THOMAS J. BATA LIBRARY TRENT UNIVERSITY
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PALAEONTOLOGY.
PALAEONTOLOGY
SYSTEMATIC SUMMARY OF EXTINCT ANIMALS
AND
THEIR GEOLOGICAL RELATIONS.
BY
RICHARD OWEN, F.R.S.
Superintendent of the Natural History Departments in the British Museum, Fullerian Professor of Physiology in the Royal Institution of Great Britain, Foreign Associate of the Institute of France, etc.
EDINBURGH :
ADAM AND CHARLES BLACK.
MDCCCLX.
PRINTED 13Y R. AM) R. CLARK, EDINBURGH.
CONTENTS, OR SYSTEMATIC INDEX.
Introduction .
KINGDOM PROTOZOA •
Class Amorphozoa Ehizopoda
Sub-Class Polycystine^e . Class Infusoria
KINGDOM ANIMALIA
SUB-KINGDOM INVERTEBRATA PROVINCE RADI AT A
Class IIydrozoa Family Graptolitidse Class Anthozoa Bryozoa . Echinodermata Order Crinoidea Cystoidea Blastoidea Asteroidea Ecliinoidea Holotliurioidea PROVINCE ARTICULATA Class Annulata
CiRRIFEDIA
Crustacea
Sub-Class Entomostraca
1
5
5
8
13
14 17 17 19
19
19
21
27
29
29
32
33
33
34
37
38
39
40
41 41
304309
vi CONTENTS, OR SYSTEMATIC INDEX.
Page
Order Trilobites . . . .44
Sub-Class Malacostraca . . . .45
Class Insecta . . . . .47
PROVINCE MOLLUSC A . . . .48
Class Brachiopoda . . . .49
Lamellibranchjata . . .57
Gasteropoda . . . .69
Order Pteropoda . . . .71
FTucleobraneMata . . . .72
Pectinibranchiata . . . .73
Family Strombidse . . . .73
Muricidae . . . .73
Conidae . . . . .76
Volutidse . . . .76
Cypraeidm . . . .76
Order Holostomata . . . .76
Family Naticidae . . . .76
Cerithiadae . . . .77
Calyptraeidae . . . .77
Neritidae . . . .78
Patellidae . . . .79
Order Puhnonifera . . . .79
Tectibrancbiata . . . .80
Class Cephalopoda . . . .80
Order Tetrabranchiata . . . .80
Family Nautilidse . . . .82
Ortlioceratidae . . . .82
Ammonitidae . . . .85
Order Dibrancliiata . . . .90
Sepiadae . . . _ .90
Teuthidae . . . .90
Belemnitidae . . . .92
1 able of Extinct Genera of Mollusca . . .94
PROVINCE VERTEBRA TA . . .96
Class Pisces . . . , .99
Order Plagiostomi ... 99
Spines . . . . .100
CONTENTS, OR SYSTEMATIC INDEX. vii
Page
Teeth . . . . .105
Family Cestraciontiche . . . .106
Hybodontidse . . . .108
Squalidse . . . .110
Raiidee . . . . .113
Order Holocephali . . . .116
Genus Chimsera . . . .116
Ischiodus . . . .116
Ganodus . . . .117
Edaphodus . . . .117
Elasmodus . . . .117
Order Ganoidei . . . .118
Sub- Order Placoganoidei . . .118
Family Placodermata . . . .118
Siluridse . . . .126
Sturionidse . . . .145
Sub- Order Lepidoganoidei . . .129
Family Dipterkhe . . . .129
Genus Dipterus . . .129
Diplopterus . . .130
Osteolepis . . .130
Acanthodii . . • .130
Genus Diplacanthus . . .131
Cheirolepis . . .131
Ccelacantlii . . • .131
Genus Glyptolepis . . .131
Phyllolepis . . .132
Asterolepis . . .132
Bothriolepis . . .132
Glyptopomus . . .132
Holoptychidse . • .132
Genus Holoptychius . . .132
Rliizodus . • .132
Dendrodus . • .133
Palseoniscidse . . ■ .136
Genus Pakeoniscus . . .136
Amblypterus . • .137
Saurichthyidse . . • .138
VU1
CONTENTS, OR SYSTEMATIC INDEX.
Page
Genus Megalichthys . . 138
Saurichthys . . .138
Family Caturidae . . . .139
Genus Caturus . . .139
Pachycormus . . 140
Pycnodontes . . .140
Genus Platysomus . . .140
iEchmodus . . .141
Pycnodus . . .141
Dapednke . . . .143
Genus Dapedius . . .143
Amblyurus . . .143
Pholidophorus . . 143
Lepidotidae . . . .143
Genus Lepidotus . . .143
Nothosomus . . .144
Propterus . . .144
Leptolepidse . . .144
Genus Leptolepis . . .144
Macropomidse . . .144
Genus Macropoma . . .144
Sturionidse . . .145
Genus Chondrosteus . . 145
Order Acanthopteri . . . .146
Sub-Order Ctenoidei . . . .146
Genus Semiopliorus . . .146
Smerdis . . . .147
Sub-Order Cycloidei . . . .147
Genus Histiophorus . . . .148
Cselorhynchus . . .148
Order Anacanthini . . . .148
Family Pleuronectidse . . . .149
Summary on Fossil Fishes . . . .150
Ichnology . . . . . .152
Protichnites . . . . _ .158
Amphihichnites . . . . .163
Genus Cheirotherium . . .163
Otozoum . . . .165
CONTENTS, OR SYSTEMATIC INDEX.
IX
Page
Genus Batrachopus . . . .166
Sauropus . . . .167
Class Reptilta . . . . .168
Order i. Ganocephala . . . .168
Genus Archegosaurus . . .168
Dendrerpeton . . .182
Raniceps . . . .183
Order n. Labyrinthodontia . . .183
Genus Baplietes . . . .184
Family Labyrinthodontidae . . .185
Genus Labyrintliodon . . .189
Mastodonsaurus . . .195
Nematosaurus . . . .195
Metopias . . . .196
Capitosaurus . . . .196
Zygosaurus . . . .196
Odontosaurus . . .196
Xestorrbytias . • . .196
Order hi. Iclithyopterygia . ■ .198
Genus Ichthyosaurus . . . 200
Order iv. Sauropterygia . . .209
Genus Nothosaurus . . • .210
Pistosaurus . . • .214
Conchiosaurus . . .214
Simosaurus . . • .214
Placodus . • • .216
Tanystrophaeus . • .221
Sphenosaurus . . .222
Plesiosaurus • • .223
Pliosaurus . . • .232
Polyptychodon . • .235
Order v. Anomodontia . • • .235
Family Dicynodontia • • . .236
Genus Dicynodon . • • .237
Ptychognathus • • .238
Family Cryptodontia . • • .238
Genus Oudenodon . • • .238
Rhynchosaurus • • 239
X
CONTENTS, OK SYSTEMATIC INDEX.
Page
Order vi. Pterosauria . . . .244
Genus Dinrorphodon . . .246
Eamphorhynclius . . .246
Pterodactylus . . . .247
Order vn. Tliecodontia .... 248
Genus Thecodontosaurus . . .248
Palseosaurus . . . .249
Belodon . . . .251
Cladyodon . . . .251
Batliygnathus . . .252
Protorosaurus . . .253
Staganolepis . . .255
Leptopleuron . . .256
Order vm. Dinosauria . . . .257
Genus Scelidosaurus . . .258
Megalosaurus . . .258
Hylseosaurus . . .264
Iguanodon . . . .265
Order ix. Crocodilia . . . .271
Sab- Order 1. Ampliicoelia . . .271
Genus Teleosaurus . . - 271
Suchosaurus . . .271
Goniopholis . . .271
Sub-Order 2. Opisthoccelia . . . 272
Genus Strep tospondylus . . .272
Cetiosaurus • . .272
Sub-Order 3. Procoelia . . .273
Genus Alligator . . -273
Crocodilus . . .273
Gavialis . . . .273
Teeth of Crocodiles . . 274
Order x. Lacertilia . . . 278
Genus Raphiosaurus . . . .278
Coniasaurus . . . .278
Dolicliosaurus . . .278
Mosasaurus . . . .279
Leiodon . . . .279
Saurillus . . . .279
CONTENTS, OR SYSTEMATIC INDEX. xi
Page
Genus Macellodon . . . .279
Order xi. Opkidia . . . 279
Genus Pakeophis . . . .280
Paleryx .... 280
Laopliis . . . .280
Order xii. Ckelonia . . . .281
Genus Tretosternon . . . .281
Pleurosternon . . .281
Chelone . . . .281
Trionyx . . . .282
Emys .... 282
Plateruys . . . .282
Chelydra . . . .282
Testudo .... 283
Colossochelys .... 283
Order Batrackia . . . .283
Palfeoplirynos . . . .283
Eana ..... 284
Andrias ..... 284
Summary on Fossil Eeptiles .... 284
Class iii. Aves . . • .286
Ornitliiclinites . . . .289
Brontozoum . . . .290
Gastornis . . • • .291
Lithornis . . . . .291
Halcyornis . . • • .291
Protornis . • . • .291
Pkoenicopterus . • • .292
Fossil Eggs . . . .292
Fossil Feathers . . . .292
Apteryx ..... 293
Dinornis ..... 294
Palapteryx . . ■ • .294
Aptornis . . . • .294
ISTotornis ..... 294
Epiornis . . • • .294
Didus • • • • .294
Pezophaps . . • • .295
XU
CONTENTS, OK SYSTEMATIC INDEX.
Page
Class iv. Mammalia . . . .295
Composition of Bones . . . . .295
Law of Correlation . . . . .298
Genus Microlestes . . . .301
Dromatkerium . . . 302
Ampliitlierium . . .302
Ampliilestes . . . .303
Phascolotlierium . . .304
Stereognatkus . . .308
Spalacotkerium . . .315
Triconodon . . . .318
Plagiaulax . . . .319
Corypliodon . . . .322
Pliolopkus . . . .325
Lopliiodon . . . .329
Pakeotkerium. . . .330
Anoplotkerium . . . 232
Dickodon . . . .333
Dickobune . . . .336
Xipliodon . . . .337
Microtkerium . . .338
Hyaenodon . . . .339
Ampkicyon . . .340
Gulo .... 340
Didelpkis . . . .340
Balienodon . . . .342
Zipkius .... 342
Zeuglodon . . . .344
Halitkerium . . . .346
Macro tkerium . . .346
Pliopitliecus . . . .350
Dryopitkecus . . -350
Mesopitkecus . . .351
Dino tkerium . . . .352
Mastodon . . . .353
Elepkas . . .360
Hippopotamus . . .364
Rhinoceros . . . .366
CONTENTS, OR SYSTEMATIC INDEX. xiii
Page
Genus Chaeropotamus . . 367
Anthracotherium . . .367
Hyopotamus . . . .367
Sus . . . . . 368
Order Ruminantia . . . .368
Family Bovidae . . . . .370
Genus Bison . . . .370
Bos . . . . . 370
Bubalus . . . .370
Antilope . . . .375
Family Cervidae . . . .371
Genus Dorcatherium . . .371
Cervus Dicranocerus . . .371
Megaceros . . . .372
Cervus Somonensis . . .373
Tarandus . . .374
Martialis . . .375
Americanus . . .375
Strongylocerus Spelseus . . 375
Elaphus - . . 375
Capreolus . . . .376
Order Carnivora . . . .376
Genus Galecynus . , . .376
Felis . . . .376
Law of Correlation illustrated by Feline Structures . 377
Do. do. Bovine Structures . 380
Genus Machairodus . . . .382
Teeth of Carnivora . . . . .383
Genus Ursus . . . .384
Hyaena .... 384
Order Rodentia . . . .385
Family Leporidae . . . .385
Genus Myoxus . . . .385
Sciurus . . . .385
Lagomys .... 386
Trogontherium . . .386
Hystrix . . . .386
Lagostomus . . . .386
xiv CONTENTS, OR SYSTEMATIC INDEX.
