-opisthotics themselves are much crushed, especially at the upper end. It can be seen that, as usual, they are almost columnar bones forming the sides of the foramen magnum. The opisthotic bears a long paroccipital process (par.p.), the outer end of which is expanded and fits against the hinder face of the posterior (quadrate) ramus of the pterygoid and perhaps in part against the quadrate itself. The supraoccipital (soc.) cannot be clearly seen, owing to the crushing down upon it of the parietals. ‘The same is the case with the prootic. The dasisphenoid is concealed by the underlying pterygoids, with the exception of a small part of the anterior end; this, as usual, is underlain by the adherent parasphenoid. This bone (pas.) seems to have extended back between the basisphenoid and the pterygoids ; certainly the pterygoids cannot have met between the parasphenoid and the basisphenoid in the manner described by Williston in the case of Trinacromerum *. The free portion of the parasphenoid in front of the basisphenoid is much broken, but it can be seen to have narrowed rapidly between the posterior interpterygoid vacuities f. Anteriorly where it passes between the pterygoids it widens again suddenly and then narrows gradually to a point, giving it the appearance of a very narrow spear-head ; the ventral face is overlapped to some extent by the edges of the pterygoids, so that a greater area is exposed on the upper than on the palatal surface: this latter is flat or slightly convex from side to side. ‘The anterior end of the bone is situated about 8-5 em. in front of the anterior end of the posterior interpterygoid vacuities. * Journal of Geology, vol. xvi. (1908) p. 715. + It is proposed to use this term instead of “ posterior palatine vacuity,” to which some objections have been pointed out by Williston and others. B2 4 MARINE REPTILES OF THE OXFORD CLAY. The pterygoids (pt.) are large bones forming a great part of the palatal surface of the skull. They are of the triradiate structure usual in the group. The anterior rami are very large and their front portion much thickened: externally they unite with the palatines in a nearly straight suture. Anteriorly they seem to have united with the vomers in a complex suture, excluding the palatines from the middle line. In the middle line they meet in front in symphysis for a short distance, then are separated by a narrow anterior interpterygoid vacuity (a.p.v.), behind which they again meet for a short distance (about 4 cm.), but behind they are separated by the anterior part of the parasphenoid, which is thrust in between them for about 8:5 cm.; behind this the inner edges of the pterygoids curve away from the parasphenoid to enclose the posterior interpterygoid vacuities (p.p.v.), which are about 10-11 cm. long. Behind these openings the pterygoids again meet in median symphysis, beneath the basisphenoid and basi- occipital, which, as noted above, they largely conceal; they also cover, and in the uncrushed condition probably united with, the lower ends of the lateral (pterygoid) processes of the basioccipital. The length of the suture between the pterygoids beneath the basis cranii is about 9 cm.; the posterior third of this distance bears a strong and prominent ridge, which anteriorly bifurcates, the two branches forming prominent crests which curve outwards through about a quarter of a circle and become continuous externally with the postero-inferior edge of the lateral rami of the bones ; towards their outer ends these crests become thickened with strong tuberosities directed downwards and outwards; these prominences fit closely against similar projections of the transpalatines (¢.p.) in front, forming the downwardly directed processes of the palate seen in Sphenodon and many other reptiles, the outer edge abutting against the inner face of the mandible when the jaws are closed. The anterior border of the lateral ramus is situated a little in front of the level of the anterior ends of the posterior interpterygoid vacuities (p.p.v.); it runs out nearly at right angles to the long axis of the skull, and unites in an irregular suture with the posterior end of the palatine. Externally the lateral ramus is overlapped by the transpalatine (t.p.). The outer border of the posterior ramus is greatly thickened and rounded from above downwards; this part of the bone is prolonged backwards in a long stout process towards the quadrate, with which it unites closely; this union may be brought about by the overlapping of the posterior pterygoid process on a corre- sponding process of the quadrate, or may have been directly with the inner edge of that bone; the arrangement is obscured by crushing, but the former seems the more probable interpretation. ‘The expanded distal end of the paroccipital process (par.p ), as above described, fits closely against the hinder surface of the pterygoid-quadrate bar, which bears a shallow groove for its reception; the surfaces of contact are smooth and it seems that a certain amount of movement between the bones was possible. The upper surface of the pterygoids near the outer border of the posterior ramus, immediately behind the point of origin of the lateral ramus, bears a long oval surface for the PLIOSAURUS. 5 columella cranti or epipterygoid (col.). This bone is stout and seems to have been oval in section, narrowing rapidly towards its summit, where it no doubt joined the lower edge of the parietal, though the crushing to which the skull has been subjected has caused much dislocation in this region. The palatines (pal.) are large elongated bones; their inner borders unite in suture with the pterygoids; anteriorly they narrow considerably and they seem to join the vomers for a short distance and perhaps take a small share in the formation of the hinder border of the internal nares. Externally these bones unite in front for about half their length with the maxille, but behind this they are separated from those bones by a narrow elongated suborbital vacuity (s.o.v.) which is closed behind by the transpalatine. Hach palatine is perforated by a foramen (pal.f.), about 1 cm. in diameter, situated on the left side about 4 cm. from the hinder border of the bone and 1 ecm. from its inner edge; on the right side the part of the bone lying behind and internal to the opening is broken away, but it seems that the opening was a little further back than on the opposite side. The vomers (v.) (prevomers of Broom) are large bones about 40 cm. long and for the anterior four-fifths of their length anchylosed together. Anteriorly they run forwards some distance between the premaxille, behind which they are in contact with the maxille, thus excluding the premaxille from any share in the enclosure of the internal nares. On their palatal surface the vomers are overlapped to a considerable extent by the palatal plates of the maxille and premaxille; between the second maxillary teeth the width of their exposed surface is reduced by this overlap to a narrow strip less than a centimetre wide. Between the internal narial openings the united vomers form a bar, convex from side to side; at about the middle of these openings the width of the bar is about 3 cm., but at the posterior end it widens to about 4°8 cm. Behind the narial openings the bones widen into a fan-shape and unite with the pterygoids in the middle line by an irregular suture; external to this they have a short union with the palatines, and external to this again they join the maxilla. In no specimen, however, are the relationships of the bones in this region very clearly shown. The premacille (pmx.) consist of the massive dentigerous portion forming the anterior part of the snout, and the long slender facial processes which run back on the dorsal surface of the skull to a point some distance behind the external nares, where they unite in suture with the anterior ends of the frontals or perhaps the parietals (see below). ‘The premaxille bear five teeth each; of these the first pair are small, directed forwards and nearly in contact with one another on the middle line. ‘The second, third, and fourth increase in size, the two last being very large; the fifth is again small. Between the last premaxillary tooth and the first on the maxilla is a diastema about 6 cm. long, crossed at about the middle by the premaxillo-maxillary suture. On the palate this suture runs inwards and a little hackwards to the vomer, 6 MARINE REPTILES OF THE OXFORD CLAY. defining a short palatine process which, however, does not reach the internal narial opening. Immediately internal to the alveoli there is a deep groove, at the bottom of which the tips of the replacing teeth appear; the inner wall of the groove forms a prominent ridge which, joining that of the opposite side, forms an elongated raised triangular area at the middle of the anterior end of the palate. By the divergence of these ridges posteriorly, a short groove is formed which is closed behind by the prominent anterior end of the combined vomers. The upper (facial) surface of the anterior region of the premaxille is gently convex from side to side, and is roughened and marked by a number of small foramina opening into short longitudinal grooves. ‘The great facial processes at first narrow gradually, but at a point about 40 cm. from the tip of the snout their sides become parallel and Text-fig. 1. Restoration of the skull of Pliosaurus ferow from palatal surface. (R. 2680, about 3 nat. size.) @.p.v., anterior interpterygoid vacuity; 5oc., basioccipital; zmar., internal nares; ma., maxilla: pal., palatine; pal.f., foramen in the palatine; par.p., paroccipital process; pas., parasphenoid; pma-., premaxilla ; p.p.v., posterior interpterygoid vacuities ; pt., pterygoid; g., quadrate; s.orb., suborbital vacuity ; t.p., transpalatine; v., vomers. continue so to their union with the frontals (or parietals). They are separated from the external nares by a band of bone, which seems to be composed anteriorly of a process of the maxilla, and behind by part of a bone here regarded as a nasal (see below). The maazille (mx.) are very large bones, each beariug about twenty teeth; of these the first two are small, the third and fourth very large. Behind these there is a decrease in size to the ninth, but the tenth and eleventh are again large ; behind these there is a gradual decrease to the end of the series, the hindmost teeth being very small. Seen from the side the margin of the jaw presents a sinuous outline, the first convexity being in the premaxilla, the next beneath the third and fourth maxillary PLIOSAURUS. ( teeth, the last at the tenth and eleventh. As already mentioned, the palatine plate of the maxilla overlaps the vomer to a considerable degree in front. Opposite the internal nares it is raised into a high cristiform ridge which is perforated by a foramen and forms the outer wall of the narial opening. Behind this the maxilla unites with the palatine for some distance, but is then separated from it by the narrow suborbital vacuity (s.ord.) as above described; the transpalatine (¢.p.) joins the maxilla to the pterygoid and closes this vacuity posteriorly. At its hinder extremity the maxilla sends a long process beneath the jugal, nearly as far as the anterior end of the zygomatic process of the squamosal. Within the alveolar margin as far back as the anterior end of the suborbital vacuity there is a deep groove, with a series of pits in which the tips of the crowns of the replacing teeth are seen. The facial surface of the maxilla is gently convex from above downwards. ‘The maxillo-pre- maxillary suture has already been referred to; 1t seems to terminate opposite the middle point of the external narial aperture (nar.), where the process of the maxilla which forms the hinder part of its inner margin joins a corresponding process of the bone which may be the nasal (?7.). The maxilla also forms the outer border of the nares, from the postericr angle of which a suture runs back towards the orbit, separating the maxilla from the (?) nasal. Posteriorly it seems to be excluded from the orbit by an element which may be the lachrymal (/.). The jugal (j.) is a small bone which at its hinder end joins the zygomatic process of the squamosal by a vertical suture. On the ventral border for the greater part of its length it joins the backward prolongation of the maxilla. Above, it unites posteriorly with the ventral end of the postorbital, and anteriorly it seems to have formed the postero-inferior part of the border and floor of the orbit. It probably also has a short coutact with the transpalatine. The postorbital (p.orb.) is a roughly triangular bone, the lower edge of which unites with the jugal, the anterior edge forms the lower part of the hinder border of the orbit, while the posterior border forms part of the edge of the temporal fossa. On its inner surface this bone bears a greatly thickened ridge which seems to separate the orbital region from that belonging to the temporal fossa: the relations of its upper end to the neighbouring bones are not known. The squamosal (sq.) consists of a comparatively slender zygomatic bar, a stout dorsal branch, and a broad short ventral portion closely adherent to the quadrate. ‘The dorsal ramus probably met its fellow on the middle line, the two forming the upper border of the occipital region of the skull to the exclusion of the parietals which they overlie. The quadrate portion is apparently fused with the quadrate; its ventral border is convex and forms a prominent rounded ridge a little distance above the articular surface of the quadrate: this ridge is most prominent on the inner side, where, between it and the quadrate condyle, there is a deep groove. The comparatively slender zygoraatic process unites anteriorly with the jugal in a vertical suture. 8 MARINE REPTILES OF THE OXFORD CLAY. The quadrate (q.) is a remarkably Jarge and massively constructed bone. The body is concave from side to side anteriorly and convex posteriorly. The posterior surface is to a large extent concealed by the overlapping squamosal. The ventral end bears the very large articular condyle, the form of which will be best understood from the figure (Pl. I. fig. 1); it will be seen that the articular surface is divided by an oblique ridge into a smaller postero-internal and a larger antero-external region. From the inner border of the bone immediately above the condyle, it appears that a process arose, which was overlapped by the posterior limb of the pterygoid. The parietals ( par.) in their middle region form the high sagittal crest between the very large temporal fosse; posteriorly they widen and project considerably behind the supraoccipital, with which they unite below. It is not quite clear to what extent they were overlapped by the dorsal rami of the squamosals, but probably, as stated above, these bones met in the middle line and formed the actual upper border of the posterior face of the skull. Beneath the outer temporal crest the bones widen to form the roof of the cranial cavity, and a little behind the pineal foramen they unite by their lower borders with the upper ends of the columelle cranii (epipterygoids). In front of this they widen and diverge to enclose the pineal foramen (p,f.), of which they seem to form the whole margin, at least on the outer face of the skull. The relation of the parietals to the frontals is obscure in the specimens examined: in the former description it was stated that the two bones were probably anchylosed, but that there seemed to be traces of a suture on the sides of the pineal foramen. Judging now from the better-preserved skulls of Peloneustes (see p. 40) it seems probable that, though the frontals may have extended back to the pineal opening on the inner side of the skull, on the outer surface they are overlapped by a pre-pineal extension of the parietals (fr. in Pl. I.) which meets the posterior ends of the facial processes of the premaxille, thus excluding the frontals from the middle line, at least on the outer surface of the skull. If this interpretation is correct, then the names of some of the other elements of the skull-roof will be different from those given in the earlier description and plate. At about the level of the pineal foramen the outer edge of the parietal unites with an element which must be the postfrontal (po.f.). In front of this is another element which helps to form the upper edge of the orbit; this was regarded as a prefrontal and is marked pr.f. in Pl. I., but probably it is the outer part of the frontal which, judging from the skull of Peloneustes, meets or nearly meets its fellow in the middle line beneath the parietals and extends back to the pineal foramen. The true prefrontal is probably the bone marked ?s.0rb. and ta. in Pl. I.; it extends forwards to meet the maxilla and is produced anteriorly into a narrow process, forming the inner border of the external narial opening: it is possible that a nasal element is represented by this part of the bone, but no suture is visible. The anterior portion of the orbital border is formed by an element separated from PLIOSAURUS. 9 the maxilla by a curved suture, and in contact above for a short distance with the prefrontal; this element is probably the dachrymal (/.). It is produced inwards into a broad ridge, which forms the anterior wall of the orbit, and curving upwards and backwards becomes continuous with the rounded crest on the lower surface of the cranial bones which marks the inner limit of the orbit. The external nares (nar.) are oval apertures about 5 cm. long, situated about 57 cm. from the tip of the snout, that is to say some distance behind the internal nares. ‘The distance between them is about 9°5 cm., probably exaggerated by the crushing the skull has undergone. As above described, the posterior outer and half the inner border are formed by the maxilla, the remainder being enclosed by the bone here regarded as the nasal. In Pliosaurus a well-developed sclerotic ring seems to have been present, though so far it is only known from a few plates. Each plate consists of fibrous-looking bone; the outer and inner borders are concentric and the outer the longer, while the lateral edges are nearly straight and are grooved or tongued, as the case may be, for union with the adjacent plates. The outer and inner borders are thin and sharp and are irregularly serrated; the bone thickens regularly to a line a little nearer to the inner than to the outer border. These plates differ from those of Ophthalmosaurus in being only gently convex externally and concave internally, and not curving round on the back of the eye-ball. Mandible (Pl. II. figs. 1, 1a@).