Page
Genus Echimys . . . .386
Ctenomys . . . .386
Ctelogenys . . • .386
Geographical Distribution of Pleistocene Mammalia . 387
Europceo- Asiatic . . . . .387
Genus Merycotherium . . .387
Elasmotherium . . .387
Sivatherium . . . .387
Macacus . . . .387
Camelopardalis . . .388
South American . . . . .389
Mylodon . . . .389
Megatherium . . . .390
Megalonyx . . . .391
Scelidotherium . . .391
Giyptodon . . . .392
Toxodon . . . .393
Macrauchenia . . . .393
Protopithecus . . . .393
Australian . . . . . .393
Thylacinus . . . .393
Dasyurus . . . .393
Macropus . . . .394
Diprotodon . . . .394
Nototherium . . . .395
Phascolomys . . . .395
Tliylacoleo . . . .396
Geographical Distribution modified in past time . .397
Extinction of Species . . . . .397
Nestor productus . . . . .399
Alca impcnnis . . . . . .400
Kytina ....... 400
Bubalus (Ovibos) moschatus . . . .401
Antiquity of the Human Species . . .401
Flint Weapons in Stratified Gravel . . .401
Do. in Caves .... 402
Origin of Species . . . . .403
Hypothesis of Buffon . . . . .404
CONTENTS, OR SYSTEMATIC INDEX. XV
Page
Hypothesis of Lamarck ..... 404
of “ Vestiges of Creation” . . . 404
of Mr. Wallace .... 405
of Mr. Darwin .... 405
Summary of Succession and Geological Eelations of Mam¬ malian Orders . . . . .407
Succession of Classes ..... 408
Comparison of Uniformitarian and Progressional Evidences 409
Conclusion . . . . . .411
Cuts 2 to 22 inclusive are from Original Drawings by S. P. Woodward, F.G.S.
1' A LAE ON T 0 L 0 0 Y.
Palaeontology* is the science which treats of the evidences in the earths strata of organic beings, which mainly consist of petrified or fossil remains of plants and animals, belonging, for the most part, to species that are extinct.
The endeavour to interpret such evidences has led to comparisons of the forms and structures of existing plants and animals, which have greatly and rapidly advanced the science of comparative anatomy, especially as applied to the animal kingdom, and more particularly to the hard and enduring parts of the animal frame, such as corals, shells, spines, crusts, scales, scutes, bones, and teeth.
In applying the results of these comparisons to the restora¬ tion of extinct species, physiology has benefited by the study of the relations of structure to function requisite to obtain an idea of the food and habits of such species. It has thus been enriched by the well-defined law of “correlation of structures.”
Zoology has gained an immense accession of subjects through the determination of the nature and affinities of extinct animals, and its best aims have been proportionally advanced. Much further and truer insight has been carried into the natural arrangement and subdivision of the classes of animals since palaeontology expanded our survey of them.
The knowledge of the type or fundamental pattern of certain systems of organs, e.g., the framework of the Verte-
* From Ku'kcurjg, ancient; ovra, beings; Xoyoc, a discourse.
B
PALEONTOLOGY
2
brata and tlie teeth of the Mammalia, has been advanced by the more frequent and closer adherence to such type dis¬ covered in extinct animals, and thus the highest aim of the zoologist has been greatly promoted by palaeontology.
But no collateral science has profited so much by palae¬ ontology as that which teaches the structure and mode of formation of the earth’s crust, with the relative position, time, order, and mode of formation of its constituent stratified and unstratified parts. Geology, indeed, seems to have left her old handmaiden mineralogy, to rest almost wholly upon her young and vigorous offspring, the science of organic remains.
By this science the law of the geographical distribution of animals, as deduced from existing species, is shown to have been in force during periods of time long antecedent to human history, or to any evidence of human existence ; and yet, in relation to the whole known period of life-phenomena upon this planet, to have been a comparatively recent result of geological forces determining the present configuration and position of continents. Hereby palaeontology throws light upon a most interesting branch of geographical science, that, viz., which relates to former configurations of the earth’s sur¬ face, and to other dispositions of land and sea than prevail at the present day.
Finally, palaeontology has yielded the most important facts to the highest range of knowledge to which the human intel¬ lect aspires. It teaches that the globe allotted to man has revolved in its orbit through a period of time so vast, that the mind, in the endeavour to realize it, is strained by an effort like that by which it strives to conceive the space dividing the solar system from the most distant nebulae.
Palaeontology has shown that, from the inconceivably remote period of the deposition of the Cambrian rocks, the earth has been vivified by the sun’s light and heat, has been
PALAEONTOLOGY
o
o
fertilized by refreshing showers, and washed by tidal waves ; that the ocean not only moved in orderly oscillations regu¬ lated, as now, by sun and moon, but was rippled and agitated by winds and storms ; that the atmosphere, besides these movements, was healthily influenced by clouds and vapours, rising, condensing, and falling in ceaseless circulation. With these conditions of life, palaeontology demonstrates that life has been enjoyed during the same countless thousands of years ; and that with life, from the beginning, there has been death. The earliest testimony of the living thing, whether coral, crust, or shell, in the oldest fossiliferous rock, is at the same time proof that it died. At no period does it appear that the gift of life has been monopolized by contemporary individuals through a stagnant sameness of untold time, but it has been handed down from generation to generation, and successively enjoyed by the countless thousands that consti¬ tute the species. Palaeontology further teaches, that not only the individual, but the species perishes ; that as death is balanced by generation, so extinction has been concomitant with the creative power which has continued to provide a succession of species; and furthermore, that, as regards the various forms of life which this planet has supported, there has been “ an advance and progress in the main.” Thus we learn, that the creative force has not deserted the earth during any of the epochs of geological time that have succeeded to the first manifestation of such force ; and that, in respect to no one class of animals, has the operation of creative force been limited to one geological epoch ; and perhaps the most important and significant result of paheontological research lias been the establishment of the axiom of the continuous operation of the ordained becoming of living things.
The present survey of the evidences of organic beings in the earth’s crust commences with the lowest or most
4
PALAEONTOLOGY
simple forms, and embraces chiefly tlxe remains of tlie animal kingdom.
A reference to the subjoined “Table of Strata” (fig. l) will indicate tlie relative position of the geological formations cited. Tlie numerals opposite tlie right band give the approxi¬ mative deptli or vertical thickness of the strata.
Organisms, or living things, are those which possess such an internal cellular or cellulo-vascular structure as can receive fluid matter from without, alter its nature, and add it to the alterative structure. Such fluid matter is called “ nutritive,” and the actions which make it so are called “ assimilation ’ and “ intus-susception.” These actions are classed as “ vital,” because, as long as they are continued, the “ organism” is said “ to live.”
When the organism can also move, when it receives the nutritive matter by a mouth, inhales oxygen and exhales carbonic acid, and developes tissues the proximate principles of which are quaternary compounds of carbon, hydrogen, oxygen, and nitrogen, it is called an “ animal.” When the organism is rooted, has neither mouth nor stomach, exhales oxygen, and has tissues composed of “ cellulose” or of binary or ternary compounds, it is called a “ plant.” But the two divisions of organisms called “plants” and “animals” are specialized members of the great natural group of living things; and there are numerous beings, mostly of minute size and retaining the form of nucleated cells, which manifest the common organic characters, but without the distinctive superadditions of true plants or animals. Such organisms are called “ Protozoa,” and include the sponges or Amorgghozoa, the Foraminifera or Rhizopods, the Polycystincce, the Diatomacqce, Desmidice, Gregarince, and most of the so-called Pulygastria of Ehrenberg, or infusorial animalcules of older authors.
PALEONTOLOGY
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PROTOZOA.
Class I.— AMORPHOZOA.
Fossil sponges take an important place among the organic remains of the former world, not only on account of their great variety of form and structure, hut still more because of the extraordinary abundance of individuals in certain strata. In England they specially characterize the chalk formation, — ■ extensive beds of silicified sponges occur in the upper green¬ sand, and in some beds of the oolite and carboniferous lime¬ stone. In Germany a member of the Oxford oolite is called the “ spongitenkalk,” from its numerous fossils of the present class.
Existing sponges are divided into horny, flinty, and limy, or “ceratose,” “silicious,” and “calcareous,” according to the substance of their hard sustaining parts, which parts are commonly in the shape of fine needles, or spicula, of very varied forms, but in many species of sufficient constancy to characterize such species. The soft organic substance called “ sarcode” appears to be structureless, and is diffluent ; it is uncontractile and impassive, but consists of an aggregate of more or less radiated corpuscles, in some of which the trace of a nucleus may be discerned. The larger orifices on the surface of a sponge are termed “ oscula,” and are those out of which the currents of water flow : these enter by more nume¬ rous and minute “ pores.”
The calcareous sponges abound in the oolitic and creta¬ ceous strata, attaining their maximum of development in the chalk; they are now almost extinct, or are represented by other families with calcareous spicula. The horny sponges appear to be more abundant now than in the ancient seas, but their remains are only recognisable in those instances where they were charged with silicious spicula.
G
PALEONTOLOGY
M. d’Orbigny enumerates 36 genera and 427 species of fossil sponges ; and this is probably only a small proportion of the actual number in museums, as the difficulty of deter¬ mining the limits of the species is very great, and many remain undescribed.
PalcBospongia and A canthospongia occur in the lower Silu¬ rian ; and Stromatopora, with its concentrically laminated masses, attains a large size in the Wenlock limestone. Ste- ganodictyum, Sparsispongici, and species of Scyphia, are found
Arnorphozoa ; Rldzopoda.
1. Siphonia pyriformis, Goldf. ; Greensand , Blackdcnvn.
2. Guettardia Tbiolati, D’Arch. ; U. Chalk, Biarritz.
3. Ventriculites radiatus, Mant. ; U. Chalk, Sussex.
4. Manon osculiferum, Phil. ; U. Cliallc, Yorkshire.
5. Fusulina cylindrica, Fisch. ; Carboniferous, Russia.
6. Flabellina rugosa, D’Orh. ; Chalk, Europe.
7. Lituola nautiloidea, Lam. ; Chalk, Europe.
8. Nummulites nummularia, Brug. ; Eocene, Old World.
9. Orhitoides media, D’Arch. ; U. Chalk, France.
10. Ovulites margaritula, Lam. ; Chalk, Europe.
in the Devonian ; and Bothroconis, Mamillopora, and Tragos, in the Permian or magnesian limestone. Several genera are common to the trias and oolites, and several more are peculiar
AMORPIIOZOA
7
to the latter strata. The Oxfordian sponges belong chiefly to the genera Eudea, Hippalimus. , Cribrispongia, Stellispongia, and Cupulispongia. Their fibrous skeleton appears to have been entirely calcareous, and often very solid; their form is cup-shaped, or manxrnillated, or incrusting, and many have a sieve-like appearance, from the regular distribution of the excurrent orifices ( oscula ) over their surface.