—The mandible is distinguished from that of Pelo- neustes in having a somewhat shorter symphysis (sym.), which, at the same time, is longer than that found in Simolestes. The symphysial region extends back to the seventh tooth, and between the third and fifth teeth it widens considerably; it is formed almost entirely by the dentaries, the splenials only entering into it for a short distance on the ventral side. The upper surface of the symphysis between the rows of alveoli is raised into a prominent ridge, on either side of which is a series of depressions probably marking the places in which the replacing teeth developed ; posteriorly the ridge divides, passing into the raised inner alveolar borders of the rami. These diverge from one another at a very acute angle; at first they are straight, then curve gently inwards to the articular surfaces for the quadrates. The anterior part of each ramus, as far back as the coronoid angle, is formed externally by the large dentary, the inner face of which is covered by the closely adherent coronoid (sp/. in fig. 1) and splenial, the latter of which roofs in the dental canal. The coronoid (spl. in Pl. II. fig. 1) is a very long thin strip of bone very closely adherent to the inner face of the dentary (d.). At its hinder end it forms the inner face of the coronoid angle, immediately beneath which it unites in complex suture with the surangular (art. & surang.). Its upper border is parallel with and close to the edge of the dentary, which forms the inner side of the groove within the line of alveoli; below it is overlapped by the splenial. Its anterior end extends to, or perhaps even enters, the symphysis. PART II, Cc 10 MARINE REPTILES OF THE OXFORD CLAY. The splenial (spl. in Pl. IL. fig. 1 @) is a long thin strip of bone closely adherent to the inner face of the coronoid above, and of the dentary and anterior prolongation of the angular below. The posterior end cannot be made out in the specimens, though probably it was as in Peloneustes (see below, text-fig. 14). Anteriorly it enters the ventral side of the symphysis for a short distance. ‘The post-coronoid portion of the mandible is composed of two pieces, (1) the fused articular and surangular (art. & surang.), (2) the angular (ang.). The former constitutes the upper part of the post- articular process (p.a.p.), bears the articular surface, in front of which its upper border, which is thickened and flattened above, slopes up to the coronoid angle; beneath this the bone unites with the coronoid on the inner, and the dentary on the outer side, ventrally it unites with the angular. ‘The articulation for the quadrate is a concave kidney-shaped surface ; its concave anterior rim is strengthened by a strong prominence situated rather to the inner side; the outer and posterior borders are also rather prominent. On the anterior side of the outer concavity there is a deep pit, probably for the attachment of a ligament. The angular is a large bone and constitutes the lower border of the jaw to within a short distance of the symphysis; posteriorly it unites with the surangular and articular above, and in front of the level of the articular surface, probably with the posterior prolongation of the splenial. In front of the coronoid angle it is prolonged forwards as a tapering process, uniting with the dentary on the outer side and the splenial on the inner side. The teeth (Pl. II. figs. 2-4) in the lower jaw are about 28 in number on either side; of these seven are in the symphysial region. ‘The anterior pair is small, close together, and directed nearly straight forwards; the next five pairs are large and about equal in size; they are directed forwards, outwards, and upwards, but the last tooth in the symphysis is smaller and does not seem to have been directed forwards. The teeth in the rest of the ramus are smaller than the large symphysial teeth, and remain about equal in size till the last four or five, which rapidly diminish. The structure of the individual teeth is the same in the upper and lower jaws. They have been described and figured by Lydekker in the Quart. Journ. Geol. Soc. vol. xlvi. (1890) p. 49, ple've fig. 1. Each tooth, as a whole, is curved and is nearly circular in section throughout its length. The root is very large, considerably larger than the enamel-clad crown, and its surface is quite smooth ; the pulp-cavity is open below and is large, extending some distance up into the crown. The form of the crown varies somewhat in different parts of the jaw. In the smaller posterior teeth (Pl. II. figs. 4, 4a) it is smaller in proportion to the root and more sharply curved than in the larger teeth. In all the crown, which terminates in a sharp point, is more or less curved; the outer convex face is covered with nearly smooth enamel (Pl. II. fig. 2a), but on the remainder of the surface the enamel bears numerous sharp ridges, which start from the base of the crown and extend towards the apex to a varying extent: a few of the stronger ridges may actually reach the tip. ‘Towards the base of the crown some PLIOSAURUS. a: of the ridges may bifurcate and, in some of the largest teeth, the enamel is raised into vermiculate sculpture. In some cases the smooth outer face may show traces of the flattening which, in the later Kimmeridgian forms, is carried so far as to give the crown of the teeth a more or less trihedral section *. Near the base of the crown, on what is probably the posterior side, there is often a surface (PI. IT. figs. 2, 2 6, w.s.) from which the enamel has been completely worn away. These teeth seem to be identical with those described by Sauvage (Bull. Soc. Géol. France, [3] vol. i. (1873) p. 378) under the name Liopleurodon ferox, from the Oxford Clay of Boulogne, and it was on this account that the name Pliosaurus ferox was adopted for the species to which the remains here described belong. Vertebral Column (text-figs. 2-3)—No very well-preserved and complete vertebral column is available for description; that associated with the skull and mandible (R. 3536) above referred to is the most nearly complete, but the vertebrae, particularly in the dorsal and caudal regions, are much crushed and the neural arches are for the most part lost. The atlas and axis have their centra closely fused together in the adult. The centrum of the atlas (odontoid) forms the middle portion and the neural border of the cup for the occipital condyle. ‘The supero-lateral portions of the border of the cup were evidently formed by the ventral ends of the neural arch, but this is not preserved in any specimen. The ventral portion of the cup was formed by the anterior wedge- bone. ‘The centrum of the axis is oval in section, the long diameter being transverse. Anteriorly it is closely united above with the odontoid, and below with the posterior face of the hinder wedge-bone, which is interposed between the centra of the atlas and axis ventrally. Judging from the structure of the atlas and axis in Peloneustes (see below, p- 47, figs. 15, 16), the bases of the pedicles of the neural arch were very large, forming the supero-lateral portions of the atlantal cup, as above noted, and extending down to unite by a broad surface with the upper angles of the anterior wedge-bone, thus excluding the odontoid from any share in the formation of the sides of the atlantal cup, such as is seen in Muranosaurus (see Part I. pp. 92-93, text-fig. 49) and Crypto- cleidus. In this manner of forming the atlantal cup, Pliosaurus and Peloneustes resembie some Liassic Plesiosaursf and also the North American Cretaceous genus Trinacromerum (Dolichorhyncops) described by Williston ~. On the lateral surface the united atlas and axis bear a large facet for a rib, the greater part of which is on the axis, but apparently both the centrum of the atlas and the second ventral wedge- * See Owen’s figure of tooth (Brit. Mus. 37408) of Pliosaurus macromerus, Phillips (P. grandis, Owen), in ‘“ Reptilia of the Kimmeridge Clay ” (Mon. Pal. Soc. 1863), pt. ii. pl. xii. + Barrett, “On the Atlas and Axis of a Plesiosaur,” Ann. & Mag. Nat. Hist. [3] vol. ii. (1858) p. 361, pl. xiii. + “ North American Plesiosaurs, Pt. I.,” Field Columbian Museum, Geological Series, vol. ii. no. 1 (1908) p- 32, pl. xxii. fig. 5. c2 12 MARINE REPTILES OF THE OXFORD CLAY. bone share in the formation of the antero-ventral portion of the facet, as is also the case in the atlas and axis of TZrinacromerum (Dolichorhyncops) figured by Williston *. In Peloneustes the rib-facet is borne on the centrum of the axis alone, the second ventral wedge-bone being much smaller than in Pliosaurus. ‘The posterior face of the centrum of the axis is evenly concave, with a well-marked pit in the middle. The remaining cervical vertebre (text-fig. 2) are about eighteen in number. ‘Their centra are characterised by their shortness, the length in the mid-ventral line, where they are thickest, being less than half the vertical diameter of their articular faces. Text-fig. 2. Cervical vertebra of Pliosaurus ferox: A, from front; B, from left side. (R. 3536, } nat. size.) a.z., anterior zygapophysis ; c.r., cervical rib; ».sp., neural spine; p.z., posterior zygapophysis. These are nearly circular in outline, the transverse diameter being a little longer than the vertical; beneath the neural canal the upper border is slightly concave; the surfaces are gently concave, with a median pit of such depth that the anterior and posterior pits can only be separated by a very thin layer of bone, but in no case have they been seen actually to communicate with one another. On the ventral side the articular faces have a well-defined rim or border, which in some cases may form a slight hypapophysial prominence, which looks as if it may be formed by a now com- pletely fused intervertebral wedge-bone. ‘The neural surface is slightly concave from side to side; the facets for union with the pedicles of the neural arch are diamond- * Op. cit. PLIOSAURUS. 13 shaped and extend from one end of the centrum to the other. From the outer angle of these facets a slight ridge runs down the side of the centrum, becoming continuous below with the low prominence which bears the diapophysial and parapophysial surfaces for the articulation with the ribs. These surfaces taken together are pear- shaped, the rounded end being at the bottom, the pointed one at the top; they are in close apposition, being divided only by a slight groove which terminates at each end ina notch. The ventral surface of the centrum between the rib-facets is convex from side to side and slightly concave from before backwards. There is a pair of large nutritive foramina, the openings being about halfway between the mid-ventral line and the rib-facets. The neural arch is high, the pedicles being relatively long; they widen out con- siderably at their lower end. ‘The anterior and posterior zygapophyses (a.z. and p.z.) are large; their articular surfaces are oval and are slightly concave and convex, respectively, from side to side, and look forwards and backwards to a considerable extent. In this region the anterior and posterior zygapophyses are united by a ridge running upwards and backwards. The neural spine (v.sp.) is high and not very broad from before backwards; at the same time it is of considerable thickness from side to side, being much less compressed laterally than in the Elasmosauride. The anterior border of the lower part of the spine is thin and sharp-edged; it runs down to the anterior border of the arch between the anterior zygapophyses. Higher up the anterior border becomes thickened and rounded, and at the summit widens out and is roughened. ‘The posterior face of the spine is flattened above and concave from side to side below, the concavity between the posterior zygapophyses being very deep and having deep pits for the attachment of ligaments. The dorsal vertebree are badly preserved in all specimens. It can be seen that the centra were much longer than in the cervical region, the longest being probably from about the middle of the back, where the articular faces are nearly circular in outline and very slightly concave ; the sides of the centra are strongly concave in a longi- tudinal direction. The surfaces for union with the neural arch are very long, extending nearly the whole length of the centrum; the neural surface between these facets is very narrow. About two centimetres on either side of the middle line is a nutritive foramen, and there is another pair situated high up on the side. No good specimen of the neural arch in this region is available for description. It can, however, be seen that the pedicle of the arch was stout and that the transverse process was thick and bore a broad facet for the rib at its thickened extremity. The roof of the neural arch is broad and the stout neural spine is situated towards its hinder portion. The anterior border of the neural spine is continuous below with a deep groove which extends to the anterior border of the arch; its edges are raised and it encloses a roughened surface for the attachment of ligament. ‘The lower end of the posterior border of the neural spine is also deeply hollowed. 14 MARINE REPTILES OF THE OXFORD CLAY. The caudals (text-fig. 3), which are about 25-50 in number, have the centra rapidly shortening as the series is followed backwards, and the last four or five diminish in size very suddenly, the terminal centrum being a small irregularly-shaped nodule of bone, which, however, seems to have borne a rudimentary neural arch, but, so far as can be made out, neither caudal ribs nor chevrons. In the anterior caudals the articular surfaces of the centra are nearly circular in outline and are gently concave with a deep median pit. The neural surface (v.c.) is narrow, particularly in the middle where it is encroached upon by the deeply concave facets for the neural arch (a.f.). The sides of the centra are concave in a longitudinal direction ; on either side they bear a short prominence (7.f.) with the summit of which the single-headed caudal rib articulated or fused: the nutritive foramina are situated just beneath these costal prominences. ‘The ventral surface of the centrum is only slightly concave in a longi- tudinal direction ; on its anterior and posterior edges are the semicircular chevron- facets (¢.f.), the anterior looking downwards and forwards, the posterior, the larger of the two, downwards and backwards. Text-fig. 3. Centrum of a caudal vertebra of Pliosawrus ferow, from behind and from the left side, (R.3586, 3 nat. size.) a.f., facet for union with neural arch; c.f., facets for chevrons ; 7.c., floor of neural canal ; r.f., facet for rib. Ribs (text-fig. 4).—So far as has been observed, there is no rib on the atlas; that on the axis is not well known, but seems to have been single-headed and to have articulated with a large facet borne mainly by the axis and partly by the second intervertebral wedge-bone and the odontoid. This facet shows no trace of division into an upper and a lower portion; in Peloneustes the rib of the axis is double-headed and borne by the centrum of the axis only. Behind the axis all the cervical ribs (text-fig. 4) are double- headed, with the possible exception of one or two posteriorly: the upper (diapophysial) head (¢.) being separated from the lower (parapophysial) (/.) by a well-marked cleft which is continued on to the anterior and posterior face as a short deep groove. The distal end of the cervical rib is strongly compressed from above downwards and is produced backwards into a short angle (p.). The upper side of the proximal surface is roughened as if for the attachment of muscle, and from this point a ridge runs On PLIOSAURUS. 1 down to the postero-external angle. The two or three hindmost cervical ribs are longer and more slender than those in front and form a transition to the dorsal type. Their articulation is single, or at least the separation between the head and tubercle is only very slightly marked and does not amount to a real division. Cervical ribs in this genus have been figured by Lydekker, Quart. Journ. Geol. Soc. vol. xlvi. (1890) pl. v. fig. 2 (see also text-fig. 4). The dorsal ribs are very strongly developed ; they articulate by a single head, the concave surface of which is oval, the long axis being vertical. Immediately external to the head the rib narrows rather quickly for a short distance, then remains about the Text-fig. 4. Cervical ribs of left side of Pliosaurus ferox. The articular end and the anterior face of each are shown : A, from the anterior part of the neck; Band C, farther back. (R. 2446, 3 nat. size.) h., head of rib; p., posterior angular process ; ¢., tubercle of rib. same thickness to its lower end. It is somewhat compressed from before backwards and was probably grooved slightly along its posterior and perhaps its anterior surface, but owing to the crushing undergone by the specimens this is not certain. .Some dorsal ribs of a very young individual (R. 3557) have been found in a quite uncrushed condition and present peculiar features. The articular head is small, its diameter being almost the same as that of the rib just outside it; its facet is flat and nearly circular with a slight ventral angle. External to the head, the rib runs first straight, then curves down, thickening gradually till near its distal end, when it again contracts and 16 MARINE REPTILES OF THE OXFORD CLAY. terminates in a slightly concave surface, in which the bone appears to be made of a closely compressed bundle of individual bone-fibres. Evidently this was a sort of growing point, and immediately above it the surface is perforated by many vascular foramina which run upwards. ‘Throughout nearly its whole length the rib is nearly circular in section, there being no trace of grooving: moreover, it appears to have been very heavy and solid in texture, somewhat like the rib of a Sirenian. The caudal ribs are not well known, They articulate with the centrum by a single head, the surface of which is nearly flat. The body of the bone is compressed from Text-fig. 5. Immature left coracoid of Pliosaurus ferox: A, from above ; B, symphysial surface. (R. 2738, about 1 nat. size.) a.p., anterior prolongation ; gl.c., glenoid cavity ; sc.f., facet for scapula ; sym., symphysial surface. above downwards and curves a little backwards; the anterior and posterior edges seem to have formed strong cristiform ridges. Shoulder-girdle (text-fig. 5).—No complete specimen of the shoulder-girdle is known, but some isolated bones have been found and can be definitely determined as belonging to Pliosaurus, because they are similar in form, at least so far as can be made out, to the bones of the imperfect shoulder-girdle associated with the skeleton R. 3536, of which the skull is preserved. PLIOSAURUS. iL¢f The scapula isa triradiate bone. The posterior ramus, which unites with the coracoid and forms the anterior half of the glenoid cavity, is triangular in section, the inner angle being sharp, the outer more rounded, while the lower forms a tectiform ridge, becoming sharper as it is traced forwards to the anterior angle of the bone and dividing the ventral from the outer surface of the dorsal ramus. ‘The articular end is much thickened and bears the surfaces for union with the coracoid and for the glenoid cavity: the former is triangular in outline and makes an angle of about 100° with the latter, which is longer and slightly concave. The dorsal ramus is broad and fiat, but no specimen showing its exact form is known. The anterior (ventral) ramus is not known in any specimen belonging to this species, but probably it was very similar to that of the scapula of a Pliosaur from the Kimmeridge Clay (Brit. Mus. R. 287), which in other respects it resembles. In this it is greatly expanded at its inner end and is broadly rounded. The scapula is also similar to that of Peloneustes, except that the expansion of the ventral ramus is considerably greater. Probably the ventral rami did not quite meet in the middle line, but had an interclavicle wedged between them as in Peloneustes. The coracoid (text-fig. 5) is here described from an isolated complete example about the same size as that belonging to the skeleton above noticed. The greater part of the bone is very thin, the thickened portion lying between the surfaces for the scapula and glenoid cavity on the outer side and the deepened portion of the median symphysis on the inner side. From before backwards the symphysial border is nearly straight. An- teriorly, as mentioned above, it is much deepened for a short distance, giving rise to a strong convexity on the visceral face and a slight concavity below (text-fig. 5, sym.). Anteriorly the middle portion of the bone is prolonged forwards (a.p.), the outer side of the prolongation being the thin anterior edge of the bone which extends to the facet for the scapula; there is no evidence that the anterior prolongation was in contact with the ventral ramus of the scapula; it was fringed with cartilage, at least on its anterior and inner sides. The outer border of the bone behind the glenoid cavity is concave, the hinder convex or irregular; there is no very well-marked postero- external process. ‘The surface for union with the scapula is triangular and much roughened with ridges; the base of the triangle marks the line of union with the glenoid surface, which is very large and in the fcrm of half an oval; it is gently concave, and its surface is smoother than that for the scapula. ‘The angle between the glenoid and scapular surfaces is more obtuse than in Cryptocleidus, and measures about 150°. The posterior border of the coracoid is grooved and evidently was fringed with cartilage in life. The clavicular arch is unknown in the genus: probably it was closely similar to that found in Peloneustes (p. 56). Fore Limb (text-fig. 6, B).