The greensand of Faringdon in Berkshire is a stratum prolific in sponges, chiefly cup-shaped and calcareous, of the genera Scyphia and Chenendopora ; or mammillated, like Cnemidium and Verticillopora. The Kentish rag is full of sponges, which are most apparent on the water-worn sides of fissures. Some beds are so full of silicious spicula as to irritate the hands of the quarrymen working those beds. The green¬ sand of Blackdown is famous for the number and perfect preservation of its pear-shaped Siphonim (fig. 2, i) ; whilst those of Warminster are ornamented with three or more lobes. The latter locality is the richest in England for large cup¬ shaped and branching sponges (Polypothecia), which are all silicified : the long stems of these sponges have been mistaken for bones. The sponges, chiefly ftiphonice, of the upper green¬ sand of Farnham are infiltrated with phosphate of lime, and have been used in agriculture.
The sponges of the chalk belong to several distinct families. Choanites resembles the Siphonict, but is sessile, and exhibits in section, or in weathered specimens, a spiral tube winding round the central cavity. It is the commonest sponge in the Brighton brooch-pebbles. Others are irregularly cup-shaped and calcareous ; and many of the Wiltshire flints have a nucleus of branching sponge ($. cldvcllcitc (). The chalk flints, arranged in regular layers, or built up in columns of “ Bara- moudrae,” all contain traces of sponge structure, and their origin is in some measure connected with the periodic growth of large crops of sponges. Frequently the crust or outer
8
PALAEONTOLOGY
surface only of tlie sponge has been silicified, while the centre has decayed, leaving a botryoida.1 or stalactitic cavity. The cup-sliaped sponges are almost always more or less enveloped with flint, which invests the stem and lines the interior, leaving' the rim exposed. The sponges of the Yorkshire chalk are of a different character : some are elongated and radiciform, others horizontally expanded, but they contain comparatively little silica ; while those belonging to the genus Manon (fig. 2, 4), having prominent “ oscula,” are superficially silici¬ fied, and will bear immersion and cleaning with hydrochloric acid. The largest group of chalk sponges, typified by Ventri¬ culites (fig. 2, 3), have the form of a cup or funnel, slender or expanded, or folded into star-like shape ( Guettardici , fig. 2, 2), with processes from the angles to give them firmer attach¬ ment. Some have a tortuous or labyrinthic outline, and others are branched or compound, like Brachiolites. Curious sections of these may be obtained from specimens enveloped with flint or pyrites. The burro wing-sponge, Ciiona, is com¬ monly found in shells of the tertiaries and chalk. The great cretaceous Exogyrce of the United States are frequently mined by them ; and flint casts of Belemnites and Inocerami are often covered by their ramifying cells and fibres. Thin sec¬ tions of chalk flints, when polished and examined with the microscope, sometimes exhibit minute spherical bodies ( Spini - ferites ) covered with radiating and multicuspid spines. From their close resemblance to the little fresh-water organism
o
Xanthidium, they long bore that name ; but they are certainly marine bodies, and probably the spores of sponges.
Class II.— RHIZOPODA.
%
The organisms of this class are small and for the most part of microscopic minuteness, of a simple gelatinous structure, commonly protected by a shell. The most simple
RHIZOPODA
9
rhizopods, called Amoeba, present a globular form when contracted, but can extend portions of their substance (“ sar- code”) like roots, and use them to draw along the rest of the mass, like the feet or tentacles of polyps, whence the name of the class. These root-like processes can also attach themselves to foreign particles, and draw them into the “ sarcode,” or substance of the body, where the soluble organic part, so “ intus-suscepted,” may be assimilated, the insoluble part being extruded. A solid hyaline corpuscle or nucleus is commonly discernible in the interior of the Amoeba, sometimes accompanied by one or more clear contractile vesicles. 'When the productions of the sarcode are numerous, filiform, and seemingly constant, radiating from all parts of the body, the rliizopod presents the characters of Actinophrys. When the tentacles are produced from only one extremity of the body we have the genus Pamphagus. When such a rhizopod is enclosed in a membranous sac it is a Difflugia ; if the sac be discoid with a slit on the flat surface for the protru¬ sion of the tentacles, it is an Arcella. In other rhizopods the sac is calcified, or becomes a “shell,” which is sometimes simple, but usually consists of an aggregate of chambers, inter-commu¬ nicating by minute apertures, whence the name Foraminifera given to the testaceous rhizopods. These chambers grow by successive gemmation from a primordial segment, sometimes in a straight line, more commonly in a spiral curve ; and each segment so developed has its own shelly envelope. As, how¬ ever, they are organically connected, the whole seems to form a “chambered” or “ polythalamous” shell. The last-formed segment is usually distinguished by the very long, slender, pellucid, colourless, contractile filaments which have suggested the name “ Rhizopods” for the class. But, in the Foraminifera, both the outer wall and the septa of the compound shell are perforated by minute apertures, through which either connect¬ ing or projecting filaments of the soft organic tissue can pass.
10
PALAEONTOLOGY
The several segments or jelly-tilled chambers are essentially repetitions of each other ; and there is no proof that the inner and earlier segments derive their nourishment from the outer and last-formed one. A Foraminifer may therefore be regarded either as a series of individuals, organically united, or as a single aggregate being, compounded according to the law of vegetative repetition.
The minute chambered shells of Foraminifer a enter largely into the composition of all the sedimentary strata, and are so abundant in many common and familiar materials, like the chalk, as to justify the expression of Button, that the very dust had been alive. The deep-sea soundings of the Atlantic Telegraph Company have shown that the bed of that great ocean, at a depth approaching, or even exceeding, two miles, is composed of little else than the calcareous shells of a Globigerina and a few other Rhizopods, with the silicious shields of the allied Polycystinece. The composition of the chalk is extremely similar : when the finer portion, amounting to half or even less, has been washed away, the remaining sediment consists almost entirely of foraminated shells, some perfect, others in various stages of disintegration. They have also been found in other marine formations, which are soft enough to be washed, down to the Lower Silurian ; and in the hard limestones and marbles they can be detected in polished sections, and in thin slices laid on glass. The greater part of these shells are microscopic, but some of the large extinct Foraminifera, called, from resembling a piece of money, “ Nummulites,” are two inches in diameter.
The generic divisions in use for these shells were mostly invented by M. d’Orbigny, but on artificial grounds, viz., exclusively upon the plan of growth, or mode of increase in the number of chambers. The structure and anamorphoses of these complex atoms have been recently investigated by Messrs. Williamson and Carpenter, and especially by Mr.
EHIZOPODA
11
W. K. P arker. The following are the primary groups of Foraminifera in the system of d’Orbigny : —
1. Monostega, — Body consisting of a single segment : shell of
one chamber.
2. Stichostega. — Body composed of segments disposed in a
single line : shell consisting of a linear series of chambers.
3. Hclicostega. — Body consisting of a spiral series of segments :
shell made up of a number of convolutions.
4. Entomostega. — Body consisting of alternate segments spirally
arranged : shell chambers disposed on two alternating axes forming a spiral.
5. Enallostega. — Body composed of alternate segments not
forming a spiral : chambers arranged on two or three axes which do not form a spiral.
G. Agathistega. — Body consisting of segments wound round an axis : chambers arranged in a similar manner, each investing half the entire circumference.
A somewhat different arrangement has been adopted by Scliultze, who divides the Polythalamia into three sections, viz. —
1. Helicoidea, including those forms in which the several
chambers of the shell are arranged in a convolute series, and answering to the last four orders of d’Or¬ bigny.
2. Rliabdoidea, in which they are placed in a direct line
( Stichostega , d’Orb.) ; and
3. Soroidea, where they are disposed in an irregular manner
(. Acervulina ).
Lagena is a genus of Monostega, or single -chambered Foraminifera, with a flask-shaped shell, sometimes pre¬ senting a beautiful fluted exterior. Entosolenia is like a
PALEONTOLOGY
1 9
Lagena, with the tubular neck inverted into the cavity of the shell.
Among the many-chambered Foraminifers the modifica¬ tions of form seem endless. Nodosaria resembles a cylin¬ drical beaded rod : Gristellaria begins by being spiral and afterwards becomes straight : most species are wholly spiral : in some, as Nummulites, the convolutions are on the same plane : in many the spiral turns obliquely round an axis, and gives the shell a trochoid form.
Upwards of six hundred and fifty-seven fossil species, belonging to seventy-three genera, have been described : they commence in the palaeozoic age, increase in number and variety with each successive stratum, and attain their maxi¬ mum in the present seas. Most of the fossil genera, and even some of the species, pass through many formations ; indeed, if correctly observed, the existing forms are the oldest known living organisms. Dentcdina communis, Orbitolites complanatus, Rosalina itcdicci, and Rotcdina globulosa, all living species, are said to be found in the chalk; Rotcdina umbi- licata ranges to the gault ; and Wcbbina rugosa is common to the upper lias, the chalk, and present sea. It has, however, been observed, that fossil Eliizopods, set free by the disinte¬ gration of rocks, are mingled with the recent shells on every beach ; and Mr. M'Andrew has obtained them in this condi¬ tion from great depths of the mid-channel.
The earliest important form is the Fusulina (fig. 2, 5), which forms layers many inches, or even feet, in thickness in the carboniferous limestone of Russia. The recent genera Dentalina and Textidaria are found in the magnesian lime¬ stone ; Nodosaria, Gristellaria, and Rotcdia, in the lias. Fla- bcllina (fig. 2, 6) is peculiar to the chalk ; Orbitoides (fig. 2, 9) to the chalk and tertiary series ; Ovulites (fig. 2, 10) is peculiar to the eocene tertiaries ; Operculina, Orbitolites, and A Iveolina appear first in the tertiary, and are still living. The Lituola
KHIZOPODA
13
(fig. 2, 7) occurs in tlie clialk and chalk flints, and lias been described as a species of “ Spirolinite ” Many of the cretace¬ ous Foraminifera contain a brown colouring matter, which remains after the shell has been dissolved with weak acid, and has been regarded as the remains of the organic substance which once filled all the cells.
The “ calcaire grossier,” which is employed at Paris as a building-stone, contains Foraminifera in such abundance that one may say the capital of France is almost constructed of those minute and complex shells.
But it is in the middle eocene, or “ nummulitic period,” that the Ehizopods attained their greatest size, and played their most important part. Wherever limestones or calcare¬ ous sands of this period are met with, these Foraminifers abound, and literally form strata which in the aggregate become mountain masses. These “ nummulitic limestones” are found in Southern Europe, in Northern Africa, and in India ; they also occur in Jamaica. The commonest form is the Nummulite (fig. 2, s), which occurs in the building-stone of the Great Pyramid. The Nummulites were evidently sedentary organisms ; and, in the large thin species, one side is moulded to the inequalities of the sea-bed on which it grew.
Polycystinece. — The tertiary marls of Barbadoes afforded to Ehrenberg an extensive series of novel and extraordinary microscopic organisms, composed of silica, but foraminated like the shells of the Ehizopods. The same forms, and others similar to them, have been met with in the deep-sea mud of the Gulf of the Erebus and Terror, and more recently in the mud of the North Atlantic soundings. They are quite dis¬ tinct in form and character from most of the silicious-shielded Diatomacea% but some of them resemble the Coscinodiscus and Adinocydus. No less than 282 forms, grouped in 44 provi¬ sional genera, have been described.
PALAEONTOLOGY
u
Class III.— INFUSORIA.
( Pulygastria , Ehrenberg.)
Numerous genera and multitudes of so-called species of free and locomotive microscopic organisms, which, because they do not present the distinctive characters of plants or animals, have been by turns referred to one or other kingdom, possess shells of flint, and consequently enter largely into the domain of fossil evidences of former life. The silicious shells of these infusory organisms present under the microscope the most definite as well as beautiful characters of form and sculpture, which are as recognisable and distinctive as those of the calcareous shells of Mollusca. The plates of the incom¬ parable works and memoirs of Ehrenberg abound with exact figures of the delicate sheaths, shells, and shields of' the lori- cated Infusoria of past and present seras of life, the deposits of which, by reason of their pure, flinty, atomic constitution, were known in the arts long before science had detected their nature and vital origin. In 1836 portions of the stone called “ tripoli ” or “ polierscliiefer ” (polisliing-slate of lapidaries) were microscopically examined by Ehrenberg, who discovered it to be wholly composed of the silicious shells of Infusoria, and chiefly of an extinct species called Gaillonclla distans. At Bilin, in Bohemia, there is a single stratum of polierschiefer, not less than fourteen feet thick, forming the upper layer of a hill, in every cubic inch of which there are forty-one thousand millions of the above-named organic unit. This mineral like¬ wise contains shells of Ncwicula, Bacillaria, Actinocjclus, and other silicious organisms. The lower part of the stratum con¬ sists of the shells compacted together without any visible cement ; in the upper masses the shells are cemented together, and filled by amorphous silicious matter formed out of dissolved shells. At Egea, in Bohemia, there is a stratum of two miles
INFUSORIA
15
in length, and averaging twenty-eight feet in thickness, of which the uppermost ten feet are composed wholly of the silicious shells of Infusoria, including the beautiful Campylo- discus ; the remaining eighteen feet consist of the shells mixed with a pulverulent substance. Corresponding deposits of the silicious cases of Infusoria have since been discovered in many other parts of the world, some including fresh-water species, others marine species of Infusoria.
The conditions of such depositions will be readily under¬ stood by examining the sedimentary deposits of bogs and of stagnant or slow-flowing sheets of water. In warm latitudes and seasons, such water swarms with infusorial life, and the indestructible cases of the loricated kinds are found in great quantities in the sedimentary deposits. Beneath peat bogs they have been found to form strata of many feet in thickness, and co-extensive with the turbary, forming a silicious marl of pure whiteness. A quantity of pulverulent matter is deposited upon the shores of the lake near Uranea, in Sweden, which, from its extreme fineness, resembles flour : this has long been known to the poorer inhabitants under the name of “ berg- mehl,” or mountain-meal, and is used by them, mixed up with flour, as an article of food. It consists in great part of silicious shells of Infusoria, with a little organic matter. With regard to the source of fossil infusorial remains in sea-water, the fol¬ lowing evidence is given in the United States Coast Survey, 1856 : —
Soundings of the gulf-stream near Key Siscayne, Florida, varying in depths from 1 17 fathoms to 205 fathoms, give a light greenish-grey mud composed chiefly of Foraminifers, Diatoms, Polycystins, and Geolites, in a profusion only sur¬ passed by the fossil polycystinous strata of Barbadoes. The Foraminifers compose the largest part of these muds, including Textularia Americana, Marginida Bachei, and other forms, particularly many species of the Phcatilia of Fhrenberg,
PALEONTOLOGY
1G
which liad been supposed to live only in shallower haunts. The silicious shells of Diatoms abound in the residue, after the calcareous Foraminifers have been dissolved by acid. I he inorganic portion of the soundings is chiefly quartz sand, and its proportion is quite small.
Such manifestations of life, with its mineral results, have been detected from the earliest sedimentary deposits to the present time ; but as regards the Infusoria, they are given on the grandest scale in formations of the tertiary age. The town of Richmond, in Virginia, Lnited States, is built on barren silicious strata of marine origin and tertiary age. The strata are twenty feet in thickness, composed chiefly of infu¬ sorial flint-shells, including the well-known and beautiful microscopic objects, Actinocyclus and Coscinodiscus.
Most of the infusorial formations, as the polishing-slates at Cassel, Planitz, and Bilin, are astounding monuments of the operation of microscopic organisms at former periods of the history of this planet. The minute size, elementary struc¬ ture, tenacity of life, and marvellous reproductive power of the Infusoria have enabled them to survive as species those destroying causes which have exterminated contemporaneous higher forms of organism. Species of Bacillaria still exist which were in being at the period of the deposition of the chalk. Existing species of Diatomacecc have been detected as low down as the oolite. The discovery by Ehrenberg of more than twenty species of silicious-slielled Infusoria, fossil, in the chalk and chalk-marls, which are identical in species with some now living in the bed of the Baltic, is an instructive addition to the obscure history of the introduction of species of living things in this planet, and must add greatly to the interest of the infusorial class in the eyes of the geo¬ logist and philosopher. “For these organisms,” writes Ehren¬ berg, “ constitute a chain which, though in the individual link it be microscopic, yet in the mass is a mighty one, connecting
INVERTEBRATA
17
the life-phenomena of distant ages of the earth, and proving that the dawn of the organic nature co-existent with us reaches further back in the history of the earth than had hitherto been suspected.” “The microscopic organisms are very in¬ ferior in individual energy to lions and elephants, but in their united influences they are far more important than all these animals.” If it be ever permitted to man to penetrate the mystery which enshrouds the origin of organic force in the wide-spread mud-beds of fresh and salt waters, it will be, most probably, by experiment and observation on the atoms which manifest the simplest conditions of life.
ANIMALIA.
INVERTEBRATA.
Remains of invertebrate animals occur in strata of every age, from the partially metamorphic and crystalline rocks of the Cambrian system to the deposits formed by the floods of last winter and the tides of yesterday. They are found in every country, from the highest latitude attained by Arctic voyagers to the extremities of the southern continents, and at the greatest elevation hitherto climbed in the Andes or Hima¬ laya. If some classes — -e. g., Tunicata, A calepha; — seem not to be represented in stratified deposits, they are such as, either from the soluble or perishable tissues composing the entire frame, could not be expected to be fossilized under any con¬ ceivable circumstances ; or from the same cause, are only not so recognisable at one of their metagenetic phases. Evidence of compound Hydrozoa — i. e., of the polypes which Ellis called “Corallines” — and especially of the genus Campanularia, would show that the acalephal type and grade of organization had been manifested at the period of the formation of the strata containing such fossil Polypi. With the above seeming
C
18
PALAEONTOLOGY
exceptions, every class of invertebrate animal is represented, by fossil remains.
They consist of corals and shells, of the petrified skeletons of star-fishes and sea-urchins, of the hard coverings of crabs and insects, of the tracks and shelly habitations of worms, and of impressions of surfaces, and casts of cavities, of organisms, retained by the matrix after the animals had perished.
The condition in which invertebrate fossils occur depends on the nature of the matrix and other accidental circum¬ stances ; for while some are scarcely altered in composition, or even in colour, others are silicified or infiltrated with car¬ bonate of lime. Some may be cleared by the action of acid or exposure to the weather, and some require the chisel of the mason or the mill of the lapidary for the proper exhibition of their structure.
Multitudes of recent species are fossilized in the newer tertiaries whose history can be made out perfectly from living specimens ; but the number of these diminishes gradually in each older stratum, while the proportion of extinct forms is ever on the increase. No living species more highly organized than a Rhizopod is found in the secondary rocks. Recent genera extend further back in time ; indeed a few may be recognised in strata of palaeozoic age, shedding a light on the probable affinities and conditions of their associates. Many of the smaller groups of genera, called families, disappear in the secondary, and still more in the palaeozoic period, and are to a limited extent replaced by groups which no longer exist. But as to the larger groups of Protozoa and of true inverte¬ brate animals, it may be affirmed that every known fossil belongs to some one or other of the existing classes, and that the organic remains of the most ancient fossiliferous strata do not indicate or suggest that any earlier and different class of beings remains to be discovered, or lias been irretrievably lost, in the universal metamorphism of the oldest rocks.
POLYPI
19
Province I.— KADIATA *
Sub-Province POLYPI.
A polype is a small soft-bodied aquatic animal which generally presents a cylindrical oval or oblong body, with an aperture at one of its extremities surrounded by a crown of radiating filaments or “ tentacles.” This aperture leads to the digestive cavity, which, in most Polypes, is without intes¬ tine or vent. A very large proportion of these animals has organs of support, called “polyparies” or corals, of various form and substance, but for the most part consisting of car¬ bonate of lime ; and, as a general rule, locomotion is lost with the development of the polypary, which usually attaches the polype to some foreign body. The organization of the soft tissues is in general simple ; the faculties of the Polypes are very limited ; and the vital phenomena, save those of irrita¬ bility and contractility, are inconspicuous. Nevertheless, the influence of the combined powers of some of the species, in adding to and modifying the crust of the earth, is neither slight nor of limited extent.
Class I.— HYDROZOA.
Char. — Polypary, when present, flexible, external ; for the most part developing cells for the polypes according to regular patterns.
Family I. — GRAPTOLnmyE.
To this class may probably belong the organic remains called “ Graptolites,” which are exclusively and characteris¬ tically Silurian fossils. A certain knowledge of their affinities
jr0r the characteristic organization of the provinces, classes, orders, and families of Invertebrate e, reference may he made to the writer’s “ Lectures on Invertebrata,” 8vo, Longmans, 1855.
20
PALEONTOLOGY
would require examination of tlie soft parts ; and tlie family lias long been extinct. Indications of tlie flexible consistency of the polypary, and M. Barrande’s statement of the existence of a cylindrical canal in its axis, which he conjectures to have contained the common connecting tissue of the polypes, have weighed with the writer in placing the Cfraptolites provision¬ ally in the present class of Polypi. The axis of the polypary is sometimes straight (fig. 3, 3), sometimes spiral (fig. 3, 6). The ordinary form, as given by the Graptolites prioclon (fig. 3, 3),
Fig. 3.
Hijdrozoa; Anthozoa; Bryozoa.