—Unfortunately no very complete specimen of the fore paddle is available for description, but since, so far as it is known, it is closely similar PART II. D 18 MARINE REPTILES OF THE OXFORD CLAY. to that of Peloneustes, of which good specimens are described and figured below, this is not of great importance. The fore paddle is smaller than the hind, as is usual in this family. The humerus (h.) has a well-developed great tuberosity (¢b.), beneath which it widens gradually to Text-fig. 6. weft * Wy rr fF ny , Hi :, i nq A, imperfect left hind paddle of Pliosaurus ferox (R. 2446) ; B, proximal portion of right fore paddle of same species or Peloneustes evansi (R. 2437). (1 nat. size.) 7., femur, fibula; /ib., fibulare ; %., humerus ; int., intermedium ; mt., metatarsal ; 7., radius; ¢., tibia ; ib., tuberosity of humerus ; éib., tibiale; t., trochanter of femur: w., ulna. the distal expansion, there being no narrowing in the shaft, such as is usual in the Elasmosaurs. The distal end is considerably expanded, more so relatively than it is in the femur. The radius (7.) and ulna (u.), which have been figured by Lydekker PLIOSAURUS. 19 (Quart. Journ. Geol. Soc. vol. xlvi. (1890) pl. v. fig. 4), are very similar in form to the tibia and fibula, but a little less elongated ; they articulate with one another proximally and distally, but are separated in the middle by an oval vacuity. The radius is longer than wide; in the ulna the reverse is the case. Distally these two bones articulate Text-fig. 7. Pubes and ischia of Pliosaurus ferox. (R. 3536, 54, nat. size.) acet., acetabulum ; 21.f., facet for ilium ; is., ischium ; pu., pubis. with at least three elements, the radiale, intermedium, and ulnare, and probably there was also a postaxial accessory ossicle. ‘There are three distal carpals and, as usual, the fifth metacarpal articulates with the ulnare. The metacarpals are much com- pressed on the plane of the paddle, the phalanges rather less so, so that they are D2 20 MARINE REPTILES OF THE OXFORD CLAY. oval in section; they are much constricted in the middle. The number of phalanges in the several digits is unknown. Pelvis (text-fig. 7).—An isolated specimen of the ¢ium, probably belonging to this genus, shows that it was very similar to that of Peloneustes described below (see p. 59). The pudis (pu.) is an immense plate of very thin bone; there is a thickened portion extending from the articular region to the posterior part of the median border, where the symphysial surface is somewhat thickened. When the bone was uncrushed the symphysial border must have been straight and extended nearly the whole length of the bone. ‘The posterior edge is thin and sharp, and is concave; the postero-external angle is thickened and bears two surfaces—one, looking backwards, for union with the ischium, the other forming the anterior part of the acetabulum (acet.); these surfaces make a very obtuse angle with one another. In front of the articular surfaces the outer border of the bone is concave, then it passes by a strongly convex curve on to the anterior border, which is also convex and shows signs of having been fringed with cartilage in life. The tschium (7s.) is likewise a thin, greatly expanded bone, its ventral portion being much elongated. In the uncrushed bone there would be a long straight median symphysial surface for union with the opposite ischium; owing to the thickening of the bone opposite its neck, this symphysial surface is deepest in that region. ‘The anterior border is concave and sharp, forming the posterior edge of the obturator foramen. ‘The articular head is borne by a relatively narrow neck, in which the bone is thicker than in the expanded median portion; it bears three articular surfaces as usual—one, looking forwards, for union with the pubis; a second, looking outwards and a little forwards, forming the middle part of the acetabulum; and a third, the hind- most, looking upwards and backwards, for union with the ilium (é/,f.). The pelvis seems to have been closely similar to that of Peloneustes described below (p. 59). In the specimen here figured both the pubes and ischium have been completely flattened by pressure: in their natural condition they must have been gently convex below and concave above. Hind Limb (text-fig. 6, A).—The hind paddle is very similar to the fore, and is also much the same as the hind paddle of Peloneustes described and figured below (p. 59, text-fig. 23, B). It is, however, larger than the fore limb, and the femur is perhaps rather less expanded distally, while the tibia and fibula are rather more elongated than the radius and ulna, which they otherwise resemble. The proximal row of tarsals (tibiale, intermedium, and fibulare) are much like the corresponding bones in the fore paddle, and the same may be said of the rest of the tarsals, metatarsals, and phalanges. PLIOSAURUS FEROX. 21 Pliosaurus ferox, Sauvage, sp. [Plates I. & II.; text-figs. 1-7.] 1873. Liopleurodon ferox, Sauvage, Bull. Soc. Géol. France, [3] vol. i. p. 378. 1880. Polyptychodon ferox, Sauvage, Bull. Soc. Géol. France, [3] vol. viii. p. 544. 1889, Pliosawrus ferox, Lydekker, Catal. Foss. Rept. Brit. Mus. pt. ii. p. 145. Pliosaurus pachydirus, Seeley (Index to Aves, etc., in Woodwardian Museum, 1869, p. 118), and Thaumatosaurus mosquensis, Kiprijanoff (Mém. Acad. Imp. St. Pétersbourg, vol. xxxi. (1883) art. 6, p. 27), are perhaps synonyms. Type Specimen.—A tooth from the Oxford Clay of Wast near Boulogne-sur- Mer. The teeth in this species are circular in section, not trihedral as in the Kimmeridgian species. Lydekker regards this form as probably ancestral to P. macromerus. All the following specimens from the Leeds Collection were obtained from the Oxford Clay in the neighbourhood of Peterborough. R. 2680. Nearly complete skull with numerous isolated teeth. This specimen is figured on PI. I. and was described and figured in Quart. Journ. Geol. Soe. vol. liii. (1897) p. 177, pl. xii. The whole has been somewhat crushed from above downwards, and the bones of the roof are thus somewhat difficult to determine. The dimensions (in centimetres) of this specimen are :— Length from tip of snout to occipital condyle. . . . . . 1120 a 3 5 anterior angle of external nares. 57:0 3 Fe sh a ‘n internal nares . 36:0 Length from tip of snout to posterior end of the facial processes of the premaxillas.. \sum cq hea eee aie sm AsO iheneth,olithe-externalinaresi is), bso) caedeyatel) Oy a) i 5:0 a jo. internal nares), cporaletsone enw teu: chew lence 65 = posterior interpterygoid vacuities . . . 11:0 Width of skull between the outer angles of the pintaise (perhaps exaggerated by crushing) . ..... . . 50:0 Width of skull at level of transpalatine bone. . . . . . 480 p 3 middlevofanternalinares’. 4 sf .. 3) .. « 29:0 =p - atidiastemar., 2 KS at widest part of prema opiate A eT 2) Width of articular surface of quadrate . . . Re ee Wed ete) Greatest (transverse) diameter of occipital cous Buy ot eo 6-5 Teeth (PI. II. figs. 2, 2a, 26, 3, 4,4 a): Largest. Smallest. Length along outside of curve . ... . 23°5 6-2 Tengthvor crowns ere il ati oe tens: 8-5 2:0 Diameter at base of crown ...... 2-8 itl 22 MARINE REPTILES OF THE OXFORD CLAY. R. 3536. A oreat part of the skeleton of a very large individual. The parts preserved are :— skull, mandible, many teeth, atlas and axis (fused), and twenty other cervical vertebra (text-fig. 2) mostly wanting neural arches and ribs; twenty-three centra of dorsal vertebra and fourteen caudals (text-fig. 3) ; numerous neural arches and cervical, dorsal, and caudal ribs ; ventral ribs ; portions of coracoid and scapula, humerus, radius, ulna, and numerous paddle-bones ; pubes and ischium (text-fig. 7). The skull in this specimen wants the roof between the external nares and the pineal foramen ; the middle portion of the palate and the zygomatic arches are also wanting. The presence of sclerotic plates (see page 9) in this specimen is of interest. No teeth, except some of the uncut crowns of successional teeth, were found in situ. The cervical vertebre are fairly well preserved, the neural arches and the cervical ribs in all cases separate ; dorsals and caudals much crushed. The terminal caudals are present, showing the very rapid diminution in the size of the centra at the end of the tail. The shoulder-girdle is badly preserved, but the proximal part of one fore paddle is in good condition. The humerus shows well that the distal expansion was a little more marked than in Peloneustes, and that the whole bone was more slender than in Simo- lestes. The enormous pubes and the ischium have been crushed out to nearly flat plates of bone. The approximate dimensions (in centimetres) of this specimen are :— Skull: length from quadrate to tip of snout . oe lo#:O i » occipital condyle to tip of snout . . . 1265 transverse diameter of occipital condyle . . . . . 8-0 width between outer ends of quadrates . . . . . 72:0 widbhrol quadrate sass see cee sn is ucn en yn elo:0 width of snout at constriction . . . . . . . . 137 7 # », Widest part of anterior expansion . 15-4 Mandible: extreme length .-. . .... =.=... . 1540 fenothvofsymphysisiee 8) 22's ee eeers te = eoUc0 width just behind symphysis . . . . . . . 17-0 5) pOlmarticularsurtace= a=. = a-e oe ve lO length of postarticular process. . . - . . . 10°5 Teeth: Length along middle of curve. . . . 19:0 78 Heishiofcrown) = = 4%) 6... aitD 7:0 2°35 Greatest diameter of base of crown. . 3:0 27 15 - - ae Anterior Merbebraa, “ehccccstssesesvoscestss peeeand aN ise, een Gana caudals. Length of centrum on mid-ventral line . 5:6 4-9 4:3 5:0 51 60. ues Width of posterior face of centrum . . 10:0 12-0 115 12:8 12°5 10°5 10-0 Height of posterior face of centrum . . 89 10-4 10°6 11-0 11°5 86 pil » totupofneuralspine . . . . ae 30:9 32:9 33°0 SmOumeuralcanchy <0 2) ows) fue) a te 22-2 PAIETG Oimentalispineysn ss) nena. ne a 17°3 17-0 PLIOSAURUS FEROX. 23 Coracoid; width from outer angle of glenoid surface to EAMEN ASS. Volo 6! fd Oona! ostMo Jia seg) Solas eae, distance from anterior angle of surface for scapula to posterior angle of glenoid cavity . . . . . 25:0 Scapula: width ofarticularend . . . « -» = « 4.4. LET WRU TIOG c) ita sree \oadeteg Fea) mote siul ce «eye Sea tap ck iad Of Einmerus;: yen cuhpie-wciarie stole teeter ne 53°8 width of upper end (crushed) . . . . . . . 162 sy eShattvabsmoarrowest) Glico oa oe) ye L2so ee LOWerienObasticy | usenet cen Seek! clase Ore Radius lenethy(anterior|porder)y = ss ay ee Ld nyalatde Gortonolinelly ase Sle Bie iG | Gy ala bie Usp ase IIe?) Uilnasilenethy(@pproxctonliy;) yy ete ce snes eo Aline a eeneLOnL Wadbhig(proximal) igs seeps SoeWiee le trump eaie a Misc ten Ose Pubis (approximate only) : ereatestilencthemcwern ce (Gibatas acl acmenn rl es eae Or0 % Widthivher Ure aiGele a Ce ata ee Sol, (OOO widthvortarticular: region! S02 4) bc wy , euelee lengthvof symphysial borders .3 & 2) sy) 3 3 8 78:0 Ischium (approximate only) : preatestlenothiot blader.) 4) siti 2 wit etal eo foe Senecs:O width onmblademtmiddle: im set cierto, oe 270 mee AMMO C Hiren te alla oh wig natu mee ya ek Wace binaha genni Seren bs varticularhead® 4° sat awa) et cote est on 3200 s R. 2446 (Leeds Coll. 12). Portions of the skull and skeleton of a large individual. The parts preserved are :—exoccipital, anterior portion of premaxille, vomers, pterygoids, palatines, transverse bones, and numerous fragments of skull: symphysial and both articular portions of the mandible, also many fragments ; numerous teeth (one figured by Lydekker in Quart. Journ. Geol. Soc. vol. xlvi. (1890) pl. v. fig. 1); centra of ten cervical vertebrze (one figured loc. ct. fig. 2), centra of two dorsal vertebree and three caudals, neural arch of atlas and four others (loc. cit. fig. 3); second subvertebral wedge-bone ; cervical ribs (text-fig. 4, also loc. cit. fig. 2) ; imperfect humeri, radius, and ulna (loc. cit. fig. 4), femora, tibize, and fibulee (text-fig. 6, A), and numerous other paddle-bones. In this specimen the skull is too much broken to supply any information of importance, the teeth are most perfectly preserved (see Lydekker’s figure referred to above). The symphysial portion of the mandible shows very well the extent to which the splenia] takes part in its formation. One of the median teeth remaining in the anterior portion of the premaxille shows that in this region the upper teeth bit against the lower and were greatly worn thereby ; further back traces of wear are rarely seen, the upper and lower teeth interlocking, not biting against one another. 24 MARINE REPTILES OF THE OXFORD CLAY. Some dimensions (in centimetres) of this specimen are :— Mandible: width across symphysial region at narrowest DOL eMes MST ee eerie he Pe 0 ne ot Te. a Pitas ell VE eC Teeth : Length along curve. . . ... . 210 20:7 8-0 TESA OFGiang ee G Yao co 6 a 79 2-9 Diameter of base of crown . .. . 27 20 14 Greatest diameter of root. . . . . 32 By eye Cervicals. Caudals. Ds jane mane eeeee peiebe hy eae set Wertebrie a. -<.censc pu., Pp is concave, the posterior is convex; distally it bears two facets inclined to one another, for the intermedium and ulnare. The usual three proximal carpals (radiale, inter- medium, and ulnare) are present. Proximally the radiale and ulnare articulate only with the radius and ulna respectively; the intermedium unites with the radius by a short facet and with the ulna by a long one. The arrangement of the rest of the fore paddle-bones is not certain. (3b) bo MARINE REPTILES OF THE OXFORD CLAY. Pelvis (text-fig. 10).—This is chiefly remarkable for the large size and extreme thinness of the pubes and ischia and for the great elongation of the latter. The pubis (pu.) isa broad sheet of bone; its inner (symphysial) border is nearly straight and is a little thickened in its posterior third. ‘The anterior edge is broadly convex and in life was fringed with cartilage. ‘The outer border is sharp and concave. Postero- externally the bone is somewhat thickened and bears two surfaces, the anterior forming the front of the acetabulum, the posterior, making a very obtuse angle with it, uniting with the ischium, there being, as usual in the group, no union between the pubis and ilium. Internal to the surface for the ischium the posterior border is sharp and concave, forming the front of the obturator foramen, which seems to have been closed by a backward projection of the median portion of the pubis meeting a corresponding forward projection of the dschiwm (és.). This latter is, in the main, a greatly elongated plate of bone uniting with its fellow in the middle line ina straight suture; at its anterior end it is somewhat thickened, so that the symphysial surface is there deepened. Posteriorly the bones diverge a little from one another, but in life were probably united by cartilage for some distance behind the true symphysis. The posterior end of the bone is rounded, the outer border concave. The prominent thickened antero-external region is separated from the main body of the bone by a neck ; it bears, as usual, three facets, the anterior for union with the pubis, looking directly forwards, the middle one forming the middle part of the acetabulum (acet.), and the posterior looking somewhat upwards and outwards for articulation with the ilium. Internal to the pubic facet the anterior border of the bone is sharp and concave, forming the hinder border of the obturator foramen. Internal to this, again, is the median prominence for union with the pubis, the pubic-ischial symphysis being, as above noted, continuous from end to end of the pelvis. The zlium (il.) is greatly crushed, particularly at its upper end, which seems to have been somewhat expanded ; at the distal end there are the usual two facets, one for union with the ischium, the other forming the posterior portion of the acetabulum (acet.). Hind Limb (text-fig. 9, B).—The femur is considerably longer than the humerus, but is very similar in form. The trochanter (t.) is well developed and is defined posteriorly by a shallow groove, which extends some distance down the posterior face of the shaft, the outer border of the lower end of the groove bearing a strong angular prominence (m.7.) with rugose surfaces for the attachment of muscles; beneath this point the shaft is oval in section, though the antero-posterior diameter is not much greater than the vertical one. The distal expansion is similar to that of the humerus. It bears two facets for union with the tibia and fibula, and for the rest seems to have been fringed with cartilage. ‘The tibia (t.) and fibula (f.) are almost exactly similar in form to the radius and ulna, though perhaps a little longer in proportion to their width. Their relation to the proximal row of tarsals is the same as that existing between the radius and ulna and the proximal row of carpals. SIMOLESTES VORAX. 33 R. 3319. An imperfect and much crushed specimen. The parts preserved are :—Skull and mandible (PJ. III. figs. 1, la); twenty cervical vertebrae, some with neural arches (Pl. ILI. figs. 4, 4a, 40); thirty dorsals and nineteen caudals, all distorted and for the most part wanting arches and ribs; scapule and coracoids (text-fig. 8), humeri (text-fig. 9, A), right radius and ulna (text-fig. 9, A), pelvis (text-fig. 10), femora (text-fig. 9, B), left tibia and fibula (text-fig. 9, B), and a number of other paddle-bones. Type specimen described and figured in Ann. Mag. Nat. Hist. [8] vol. iv. (1909) pp. 424-429, text-figs. 4-7. The approximate dimensions (in centimetres) of this specimen are :— Skull (Pl. IIT. figs. 1, 1a): Length from occipital condyle to tip of snout... . . 780 Width between the outer angles of the quadrates . . . . 51:0 Diameter of occipital condyle. . . . al fics Wee Wat ey oe | ROHS) Width of the articular end of the iandiate eee er Reel o Mandible (Pl. ILI. figs. 1, 1 «): Greatestlengths "2745 lite ea ee Pees Se, we | fc0 Length of symphysis . . . a iit le il eae Meee en Lbs} Width at posterior end of apmplveis oA a ae 1873 Middle cervical vertebra (Pl. III. figs. 4, 4a, 4 b) diengsthvinimid-=ventraluline 7.) Gels Gel nnn, fuente Wraidthofeentromie ane ete Se tre ee eI GO TOI OD Gi coal cnc yey cette Teel Mati yt ce itia Usihcak Meer Me AUM ES Hee eee WAG) pn) tostoplotneuralspincre es coterie ety oemeca meio Scapula (text-fig. 8): Greatest length -. .°. . °.°. : cuales ate eee OL Length from anterior angle to op of sore ramus in a Straightline: 6 ouh.o \ suceeesnhc nt snetsn? eset sph cee Ream Oe Wiadthrofineckses e425 Sate panes ene ce emer ay de Leedy Coracoid (text-fig. 8, A): 1 DFaY0 (Pe sthas holies doe a8: wtb Mb tidedtin Paar iu ree tos ca lun ge) Width at narrowest pomt. . . . 3s202;0 » between the glenoid cavities of ite two shone as MOUNtCC Mune sue shoe ele sumer cat) seni es mete 560-0 Humerus (text-fig. 9, A): Hen othe nay 2a Rod Route ons Maid Loe Abinnaiiy seizes 50) Wadthofshattatnarrowest) 2) 3) fe ee) LOGS BS distalbexpansionis cm) cecil) ny) ol ee Ian Moma o1e Pubis (text-fig. 10) : Greatestilengthign cy mien ice cme maciel 4) enw ele eel O0z0 3 WCC eS A FN ONE MOET PRON a NO EHR We Se Phoncee ops AO () Ischium (text-fig. 10): Greatest length . ... . ae anaes Mand eo ala CGN) 4, width opposite ror Tata Rik tele pon lagen Fae tats ¥21(0) Widthtokneckt? (ey aict ck cuca mestne: ein quten eee tna Mpeg tO PART If. F 34 MARINE REPLILES OF THE OXFORD CLAY. Tlium (text-fig. 10) : TDN Se Loerel Oo) Go iad BS ee eG foto sc 31-0 IWadthrotedistaliend emer ge ey fe <1) gore en prope rag pe Sem ae Femur (text-fig. 9, B): Meno bh inewecws) acy he pases te 50-0 Greatest widtb at proximal end . 15:0 Width of the shaft at narrowest. 98 on distal expansion . 27-5 R. 3170. Portions of skull, nearly complete mandible, teeth, anterior wedge-bone of atlas, numerous much-crushed centra of vertebrae, including five cervicals and ten caudals ; imperfect scapule, portions of coracoids ; humeri, radius, ulna, ?ilium, femora, tibis, fibulee, and numerous paddle-bones. The dimensions (in centimetres) of this specimen are :— Skull: width of articular end of quadrate . . . (approx.) 87 Mandible: length bt hia ts yO com 6) oy On Oe ee length of symphysis. . . . . . . (approx.) 14°0 WwidthtoL symphysis). tye ms 0s (1 uence ie irs mee 4io 5). behind’symphysisiys- ju)-ane Geiser ee) eye) lass >) OL articnlarsuriace <7. $5.) approx.) 19:2 Scapula: width of articular head . . ... 1... =... . Q4 “A middle of ascending ramus . . . . . .) 49 inmerus Of lateral border . . ... 13:0 Ilium: width of expanded upperend. . . .... .. 