1. Proto virgularia dichotoma, M'C.; Silurian, Dumfries.
2. Oldhamia antiqua, Forbes; Cambrian, Wicklow.
3. Graptolites priodon, Brun. ; Silurian, Britain.
4. Didymograpsus Murchisoni, Beck ; L. Silurian, Wales.
5. Diplograpsus folium, His. ; L. Silurian, Britain.
6. Rastrites peregrinus, Barr; Silurian, Bohemia.
7. Ccenites juniperinus, Eichw. ; U. Silurian, Dudley.
8. Ptilodictya lanceolata, Lonsd. ; U. Silurian, Tortworth.
9. Archimedipora Archimedea, Lesuer. ; Carboniferous, Kentucky.
10. Ptilopora pluma, M'C. ; Carboniferous, Ireland.
1 1. Fenestrella membranacea, Ph. ; Carboniferous, Britain.
is serrated on one side only, and is found abundantly in the Cambrian or older Silurian beds of Scotland and Wales ; it occurs also in the Ludlow rocks. The double Graptolites
ANTHOZOA
21
( Diplograpsus, , fig. 3, 5, and Lidymograpsus, fig. 3, 4) are Cam¬ brian forms. Rastrites (fig. 3, 6) bad the polypes only in one side, and they are less crowded : it characterises Barrande’s divi¬ sion E of the Lower Silurian beds of Bohemia, and has not yet been found in Britain. The Graptolites occur in argillaceous strata, especially in the mud-stones of Wales and Cumberland, and in the alum-slates of Sweden. These beds remind one of the mud bottoms in which the Virgularia and other long and slender graptolite forms of “ Pennatulidse” flourish in forest¬ like crowds. The primeval Graptolite may have presented a more generalized polype structure than is now met with in the specially differentiated Sertularians and sea-pens.
Class II.— ANTHOZOA.
In this class of Polypes the tentacles are hollow, and, in most, with pectinated margins. The polypary is usually in¬ ternal, and forms the bodies more properly called “corals and “ madrepores.”
Asteroida. — Great doubt attaches to some of the fossils referred to this class of Polypi. The terms “ Gorgonia” and “ Alcyonium” have been applied to objects not well under¬ stood, and usually proving to be Bryozoa and sponges. The Lower Silurian fossil called Pyritonema consists of a fasciculus of silicious fibres, and has been supposed to be related to the glass zoophyte ( Hyalonema ). The miocene deposits ol Pied¬ mont contain a species of the Mediterranean genus Gorallium, an Antipathes, and an Isis (or Isisina, d’Orb.), which is also found in Malta. The London clay contains one coral ( Graphic land), referred to the Pennatulidoe , and two Gorgonidce (. Mop- sea and Websteria).
Actinoida. — The lamelliferous or stony corals are (next to the Testacea) the largest and most important class ol invertebrate fossils. They attained a great development in
22
PALAEONTOLOGY
the earliest seas, and were perhaps more widely diffused and individually abundant in the Silurian age than at any subse¬ quent period. “ Reef-building ” corals are now confined to warm seas, and are wanting even on great tracts of tropical coast. The Oculina is the only large coral now found in the north. But in palaeozoic times the representatives of the modern Astraeas and Caryopliyllias extended as far northward as Arctic voyagers have penetrated ; and at a much later period they formed reefs of considerable thickness and extent in the area of the coralline oolite. The Silurian limestone of Wenlock Edge is itself a coral reef thirty miles in length ; and the Plymouth limestone and carboniferous limestone have frequently the aspect of coral-banks skirting the older regions of Cambrian slate and Devonian “ killas.” The structure of coral-banks may be studied in the lofty limestone cliffs of Cheddar, and in the wave-worn shores of Lough Erne, as well as in the uplieaved coral islands of the southern seas. In the fields about Steeple-Ashton, every stone turned up by the plough is a coral ; and our inland quarries and chalk-pits afford to the palaeontologist materials for the study of a class almost wholly wanting on the present sea-shores of Europe. The history of the British fossil corals, as given by Milne Edwards and I [' time in the “ Monographs of the Palseonto- graphical Society,” exhibits, equally with that of the fossil shells by other authors, a transition from a state very different from that which now subsists in our part of the world, and a gradual approximation to the present order of things.
In the palaeozoic strata the corals belong chiefly to two extinct orders \ those of the secondary period more resemble living corals of warmer climates than ours ; and the few ter¬ tiary genera and species resemble those of Southern Europe and our own coast.
I he distinction between one large group of the palaeozoic Actinoida {Cycttliopliyllidcd} and more modern corals consists
ANTHOZOA
23
in tlie quadripartite character of their plaited cups or stars, whereas the lamellae (or septa)) of the other families are deve¬ loped in multiples of G. A remarkable exception exists in the Holocystis (fig. 5, 8), an Astrea-like coral with quadripartite stars, which is found in the lower greensand. The old-rock corals are also remarkable for the manner in which they are partitioned off by horizontal “ tabulae” (fig. 1, 3), like the septa of the Nautilus and Spondylus. This character obtains not
Palaeozoic Corals ( Anthozua ).
1. Amplexus Sowerbyi, Pli. ; Carboniferous , Ireland.
2. Cyathophyllum turbinatum, Lin. ; U. Silurian , \\ enlock.
3. Cyathophyllum subturbinatum (section); U. Silurian, Wenlock.
4. Cystipliyllum Siluriense, Lonsd. ; U. Silurian, Wenlock.
5. Zaphrentis Phillipsi, M. Edw. ; Carboniferous, Someisot.
6. Lithodendron irregulare, Ph. ; Carboniferous, Europe.
7. Lithostrotion striatum, Plcm. ; Carboniferous, Europe.
8. Acervularia luxurians, Eicb. ; U. Silurian, Europe.
9. 1-Ieliolites interstincta, Wahl. ; U. Silurian, Europe.
10. Syringopora ramulosa, Goldf. ; Carboniferous , Euiope.
1 1. Halysites catenulatus, L. ; Silurian, Northern Regions.
12. Favosites Gothlandica, Lam. ; Silurian, North.
only in the Cycitliopliyllidce, but also in the Millcporidcc, Favo- sitidce, and other palaeozoic families. Of the 129 Silurian corals, 121 belong to the tabulated divisions.
24
PALiEONTOLOGY
The Devonian system contains about 150 described corals, the carboniferous limestone 76, and the magnesian limestone only 5 or 6. The commonest forms of simple, turbinated corals, are Gyatliophyllum (fig. 4, z and 3), which exhibits four slight fossulce in its cup, and is often supported by root-like processes. I11 Zaphrentis (fig. 4, 5) there is but one deep fossula. Amplexus (fig. 4, 1) is a characteristic carboniferous fossil, nearly cylindrical, and often so straight and regular in its growth as to have been originally described as a chambered shell. The radiating septa are very slight, and the horizontal partitions simple, flat, and almost as regular as the septa of the Orthoceras. In the Silurian Cystipliyllum (fig. 4, 4) the lamellae are also evanescent ; but the tabulce are represented by numerous vesicular plates. The corals of these genera are not always solitary, or merely in groups ; some species of Gyatliophyllum, constantly form compound masses, with cups rendered polygonal by contact, like G. regium of the Bristol limestone. The allied genus Accrvularia (fig. 4, 8) resembles an Astrcca, and exhibits, in a remarkable manner, the multi¬ plication of its corallites by calicular gemmation. The genus Lithostrotion (fig. 4, 7) of the carboniferous limestone is also compact and astraeiform, but the new corallites are produced by lateral gemmation. Corals, with the same structure, but not compact, are known by the name Lithodendron (fig. 4, 6). The “ chain-coral” Halysites (fig. 4, n) and Syringopora (fig. 4, 10) resemble, at first sight, the recent asteroid Tubiporidce : in Halysites the radiating septa are quite rudimentary ; and in Syringopora the tabulae are funnel-shaped, forming a central axis to each tube. The Favositidce (fig. 4, 12) are mostly very regular both as to their polygonal shape and transverse tabulae ; the cells of adjacent corallites are connected by pores, either in the sides or angles of the walls ; the septa are rudimentary. In the genus Ghcetetes the tubes are always slender, and much elongated, and their walls imperforate. Michelinia resembles
ANTHOZOA
25
the fruit of the Ndumbium ; it has vesicular tabulae and root-like processes to its basal plate, ffeliolites (fig. 4, 9), of which many species are found in the Silurian and Devonian limestones, is related to the recent Milleporce. The radiating septa are distinct, and the tabulae regular ; the interspaces between the stars are filled up with fine and regular tubes. One genus of Fungidce ( Palceocyclus ) occurs in the Upper Silurian.
Fig. 5.
Secondary and Tertiary Corals ( Anthozoa ).
I. Turbinolia sulcata, Lam. ; M. Eocene , Europe. z. Diploctenium lunatum, Brug. ; Chalk, France.
3. Micrabacia coronula, Goldf. ; U. Greensand, Europe.
4. Aspidiscus cristatus, Lam. ; Cretaceous (?), Algeria. '
5. Cyclolites elliptica, Lam. ; L Chalk, France.
6. Parasmilia centralis, Mant. ; U. Chalk, England.
7. Pachygyra labyrinthica, Mich. ; L. Chalk, France.
8. Holocystis elegans, Lonsd. ; L. Greensand, Isle of Wight.
9. Montlivaltia caryophyllata, Lam. ; Great Oolite, France.
10. Stylina Ue la Bechei, M. Edw. ; Corallian, Ailts.
II. Thecosmilia annularis, Flem. ; Corallian, A ilts.
The British secondary corals are not very numerous ; for although specimens abound in the coral-rag districts, only fourteen species are found in that formation. Altogethei, sixty-five species are found in the English oolites, and twenty-
20
PALEONTOLOGY
two in the chalk and greensands. These are mostly Astrceidcc, or related to Fungia. Three common forms in the oolites are Montlivaltia (fig. 5, 9), Stylina (fig. 5, 10) and Thecosmilia (fig. 5, 11). The English cretaceous strata afford the Holocystis (fig. 5, 8), which is the most recent coral with quadripartite septa ; Trochocyathus and Parasmilici (fig. 5, 6 ), resembling the recent Gyathina ; and the little “Fungia” coronula (fig. 5, 3), described in two genera of distinct orders (Micrabacia and Stephanophyllia) in the “ Monographs of the Pakeonto- graphical Society.” The lower chalk of France and Germany contains many other corals, especially Cyclolites (fig. 5, 5), P achy gym (fig. 5, 7), and Diplodenium (fig. 5, 2). The Aspi- discus (fig. 5, 4) was sent by Dr. Shaw from Algeria.
The English eocene strata contain twenty-five corals, all extinct, and belonging to fifteen genera. These include an Astrcea ( Litharcea Websteri ), which grows on the water-worn flint pebbles ; a Balanophyllia, similar to the existing coral ; a Dendrophyllia , which is the oldest member of the genus ; an Oculina ; and eight species of the genus Turbinolia (fig. 5, 1). The corals of the English pliocene are mostly Bryozoa ; only four true corals have been found in the coralline crag belong¬ ing to the genera Sphenotrochus, Flabellum, Gryptangia, and Balanophyllia, all reputed extinct, although the first is very closely related to the living Sphenotrochus Macandrewi.
The total number of fossil corals enumerated by M. d’Orbigny in the “Prodrome de Paleontologie,” amounts to 1135, grouped under 216 genera. But notwithstanding all the labour which has been bestowed on this branch of palaeonto¬ logy by Goldfuss, Miclielin, Lonsdale, and Milne Edwards, species are continually discovered or brought home from abroad which are altogether new, and cannot be placed in any of the constituted genera.
BllYOZOA.
27
Class III.— BRYOZOA.
Char. — Tentacles of t-lie polype hollow, with ciliated margins ; alimentary canal with stomach, intestine, and anus ; polypary, when present, external, horny, and calcareous.
The metamorphoses which the Bryozoct undergo are like those of the lower Polypi ; the embryo developed from the ovum is an oval, discoid, or subdepressed body, with a general or partial ciliated surface, by which it enjoys a brief locomo¬ tive life after its liberation from the parent. The Bryozoa are allied to the compound Ascidia ; but not one of the ascidian Molluscoids quits the ovum as a gemmule swimming by means of cilia ; and no Bryozoon quits the ovum in the guise of a Cercarian or tadpole, to swim abroad by the alternate inflexions of a caudal appendage. In a progressive and con¬ tinuous series of teachings, by pen or word of mouth, the place of an osculent or transitional group is governed by convenience, by considerations of how best to teach by com¬ parison and easy gradation. The real merits of the man who would make scientific capital by changing the position of such group, and by imputing error or ignorance to the author from whom he may differ in this respect, are easily weighed and soon understood.
The Bryozoa, whether regarded as the highest organized Polypes, or as the lowest organized Mollusca, or as an inter¬ mediate type, are treated of in systematic palaeontology in the position here assigned to them. The practical palaeontologist finds himself compelled to arrange and study the fossil Bryozoa along with the corals, if only on account of the diffi¬ culty he, in many cases, experiences of determining to which class of Polypi his specimens belong. M. d’Orbigny, who has devoted much attention to this class, enumerates 514 fossil species, distributed in 73 genera. This number must be \ eiy
28
PALAEONTOLOGY
far below tlie real one, since the Bryozoa of the chalk, which alone have been carefully examined, amount to 213 species ; while only two species are known from the trias, none at all from the lias, and only five from the upper oolites, so rich in corals and sponges. In the “ Cours Elementaire” of d’Orbigny the fossil Bryozoa are stated to amount to 1676.
Of the 19 or 20 palseozoic genera, none extend into the secondary strata ; but of the 18 oolitic genera, Entalophora and Defrancia range onwards to the tertiaries ; and Alecto, I'dvienea, and Eschara still survive. The oldest known fossil, Oldhamia (fig. 3, 2), is supposed to be a Bryozoon. The most common palaeozoic form is Fenestrella (fig. 3, n), resembling the recent “ lace-coral”; there are 35 species, ranging from the Lower Silurian to the Permian. One of its modifications re¬ sembles a feather (Ptilopora, fig. 3, 10), and is found in the carboniferous limestone. Another, more remarkable, has a spiral axis ( Archimedipora , fig. 3, 9), and occurs in the same formation in Kentucky. One of the oldest genera is Ptilo- dictya (fig. 3, 8), of which seven species are found in the Lower Silurian formations. The slabs of Silurian limestone obtained at Dudley are covered with myriads of small and delicate fossils, including many Bryozoa. Some of these are spread like a film over other fossils, and have been doubtfully re¬ ferred to the modern genera Discopora and Berenicea ; others, with slender branches, and erect or creeping, are called Mille- poras, Heteroporas, and Escharinas. The genus Ccenites (fig. 3, 7), perhaps belongs here. The magnesian limestone con¬ tains several large “ lace-corals” of the genera Fenestrella, Synocladia, and Phyllophora ; and two branching species of Thamniscus and Acanthocladia. The oolites afford many small incrusting species related to Diastopora, and branching forms like Terebellaria and Ghrysaora. In the chalk, the Escharas are most numerous, and Lunulites and Cupularia first appear. Some thin beds of the lower chalk are almost composed of
ECHINODERMATA
29
Bryozoa, mingled with Foraminifera. The coralline crag of Suffolk takes its name from the great abundance of Bryozoa it contains, among which Eschara, Cellepora, Fascicularia, Theo- noa, Hornera, Idmonea, Flustra, and Tubulipora are the most important.
Class IV.— ECHINODERMATA.
(Star-Fishes, Sea- Urchins.')
Char. — Marine ; commonly free, repent animals, with the integument in most perforated by erectile tubular ten¬ tacles, hardened by a reticulate deposit of calcareous salts, and in many armed with spines.
The fossil Eadiata present a mine of comparatively unex¬ hausted riches to the palaeontologist. More difficult of study than shells, and less uniformly present in all strata, the enduring remains of echinoderms and corals are unsurpassed in beauty of form and structure, and in the value of the evi¬ dence they afford.
The present summary of the extinct forms of Echinoder- nata will commence with
Order 1. — Crinoidea.
Char. — Body with ramified rays, supported temporarily or permanently on a jointed calcareous stem ; alimentary canal, with mouth and vent, both, as in Bryozoa, approximated.
The “ stone-lilies,” or crinoid star-fishes, formed a nume¬ rous and important group in the palaeozoic seas, where they obtained their maximum number and variety. M. dOrbigny describes thirty-one palaeozoic genera, two triassic, ten oolitic, and four cretaceous— of which latter three (. Pentacrinus , Bour- gueticrinus and Comahda) are found in the tertiaries and mo-
30
PALAEONTOLOGY
deni seas. The Crinoidea differ from the other echinoderms in haying the generative organs combined with the arms, and opening into special orifices near their base. ISTearly all the
Fig. 6.
Crinoidea ; Blastoidea ; Cystoidea.
1. Sphseronites aurantium, Wahl.; L. Silurian, Sweden.
2. Pseudocrinus bifasciatus, Pearce; U. Silurian, Dudley.
3. Pentremites florealis, Say; Carboniferous, Ohio.
4- Crotalocrinus rugosus, Mill. ; U. Silurian, Dudley.
5. Poteriocrinus (joint of column) ; Carboniferous, Yorkshire.
6. Encrinus entrocha ; L. Muschelkalk, Germany.
7. Apiocrinus Tarkinsoni, Mill. ; Bradford Clay.
8. Pentacrinus basaltiformis, Mill. ; Lias, Lyme.
9. Marsupites ornatus, Mill. ; Chalk, Sussex.
genera, except Comatula and Marsupites (fig. 6, 9), appear to have been attached either by the expanded base of the column, as in Apiocrinus , or by jointed processes, as in Bourgueticrinus. In many instances the lower part of the column throws out innumerable root-like side-arms, which strengthen and support it. The column is comparatively short in Apiocrinus Parkin- soni, and extremely elongated in Pentacrinus Hiemeri. It is round in nearly all the palaeozoic Crinoids ; and when five¬ sided, the articular surfaces of the joints are simply radiated, as in the rest. These joints are perforated in the centre, and
ECHINODERMATA
31
when detached, are the “ St. Cutlibert’s beads” of story (fig. 6, s)* In Platycrinm the stem is compressed, and the arti¬ cular surfaces are elliptical. In the genus Pentacrinus, which commences in the lias, the sculpturing of the articulations is more complex (fig. 6, 8), but it is quite simple in the other modern genera. The body of the Crinoid is composed of poly¬ gonal plates forming a cup, which is covered by a canopy of smaller plates. The mouth is often proboscidiform ; the anal orifice is near it. The five arms which crown the cup are sometimes nearly simple, but feathered with slender, jointed fingers ; in other genera they divide again and again, dichoto- mously ; and in two remarkable Silurian forms, Anthocrinus and Crotalocrinus (fig. C, 4), these subdivisions are extremely numerous, and the successive ossicles are articulated to each other laterally, forming web-like expansions, similar in appear¬ ance to the coral Fenestrella (fig. 3, n). Other remarkable Silurian Crinoids belong to the genera Glyptocrinus, Eucalyp- tocrinus, Geocrinus (the “ Dudley Encrinite”) and Garyocrinus. Several are common to the Silurian and Devonian, as Me- locrinus, Cycithocrinus, and Rliodocrinus ; the two last, and Poteriocrinus, extend into the carboniferous formations. Gu- pressocrinus and some others are peculiarly Devonian ; Platy- crinus, common to Devonian and coal formations ; and many genera (including the “ nave Encrinite” — Actinocrinus, Gil- bertsocrinus, and Woodocrinus ), are proper to the carboniferous limestone. The famous “ lily Encrinite” ( Encrinus entrocha, fig. 6, 6) is characteristic of the middle trias, or “ muschel- kalk ;” the “ clove Encrinite” ( Eugeniacrinus , fig. 7, 9) abounds in the Oxfordian oolites of Germany ; Apiocrinus, Milleri- crinus, and several forms related to GomcUula — e.y., Pterocoma and Saccosoma — are also peculiarly oolitic. The “ tortoise
* Casts, in chert, of the canal which passes down the crinoidal column are called “ screw stones and those limestones which abound in columns and detached joints are called “ entrochal marbles.
32
PALAEONTOLOGY
Encrinite” ( Mccrsupites , fig. 6, 9), is found only in tlie chalk, along with Bourgueticrinus (fig. 7, 10) and the bodies of Co- matulce, which, when they have lost their arms and claspers, are called “ Glenotremites.” (Fig. 7, 7, — upper surface with sockets of the five arms ; 8, — under surface, showing articula¬ tions of claspers, and the scar of the larval stem.)
Order 2. — Cystoidea.
This order was established by Yon Buch for a small group of palaeozoic echinoderms formerly included with the Cri- noiclcoe. They have a globular body covered with close-fitting polygonal plates attached by a simple jointed stem. The mouth is minute, and opposite to the stalk ; close to it is the small anal opening ; and a little more distant the generative orifice, covered by a pyramid of five or six little valves. Some of the genera, like Pseudocrimes (fig. 6, 2), have two or four tentaculiferous arms, bent down over the body and lodged in grooves, to which they are anchylosecl. Others, like the Bphceronites (fig. 6, 1), have only obscure indications of ten¬ tacles situated close to the mouth. In Pseudocrinus and some other genera two or three pairs of lamellated organs, called pectinated rhombs, are placed on the contiguous margins of certain body-plates. They are supposed not to penetrate the interior, and no office has been conjecturally assigned to them ; but Professor Forbes suggested that they might represent the “ epaulettes” of the larval Echinidce, to which group he sup¬ posed the Cystidean bore the same relation as the Crinoids hold to the star-fishes. There are nine genera, of which eight are found in the British strata — four in the upper and four in the lower Silurian.
ASTEROIDEA
S3
Order 3. — Blastoidea.
A separate order has been proposed for another small group of palaeozoic iossils typified by Pentremites (fig. 6, 3^. The body is globular or elliptical, and supported on a small, jointed stalk, with radiated articular surfaces and irregular side-arms. It is composed of solid polygonal plates, with a minute 01 al oiifice at the summit surrounded by five other openings, four of which are double and ovarian, the fifth rather larger and anal. There are five petaloid ambulacra of variable length, converging to the mouth, furrowed down the centre, and striated across. According to the observations of Dr. Ferdinand Roemer, these supported numerous slender, jointed tentacula, indicated by the rows of marginal pores. One spe¬ cies is found in the upper Silurian, six in the Devonian, and twenty-four in the Carboniferous, which has received the name of “pentremite limestone” in the United States, on account of the abundance of these fossils it contains.
Order 4. — Asteroidea.
( Sea-Stars , Brittle Stars.)
Char. — Body radiate ; integument hardened by calcareous pieces, and more or less armed with spines ; no dental apparatus.