1156 FA shaft at narrowest . .. . a ATT 5) lower end (acetabular and ischial area) 2: (85 Gane IG 6 6) oo & ofa oo) AON A considerable portion of a skeleton including the anterior part of the mandible, six teeth (Pl. IV. fig. 5) and numerous fragments, several vertebral centra from the dorsal and caudal regions, portions of ribs, portions of the pectoral and pelvic girdles, imperfect fore paddles, and nearly complete hind paddles. This specimen was described by Lydekker in Quart. Journ. Geol. Soc. vol. xlv. (1889) p. 48 e¢ seqq., the mandible being figured on pl. ii. fig. 1, a tooth in text-fig. 4, the restored coracoids in text-fig. 5, the restored pubes and ischia in text-figs. 7 &.8, a part of a fore paddle in text-fig. 9, two vertebrae on pl. ii. figs. 2 & 3. These text-figures are reproduced in Catal. Foss. Rept. Brit. Mus. pt. i. (1889) as text-figs. 49, 51-54. The dimensions (in centimetres) of this specimen are :— Mandible: length of'symphysisi, (5 0 «os 6) ete ees oS Humerus: width of distalexspansion . . . . . . - .*. 20:7 Radius): length of preaxial border. 2). «1. se 0. 4 uae eoea humeraleborder is go 0%. aiken ey (ope eee! Winalseresteshwidthio., i eeuucimue ue Glaciers aac: Ne anceet ae mene Oa FA length eeeane tc x ie nu) Clk Re OLS Kempston, near Bedford.. Presented by F. W. Crick, Esq., 1888. PELONEUSTES EVANSI. (il Peloneustes evansi, Seeley, sp. [Text-figs. 27,B; 28, 29.] 1869. Pliosawrus evansi, Seeley, Index to the Fossil Remains of Aves, etc., in the Woodwardian Museum, Cambridge, p. 116. 1871. Pliosaurus ? grandis, Phillips, Geology of Oxford, p. 317. 1877. Pliosaurus evansi, Seeley, Quart. Journ. Geol. Soc. vol. xxxili. p. 716. 1890. Peloneustes evansi, Lydekker, Catal. Foss. Rept. Brit. Mus. vol. iv. (Supplement) p. 273. Type Specimen.—Cervical and dorsal vertebre, coracoid, and numerous fragments from the Oxford Clay of St. Neots ; Sedgwick Museum, Cambridge. The type specimen was described and figured by Seeley in the Quart. Journ. Geol. Soc. Text-fig. 27. JS. aN. A Cor arté i vi HW Ne Mandible of (A) Peloneustes philarchus (R. 8803) and (B) Peloneustes evanst (R. 2443). (About +1, nat. size.) ang., angular; art. f s.ang., articular and surangular ; cor., coronoid; d., dentary; spl., splenial. vol. xxxiii. (1877) pp. 716-723, figs. 1-7. The atlas and axis, which are not fused with one another, are figured, as also are the centra of another cervical (? fourth) and the first dorsal. The coracoid is described and figured as an ischium, an error corrected in the Geol. Mag. [3] vol. iv. (1887) pp. 478-9. Mr. Lydekker in the Supplement to the Catal. Foss. Rept. Brit. Mus. vol. iv. p. 273, suggested that the mandible (text-fig. 27, B) and the paddle (except the humerus) figured by Phillips in the ‘Geology of Oxford’ (1871) pp. 317 & 318 as Pliosaurus t grandis, really belong 72 MARINE REPTILES OF THE OXFORD CLAY. to the present species, which he at the same time included in his genus Peloneustes. Recently Mr. Leeds has collected the greater part of the skeleton of a large Pliosaur, including the skull and mandible. The latter, though crushed in the opposite direction, agrees closely in structure with the jaw figured by Phillips; and the vertebre also resemble those of the type specimen of P. evansi, so that it appears that this skeleton may be referred to that species, and from it very large additions to our knowledge can be made. One consequence of this additional information about the species is, that it is found to differ very considerably from the typical species of Peloneustes, and, since some of the points of difference are of considerable importance, it is doubtful whether a new genus, in some respects intermediate between Peloneustes and Pliosaurus, should not be established for its reception. For the present, however, this species will be referred to Peloneustes and the differences between it and P, philarchus pointed out. In addition to the specimens referred to above, some other imperfect skeletons, in which the skull and mandible are not preserved, have been referred to this species. The skull is known only from specimen R. 3891 recently obtained by Mr. Leeds. It differs from that of Peloneustes philarchus in possessing a broader snout, the borders of which are straight, there being practically no constriction at the point where the maxillo-premaxillary suture crosses the alveolar border. The premaxillary teeth are six in number and are not greatly enlarged; the diastema betweeen the premaxillary and maxillary teeth is very short indeed, a character which distinguishes this skull from that of Pliosaurus. The number of maxillary teeth is smaller than in Pelo- neustes philarchus, there being only about 22 on either side. The palate is without any anterior interpterygoid vacuity, and the suborbital vacuity, if present at all, must have been very small. The symphysis of the mandible (text-fig. 27, B) differs from that of P. philarchus in being shorter, in carrying only 11-12 teeth on each side, and in not being at all expanded; in the number of teeth in the symphysis, the jaw is thus intermediate between those of P. philarchus and Pliosaurus. ‘The total number of teeth on either side of the lower jaw is 32-36. The teeth {text-fig. 28) differ from those of both Pliosaurus and Peloneustes philarchus in possessing smoother enamel, the ridges being fewer and in nearly all cases confined to the inner (concave) side of the crown. Another peculiarity of the teeth of this reptile is, that they undergo wear to an extent not observed in any other lesiosaurian ; in some cases they are worn down to a blunt stump (w.s.). ‘This peculiarity probably indicates that this species lived on some animal protected by a hard shell or armour, for it does not seem possible that the wear can have been brought about by the grinding of the teeth against one another. A similar though much less marked state of wear is sometimes to be seen in teeth of Pliosaurus and of Polyptychedon. In spite of this extreme tooth-wear, the presence of tooth-germs on PELONEUSTES EVANSI. 73 the inner side of the teeth in use seems to show that the normal tooth-replacement was in operation. The atlas and axis of this specimen, allowing for crushing and fracture, are similar to the atlas and axis of the type specimen described and figured by Seeley in Quart. Journ. Geol. Soc. vol. xxxiii. (1877) p. 716, figs. 1 & 2. The centra of the other cervicals are also like that of the fourth cervical figured by Seeley. As in Peloneustes philarchus, the length of the centrum in the mid-ventral line is greater than that of the dorsal side. The neural arches are high; the zygapophyses are strongly developed, the articular surface of the anterior zygapophysis in most of the cervicals being gently convex, the surface of the post-zygapophysis being correspondingly concave. The neural spines seem to have increased in height from before backwards; they differ Text-fig, 28. Teeth of Pcloneustes evansi. (R. 3891, 2 nat. size.) w.s., Surface of wear. widely in form from those of Peloneustes philarchus in that, instead of being com- pressed from side to side, they are flattened from before backwards, particularly at their upper ends, towards which they widen out ; the anterior face bears a number of rough ridges, running from the base of the spine to the summit. ‘This flattening may have been produced in part by post-mortem pressure, but since it occurs on the neural spines of all the cervicals, it was no doubt present in the living animal and indicates that the movements of the neck were in some way different from those habitual to Leloneustes philarchus; the cervical ribs are similar to those of that species. ‘The dorsal centra are much crushed, but were perhaps rather shorter PART II. L 74 MARINE REPTILES OF THE OXFORD CLAY. in proportion to their width than in the other species; the chevron-facets on the caudals are large. : A number of peculiarly shaped bones (text-fig. 29), preserved with this skeleton, are here regarded as sacral or anterior caudal ribs. At their proximal end they bear a head (h.) with two facets for union with the lower part of the neural arch and with the centrum ; distally they expand into a broad blade, which curves somewhat downwards and is strengthened on the ventral surface by a ridge (7.) running out from the head. They vary in form at their onter ends: in some there is a large terminal facet, perhaps for union with the ilium; in most the outer end is produced forwards and backwards into a short process terminating in a flat facet (f.), which probably united with the corresponding facet on the rib before and behind. ‘This arrangement would add greatly to the rigidity of the sacral and anterior caudal regions, a condition probably connected with the great development of the hind paddles. Text-fig. 29. Sacral ribs (?) of Peloneustes evansi: A, B, from above; C, from below. (R. 3891, 4 nat. size.) Fy facet for contact with next rib; h., articular head; 7., strengthening ridge. Of the pelvis only the iia are preserved. These expand dorsally into a broad triangular blade much as in Pliosaurus, and, as will be seen from text-fig. 25, B, in Peloneustes phitarchus also. The upper border is greatly roughened and bears a surface probably for union with the outer end of one or more of the expanded ribs noticed above. The upper part of the outer face of the posterior border has a strongly developed rugosity for muscle-attachment. The fore and hind paddles are much the same as in Peloneustes philarchus, except that the distal expansion of the humerus and femur is perhaps a little more marked, and the femur a little larger in proportion to the humerus. PELONEUSTES EVANSI. 75 47837. Plaster cast of the imperfect atlas and axis of the type specimen ; described and figured by Seeley in Quart. Journ. Geol. Soc. vol. xxxiii. (1877) p. 717, figs. 1&2. The original, in the Sedgwick Museum, Cambridge, is from the Oxford Clay of St. Neots. The dimensions (in centimetres) of this specimen are :— Length of the centra of atlas and axis and anterior wedge-bone. 9-7 Combined length of the neural surfaces of the atlas and axis. . S81 ‘Width of posterior'face of axis)». 2 . °. °. . . (approx)! 7-9 Presented by Prof. H. G. Seeley, F.R.S., 1876. R. 1718, R.1718a. Plaster casts of the centra of the fourth and fifteenth cervical vertebrze of the type specimen ; described and the fourth vertebra figured by Seeley in Quart. Journ. Geol. Soc. vol. xxxiii. (1877) pp. 718-9, figs. 3 & 4. These figures reproduced by Lydekker in Catal. Foss. Rept. Brit. Mus. pt. ii. (1889) p. 129, fig. 39. The originals in the Sedgwick Museum, Cambridge, are from the Oxford Clay of St. Neots. The dimensions (in centimetres) of these centra are :— Fourth. Fifteenth. Length in mid-yentral line . . . . . 4 (approx.) 45 Widthiof articular face {4 3. . 75 8-9 Height of articular face . . . .. . 6:5 76 Made in the Museum. R, 2443 (Leeds Coll.). Mandible and hind paddles (except femur) of a large individual. The mandible is larger than any other jaw of Peloneustes in the Collection ; it differs from the others also in having only twelve teeth on each side of the symphysis, which is only slightly expanded, and the length of which is less than a quarter of the total length of the jaw, instead of about a third asin Peloneustes philarchus. On account of these differences from the last-mentioned species, these specimens are here provisionally referred to P. evans?, as suggested by Lydekker. The mandible is figured by Phillips in the ‘ Geology of Oxford’ (1871) p. 318, fig. 122, as Pliosaurus ? grandis. The hind paddle, which presents no important peculiarities, is figured by the same author (tom. cit. p. 317, fig. 121), but the femur shown in the figure is certainly not that of Peloneustes and probably belongs to a Cryptocleidus. Some dimensions (in centimetres) of these specimens are :— Mandible (text-fig. 27, B): extreme length . . . . . . 1150 lenctheok symp liysisiismiei car uilisia) coe calionn ie ais) Shane ZOaee greatest width of symphysis . . . ....: . 6 length of postarticular process . . . . . s . 8:3 Hind paddle : Thibiaxtleneth-olpreaxial border’ @ a ess sks a howl preatestewidthes (casement co aey oy a or omeroe cemem uel =//j Bibulassleno thi Save we Mcrae is vices alee waned eS MOURA ue ee CORSE tO SaLERe GOtse oe gga) | Wide R. 3891 (Leeds Coll.). A large part of the skeleton, including the skull, mandible, atlas and axis, and sixteen other cervical vertebree, thirty pectorals, dorsals and (?) sacrals, sixteen caudals, L2 76 MARINE REPTILES OF THE OXFORD CLAY numerous separate neural arches, cervical, dorsal, sacral, and caudal ribs, fore paddles, ilia, hind paddles. The skull is covered with serpule, which seem to indicate that it was exposed on the sea-bottom for some time before becoming embedded in the sediment. It is greatly crushed, and the same is the case with the mandible, in which the lateral compression has much deepened the rami, thus giving the jaw a very different appearance from the mandible figured by Phillips (see also text-fig. 27, B), in which the compression is in the opposite direction. Four teeth are shown in text-fig. 28. Most of the neural arches and the cervical and caudal ribs are separated from their centra. Some dimensions * (in centimetres) of this specimen are :— Skull: length from occipital condyle to tip of snout . . . 95:0 length from anterior end of pineal foramen to tip of SOUL Peewee Ac sesapeesyicare Wier (om Commies tiers meen releO) width where the maxillo-premaxillary suture crosses the alveolar border . . . - . . . (approx.) 9-5 Mandiblecglengthiyciuss meg imetescMiet eon ister, ee aera te 116-0 > OL symphysis! % =. \sl9 fs (approx) We2p7D s) OF postarticular region <= =.) ee 9-2 depth at coronoid process . . ...-.. .. 168 3 hinder end of symphysis. . . . . . 76 Vette ee eae: Atlast Anterior Posterior Middlet Anterior and axis. cervical. cervical, dorsal. caudal. Length in mid-ventral line . 9°5 4:0 4:6 5d 4:0 Width of posterior face of Centrum! | sus se ee ONT TA 8-4 9°7 8:2 Height of posterior face of Cen My seek ace BOUT) 6-4 6:8 10-4 76 Height to summit of neural SPINCrpbren ast, Mente te ke eel Re a 16:9 Ae 22°8 Lab OR EM log Mae ete Ge opean (okecr Boenom eo anaes oe eh Avid ChyOR Ip periend wa cee cei Mla top een ol 4. a5 shaft. abmarrowest’ . 7. ss = = « L036 - distaliexpansion” . 9. 2) < awa ve) es Pr2eeO inmislength: eeque ie Wee nids we Wor Be eettns eo. o ce Oe amr GO Aa OLUppersborden wee sae: gs ee) eo) el eG: width of shaft at narrowest 5°8 3 articular end 11-2 Femur: length 55°5 width of upper end . 17-5 “ shaft at narrowest ales) > distal expansion . 28:1 R. 2445 (Leeds Coll. 9). Basioccipital, one exoccipital, atlas, axis, and the centra of thirteen other cervicals, all wanting the neural arches and ribs, numerous separate cervical ribs, * The errors due to distortion are very considerable, especially in the skull and mandible. + These measuremenis are only approximate. PELONEUSTES EVANSI. 17 portions of the coracoids. This individual, though large, is still young, judging from the condition of the atlas and axis; it is therefore possible that it may be a young Pliosaur. In the atlas all the elements are separate and the centrum is not fused with that of the axis; this latter is fused with the second subvertebral wedge-bone, though the line of union is for the most part distinct ; there are some indications that there may have been a small third subvertebral wedge-bone between the axis and the third cervical. Some dimensions (in centimetres) of this specimen are :— Basioccipital : transverse diameter of occipital condyle . . . a5 vertical diameter of occipital condyle. . . . 40 width between outer angles of the lateral PIOCESSCSHM twas Vite susie ober ania Ore [Gren he ayes o eG) op ol ole skull opposite the anterior rim of the orbit . 10-5 ie snout at anterior end of nasals . . . . . 4:3 width behind premaxillary expansion . . . . . . 2:9 width of premaxillary expansion . . . . ... . 38 Mandible: total length. Are 9-0 length of symphysialregion . . . . . . . . 52:0 width at hinder end of symphysis . . . . . . 73 se narrowest point behind anterior expansion 22 ts R. 3806. Nearly complete skeleton, including skull, mandible, atlas, axis (text-fig. 34, A, B), and other cervicals (text-fig. 35, A, B), dorsals (text-fig. 36), sacrals and caudals (text-fig. 38, D, H, F), numerous cervical and dorsal ribs, chevrons (text-fig. 40), seapulze and coracoids (text-fig. 41, B), humeri, radii, ulne, ilia, ischia, and pubes (text-figs. 43, 44), femora (text-fig. 45); tibiee and fibule (text-fig. 46) and bones of the hind foot (text-fig. 47) ; numerous scutes (PI. V. figs. 6-10; text-figs. 48, 49) and some portions of ventral ribs. This specimen is probably the most nearly complete skeleton of a Mesozoic Crocodile known. The dimensions (in centimetres) of this specimen are :— Sicullsitotalllens titra mvnsisee quar uns ee iu a ae SO lengthy trontronorbits ine seen yc hele wn nee Ollss3 width between outer angles of quadrates . 2 . . . 20-4 length of temporal fossee (inner side) . . . . . . 142 120 MARINE REPTILES OF THE OXFORD CLAY. Skull: width of temporal fosse. . . . - »- + «=» - « 82 —. trontals between orbitss «ven wt cee + snout opposite the anterior border of the GHOLS i6 Haube 5 Se tey tet le key RAO + snout at anterior qigie of are Sh ale ses dese aa) width behind premaxillary expansion . . . . . . 38 width of premaxillary expansion . . . . . . . . 47 Mandible: totallength . .. . id, Sa satyeIe ow awe gee OF, length of symphysial etiont. Ad 8 ee oe US) width at hinder end of symphysis . . . . . . 87 » harrowest point behind anteriorexpansion 3-2 Atlasand Third Sixth Highth Anterior Middle Posterior Anterior Middle Posterior Vertebrav......... axis. cervical. cervical. cervical. dorsal. dorsal. dorsal. caudal. caudal. caudals. Length of centrum in a mid-ventral line . . 82 53 5:2 53 5°38 53 5°5 4-9 4:9 4:2 2-3 Width of posterior face ohicentrum! 22). 39). 43:2 34 3°6 x 3°8 3°38 4-0 3D ites ky 011824 Height of posterior face olicentrumy. « . = Oso 3°9 3T 4-1 4-0 ss 3°6 36 2:8) S22 ley Height to top of neural SHINC caer, cievacdie "OC 87 8-9 3-9 8-7 8-8 8-1 8-5 73 7:0 4-Oapp. Shoulder-girdle : Scapula (text-fe. 415 B)sslenoth ~~ 29 2 es a. 1082 widthvatvarticularjend. #2 te tla jest outs 2G width of shaft at narrowest point . . . ... I+ a Uppervends yoke Me) Key Moy | eaten oe cy eho Coracoid (text-fig. 41, B): length . . . . ..... . 100 width of articular end . 5°3 = shaft at narrowest 1:3 » lowerend . 5:0 Fore limb : Humerus: length . . . . sou iG Le 4 13-0 width of oneal expansion sy exaserated Dyes CRUSHING) ewes) cubital bie aan Wale 52 width of distal articulation. Zl Ulna: length . 8-9 width of upper are 37 a lower end. 1:8 Radius: length . . 6-7 Pelvis (text-figs. 43, 44): Ilium: length of dorsal border = 9-4 height from acetabular edge to dor aa border . 6-9 length from antero-inferior to postero-superior angle 1 Ischium: length of ayitiplipeial bodens es width from articular end to posterior angle . HH te oOo bo STENEOSAURUS LEEDSI. 121 Ischium: width of neck at narrowest. . . . . +... 28 greatest width of proximalend. . . ... . 53 Pubis: ereatestlenothy ree wayen Vedios hese > os 3:0 width of lowerexpansion =.) .0.. 0%... 3.) (OT emershattati Narcowesbim an (ei cis lomo cee sie! cis, Mbp ONOTSIR CHL Meee. abn. vow Os Gy obo No | aeoul) Hind limb: Femur (text-fig. 45) : length inistraichtiline sy sta) elt 30°2 greatest width of proximalend. . . 5:3 long diameter of the middle of the shaft . i 2°9 short diameter of the middle of the shaft 2:1 Tibia (text-fig. 46): length 15°3 width of proximal end 44 5 middle of shatt 2:2 i distalkend io ryances “au deha One eyee ce eee eL SO Fibula (text-fig. 46): length. . 2. . . . . .. . . 143 First metatarsal (text-fig. 47). . . . . . i. 0 Xa, (BPE Second ,, Speen c laste h usticah tiwied Minsk cakes bcs OFA tr egewlOeo, Third ova, 5; sp Si i cM Pom ON aire kh Mine cote a SDL Fourth — ,, SARA NyE ANS TRALEE OMCGEs MET aE UTES peers 1 rer eet [054 R, 2619. Imperfect skeleton, including parts of the skull, a nearly complete mandible, atlas, axis. and eight other cervical vertebra, thirteen dorsals, two sacrals, and twenty-eight caudals, some dorsal ribs; portions of scapula and coracoid, left humerus and part of right ; ilia, portions of ischia, pubes, right femur and part of left, tibize, some bones of hind foot, numerous broken scutes. Some dimensions (in centimetres) of this specimen are :— Mandibleplengthigs yy emi itsercio e cikeser oh oiiis aire ns OZ0 length of symphysis . Gig fo! 1. ab 43:1 width at hinder end of symphysis . . . . . . 73 width at narrowest point behind the anterior CoS UEUNSON es Note Louie Lip. darian keen MeGo od ig ayo) Be width of anterior expausion . | . . . .. . 3&9 Veet OL aa Me ernie bed Atlas and Middle Last Middle Anterior Middle = Posterior axis, cervical, cervical, dorsal. caudal. caudal. caudal, Length of centrum in mid-ventral Lines toe eye chee come en eey ine Ong 43 44 48 41 39 30 Width of posterior face of CONtrUmMie ay eo She ch Cony ae tee 34 33 31 2°8 2-3 1:3 Height of posterior face of CENntruMs od ke, Feepel este weits te oe 3:3 3:2 3°5 oil 2:3 1:6 Height to top of neural spine . o7 8-0 78 76 78 6°6 50 Hhamerust:lengthis pay htace gre ineb-aicam 1.0 at tease tae sere width of proximal expansion. . . ..... 388 3 distalkends atic; «citats) Gee in hpatey, Cleo PART II. R 122 MARINE REPTILES OF THE OXFORD CLAY. Pelvis: Tlium: lereth of dorsal border . . ~- 7 Pih@pprox.) =) ait height from acetabular edge to loreal border 2 i) length from antero-inferior to postero-superior borders: dpe we Ge cieeidet ee renee (approx.)in Osi Pris: ereatest lengths. 7 22 2/42 hes Meet a, ve 10:0 width of lower expansion . . . . - (approx.) 47 , ashattabmarrowesbe 02, WeNiys cneyetey ite uae tec() Tp WDE HG AS Aa veins ole oly) Hind limb : Femur: length . « «© « 6 « Pee eee 250 long diameter of middle of shaft SW SORE SC Dre) short diameter of middle of shaft . . . . . . 27 Miia’: lengths Gera a «eles Heh bna tt SAMNe ave aN vies Micali gO: width of upper a se Riacunedtite, rex ted! tAbcee seat ae lice aun a 46 OW ORCIO ee cts i ce USI REI cates nee ear Stenessaurus hulkei, n. sp. Type Specimen.—An imperfect skeleton, including the skull (wanting the tip of the snout), an imperfect mandible, atlas, axis, and seven other cervicals, fourteen dorsals, two sacrals, seven caudals, a number of dorsal ribs (mostly imperfect), sacral ribs, ilia ischia, pubes; right femur, tibia, part of fibula, numerous bones of the hind feet ; many scutes (R. 2074, Leeds Coll. 2). This specimen was in part described by Hulke in a paper entitled ‘‘ Contribution to the Skeletal Anatomy of the Mesosuchia, based on Fossil Remains from the Clays near Peterborough ” (Proc. Zool. Soc. 1888, p. 417). He there described the vertebral column, pelvic girdle, femur and tibia, and the dermal armour, giving figures of the axis (pl. xvii. fig. 6), a cervical vertebra (text-fig. 3}, a dorsal (text-fig. 4), a caudal (textefig. 5), and a sacral with the sacral ribs (text-fig. 6). He also figures the left ilium (pl. xix. figs. 3, 4), the ischium (pl. xix. fig. 5), and the pubis (pl. xix. fig. 6). This specimen has been usually regarded as representing the S¢. edwardsi of Des- Jongchamps, but a detailed examination shows that it differs in several respects from that form, and the name Stexeosaurus hulkei is now suggested for it in honour of the late Mr. J. W. Hulke, who contributed so much to our knowledge of the Mesozoic Reptilia. In this species the snout is comparatively short and the nasals are separated from the premaxille by a shorter interval than in St. durobrivensis; their anterior angle is at the level of the thirteenth maxillary tooth ; the anterior angle of the palatines is opposite the nineteenth maxillary tooth. The anterior angle of the frontals is blunt and far behind the anterior angle of the prefrontals, a character which distinguishes STENEOSAURUS HULKEI, 123 the species from St, edwardsi and approximates it to S¢. dwrobrivensis. The symphysis of the mandible is comparatively short, about 40 per cent. of the total length; its posterior end is opposite the twenty-first tooth. ‘The splenials run into the symphysis to the level of the thirteenth tooth; in the posterior half of their symphysial region they are marked off from the dentaries by a deep groove. The teeth are relatively large. The skeleton, on the whole, is closely similar to that of St. durobrivensis; in the vertebra, however, particularly in the dorsal region, the neural spines are rather lower. The scutes also are different, the depressions being shallow, separated by wider smooth areas of bone, and, in many cases, much elongated in a transverse direction. It is a notable circumstance that none of the species of Steneosaurus from Peterborough agree exactly with the species described by Deslongchamps from the north of France ; this is probably due to a slight difference of geological horizon. At the same time some of the differences now taken to be specific may be age-characters, for nothing is known definitely as to whether changes in the proportionate length of the snout or in the character and number of the teeth may take place in the course of growth. R. 2074 (Leeds Coll. 2). Skull, imperfect mandible, atlas, axis, and seven other cervical vertebree, fourteen dorsals, two sacrals, and seven caudals ; a number of dorsal ribs, sacral ribs : ilia, ischia, pubes ; right femur, tibia, part of fibula, numerous bones of the hind feet. and many scutes. ‘Type specimen ; the axis, a middle cervical, a dorsal, a caudal, a sacral with the sacral ribs, left ilium, ischium, and pubes figured by Hulke, loc, cit. Supra. Some dimensions (in centimetres) of this specimen are -— Sills itotall lenothy is Ws) weeks © su Ruste we (anprox. in GOc0 length in front of the orbit. . . . . . (approx.) 35:0 width at outer angles of quadrates . . . . . . . 22:0 length of temporal fosse (inner side) . . . . . . 15:3 width of temporal fosse (in middle). . . . . . . 8&0 33 frontal/sibetweenticrbitsyeumei aie tee ee ee 46 AA snout at anteriorend of nasals . . . . . d-4 width behind the premaxillary expansion . . . . . ) 47 » of premaxillary expansion . 55 The measures of width are probably somewhat too great, owing to the flattening that the skeleton has undergone. Mandible approximatetlemobhy um sal cy cuit vie mie so bdsyaae tee KO length of symphysial region . . . . . . » . 28:9 width at hinder end of symphysis . . (approx.) 8:0 narrowest point behind the anterior ex- 29 PAVSLOMIMe aA hc eee anh ten Mle enw reMn OS 124 MARINE REPTILES OF THE OXFORD CLAY. First * Middle VOTRE cre onsttoonee ( saehtsiay: BENE sash Ley Waez sacral. caudal. Length of centrum in mid- ventralidineji. ste 4) ue 20 41 AL 37 45 3°9 40 Width of posterior face of CHM “Borgia ol a 8 2°6 2°8 36 36 34 31 2:3 Height of posterior face of Conti aerompcn me) aaa sete 2-9 32 od od 3:3 27 3:3 Height to top of neural spine ou 6:9 9-0 83 6:8 ae 82 The width between the outer ends of the anterior pair of sacral ribs is about 13-5 em. Pelvis: Ilium *: length of dorsal border (with spine) . . . . . 7:8 » from dorsal border to acetabular edge . . . 5:8 » from antero-inferior to postero-superior angle 8-8 Ischium*: length of symphysial border . . . . .. . 10-2 width from articular surface to posterior angle. . 10:1 a) WOLneckabmarrowest: «es la ea fie = oo greatest width of proximalend. . . . .. . 4:9 iBubiswcmlenothiers ster ee mene eles Geel meee em rey width of lower expansion . . . . « (approx.) 40 rs Nechyat MarrowGsue messi wee -) oe emo 3 UP PEriendy a weapars ewe cess pyse ameter. ae eal: Hind limb: Femur: length in straight line. . . . «2 « « . 248 greatest width of proximalend . . . . . . . 42 long diameter of the middle of the shaft . 25 short diameter of the middle of the shaft . he widthvofecondylesie a ga Jeo clus yer gmeeneed Ge 2:8 Tibia: length . 11:3 width of upperend . » 2:9 eS shaft at narrowest . ei lower end . « 129 9 Steneosaurus durobrivensis, Andrews. | Plate VI.; text-figs./31, 32, 33, 34,:C, D, 35, C, D, 37,38, A,B, C)39) 4 ar ae 1909. Steneosaurus durobrivensis, Andrews, Ann. Mag. Nat. Hist. [8] vol. ili. p. 364, pl. viii. fig. 2. 1909. ? Steneosaurus larteti, var. kokeni, Auer, Paleontographica, vol. lv. p. 224. Type Specimen.—A nearly complete skeleton, including the skull (figured in Ann. Mag. Nat. Hist. [8] vol. iii. (1909) pl. viii. fig. 2; also Pl. VI. figs. 1, 2), mandible, tecth, atlas, axis (text-fig. 34, C, D), and eight other cervical vertebrx (text-fig. 35, C, D), * Figured by Hulke (Joc. cit. supra). STENEOSAURUS DUROBRIVENSIS. 125 twelve dorsals (text-fig. 37), two lumbars, two sacrals (PI. VI. fig. 6), and thirty-eight caudals (text-figs. 38, A, B, C), cervical ribs (text-fig. 39), dorsal ribs, chevrons, scapule, and coracoids (text-fig. 41, A), humeri, radii, and ulne (text-fig. 42), pubes, ischia, ilia, femora, tibie, fibule, and many bones of hind foot; numerous scutes (Pl. VI. figs. 4, 5) (R. 3701). In March, 1909, the present writer described this species, basing the description upon the skull referred to above. _ Almost simultaneously, Auer published (/oc. cit. supra) an account of a closely similar specimen in the collection of Titbingen University, and referred it to a new variety of Steneosaurus larteti of Deslongchamps. As it seems certain that this species is distinct from S¢. /arteti, and as, moreover, the greater part of the available specimens are in the British Museum, the name Stenco- saurus durobrivensis is here employed. In this species the rostrum (Pl. VI. figs. 1, 2) is of moderate length only, the preorbital region being about 61 per cent. of the whole, while in S¢é. deedsi it is about 73 per cent. The temporal fosse are very large and about twice as long as wide; the orbits are proportionately smaller than in St. leedsi. The frontals terminate anteriorly in a very obtuse augle a little in front of the level of the anterior rim of the orbits. In the type specimen the bone is coated with a pyritous incrustation concealing the sculpture, which, judging from another specimen (R. 2865), consists of irregular pits on the frontals and prefrontals, and numerous more or less longitudinal grooves of varying length on the surface of the rostrum. In the upper jaw there are about thirty-four teeth on each side, of which thirty are borne on the maxilla; the anterior point of the nasals is about opposite the sixteenth maxillary tooth, while the anterior angle of the palatines is about opposite the twenty-second, so far as can be made out. A number of detached teeth (Pl. V. fig. 5; Pl. VI. fig. 3) said to be associated with the type skeleton are very sharply pointed, having the crowns covered with finely ridged enamel on their lower part, while the summit is smooth, somewhat compressed, and with two well-marked carinz on opposite sides; there are also some teeth with blunter points having the enamel-sculpture extending to the tips and very slightly marked carine. ‘Teeth of a similar character to these last are seen just showing their tips in the lower jaw of the type. It is doubtful whether both these forms of teeth belong to this species, differing in different parts of the jaw. In the mandible there are about thirty-one teeth on each side; the posterior end of the symphysis is opposite the twenty-fifth, the anterior angle of the splenials opposite the seventeenth. The symphysial region of the mandible occupies about 44 per cent. of its total length. As has been noted above, in correlation with the shortness of the head, the vertebrae and the bones of the limb-girdles are relatively shorter than in the long and slender skulled Sé. leedst. ‘The scutes seem to have larger and shallower pits than in S¢. /eeds?, and these do not show the tendency to elongation and arrangement in lines running 126 MARINE REPTILES OF THE OXFORD CLAY. out from the central ridge so marked in St. hulkei; but the variation of the form of the scutes in different parts of the series and in different individuals makes comparison in this respect unsatisfactory. This species is distinguished from S¢. cdwardsi* in several respects: thus in that form (1) the frontals terminate in front in an acute angle at the level of the anterior points of the prefrontals ; (2) the premaxille extend further back and are not quite so widely separated from the nasals; (3) the form of the maxillo-premaxillary suture on the palate is different, the two not interlocking in the manner seen in St. durobrivensis. In St. heberti 7 there are 39-40 teeth in the upper jaw instead of 83-34. The hinder end of the symphysis appears to be opposite the twenty-seventh or, in one specimen, the thirtieth tooth. In St. intermedius there are thirty-eight or thirty-nine teeth in the upper jaw and thirty-seven or thirty-eight in the lower, the hinder border of the symphysis being opposite the thirty-second. In this species also the symphysis forms about 52 per cent. of the total length of the mandible, while in S¢. durobrivensis the proportion is about 44 per cent. In St. Jarteti the anterior border of the frontals and the maxillo-premaxillary suture differ in form from those of the present species; in St. larteti also the anterior angle of the nasals seems from Deslongchamps’ figure to come about opposite the alveolus of the eighteenth maxillary tooth. R. 3701. Nearly complete skull and skeleton. The parts preserved are skull (Pl. VI. figs. 1, 2), mandible, teeth; atlas, axis (text-figs. 34, C, D), and eight other cervical vertebree (text-figs. 35, C, D), twelve dorsals (text-fig. 37), two lumbars, two sacrals (Pl. VI. figs. 6, 6a), thirty-eight caudals (text-fig. 38, A, B, ©); cervical and dorsal ribs (text- fig. 39); chevrons; scapule, coracoids (text-fig. 41, A); humeri, radii, and ulne (text-fig. 42), pubes, ischia, ilia ; femora, tibiae, fibula, and many bones of the hind feet; scutes (Pl. VI. figs. 4, 5). Type specimen described loc. cit. supra. The dimensions (in centimetres) of this skeleton are :— Skull (Pl. VI. figs. 1, 2): aRotalglen@the £7 lpia marsiey) Wor opi se peti matte tee eaiean es Tet 50 Length in front of orbit een ie 450 Width between outer angles of quadrate. . . . . . . 240 Length of temporal fosse (inner side). . . . . . . . 18-0 ‘Width of temporal fosse (inner side). . . . . .. . 88 es trontalsibetweenvorbits!- 0s) fis eth ent = middlecofisnotity oils Sales aie see Bos eee Width behind premaxillary expansion. . . . . . . . 48 Width of premaxillary.expansion . *. . 5 = = 2° uu O77 * Deslongehamps, Bull. Soc. Linn. Normandie, sér. 2, vol. i. (1868) p. 155, as Teleosaurus; see also Deslongchamps, Notes Paléontologiques, p. 239, 7 Morel de Glasville, Bull. Soc. Géol. France, sér. 3, vol. iv. (1876) p- 842; also vol. vii, (1880) p. 318. STENEOSAURUS DUROBRIVENSIS. 12 Mandible: Total lengthy Toph «trees 85°0 Length of symphysial region . 375 Width at hinder end of symphysis . : 10-2 5 narrowest point behind anterior expausion . 3°8 Atlasand Third Middle Postericr Anterior Middle Vertebrie..........s0+. axis. cervical, cervical. cervical, dorsal. dorsal, Lumbar. Length of centrum in mid- veutralilinets.) 2:aesp ia 86 50 44 4-7 51 53 4-9 Width of posterior face . . 37 33 AD 4-4 4(app.) 43 45 Heigit of posterior face. . 4:0 40 4:3 4:5 45 4-7 Bey) ,, totop of neural spine 79 9-0 S22 11:3 10:9 9-4 10-1 Width between the outer ends of the transverse processes te 35 Oo go 13°3 15:2 15:2 Sacrals, Anterior Middle Posterior First. Second. eaudals. eaudals. caudals. Length of centrum in mid- ote gece s CN aie wentralelinew camenisea ane e 48 47 Ad 45 45 4:2 4-0 36 Width of posterior face. . 3°8 4:7 38 3°6 3-4 BH} 2-0 ie Heivht of posterior face. . 4(app.) 4:3 4:5 45 3:9 3°6 2:5 2-0 » totopofneuralspine 106 11:1 12:0 12:2 IOs 10:8) 6-1 5'0 (app.) Width between the outer ends of sacral and caudal ribs . 16 15° 13-4 11-7 (app.) 9(app.) .. he Re The anterior face of the first sacral is 4°5 em. wide and 3°9 em. high, Shoulder-girdle (text-fig. 41, A): Scapula: greatest length 9-1 widthyatiarticularendis c, .juese ey mess (ete en 250 ss middlexoiesh alias: wir usc ce a elt ye Cpe aTex: 3 Upperlend cw aura iesee a Ne rie see see em Coracoid: greatest length . 10°9 width! otvarticulariendis) 2 elyists hao jae ier er OLS ss SA ELA ee sare tlic enet Hea tere be ee aE. ‘5 lowwertend ya ee ety af at eeu sp POM) oS Fore limb (text-fig. 42): Tetanus eretas eae) 6 pb 6 Moe age 12:2 width of upper end at deltoid crest . . . . . 4:8 * shaft at narrowest point . . . . . 2 yi lower end 221 Radius: length al Ulna: length . 8-9 Pelvis: 9-5 Jlium: length of dorsal border acts height from acetabular edge to dorsal border . . . 71 length from antero-inferior to postero-superior angle 10°8 “Sy 128 MARINE REPTILES OF THE OXFORD CLAY. Ischium: length of symphysial border. . . . (approx.) 14:5 width from articular end to posterior angle. . . 13:0 ayy OL Meck: ab MATTOWESHat: Mayle tater Wee RE MOAS greatest width of proximaleud. . . . . . . ST Rubisevoreatestulength tus deer dons ouu/-Oeesihve MMe hem usa eae hs etnleaO Midthrotdlowerexpansionsy val fe vies were) ay eer to BOSS) 5 shaft.at narrowest point. << . .-. . . Il 5 Wyyae Gat GG ae woree es GH aa ote EES Hind limb: Memur: length in.straightiine™. 2 5 2°. 3 ©. .7.° Siz greatest width of proximalend . . . . . .:. 50 long diameter of the middle of the shaft. . . . 3-0 short diameter of the middle of the shaft. . . . 2:3 etibiaielenouhy.. bec setae meee ete MAb t= LaPeer EL) widthyorproximAlvend! Ssuua mks | ees een eens S - middlesoishattves yeas) aeheeey eey espe aes as distalifendicnas at ue eee a RRC ioe OD hibula\-slengthie we: Geese Gem corre ck oki nee eth Imeteeee loz hirstpmetavarsal :glenp heuer i eeu ent een mauens us ete o oS) R. 2865 (Leeds Coll. 28). Imperfect skeleton. The parts preserved are:—Skull; atlas, axis, and seven other cervical vertebrae, fourteen dorsals, two sacrals, and twenty-three caudals ; cervical and dorsal ribs; chevrons; ischia, one pubis, femora, tibise, and fibula, numerous bones of foot and many scutes. This skeleton is that of a larger and presumably older individual than the type specimen. The skull differs in some details : e.g., the rostrum appears to be relatively a little longer. It approximates in form to the specimen figured by Auer as St. larteti, var. kokeni. The diagrammatic text-figures nos. 31-33 are founded mainly on the skull of this specimen. Some dimensions (in centimetres) of this specimen are :— Skull: Total length from tip of snout to occipital condyle. . . . 93:5 thensthunstrontioLorbiti ye we. a. cls euliep ee es eee OGIO Width between the outer angles. Beit coe as OL thequadrates| G2. =] 2 a. i(approx.) soles Length of temporal fosse (inner side). . . . . . . . 225 Width of temporal fosse (anteriorend) . . . . . . . 98 3 frontalsihetween.orbits (; = =. =. «©. « = « sec = 35 snout at anteriorend of nasals. . . . . .. 82 ; snout behind the premaxillary expansion. . . . 5°5 * = premaxillary expansion (crushed) . ri) * Somewhat exaggerated by crushing. STENEOSAURUS DUROBRIVENSIS, 129 Veortebree® sssssontss Fea aetna ean VS contdiyan aaa jeakaal ° feudal Length in mid-ventral line . 10:5 7:0 54 5:5 55 51 5d Width of posterior face of Centrumey eae aca cates 44 53 58 54 57 5:0 40 Height of posterior face of Sian BO eae a 5:2 55 5:7 6-2 5:5 5:8 4:6 Height to top of neural spine a 15°3 14:5 13°3 12:3 14:3 13-7 Width between outer ends of transverse processes, and sacral or caudal ribs. . a3 Me a 19°3 21:6 16°6 Ischium: length of symphysial border . . . . (approx.) 16:0 width of neck at narrowest point. . . . . . . 52 a5 MPPErser dimen h ety Mkt congheey coli caster vnc! ars GO Rubissvoreatestlengthie calcite atcie eset yun Se nlG:6 Wwidbhiondistaleexpansiomancss. ys) eo els fe ee 9 % Meckyab Marcrowestus + ae hous caeees ype cols) Ua EO) i" TIP PETAOT Gy Pits ie elas mere Muy col cae la eih ne ee) Wemurs lenptbyinistraishbyline eh tet aieiges oles okra = 4SO:0 greatest width of proximalend. . . . ... . 74 nbinmlen othe cen tr ec enqumtalrss o-y gtuine eaten eG R. 2075 (Leeds Coll. 3). Imperfect skeleton of an individual rather larger than the type specimen. The parts preserved are portions of skull and mandible, atlas and axis, five other cervicals, about seventeen dorsals, one sacral and twenty-three caudals, some scutes. The two following specimens, in which the skull is badly preserved, are referred provisionally to the present species :— BR. 2076 (Leeds Coll. 4). An imperfect skeleton of an individual rather larger than the type specimen. The parts preserved are portions of the skull and mandible, the centra of the atlas aud four other cervical vertebrae, six dorsals, two sacrals, and eight caudals (the neural arches in the cervical and dorsal regions are nearly all separated from the centra) ; cervicul and dorsal ribs, chevrons, ilia, femora, a tibia and fibula, bones of hind foot, numerous scutes. The dimensions (in centimetres) of some of the bones are :— Vertebral centra ss... Atlas, ada at Anterior Cae —~ Length in mid-ventral line . ae 6-4 a3 5:9 55 Width of posterior face . . 