Asteriadce and Ophiuridce.— Fossil star-fislies, though less common, have a wider range than their allies the fossil urchins, being found amongst the earliest organic forms. Palceaster, Protaster (fig. 7, 6), and Lepidaster (fig. 7, 5), are Silurian star¬ fishes, presenting many anomalies, and scarcely referable to any existing families. Tropidaster, Pleuraster, Aspidura, Oplri- urella, and Amphiura are oolitic genera ; Ophioderma, Luidia, Astropccten range from the lias to the present seas ; Stellaster
b
PALAEONTOLOGY
o f
and Arthraster are peculiar to the cretaceous ; and Ophiura,
Fig. 7.
Galeritidce ; Asteriadce ; Crinoidea.
1 . Pygaster semisulcatus, Ph. ; Inf. Oolite, Cheltenham.
2. Ananchytes ovatus, Lam. ; U. Chalk, Europe.
3. Galerites albogalerus, Lam. ; U. Chalk, Kent.
4. Scutella subrotunda ; Miocene, Malta.
5. Lepidaster Grayi, Forbes; U. Silurian, Dudley.
6. Protaster Miltoni, Salter ; L. Ludlow rock, Salop.
7. Comatula (Glenotremites), upper surface of body.
8. Comatula (lower surface) ; Chalk, Sussex.
9. Eugeniacrinus quinquedactylus, Sclil. ; Oxfordian, Wurtemberg.
10. Bourgueticrinus ellipticus, Mill. ; Chalk, Kent.
Astrogonium, Greasier, and Goniodiscus are both cretaceous and living.
Order 5. — Echinoidea.
(Sea- Urchins.)
Char. — Body spheroid or discoid, incased in a crust of in¬ flexibly-joined calcareous plates, and armed with spines ; dental system complex, arranged so as to resemble a “ lantern.”
The Echinoidea appear first in the carboniferous limestone and attain their maximum in the cretaceous strata. In all
ECHINOIDEA
35
secondary and more modern Echinidce, tlie shell is composed of five double rows of ambulacral plates, and five inter-ambu- lacral ; bnt in the Palcechinus (fig. 8, i) of the carboniferous limestone there are six rows of inter-ambulacral plates, and in Perischodomus five. Only detached plates of A rchmocidaris
Fig. 8.
Echinidoe; Spatangidce.
1. Palaschinus sph serious, Scouler ; Carboniferous, Ireland.
2. Archseocidaris Urii, Flern. ; Carboniferous, Ireland.
3. Cidaris glandifera, Goldf. (spine); Jura, Mount Carmel.
4. Hemicidaris intermedia, Flem. ; Corallian, Caine.
5. Salenia petalifera, Desm. ; U. Greensand, Wilts.
6. Disaster ringens, Ag. ; Inferior Oolite, Dorset.
7. Hemipneustes Greenovii, Forbes; U. Greensand, Blackdown.
8. Catopygus carinatus, Goldf. ; U. Greensand, Wilts.
(fig. 8, 2), have been seen, and these, by their six-sided form, seem also to have been arranged in more than double series. Normal Echinidae, of the existing genus Cidaris, abound in the upper trios. Some of the secondary species of Cidaris have the ambulacral pores widely separated (== Rhabdoci- daris ) ; in others the rows of pores are doubled {= Difloci- daris ). The genus Hemicidaris (fig. 8, 4), distinguished by the large spine-bearing tubercles on the lower part of the ambulacra, ranges from the trias to the chalk-marl. Diademcr,
PALAEONTOLOGY
36
with smooth, solid spines (=Hemidiadema), appear in the lias, and continue to the chalk, where the modern type, with annulated, hollow spines, appears. Echinopsis also occurs in the lias ; and Acrosalenia, a genus characteristic of the oolites, and distinguished from Scdenia by its perforated tubercles. A crocidciris and Hcliocidaris, with Glyptieus , and several other sub-genera of Echinus, are also peculiar to the oolites. Salenia (fig. 8, 5) with its ornamental disk, is characteristically creta¬ ceous. Arbacia and Temnopleurus appear first in the eocene. The Gassidulidce commence in the oolites, with Pygaster (fig. 7, 1) and Holectypus, and abound in the cretaceous system. Galerites (fig. 7, 3), Discoidea, Pyrina, and Gassidulus are pecu¬ liar to the chalk. The Clypeastridce are represented in the oolites by numerous species of Echinolamptas and Nueleolites (or Glypeus) ; the latter genus attains a large size. The sub¬ genus C atopy gus (fig. 8, s) is peculiar to the cretaceous series. Conoclypeus occurs in the chalk and tertiaries. Clypeaster flourished most in the miocene age ' many large species are found in the south of Europe, Madeira, and the West Indies. Numerous genera, remarkable for their flattened form, and popularly known as “ cake-urchins,” are peculiar to the ter¬ tiaries and existing seas. Lenita and Scutellina are eocene ; Scutella (fig. 7, 4) is miocene. Mellita and Echinarachnius are both fossil and recent. The heart-shaped urchins ( Spatan - gidce), are only remotely represented in the oolites by Disaster (fig. 8, 6) ; they are numerous in the chalk, to which Micraster , Epiaster, Hemipneustes (fig. 8, 7), Archiacia, Holastcr, and Ananchytes (fig. 7, 2), are peculiar. Toxaster is characteristic ol the lower neocomian. Hemiaster is cretaceous and tertiary. Spatangus, Eupatagus, Brissus, Ampliidotus, and ScMzaster are tertiary and recent forms.
The shell of the Echinodermata lias the same intimate structure in all the orders and families, and in every part of the skeleton, whether “ test,” or “ spine,” or “ tooth.” The
HOLOTIIURIOIDEA
37
smallest plates resemble bits of perforated card-board, and the largest and most solid are formed of a repetition of similar laminae. In a few membranous structures, minute spicula, curved, bi-hamate, or anchor-shaped, are met with. They are always composed of carbonate of lime ; but owing to their porosity, fossil examples are commonly impregnated with earth, or pyrites, or silica, and form bad subjects for micro¬ scopic investigation. Without, however, losing their organic structure, the fossil Echinoderms exhibit a cleavage like that of calcareous spar, by which the smallest ossicle of star-fish or Crinoid may be recognised : this peculiarity is most strikingly obvious in the great spines of the Gidaris (fig. 8, 3), or the enlarged column of the “ pear Encrinite ” (fig. 6, 7). Examples of the latter may be seen which had been crushed when recent, and before the sparry structure was superinduced.
Order 6. — Holotiiurioidea.
(Sea- Cucumbers, Trepang .)
Char. — Body vermiform ; integument flexible, witli scattered reticulate calcareous corpuscles, or beset with small anchor-shaped spicula.
The Ilolothurioid order presents scarcely any examples likely to be met with in a fossil state, except the genus P solus, of whose imbricated shield a fragment has been found by Mr. Richmond in the northern drift of Bute. Count Munster has figured the microscopic plates, apparently of a Holothuria, from the chalk of Warminster ; and the anchor of a Synapta from a still older formation, — the upper oolite of Bavaria. Micro¬ scopic observers will doubtless meet with many such detached plates and spines when searching for Polycystinese and otliei Rhizopods in the oolitic and cretaceous strata ; but it is scarcely probable that the order has dated far back in time.
* Beitrage, heft 6, 1843.
PALAEONTOLOGY
38
Province II. — AETICULATA.
In the great division of invertebrate animals called A rti- cuiata the brain is in the form of a ring encircling the gullet. A double ganglion above the tube supplies the chief organs of sense. The ganglions below the tube are connected with two chords which extend along the ventral surface of the abdomen, and are in most species united at certain distances by double ganglions, which are connected with the nerves supplying the body segments and their appendages. The body presents a corresponding symmetrical form. The skeleton is external, and consists of articulated segments of a more or less annular form. The articulated limbs, in the species possessing them, have a like condition of the hard parts, in the form of a sheath which incloses the muscles. The jaws, when present, are lateral, and move from side to side.
The worm, the lobster, the scorpion, and the beetle, ex¬ emplify this province.
The articulate division of the animal kingdom, most uni¬ versally distributed and numerically abundant at the present day, is least perfectly represented amongst the relics of the former world. Their cliitinous integuments, often hardened with earthy salts, are quite as capable of preservation as the shells of the Mollusca, and remains of them are met with in all aqueous deposits ; but that manifold, complex organization, which in the recent state fits them so admirably for generic and specific comparisons, is fatal to their entire preservation, and the fossil examples are often so fragmentary as to admit of little more than the determination of their class and family.
The most ancient fossiliferous rocks bear imprints which have been regarded as the tracks and burrows of marine worms. With these are found Crustacea of the lowest division, and of a group which is wholly extinct. A little later appear the
ANNUL AT A
39
Phyllopods, Copepods, and other existing orders of Entomos- traca. Only a few obscure forms, doubtfully referred to the higher division, Malacostraca, have been found in the carboni¬ ferous and Permian systems. The secondary strata contain abundant remains of Isopods, and of lobsters and hermit-crabs. True crabs ( Brachyura ) abound in the oldest tertiaries. Air- breathing insects and Arachnida existed even in the palaeozoic age ; the “ sombre shades” of the carboniferous forests were not “ uncheered by the hum of insects nor were the insects blind, like those which now inhabit the vast caverns of Ken¬ tucky and Carniola. The Articulcita which come latest are the Cirripedes, whose lowest family appears in the lias ; while the Balanidce are only found in the tertiaries.
The number of fossil Articulata catalogued and described forms but a very small proportion of those which have pro¬ bably existed. Bronn enumerates 1551 fossil insects, 131 arachnids, 894 crustaceans, and 292 anellides. Darwin de¬ scribes 69 fossil cirripedes, 12 of which are living species.
Class I.— ANNUL ATA.
( Worms, Tube-Worms, Nereids.)
Char. — Body soft, symmetrical, vermiform, annulated, with suckers, or setae, or setigerous tube-feet ; blood ot a red colour in most.
The peculiar markings on the surface of the old Cambrian slate rocks, conjectured to afford the earliest indications of the existence of marine worms, are not without suspicion as to their origin. The so-called “ Xereites bear considerable resemblance to other ecpxally ancient impressions which have been described as Zoophytes, under the name of Protovirgu- laria (fig. 3, i). Xo such doubt attaches to the worm-tiacks which abound in the thin-bedded sandy strata of the foiest- marble ; and the “Cololites” of the lithographic limestone are
40
PALEONTOLOGY
most probably the castings of worms. Long calcareous tubes occur in the upper Silurian and carboniferous strata, which have received the name of Serpulites. The Microconclms of the carboniferous period is now regarded as an Anellide ; and in all the later formations, tubicolar Anellides, especially of the genera Serpula, Spirorbis, and Vermilia abound. Some of these, although attached and gregarious, are so regular in their growth as to have been usually called Vermeti, but are now placed in the genus Vermicularia. Spiroglyphus, and some other shell-excavators, are indicated in the tertiaries. Amongst the problematic fossils of the pakeozoic strata, two are supposed to be anellidous, viz., the Tentaculites (fig. 10, 7), which was apparently free, and almost always regular in its growth, so as more to resemble one of the gregarious Pteropods ; and the Gomulite (tig. 10, s), which is attached when young, singly or in groups, to Silurian shells and corals : the structure of its shell is vesicular, and the cavity resembles a series of inverted cones. The unattached and gregarious Ditrupa appears in the upper chalk, and abounds in the London clay and crag.