4:3 53 47 41 37 Height of posterior face. . 47 ot 4-2 47 41 * The vertebre are so much crushed that only approximate measurements can be made. PARE TI. S 130 MARINE REPTILES OF THE OXFORD CLAY. Hlimm::Wlengthvolidorsaliborders vs. "ie Rare) nee LORS height from acetabular edge to dorsal border. . . . 7:9 length from antero-inferior to postero-superior border. 13-0 Memurylencsthanistraight lime i996 «6 2 We seu yes oe nooo greatest width at proximalend. . . . - .. . 63 long diameter of middle of shaft . . . . . . . 41 short diameter of middle of shaft . . . . . .. 28 pbibiawileng thes toatecumem feist che yeu) chaislae met nics amet nceeece tonne widthtotproximalvend, 5 oe elie tie Ge ew tase ney ghee) “5 distaliend. Sx esen vic ch oo Roe acs Bilbular steno thaws sates eeree cen yesey Te. Us icons asm gies ween) R. 2073 (Leeds Coll. 1). Imperfect skull and mandible, seven cervical vertebree and fifteen dorsals, ilia, ischia, femora, tibiee (one imperfect), fibula, and some bones of the hind foot. The dimensions (in centimetres) of some of the bones are :— Tlium: length of dorsal border . . - . . . . (approx.) 10°5 height from acetabular to dorsal border . . . . . 79 length from antero-inferior to postero-superior angle . 13:2 Femur: length in straight line. ©. . 2. 1... » . .. 343 ereatest width of head’. 9.9.0.9. 59. 2) 2 woe G20 Tibiaimlencthival yar ay ee ecient meee ts oe aterm, SENG. 0 Steneosaurus obtusidens, Andrews. [Plate VII.; text-fig. 50.] 1909. Steneosaurus obtusidens, Andrews, Ann. Mag. Nat. Hist. [8] vol. iii. p. 306, pl. ix. fig. 2. Type Specimen.—A considerable portion of a skeleton of a very large individual. The parts preserved are skull and mandible (figured and described, loc. cit. supra, pl. ix. fig. 2, also Pl. VII. fig. 1), numerous teeth (PI. VII. figs. 2-4), atlas, axis, and five other cervical vertebre, eleven dorsals, two sacrals (text-fig. 50), nineteen caudals (Pl. VII. fig. 5), numerous cervical and dorsal ribs, chevrons, one scapula, parts of the humerus, ulna, ilia, ischia (Pl. VII. fig. 7), part of one pubis, right femur and part of left, tibia, fibula, astragalus, caleaneum and other bones of the hind foot, and numerous scutes (Pl. VII. fig. 6), mostly broken. (R. 3168.) This species is distinguished mainly by the form of the teeth (PI. VII. figs. 2-4), which are blunt and rounded at the tips; the enamel bears a sculpture of fine ridges, parallel to one another in the lower part of the crown, but more irregularly arranged on the summit; on both the anterior and the posterior faces there is one more strongly marked ridge running from base to summit of the crown. It should be noted that some of the replacing teeth in the type skull of St. durobrivensis are of somewhat similar form, and although other differences between that species and the present one STENEOSAURUS OBTUSIDENS. 131 exist, the possibility that the specimens upon which the latter is based may be very old and large individuals of S¢. durobrivensis cannot be entirely ignored. The type specimen is a very large and presumably old individual, the skull of which, in its general proportions, is similar to that of Steneosaurus durobrivensis, and if it were not for the peculiarity of the teeth, might almost have been referred to that species ; but since, so far as I am aware, there is no evidence of considerable change in tooth-form during the life of these animals it is better to separate the present species, especially as this distinction is supported by some other characters. In the skull (Pl. VII. fig. 1) the rostrum is very thick and massive, perhaps more so than in the other species. The orbits are large and oval; the frontal terminates anteriorly in an obtuse angle about on a level with the anterior border of the orbits: its surface is ornamented by a number of obscure ridges radiating from the centre. There is a small slit-like antorbital foramen about 7 cm. in front of the orbit. The rostrum has its upper surface strongly convex from side to side, and at its anterior end seems to have curved a little upwards; in front of the orbits it narrows very gradually to a point about 16 cm. behind its anterior end, where it is only 7°35 cm. wide; in front of this the premaxillary region is expanded. ‘The total number of teeth in the upper jaw cannot be made out. In this skull the length of the preorbital region is about 51 per cent. of the whole; in St. leedsi it is about 75 per cent. and in S¢. durobrivensis about the same as in the present species, in which, however, the rostrum seems to narrow rather more gradually. The mandible is very massively constructed. ‘The symphysial region, which extends back to about the level of the twenty-fourth tooth, occupies about 42 per cent. of the total length, is flattened ventrally, and has a considerable anterior expansion, greatest at the fourth tooth. In St. leedsi the symphysis occupies about 58 per cent. of the total length of the mandible, in S¢. hulket about 40 per cent., and in St. durobrivensis 44 per cent., these two species in this respect being very similar to the present one, The lower teeth are about 28 in number on each side. The first two are small, then follow two large teeth closely crowded together, behind these again there is a small tooth followed by an increase in size till near the hinder end of the series. One peculiarity in the dentition of the type specimen, is that about half the teeth in the lower jaw bite into deep pit-like sockets in the maxilla, the walls of these sockets forming slight prominences along the outer alveolar border of the upper jaw. It is, however, uncertain whether this remarkable character is normal, and it seems that the condition may have been produced by great pressure which forced the points of the lower teeth into the maxille while the bone was in the semi-plastic state which many of the specimens in the Oxford Clay seem to have passed through. The structure and proportions of the cervical, dorsal, and caudal vertebrae seem to be very similar to those of the corresponding vertebre in S¢. durobrivensis, but in the s2 132 MARINE REPTILES OF THE OXFORD CLAY. sacral region of the type specimen (the only one in which this part of the skeleton is preserved) a remarkable condition is found, there being apparently three sacrals (text- fig. 50). The explanation of this appearance seems to be, that the ribs of the first caudal have greatly enlarged and resemble sacral ribs, taking part in the support of the ilium. The two true sacrals are similar to those of St. durobrivensis, except that the outer end of the ribs of the second, instead of having a facet on its anterior face only, for union with the end of the rib of the first sacral, has also a facet on its hinder face for union with the massive rib of the first caudal; the postero-dorsal flange of the second sacral ribs also seems to have been lost, though a similar ridge may have been present on the first caudal rib. This is a massive structure like the ribs of the true sacrals; it is trihedral in section and much expanded at its outer end, where it bears two irregularly roughened surfaces, one, Text-fig. 50. Sacral and first caudal vertebra (restored) of Stencosaurus obtusidens, from above (R. 3168, 3 nat. size). er, caudal rib; il.s., iliac surface of sacral ribs ; il.s.?, doubtful iliac surface of caudal rib ; s.r.1, s.7.2, first and second sacral ribs. the largest, apparently for union with the posterior part of the ilium, the other looking forwards for union with the corresponding facet on the posterior side of the outer end of the second true sacral: as above noted, the postero-superior angle may have been produced into a flange such as is seen on the posterior side of the second sacral rib in S¢. durobrivensis (Pl. VI. fig. 6) and in Mycterosuchus (text-fig. 52). The ilium in this specimen has a much roughened surface behind that for the second sacral rib, probably for union with the outer end of the enlarged caudal rib, but in another still larger specimen referred to this species there is no trace of this surface, although those for the two true sacrals are well defined. From this it appears likely that the condition in the type specimen may be an individual peculiarity. STENEOSAURUS OBTUSIDENS. 133 In the rest of the skeleton the similarity to that of S¢. durobrivensis is so great that special description is unnecessary. In the case of the coracoid the ventral end is more expanded than in that species, and the bone is very like that of Mycterosuchus (text-fig. 54), but this expansion is probably merely the result of more extensive ossification consequent upon advanced age. The dorsal scutes (Pl. VII. fig. 6) differ considerably from those of the other species. The pits are mostly shallow and elongated; they are arranged in lines radiating in most cases from the middle of the keel, and sometimes almost running together to form shallow grooves. R. 3168. Skull (PI. VII. fig. 1) and mandible, teeth (Pl. VII. figs. 2-4), atlas, axis, and five other cervical vertebree ; eleven dorsals, two (? three) sacrals (text-fig. 50), nineteen caudals (Pl. VII. fig. 5), numerous cervical and dorsal ribs, chevrons, one scapula, an imperfect humerus, an ulna, ilia, ischia (Pl. VII. fig. 7), one pubis, femora (one imperfect), incomplete tibiee and fibule, bones of the hind foot, portions of ventral ribs, and numerous scutes (Pl. VII. fig. 6). Type specimen, the skull and mandible of which are described and figured in Ann. Mag. Nat. Hist. [8] vol. iii. (1909) p. 306, pl. ix. fig. 2. The skull, though much broken, is less fattened than usual; the vertebree are nearly all crushed and distorted. The dimensions (in centimetres) of this specimen are :— Skull (PI. VIE. fig. 1) : ” Rotalilengths sew cuts se eiceitt ieee aate coe ae ces ete MIELIG:() Wen otheint front: olorbib wa eugene tennessee t-te e170) Width between outer angles of quadrates . . . 2. . 2) 87°5 Length of temporal fossa (inner side). - . .- . . . . 33:0 Widthyot temporaltossa! as ce pa) eee) ek en een) LO) i. frontals’ between Orbits) yikes le, Sse reat eee 85 ep snout opposite anterior end of nasals. (approx.) 9-0 oF snout behind premaxillary expansion . . . . a ~ premaxillary ©xpanslomy. Je nai ase a ial te 9-5 Mandible : Totallencthycey se) fe AV ya ee cee oe mere ep ie, oe O) engthiof symphysialirecion. | vs ssa es 8 O80 Width at hinder end of symphysis . . . . . 2... 14:0 narrowest point behind anterior expansion 6-2 Varteh Atlasand Middle Dorsale Sacrals. First Anterior Posterior Se OTe ae tia: axis. cervical, % Ist. 2nd. caudal. caudals. caudal, . . fame S fame trial aS Length of centrum in mid- veutralilines 0s vee LO) 7-2 6:5) 7:0 5:3 59 (S70 RS 5-4 Width of posterior face. 5:8 TA eG wel 183 1183) 50 49 4-2 Height of posterior face 72 72 82 58 6:0 70 55 5:8 38 Height to top of neural spine. Iris ae ve LO APPaee Lod aS 10-0 134 MARINE REPTILES OF THE OXFORD CLAY. The width between the outer ends of the ribs in the first sacral is 27:4 em., in the second 24°7 em., and in the first caudal 25:0 cm. Scapula: length. . . |. Cree Aemom Hider tants Al OR7 width of articuiar hd Mees /arue Op moe orl ~ middlevorishatbieses 6 ss) a) yoo) tel ees moc, ES UIPPCIeeN dae emecy Vener) ca asln sty Mec med eae eno) Tlium: length of dorsal border . . . . . Roaiceere urd koytl height from acetabular border to agree san he ee LIES length from antero-inferior to postero-superior angle . 18-2 Ischium: length of symphysial border. . . . . . «. . . 202 width from articular end to posterior angle . . . 20-1 width of neck at narrowest. . . . . . . . . 55 greatest width of proximalend. . . . .... 88 Femur: length in straight lime . . . ...... =. . 456 Widthxo: upperend.e false se ee ee eee eLene aad long diameter of middle of shaitt. . . . . 2. . 2) 43 short diameter of middle of shaft . . . . . . . 3d greatest width at condyles. . . . ..... =. «56 Dubiassapprommeatedenpin Ws) caer cea ea ln ee a ey ea InS widthiotimppermend Yaka ms 9) lel ae ashe, Povey cb ee COLO) R. 3169. Portions of the skeleton of a large individual probably belonging to this species. The parts preserved are tracheal rings, left coracoid, right scapula, radius, ulna, right ilium, pubis (Pl. VII. fig. 8), femora, tibize, bones of hind foot, scutes. In this specimen a few of the ossified tracheal rings are in a remarkably good state of preservation. The dimensions (in centimetres) of this specimen are :— Tracheal ring: long diameter 32 short diameter DET preatest thickness. . . . . ~... . O8 Coracoid: greatest length. . . . . . =. . +... . 162 width of shat aimnarromest = js use) wel eee! ee ween: OSL length of the scapular border . . . . . . . . 40 approximate width of lowerend. . . . . . . 85 peapulasvereatestylenoth: . 2 3 1. sf o 5 & ee oy 1 ee tosO MAdthiatmpperyentn .. Gael tout tery, Vou ea ue eNIO:O width.otsshathiatinarrowesth « i. Ma 20 (5) ease 6 oS (Ulnar eng thiae ene siaplesta dor bcs sleet bey een ee ener lel width of upper expansion . . . . . . (approx.) 55 Ilium: length of dorsal border. . . . Te Aree uneasy height from acetabular to dorsal bande aeiey th aie He length from antero-inferior to postero-supericr berder. 16-1 emur: length inistraipht line we iis. ue) vem) eeanee emer width of headj. o smee +: 2 ietils) Ee eae Ore long diameter of middle of so PY ag CS MYCTEROSUCHUS. 13% (Sh) Or TYemur: short diameter of middle of shaft . . . . . . 4-0 widtho£ cond ylesi, a0.) sph sh sl Jain CAPPLOX.)) O73 Tibiasy lengthiee 7%.) 19°7 width of upper end 57 45 lower end 4:8 Front metatarsal : length . 12:0 R. 3898. Left ilium, ischium, and femur of a very large individual, probably of this species. The dimensions (in centimetres) of these bones are :— Ilium: leneth of dorsal border . a sec 19-0 height from acetabular to dorsal border . 12°5 length from antero-inferior to postero-superior angle . 22:9 Ischium: length of symphysial border . . . . (approx.) 25:5 width from acetabular surface to posterior angle . 23°5 width of neck “Wes 6°8 greatest width of the proximalend . . . . . . 12:0 Femur: length inastraight line ©... . 4. . .-. = .-53:0 greatest width of proximalend. . . ..... 965 long diameter of middle of shaft . .. . ... 59 short diameter of middle of shaft . . . (approx.) 4:0 This is the largest Steneosaur recorded from this horizon. Genus MYCTEROSUCHUS, nov. Large Mesosuchian Crocodiles in which the snout is greatly elongated and sharply marked off from the cranial region of the skull, which narrows very rapidly immediately in front of the orbits. The alveolar borders are straight and the teeth slender, though not excessively so; they were probably not directed outwards as in Teleo- saurus. The temporal fossz are relatively smaller and especially shorter than in the typical Steneosaurs. The upper surface of the skull exhibits a strong rugose sculpture, especially on the frontals. In the mandible the symphysis is long, but is less than two-thirds of the total length. The fore limb is less reduced than in Stencosaurus, and in the humerus both distal condyles are well developed. ‘The tail is very long and the caudal centra are strongly compressed laterally : their neural spines are broad and high, and in the middle and posterior regions deeply notched both anteriorly and posteriorly. The dorsal armour was heavy, the scutes being much more massive than in Stencosaurus. This genus has been established for the reception of the only known species, Mycterosuchus nasutus, from the Oxford Clay of Peterborough, a form which differs considerably from any of the species of Steneosaurvs, and in the sudden narrowing of the snout has some similarity with Teleosaurus, frora which, however, it is distinguished by (1). the straight alveolar borders with downwardly directed teeth, (2) the relatively larger size of the superior temporal fossee, and (8) the relatively larger head. 136 MARINE REPTILES OF THE OXFORD CLAY. Mycterosuchus nasutus, Andrews. [Plate VIII.; text-figs. 51-54. ] 1909. Stencosaurus nasutus, Andrews, Ann. Mag. Nat. Hist. [8] vol. iii. p. 302, pl. ix. fig. 1. Type Specimen.—A considerable part of a skeleton, including the skull (Pl. VIII. fig. 1), mandible (Pl. VIII. fig. 2), atlas, axis, and nine other cervical vertebra, two or three crushed dorsals, forty-two caudals (Pl. VIII. figs. 4-9), left coracoid and scapula (text-fig. 54,C), left humerus (text-fig. 54 A, B) and ulna, left and part of right femur, right tibia and fibula, astragalus, calcaneum, metatarsals, and other foot- bones, also numerous scutes (Pl. VIII. figs. 4,10). The skull was figured in Ann. Mag. Nat. Hist. [8] vol. iii. (1909) pl. ix. fig. 1. (R. 2617.) The skull (Pl. VIII. fig. 1) in the type specimen has been much compressed verti- cally and the snout is somewhat curved round to the right. In some respects it approaches the Teleosaurus-type, particularly in the rapid preorbital narrowing of the skull. The orbits seem to have looked more directly forwards than in Steneosaurus. The frontals, prefrontals, outer face of the squamosals, and the parietals, all have their surface sculptured by strongly-marked pits and rugosities, which occur even on the summit of the high sagittal crest ; the surface of the snout is also sculptured, but here the rugosities are less marked and run, in the main, in a longitudinal direction. ‘The premaxillary expansion (pma.) was considerable and probably bore four teeth on each side, of which the two hindmost are enlarged and set closely together; each of the maxillze bears about thirty-eight teeth, which are nearly equal in size throughout the series. The crowns of the teeth (Pl. VIII. fig. 3) are slender and sharply pointed ; the enamel is marked by a series of very fine longitudinal ridges, one of which, on the outer side, is rather more strongly marked and continuous than the others. The mandible (Pl. VIII. fig. 2) is slender and has been much compressed vertically. The upper surface of the symphysial region seems to have been somewhat convex from side to side, while the ventral surface is marked by an ornamentation of irregular longitudinal ridges; there is a slight expansion at the anterior end, and the third and fourth teeth are enlarged. The splenial (sp/.) extends into the symphysis as far as the level of the twenty-second tooth, and the hinder end of the symphysis is opposite the thirty-seventh tooth. There are about forty-two teeth on each side. Speaking generally, the vertebrae are similar to those of Steneosaurus, but there are some differences, especially in the caudal region (Pl. VIII. figs. 4-9). The atlas and avis are not so long as might be expected from the great elongation of the skull. The neural spine of the axis, instead of extending back nearly to the level of the hinder ends of the posterior zygapophyses and rising gradually to its hinder end as in Steneosaurus, is a low rounded crest, the highest point being near the middle of its length, behind which it slopes downwards and disappears between the MYCTEROSUCHUS NASUTUS. 137 bases of the posterior zygapophyses. The remainder of the cervicals, though perhaps slightly longer in proportion to their other dimensions than those of St. durobrivensis, are otherwise similar to them. In the type specimen the dorsal vertebre are lost or very badly preserved, but in another specimen (R, 3892) they are in good preservation. They are here found to be closely similar to those of S¢. durobrivensis, except that the neural spines are considerably thickened at their summit, terminating in a smooth, flat or slightly convex surface, while beneath this on their flat sides there are well- marked vertical ridges: this character is especially marked in the sacral region (as shown in text-figs. 51-53), and seems to be correlated with the support of a heavier armour of scutes than is found in Steneosaurus. Text-fig. 51, A, shows that the inner ends of the sacral ribs form a quite considerable portion of the concave anterior surface Text-fig. 51. SS EZ First sacral vertebra of Mycterosuchus nasutus: A, from front; B, outer end of sacral rib. (R. 3892, 3 nat. size.) a.z., anterior zygapophysis ; 2J.s., surface for ilium; n.sp., neural spine; s., suture between sacral rib and the vertebra; s.r., sacral rib. for union with the centrum of the lumbar; the extension outwards of the base of the neural arch along the dorsal edge of the sacral rib is also seen. In the figure of the second sacral (text-fig. 52) the thickening of the upper end of the neural spine is again shown, as also is the peculiar form of the outer end of the sacral rib, the postero- superior angle of which is produced backwards and upwards into a well-developed flange (/l., text-fig. 52, B), the outer edge of which must have fitted into a corresponding depression on the inner face of the ilium. ‘The caudal vertebre (Pl. VIII. figs. 4-9) differ to a considerable degree from those of Steneosaurus. In the anterior caudals the PART II. T 158 MARINE REPTILES OF THE OXFORD CLAY. articular ends of the centra are oval in outline and somewhat deeply concave; the caudal ribs are strongly developed, but did not help to support the ilium. In the first caudal no chevron-facets are present; these first appear on the second, where, in the type specimen, they are asymmetrically arranged, that on one side being, as usual, on the posterior ventral edge of the centrum, while that on the other is further forwards on the ventral surface: in this vertebra and the next the posterior portion of the centrum is detiected downwards, the tail at this point having apparently curved down from the pelvic region. ‘The neural spines are inclined a little forwards. In the rest of the tail (Pl. VIII. figs. 4-9) the centrum is mere or less compressed laterally, especially in its middle portion; the upper and lower borders of the articular faces are flattened, so that in end view the outline of the centrum is somewhat quadrate “s ve > ape “ap oT ar nae 2, “ + S 4 DO Second sacral vertebra of Mycterosuchus nasutvs: A, from beliind; B, outer end of sacral rib. (R. 3892, 2 nat. size.) Jl, flange ov outer end of sacral rib; ¢7.s., surface for ilium:; .¢., neural canal: n.sp., neural spine ; p.z., posterior zygapophysis. (Pl. VIII. figs. 5 a, 6 a), the sides being convex; the chevron-facets are borne at the hinder end of a pair of ridges which run nearly the whole length of the ventral surface of the centrum and are separated by a narrow flat or concave band of bone. The neural spines are peculiar, and differ considerably from those of the Stenecsaurs described above. In the most anterior caudals, as above noted, the spine slopes a little forwards and is thickened at its upper end. Further back in the scries (at about the sixth) it becomes upright, and behind this slopes backwards. Here it is a broad thin plate of bone extending nearly the whole length of the arch. At about MYCTEROSUCHUS NASUTUS. 139 the twelfth vertebra, or the first in which the caudal ribs are wanting, the upper portion of the spine is narrowed by a broad notch on its anterior edge (Pl. VIII. fig. 5), dividing it into the main spine behind and a narrow pointed process in front, projecting nearly vertically upwards. Still further back a posterior notch appears : at first this merely forms a kind of bay in the posterior border of the spine, but becoming larger in the more posterior vertebre, it separates off from the main spine a posterior prominence similar to that in front (Pl. VIII. fig. 6). These anterior and posterior processes of the neural spine are continued nearly to the end of the tail (PL VIII. figs. 7-8), and in the posterior vertebrae have a deceptive resemblance to zygapophysial processes, though an examination of their mode of origin shows that they are not so, but merely portions of the neural spine. In the posterior vertebre Text-fig. 53. } May) i i ae \ Ig il iwi at = eA = ) H i A Sacral vertebrae of Mycterosuchus nasutus, from below. (R. 3892, 3 nat. size.) a.¢c., anterior end of centra; ¢.s., surface for ilium; p.c., posterior surface of centrum ; s.7., sacral ribs. the main part of the neural spine shifts further and further back on the arch, and at the same time becomes smaller. The shoulder-girdle (text-fig. 54, C),in correlation with the relatively large size of the fore limb, is strongly developed, both the coracoid and scapula being much expanded at their extremities. The humerus (text-fig. 54, A, B) is large compared with that of Steneosaurus and differs from it in several other respects. Thus the upper end seems to be less bent backwards, and consequently its articular surface is more nearly terminal, At the distal end both condyles are well developed, though the radial one (¢.e.) is the T2 140 MARINE REPTILES OF THE OXFORD CLAY. larger; the two are separated by a well-marked oblique groove (?.c.g.) running from front to back of the bone. ‘The plane of the distal condyles makes an angle with that of the proximal expansion, but is not turned almost at right angles with it as in Steneosaurus. There is a well-marked deltoid prominence (d.c.). The humerus in this genus is longer than the tibia and more than half as long as the femur: in Steneosaurus the reverse is the case. The radius and ulna, though similar to those of Text-fig. 54. f &Y yy YT Aor, i Wi, 1), yy ZH, Lg N i WN : A ae cor, Left humerus and left half of shoulder-girdle of Jycterosuchus nasutus: A, humerus from front; B, distal end of humerus; C, outer side of coracoid and scapula. (R. 2617, 3 nat. size.) c.e., Yadial condyle; ¢.z., ulnar condyle; cor., coracoid; d.c., deltoid crest ; f., coracoid foramen ; gl.f., glenoid fossa; h., head of humerus ; t.c.g., intercondylar groove ; sc., scapula. Steneosaurus in form, are likewise proportionately larger. The difference of proportion between the fore and hind limb may be expressed by saying, that if the combined MYCTEROSUCHUS NASUTUS. 141 Jength of the femur and tibia be taken as 100, then the combined length of the humerus and radius will be represented in Mycterosuchus nasutus by about 54, but in Stenco- saurus leedsi and Steneosaurus durobrivensis by about 45. The pelvis is not known, and the bones of the hind limb, so far as preserved, do not appear to differ much in structure from those of Steneosaurus. The tibia is just half the length of the femur, while in Sfeneosaurus it is rather less. The dermal scutes (Pl. VIII. figs. 4, 10) ave proportionately thicker and heavier than in Steneosaurus. In the dorsal region the keel does not appear to have been well developed; the sculpture consists of a number of large, deep, and closely- set pits. RB. 2617 (Leeds Coll. 1). The greater part of the skeleton of a large individual, including nearly complete but crushed skull and mandible (Pl. VIII. figs. 1, 2), atlas, axis, and nine other cervical vertebrae, two or three crushed dorsals, forty-two caudals (Pl. VIII. figs. 4-9), left coracoid and scapula (text-fig. 54, C), left humerus (text-fig. 54, A, B) and ulna, left and part of right femur, right tibia and fibula, astragalus, caleaneum, meta- tarsals and other foot-bones. Numerous scutes are preserved, in many cases adherent to the sides of the neural spines. Type specimen, the skull and mandible bei described and the skull figured in Ann. Mag. Nat. Hist. [8] vol. iii. (1909) p. 30 pl. ix. fig. 1 (the registered no. is there wrongly given as R. 3577). ng 2, The dimensions (in centimetres) of this specimen are :— Skull (Pl. VIII. fig. 1): Votalllenpthiy ues) py eucn aes cig ne see eee OOO, Length in front of orbits. . . . St et eee TAO, Width between the outer angles of ifs nin pile mote, eAaRY) Length of temporal fosse (inner side) . . . . . . . 140 jWadthrotitemporalefossces juste meltuleve ie, eece ene neem 1:5) 7) OL trontals'betweenorbitss 4 <2 see ae 6-0 » of skull at anterior border of orbits. . . . . . 165 5, atanteriorangle of nasals:. Jo6) . 2 6 a... - 63 », behind premaxillary expansion . . . . . . . 4-2 sy OL premaxillaryexpansion: Vee) ls ey elon en fe 73 Mandible (PI. VIII. fig. 2): Total length. . . . TPN cee ea ime wan s1dOrG Length of symphysial nortan Be he ner PO ME: Meena eo yD Width at hinder end of symphysis . . . . .. . . 116 a, Dehindlanterionexpansioniy. tic seu suet ta 4:2 Owing to the crushing undergone by the skull and mandible, many of the aboye dimensions are only to be taken as approximate, 142 MARINE REPTILES OF THE OXFORD CLAY. Caudals. VOHEDSS aatictoes fe aeie| Geni ral-¢esesiGal: 9, 20 Eno) ie pUTStR. PSOEN! aeoees mse Rear RT Length in mid-ventral ING aewiees bessites aie rs kOLO, 6-4 6°8 Ge7 16:9 6:2" buf loro) 4:9 ao On onl ‘Width of posterior face . 4:5 Bid 55 ibe! noes) So) PZ) CO Gemele 9 Height of posterior face. 4°7 se 5:3 Me AOE S22 2d oe Ms 3 wee) » totopofspine.9°2 141 14:2 ws) Oei(app)1978 68:8 Gin work The numbers of the caudals in the series are only approximate, at least three are wanting from the anterior region. Shoulder-girdle (text-fig. 54, C) : Seaenibye Nein Gee ee og oem oe oo ole soeeg on RRS width of-articular end) ogee) a ey ee eee Onl sic ASHALG. a Wk Pee cle se ee ys a ae oO) 5) upper expansion . a) eps peu cers OL Coracoidi: length... = = = « 2 «.. = « approx.) Jo:0 widthiofarticularend, 92 8. 2 sme Ole lowerend, ms 2)! i) este) M(approx.) | 7-6 Humerus (text-fig. 54, A, B): length . : 211 width of proximalend . . . 7:0 Py shaft at narrowest . 2:3 Pe, lowerend . . 4 aes} WG En oo Sn oe Ge oo oe py | dies} NAabninCoyu ieee Cl 4 ye ala Ao a Fay och) 4. jlowemend’ 4. 38% OM SS son ee eee ities liad 5 oo 6 A ou oo Gg) & oe co Mamet bane JlIgs WUE wOwlS "S65 & 6 a 6 a ae yg a) VGHE ses lowerzend's,, 4 hog. ee eat ia pe er ee te ee es SMe eae te Sl OA 5 6 Ge oa Gn SUR 1G ce cw AMIN Sime “6S 5 a & 5 8 b os oh dds a ah eo PURO Wad thsofwupperientls sss meen ee hus pcre mis) eerie | fO1D Fr Hoey as Soe a de my (Epypoe)e HO) IMA ena Sf oo 4 6 om o 8 ooo Bee a> Iles WrutH Meth 6G oe ol g Geo ed ool OS! 4) eaniddlevof-shatt) fis snaumer crust ae) tee oe eb sa Mowerendic. xo 0a) Saewe, eoEdee s. Ast cee OID R. 3892 (Leeds Coll. 9). A great part of the vertebral column of a large individual. The vertebrze preserved are six cervicals (the atlas and axis are wanting), fourteen dorsals, one lumbar, two sacrals (text-figs. 51-53), and twenty-one caudals. Most of the vertebra, though somewhat distorted, are well preserved, and in most the neural arches and spines are present. METRIORHYNCHUS. 143 Some approximate dimensions (in centimetres) of some of these vertebrae are :— Middie Candals. Dorsals. First Second First Anterior caudals. Posterior ——— oo sacral, _ sacral, caudal, caudal, .—+*~——~ caudal. Length in mid- ventral line. . . 59 6:2 65 G8 58 5-9 51 6:8 6-0 58 5-3 Width of posterior face of centrum . 48 54 5:8 5:4 5:0 O5) 5:2 4-2 38 34 2°8 Height of posterior face of centrum . 5:0 51 5:3 5:5 39 4-6 45 39 33 31 2-5 Height to top of neuralispine 7. 0) VO Tl 12:8) sel 1253) blsd apps te. 11:3 9-9 9-5 Family GEOSAURID. Mesosuchia which are modified for a strictly aquatic life. Nasals large, taking a considerable share in the formation of the rostrum; they may or may not extend forwards to the premaxiliz. Prefrontals very large and overhanging the orbits, which look forwards and outwards. Premaxille with no terminal expansion. Teeth usually somewhat compressed and carinate. Vertebre with slightly concave ends. Fore limb greatly reduced and paddle-like. Hind limb large. Tail long, with the distal segment sharply bent down and supporting a large dersal fin. No dermal skeleton is known; a sclerotic ring was present in the eye. This family corresponds to the group Thalattosuchia of E. Fraas *. Genus METRIORHYNCHUS, H. v. Meyer (emend. E. E. Deslongchamps). (Isis, 1830, pt. v. p. 518, and Paleologica (1832), p. 106; emend. E. EH. Deslongchamps in Notes Paléontologiques, p. 132 (Caen, 1867).] 1890. Suchodus, Lydekker, Quart. Journ. Geol. Soc. vol. xlvi. p. 288. Exhibiting the characters of the family, but distinguished from the later Geosaurus by (1) the absence of the serration of the carine of the teeth, the enamel of which is, as a rule, raised into a varying number of fine longitudinal ridges; (2) the smaller degree of reduction of the humerus ; (3) the greater length of the tibia and fibula in comparison with the femur. Dacosawrus, from Kimmeridgian beds, is very similar and should perhaps be referred to this genus. Oxford Clay. ‘The later forms are probably all referable to Geosaurus or Dacosaurus. This genus was founded by H. v. Meyer for Cuvier’s ‘Second Gavial of Honfleur” , * “Die Mcer-Crocodilier (Thalattosuchia) des oberen Jura,” Paleontographica, vol. xlix. (1902), p. 1. + Ossenents Fossiles, ed. 2, vol. v. pt. 2 (182+), p. 143. 144 MARINE REPTILES OF THE OXFORD CLAY. described from a skull consisting partly of a skull of Metriorhynchus and partly of one of Steneosaurus, a circumstance which has led to much confusion in the use of these names. In 1867 the genus was defined in detail by E. E. Deslongchamps, the species regarded by him as typical being Metriorhynchus superciliosum, Blainy., sp. i. Fraas, in his paper on the Thalattosuchia *, distributes the different species of Metriorhynchus into three groups as follows :— 1. Forms with very short snout, the nasals reaching the premaxille; prefrontals very large; teeth strongly developed.—W. brachyrhynchus. 2. Forms with thick-set snout, but the nasals separated from the premaxille by a considerable interval ; prefrontals moderately large ; powerful dentition with less than twenty-five teeth in the upper jaw.— J. hastifer. 3. Forms with elongated snout, the nasals in spite of their length being separated by a long interval from the premaxille; prefrontals smaller and not very prominent; dentition consisting of rather slender teeth, of which there are more than twenty-five on each side of the jaws.—V. superciliosum, M. moreli, M. blainvillei. These groups, which are probably rightly considered by Fraas to be directly ancestral to the various forms of Geosaurus and Dacosaurus of higher horizons, hold good in a general way for the species now described, though some of these might be regarded as breaking down the sharp distinctions between them. Moreover, probably some of the new species are more directly in the line of descent of some of the species of Geosaurus than those previously known. In the present volume seven species of Metriorhynchus are recognised, of which three are new. The skulls range in form from a long slender type to the stout broad type which has been referred to Suchodus durobrivensis, but the transition from the one form to the other is so gradual that it seems best to retain the same generic name for all. ‘The occurrence of so many species of one genus at one locality and on the same horizon is remarkable, but perhaps this is due to the fact that these reptiles were widely ranging pelagic forms which, as in the case of the smaller Cetacea, may have been represented by many species in one marine area of distribution. Skull (Pls. IX.—XIII.; text-figs. 55-59).—The following general account of the skull in this genus is founded largely on the two skulls (R. 3699-8700) of Metrio- rhynchus brachyrhynchus (Pl. X11.) in which the palatal region is fairly well preserved, as described by Mr. E. Thurlow Leeds (Quart. Journ. Geol. Soc. vol. Ixiv. (1908) p. 345). Other specimens are referred to when they throw light cn points not determinable from these specimens. Unfortunately nearly all the skulls in the collection have been greatly crushed, so that in most cases the roof is flattened and driven down, * Paleontographica, vol. xlix. (1902) p. 1. METRIORHYNCHUS. 146 the sides being concealed and the thin bones of the palate destroyed. Besides making it difficult to work out the structure of the skull, this crushing also renders the measurements, particularly those of width, very unreliable. In its general outline (text-fig. 55) the skull seen from above is an elongated isosceles triangle; the height of the triangle (7. ¢. the length of the skull) differs much in its relative proportion to the base (7. ¢. the width between the outer angle of the quadrates) in the various species, the difference in length depending mainly on the degree of development of the rostral (preorbital) region. The premaxillary region is pointed and shows no expansion such as occurs in the Steneosaurs. The posterior (occipital) surface of the skull is triangular in outline and is by no means so depressed as in Steneosaurus, but unfortunately in nearly all cases it is greatly deformed by crushing. ‘The large temporal fossee vary somewhat in form and size in the different Text-fig. 55.. 72aP fire. Semi-diagrammatic view of skull of Metriorhynchus superciliosum, from above. al.s., alisphenoid ; boc., basioccipital ; ex.0., exoccipital ; f., frontal; for., foramen in hinder wall of temporal fossa; j., jugal; mx., maxilla; »., nasal; nar., external nares ; orb., orbit; par., parietal; pme., premaxilla; po.f., postfrontal; pr.f., prefrontal; pr.o., pro-otie ; q-, quadrate; 9.7., quadrato-jugal ; sq., squamosal, species, but may be said to be roughly quadrangular with the angles rounded off to a varying extent. The premaxille (pma.) form the anterior extremity of the pointed snout. Above, they surround the external narial aperture, which is usually an elongated heart- shaped opening, the indentation on its posterior border being formed by a pair of processes of the premaxille projecting forwards. In Geosaurus, according to Fraas*, these processes completely divide the nasal opening in the middle line, but this is not * Paleontographica, vol. xlix. (1902) p. 42. PART II. U 146 MARINE REPTILES OF THE OXFORD CLAY. seen in the specimen of Geosaurus gracilis figured in the frontispiece. In Metrio- rhynchus these processes vary much in Jength, in some cases being very short, while, according to Mr. Leeds, in some skulls of JZ. superciliosum they may extend two-thirds of the length of the nasal opening; they are often broken away and are not always completely shown in the figures. At the sides of the nares the premaxille form a thickened rounded border, low in the middle but rising anteriorly and forming in the middle line a well-marked prominence. An incisive foramen on the floor of the nasal opening has not been observed. Behind the nasal opening the premaxille are produced backwards into pointed facial processes which are thrust between the maxille. ‘These processes may actually meet the anterior angles of the nasals, thus shutting out the maxille from the median dorsal line, or they may be separated from them by an interval varying in the different species, and to some degree even in the individuals of one species. Beneath the nares the sides of the premaxille are rounded from above downwards; ventrally they are nearly flat and meet in the middle line for a short distance anteriorly, behind which they are produced back into pointed palatine pro- cesses underlying the pointed anterior ends of the palatine plates of the maxille, which are thrust like a wedge between them as far forwards as the level of the interval between the second and third dental alveoli. Each premaxilla bears three alveoli, which are separated from one another by equal intervals; the anterior tooth is a little smaller than the others. Between the last tooth in the premaxilla and the first in the maxilla there is usually a diastema of considerable length ; this region is a little concave from before backwards, and is crossed towards its hinder end by the maxillo- premaxillary suture. The maville (ma.) are very large bones forming a great part of the rostrum. They may meet in the middle dorsal line for some distance, or may be excluded from it by the junction of the premaxille and the nasals. ‘Their greatest length is along the alveolar border, which extends from the premaxille to the jugal behind. ‘The number and the distance between the dental alveoli vary considerably in the different species; thus in M. leve there are considerably over thirty teeth in each maxilla, the alveoli being set very close together, while, on the other hand, in A/. brachyrhynchus there are only about eighteen, separated by intervals equal to at least half the diameter of the alveoli them- selves. Anteriorly the palatal plates of the maxillee are thrust wedge-like between the premaxille. From this anterior angle they meet ina median suture as far back as the anterior angle of the palatines, which are interposed between them, increasing gradually in width from before backwards. ‘The palatal surface of the maxilla imme- diately within the alveolar border is raised into a ridge which forms the outer border of a longitudinal groove which gradually increases in depth from before backwards. Posteriorly the grooves thus formed run into the notches between the median and lateral points of the anterior ends of the palatines. In this region the grooves become narrow and deep, and appear to have foramina opening into their roof. At first they METRIORHYNCHUS. 147 curve towards one another till they nearly meet in the middle line; they then diverge again and die away at about the level of the hinder end of the dental series; at their posterior end they may be represented by a row of foramina only. In M. moreli and M. brachyrhynchus they terminate a little in front of the anterior angle of the palatal! vacuity. Along their median symphysis the palatine surface of the maxille is raised into a slight ridge, which in that region separates the grooves just described. Where the maxillze are separated by the palatines, their palatal surface is gently concave from side to side and continues to be so as far as the palatine vacuities. ‘The posterior prolongations of these bones form the outer border of the anterior portion of the openings just referred to and terminate about opposite their middle point; the alveoli are continued almost to the tip uf these prolongations, the upper side of which is over- lapped by the anterior end of the jugals which shut out the maxille from any share in the formation of the orbit. The facial surface of the maxilla is strongly convex from side to side, and a section of the upper surface of the snout, in the region where the maville meet in the middle Text-fig. 56. par als fr Skull of Metriorhynchus superciliosum from right side, the palatine portions of the skull being omitted. al.s., alisphenoid; f., lachrymal foramen; fr., frontal; 7., Jugal; 1, lachrymal ; Lt.f, lateral temporal fossa; ma., maxilla; 7., nasals; nar., external nares; par., parietal ; pmwv., premaxilla; po.f., post- frontal ; pr.f., prefrontal ; p7.o., pro-otic; ¢., quadrate ; q.j., quadrato-jugal ; sy., squamosal. dorsal line, makes a curve rather greater than a semicircle. This strong convexity of the snout is continued in the region of the nasals, but it is only in one or two specimens that this can be seen, for in nearly all cases the vertical crushing to which the skulls have been subjected completely distorts their form and obscures the relations of the bones to one another, especially in the neighbourhood of the orbits. The anterior parts of the facial portions of the maxille receive between them the facial processes of the premaxillee, with which they unite in a suture of varying form. Behind this they may or may not meet in the mid-dorsal line to an extent differing in the different species, and even to some degree in different individuals of the same species. Posteriorly they are separated by the wedge-like nasals, and narrow gradually to their posterior end, which is occupied by a deep groove nearly parallel with the alveolar border and continued back to the deep notch on the anterior side of the lachrymal (/.), U2 148 MARINE REPTILES OF THE OXFORD CLAY. with which bone the maxilla has at most a very short union, being separated from it to a large extent by the anterior end of the jugal. The nasals (n.) are very large elements which take a great share in the formation of the upper surface of the rostrum. They meet in suture in the middle line, and in the uncrushed condition were strongly convex from side to side (text-figs. 56, 57) ; in some species (e. g. MW. superciliosum) their posterior portion is considerably inflated. Anteriorly they narrow to a point and are thrust between the maxille to a varying degree, sometimes, as already noted, reaching the premaxille. At their posterior end they are separated from one another by the wedge-shaped end of the frontal, between which and the prefrontals they send back a process of varying form and length. Beneath the prefrontal they also send back a process, so that the anterior end of the prefrontal is fixed in a deep bay or notch on their hinder end. ‘The lower border of the ventral prolongation unites below with the lachrymal in a straight suture. ‘The St = Se Portion of skull in front of the orbit in Metrivrhynchus (?) moreli: A, front wall of orbit ; B, side of skull in front of orbit. (R. 3900, 4 nat. size.) for., iachrymal foramen; j7., jugal; /., lachrymal; ma., maxilla; n., nasal; pr.f., prefrontal ; s.f., suture for frontal; s.pt., suture for union with palatine ; ¢., tubercle in groove in prefrontal. surface of the nasals is sculptured to a degree varying in the different species: usually the sculpture in this region consists of longitudinal ridges which run into one another irregularly. The prefrontal (pr.f.) is a large and solidly constructed bone which in nearly all specimens is so crushed as to appear merely as a flat plate overhanging the orbit. Actually it consists of two parts (text-fig. 57): (1) an upper portion which overhangs the orbit and has its dorsal surface sculptured in most species, and (2) a downwardly detiected region which helps to form the anterior wall of the orbit and bears a broad groove running forwards on to the face from the orbit. The inner border of the upper portion unites posteriorly with the frontal, anteriorly with the nasal ; its anterior end, METRIORHYNCHUS. 149 as above described, being received into a deep bay in the hinder end of that bone. The outer free edge overhangs the orbit and varies in form in the different species; its posterior border usually bears a number of small irregular notches, while its outer border is thickened and passes down into the smooth ventral region. ‘This latter unites below with a process of the nasal in front and with the lachrymal behind. The groove above mentioned as running from the orbit on to the face is partially blocked at the edge of the orbit by a small pointed process (text-fig. 57, ¢.), the function of which is not known. Behind this point the bone is curved sharply inwards to form the upper part of the anterior wall of the orbit, the ventral part being joined by the lachrymal. The ventral angle of the inner end of the prefrontal, together with the lachrymal, is produced downwards into a short process terminating in a sutural surface probably for union with the palatine (Pl. XIII. fig. 2, pal.f-). The /achrymal (J.) is a solidly constructed bone which appears on the side of the face in front of the orbit, of which it forms the antero-ventral portion of the border and the lower part of the anterior wall (text-fig. 57). In front it unites with the nasal above and the jugal below ; its anterior border bears a deep notch, at the bottom of which is a small foramen (for.). From this notch the deep groove on the maxilla runs forwards as described above, but it is not certain whether the maxilla has any direct union with the lachrymal, though probably such a junction does exist for a short distance at the hinder end of the groove. At the margin of the orbit the bone is curved sharply inwards to form the front wall of that cavity. Above, it joins the prefrontal, as above described, and its ventral inner angle is produced downwards with that bone and helps to form the sutural surface for union with the palatine (Pl. XIII. fig. 2). Below, its straight ventral border joins the jugal in a broad sutural surface. The frontals ( fr.) are represented by a single bone which never shows traces of a median suture. It consists of a broad interorbital region with a median and a pair of lateral posterior processes. ‘The interorbital portion terminates anteriorly in a wedge- shaped process thrust between the posterior ends of the nasals; behind this it joins the postero-internal border of the prefrontals, behind which again it forms the posterior portion of the upper border of the orbit. The form and relations of the nasals, frontals, and prefrontals to one another are of great importance in separating the various species, as will be seen below. ‘The lateral processes run outwards, down- wards, and backwards, overlapping the anterior end of the postfrontals (po.f.) and terminating in a point. ‘The median process forms the anterior half of the ridge between the temporal fosse, joining the parietal crest behind in a complex suture ; the width of the upper surface of this median process differs in the different species, and it may, or may not, bear sculpture. In the angle between the postorbital process of the frontal and the median process a thin plate of bone, constituted by the lower edge of the frontal and the posterior edge of the postfrontal, forms a floor to the antero-internal portion of the supratemporal fossa (text-fig. 55). 150 MARINE REPTILES OF THE OXFORD CLAY. The united parietals (par.) form the posterior portion of the crest between the temporal fossee, and anteriorly they are overlapped to a considerable extent by the frontals; the portion of the sagittal ridge formed by the parietals is usually much narrower than the frontal portion, and may have a groove along its summit. Posteriorly, the bone widens out and its dorsal surface usually forms a small triangular area. The occipital surface is nearly vertical with a strong median ridge. ‘The lower edges unite with the nearly transverse upper border of the supraoccipital, except for a short distance on either side, where a pair of foramina separate the bones. Laterally, the parietals slope away and are prolonged outwards into a pair of processes which overlie the upper surface of the inner arm of the squamosals (s7.) and extend some distance down into the temporal fosse. In the cranial region the parietals unite in front with the alisphenoid (a/.s.) and behind with the pro-otic (pr.o.), which is separated from the alisphenoid by a nearly vertical suture. At the point of union of the squamosal, parietal, and pro-otic there is a foramen from which a groove runs out on the posterior wall of the temporal fossa, terminating in another foramen between the squamosal and probably the quadrate ; these foramina probably transmitted a blood-vessel. The alisphenoid (al.s.,text-tigs. 55, 56), as already noted, unites above with the parietal, the suture with which is slightly convex upwards. At its anterior end the alisphenoid seems to be continued as a narrow strip along the edge of that part of the parietal which in the crushed skulls seems to help in forming the floor of the anterior part of the temporal fossa; in the natural condition this portion of the parietal and alisphenoid would probably slope more downwards and outwards, forming the upper part of the side walls of the cranium. Posteriorly, the alisphenoid joins the pro-otic (p7.o.) ina straight suture, running nearly vertically downwards to the foramen for the fifth nerve, the upper edge of which is formed by a notch on the lower border of the alisphenoid and pro-otic at their junction with one another; this foramen may have been closed below by the inner extension of the quadrate. ‘the bone which is here regarded as the pro-otic (text-fig. 55, pr.o.) unites above with the parietal and posteriorly forms the lower border of the vascular foramen, the upper edge of which is formed by the squamosal and parietal; behind the foramen there is a short union with the squamosal. Its lower border at its junction with the alisphenoid is notched by the foramen for the fifth nerve, as described above; behind this it unites with the inner extension of the quadrate (q.). The sguamosal (sq.) is an L-shaped bone consisting of a stout anterior process uniting with the postfrontal (pestorbital) and an inwardly directed process uniting below with the quedrate and exoccipital and overlapped at its inner end by the lateral process of the parietal; below, it forms part of the border of the vascular foramen mentioned, and has a sbort union with the pro-otic. The inner faces of the two arms of the METRIORHYNCHUS. 151 squamosal pass into one another by a sharp curve, which forms the postero-external angle of the supratemporal fossa. The postfrontal (po.f.) forms the greater part of the postorbital bar, separating the orbit from the supratemporal fossa and forming an incomplete postorbital wall. At its upper end it is overlapped by the lateral process of the frontal in a V-shaped suture, and in this region its posterior edge helps to form a floor to the front part of the supra- temporal fossa, as described above, uniting with the corresponding plate of the frontal and apparently also with the anterior prolongation of the alisphenoid. ‘The outer face of the anterior part of the bone in many species is sculptured like the prefrontal. Posteriorly it is smooth, and overlaps the zygomatic process of the squamosal in a long oblique suture. Immediately behind the orbital part of its border it is produced down into an angular process which unites with a corresponding process on the upper edge of the jugal, thus closing the lateral temporal fossa in front. The quadrate (q.) is a massive bone very firmly fixed among the adjacent elements. It consists of an articular region which is directed downwards, outwards, and back- wards and terminates in the condylar surface for the mandible. This surface consists of two convexities, separated by a deep groove running obliquely inwards and forwards from about the middle of the posterior border. ‘The outer edge immediately above the outer condyle bears an elongated oval surface for union with the posterior end of the quadrato-jugal. Above this the outer edge is prolonged obliquely forwards and upwards to the squamosal, along the lower edge of which it extends forwards so as to form a short union with the postfrontal. It also sends back along the ventral face of the squamosal a process which makes an acute angle with the ascending process; the angle forms the anterior border of the external auditory opening. The body of the quadrate is prolonged inwards towards the cranial surface of the skull, uniting with the squamosal and epiotic above and probably with the pterygoid at its inner end. It seems to have formed the lower edge of the aperture for the fifth nerve. On its hinder face it is extensively overlapped by the lateral wings of the exoccipital. The quadrato-jugal (qj.) is a small bone which unites with the outer edge of the lower end of the quadrate by means of an expansion bearing an oval sutural surface. From this a short process runs forwards and is overlapped by the hinder end of the jugal; it forms the postero-inferior angle of the lateral temporal fossa. The jugal (j.) is a long slender bone. At its anterior end it terminates in a point which is thrust between the hinder end of the maxilla below and the lachrymal above, the union with the latter being a strong straight suture. Behind this it forms the suborbital bar, which is triangular in section and sometimes sculptured on its outer face. On its inner face in this region there is a narrow palatal plate which terminates posteriorly in a strong inwardly directed process ending in a sutural surface, with which no doubt the transpalatine unites, though unfortunately all the specimens are 152 MARINE REPTILES OF THE OXFORD CLAY. incomplete in this region. Behind the orbit the bone is widened by the presence of a prominence on its upper border, by means of which it unites with the postfrontal. Behind this it becomes round and narrows, terminating posteriorly in a point which overlaps the anterior end of the quadrato-jugal, thus enclosing the lateral temporal fossa below. The palatine region of the skull (Pl. XII. fig. 2; text-fig. 58) is in nearly all cases more or less completely destroyed by the crushing to which it has been subjected. In two specimens, however, of AZ. brachyrhynchus (Leeds Coll. 164-165, R. 3699-3700), this part of the skull is fairly well preserved and has been described in detail by Mr, E. Thurlow Leeds (Quart. Journ. Geol. Soc. vol. lxiv. (1908) p. 845), upon whose work the following account is for the most part founded, the same two skulls being described. Text-fig. 58. ze @ ee GPE Pine a Semi-diagrammatic figure of the palatal surface of the skull of Metriorhynchus brachyrhynchus ; partly after E. Thurlow Leeds. (About + nat. size.) boc., basioccipital; bs., basisphenoid; ew.m., median eustachian opening; i.nar., internal narial opening ; jes jugal ; l.t.f., lateral temporal fossa ; mv., maxilla ; pal., palatine ; p.fr., postfrontal ; pmax., premaxilla ; pt., pterygoid; g., quadrate ; g.7., quadrato-jugal ; s.0.7., suborbital vacuity ; ¢.p., transpalatine (restored) ; v., vomer (parasphenoid); 1, 2, 3, 4, these figures mark the levels at which are taken the sections shown with the corresponding numbers in the next figure (text-fig. 59). Other specimens in which the palate is fairly preserved are the skull of a large individual referred to M/Z. superciliosum (R. 3016) and that of a young specimen of AM. durobrivense (R. 2618) in which the vomer (parasphenoid) is particularly well shown. The palatines (pal.) unite in front with the maxille in a suture which may be nearly transverse (MV. brachyrhynchus), but usually forms a median point meeting its fellow in the middle line, and a lateral process projecting beyond the last, from which it is separated by a notch which marks the course of the deep groove described above METRIORHYNCHUS. 153 as running from the maxilla on to the palatine. Behind this the palatine unites for some distance with the maxilla, then, separating from it, forms the inner border of the suborbital vacuity. It widens out a little towards its posterior end, which terminates in an outer longer process and a shorter median one which unites in the middle line with its feliow of the opposite side, projecting backwards from the ventral border of the narial opening, which is thus divided into right and left halves. In specimens figured by Deslongchamps* the ventral border of the narial opening is shown as pointed anteriorly, the palatines being separated posteriorly by a notch: this is not the case with the specimens here described. Anteriorly the upper surface of each palatine is deeply grooved for the floor of the uarial canal, which is separated from its fellow of the opposite side by the vertical plate of the vomer (text-fig. 59, 1). A little further back there rises from the upper edge of the palatine a dorsal plate (text-fig. 59, 2, 3) sloping up to the vomer, which it overlaps, completing the nasal canals superiorly ; the dorsal plate is concave from side to side. At about the middle of the palatine the narial canals seem to have curved inwards and the dorsal plate of the palatine is thickened and united above with the downwardly directed process of the prefrontal and lachrymal. As Mr. Leeds has pointed out, the ventral process of the prefrontal in modern Crocodiles unites with the palatine and pterygoid at the anterior end of the latter and considerably behind the small vomer. The bone described by Mr. Leeds as the vomer (v.) is a large median element without, as he pointed out, any trace of division into two lateral halves, a circumstance which, taken together with the fact that it extends back to and unites with the ventral face of the basisphenoid, makes it very probable that this element should rather be regarded as a parasphenoid, the bones which are called vomers in the recent crocodiles being absent, or at least not yet certainly recognised. At its anterior end the bone is T-shaped in section, the vertical arm resting on the line of union of the palatines (text- fig. 59, 1) and forming a median wall between the nasal canals; the upper surface is grooved, the lateral arms of the T curving upwards to an increasing extent as they are followed backwards, till opposite about the middle point of the palatines they enclose a deep channel, and at the same time are considerably thickened (text-fig.59,2). The upper edges of the dorsal plates of the palatines rest against the outer part of the lower edge of these thickened arms of the T, which further back still, curve downwards, the median groove disappearing (text-fig. 59, 3). Posteriorly the dorsal plates of the palatines diverge from the vomer (text-fig. 59, 4), the roof of the narial canal being completed by the anterior ends of the pterygoids. Behind this the vomer narrows and is prolonged backwards between the pterygoids on the roof of the narial opening, where it forms a median ridge.