Class II. — CIRKIPEDIA.
( Barnacles , Acorn- Shells.)
Char. — Body chitinous or chitino-testaceous, subarticulated, mostly symmetrical, with aborted antennae and eyes ; thorax attached to the sternal surface of the carapace, with six pairs of multiarticulate, biramous, setigerous limbs ; metamorphosis resulting in a permanent para¬ sitic attachment of the fully-developed female to some foreign body.
The fossil Cirripedes belong chiefly to the sessile division, and consist of the ordinary forms of the still-existing Balanidce. They are rare in the eocene tertiary, but more abundant after¬ wards. The Balanus porcatus attains a great size in the shelly
ENTOMOSTRACA
41
beds of northern drift ; its large basal plate, when detached, is a puzzling fossil, and has caused some mistakes. A Goro- nula has been found in the middle division of the crag which has afforded so many cetaceous bones. Kemains of peduncu¬ lated Cirripedes occur in older deposits, but are mostly scarce and fragmentary. A species of Pollicipes is found adhering to drift-wood, perforated by bivalves, in the lias ; another occurs in the Oxford clay, attached in groups to drift-wood, and the shells of Ammonites, which probably floated in the sea after death. The chalk affords many species of Pollicipes and Scal- pellum, a species of the anomalous genus Verruca, and the only extinct genus of Cirripedes — Loricula (fig. 10, 6). This remarkable fossil is found attached to Ammonites, and exhi¬ bits only one side in any of the examples hitherto found. In this unsymmetrical development and the imbrication of its valves it more resembles Verruca than any other Cirriped. “ During the deposition of the great cretaceous system, the Lepadidce arrived at their culminant point : there were then three genera, and at least thirty-two species f whereas at the present day the Philippine Archipelago, which is the richest marine province, affords but five species.
Class ITI. — CRUSTACEA.
Char. — Body articulated, with articulated limbs ; head with antennae ; branchial respiratory organs ; sexes distinct ; metamorphosis in most, in none resulting in fixed indi¬ viduals.
Sub-Class 1.— ENTOMOSTRACA.
Char. — Body with more or fewer segments than fourteen ; integument cliitinous, forming in some a bivalve shell, eyes sessile.
Small bivalve entomostracous Crustacea are found in all
42
PALAEONTOLOGY
strata, and attain their maximum size in the older rocks. Minute Ostracoda, related to the recent Gypris (fig. 10, 5), swarm in the laminated fresh- water clays of the Wealden ; whilst the marine Gytheridce assist with their multitudinous atoms in building up the chalk. Amongst the Phyllopods, the gregarious Estheria covers the slabs of Wealden and of Keuper with crowds of bivalve shells which have been commonly mis¬ taken for Cyclades and Posidonomyce. Estheria abounds in the
Fig. 9.
Balceozoic Entomostraca.
x. Leperditia Baltica, Wahl. ; U. Silurian, Gothland.
2. Entomoconclnis Scouleri, M‘C. ; Carboniferous, Ireland.
3. Beyrichia complicata, Salter; L. Silurian, Wales.
4. Dithyrocaris Scouleri, M‘C. ; Carboniferous, Ireland.
5. Pterygotus Anglicus, Ag. ; Old Bed Sandstone, Ludlow.
6. Bellinurus bellulus, Kdnig. ; Carboniferous, Coalbrookdale.
7. Illfcnus Davisii, Salter; L. Silurian, Bala.
8. Phacops caudatus, Brun. ; U. Silurian, Dudley.
9. Calymene Blumenbachii, Br. ; U Silurian , Dudley.
10. Trinucleus ornatus, Sternb. ; L. Silurian, Britain.
11. Agnostus trinodus, Salter; L. Silurian, Britain.
Caithness flags of the middle Devonian series. The globose Entomoconchus (fig. 9, 2) is found in the carboniferous lime¬ stone ; Leperditia (fig. 9, 1) in the Silurian rocks of the north ; and Beyrichia (fig. 9, 3), which is characteristically Silurian,
ENTOMOSTRACA
43
may be distinguislied from the young forms of Trilobites by the unsymmetrical shape of its separated valves. Other pa¬ laeozoic Phyllopods (Ccratiocaris and Hymenocaris) related to the recent Nebalia, and having a conspicuous tail, occur in the upper and lower Silurian strata ; the genus Leptocheles (M‘C.) was founded on the tail-spines of these Crustacea. Dithyro- caris (fig. 9, 4), which resembles the recent A pus in the hori¬ zontal compression of its carapace, is found in the carboni¬ ferous limestone. The lower coal measures also contain, in their nodules of clay-ironstone, frecpient examples of Bellin- urus (fig. 9, 6), a small Pcecilopod, differing from the recent king-crab (Limulus) in the moveable condition of the body- segments. But the most extraordinary of the palaeozoic Crus¬ tacea are the Eurypterus, PLimantopterus, and Ptcrygotus (fig. 9, 5*), from the Upper Silurian and Old Bed Sandstone, of which some far surpassed the largest living lobster or king- crab in size. They have been considered an extinct family, related to the Limuli ; or as the representatives of the larval condition of the stalk-eyed Malacostraca. But the following- structures show an affinity to the Ostracocla. Their carapace is comparatively small, with compound eyes on the antero-lateral margins ; the body segments are eleven or twelve in number, without appendages, and terminated by a pointed or bilobed tail. Eurypterus has eight feet ; the others have three pairs of limbs — viz., the chelate antennae, the foot-jaws, and the na¬ tatory feet, with their fin-like palettes, which spring from the under side of their cephalo-thorax. The surface of the body and limbs often presents a peculiar imbricated sculpture, which caused them at one time to be regarded as fishes by Agassiz. The Pterygotus problematicus is supposed to have attained a length of seven feet, and some of the others were a yard long. Crustacea of this magnitude may have formed tracks on the
* This figure (by Mr. Salter) as well as several others, are taken from the Siluria of Sir E. Murchison, P.Gr.S.
44
PALAEONTOLOGY
sea-bed, like those on the Potsdam sandstone of America, cal¬ led “ Protichnites,” subsequently to be described.
Order Trilobites.
Char. — Trunk segments trilobed ; sessile compound eyes in most ; limbs aborted.
The great family of Trilobites is entirely confined to the palaeozoic age ; none are found even in the upper coal measures or Permian system. Above 400 species have been described, and grouped in 50 genera. Of these 4G are Silurian, 22 De¬ vonian, and 4 carboniferous. According to Bronn, 13 genera are peculiarly Lower Silurian, 3 Upper Silurian, 1 Devonian, and 3 carboniferous.
The skeleton of the Trilobite consists of the cephalic shield, a variable number of trunk-rings or segments, and the pygiclium or tail composed of a number of joints more or less anchylosed. In some species a labrum (or “ hypostome”) has been discovered, but no indications of antennae or limbs have ever been detected ; still there can be no doubt they enjoyed such locomotive power as even the limpet and chiton exhibit when requisite. Variations in the length of the cephalic and caudal spines (e. g. in A saphus caudatus and longi-caudatus), and in the prominence of the head-lobes, have been considered indications of difference of sex. One of the oldest and simplest forms is the minute Agnostics (fig f), n) ; it is usually found in little shoals, with only the cephalic shield preserved, as if it were the larval form of some large Trilobite. According to the observations of M. Barrande, the Sao passes through twenty stages of growth, being first a simple disc, and ultimately having seventeen free thoracic segments and two caudal joints ; the additional segments are developed between the thorax and abdomen. The Trinuclcus (fig. 9, io) with its ornamental bor¬ der, and Illcenus (fig. 9, 7), in which the trilobation is less con-
MALACOSTRACA
45
spicuous than in most genera, are characteristic of the Lower Silurian strata. Two others from the Wenlock limestone have long been celebrated, viz., Galymene (fig. 9, 9), or the “ Dudley Trilobite” so compactly rolled up ; and Asaphus (or Pliacops) caudatus (fig. 9, 8), in which the lenses of the large eyes are frequently well preserved, and visible without a glass. Each eye has at least 400 facets, and in the great AsapJms tyrannus each is computed to have 6000. In one species (AsapJms Kowalewskii ) the eyes are supported on peduncles. The largest Trilobite is Asaphus gigas ; some of the fragments indicate a creature eighteen inches long.
Sub-Class 2.— MALACOSTRACA.
Char. — Body divided into thorax and abdomen, with seven segments in each.
The Isopods are represented in the upper oolite by Arch- ceoniscus Brodicei , which is gregarious, in large numbers in the slabs of Purbeck limestone ; and in the Permian system by the Prosoponiscus (or Palceocrangon ). The problematic Pygo- cephalus, and the “ Apus dubius,” both from the carboniferous strata, are doubtfully referred to the Stomapoda, and, with the exception of the Qitocrangon of Eichter, are the oldest of the known stalk-eyed Decapods.
Macrourous Crustacea are of constant occurrence through¬ out the oolites and cretaceous strata. One of the most remark¬ able forms, Eryon (fig. 10, 3), is found in the lias (with the closely-allied Tropifer and Goleia ) and in the Oxford clay. The small lobsters of the genus Glyphea, in the oolites, and Meyeria, in the Speeton clay and greensand, are commonly the nucleus of hard nodules of phosphate of lime. The larger species of the chalk form the genus Enoploclytia. The Oxfor¬ dian oolite of Solenhofen, with its finely-laminated lithographic slates, opens like a book filled with compressed and wonder-
PALAEONTOLOGY
4G
hilly preserved shrimps and lobsters. One of them, remark¬ able for its long and slender arms (. Mcgachirus , fig. 10, 4), is also found in the Oxford clay of Wiltshire. One of the most re¬ markable repositories of fossil Crustacea is the Isle of Sheppy, where the London clay has afforded countless examples of
Fig. 10.
Crustacea; Anellida.
1. Dromilites Lamarckii, Desm. ; London Clay , Sheppy.
2. Notopocorystes Stokesii, Mant. ; Gault , Folkestone. ‘
3. Eryon arctiformis, ScM. ; Oxfordian, Solenhofen.
4- Megachirus locusta, German. ; Oxfordian, Solenhofen.
5- Cypridea tuberculata, Shy. ; Weald, Sussex.
6. Loricula pulchella, G. B. Shy.; L. Chalk, Sussex.
7. Tentaculites ornatus, J. Sby. ; U. Silurian, Dudley.
8. Cornulitea serpularius, Schl. ; U. Silurian, Dudley.
the higher organized division, including nine Brachyura, three Anomura, and five macrourous species. The island of Hainan, on the coast of China, abounds with fossil crabs of the genus Meter opthalma, which are sold in the drug-market of Skanghae. Others are found in the miocene of Malta, and of Perim Island in the Red Sea. The reputed instances of secondary Brachyura are open to doubt ; in England we have only the little Etyus Martini' (or Reussia) from the gault, for the Podopilumnus (M‘( .) is probably from some foreign tertiary deposit. Fairs
INSECT A
47
of clielate claws occur in the upper chalk, which are referred to a hermit-crab ( Mesostylus Faujasii ). Small Crustaceans, resembling in form the living Gorystes, abound in the gault (fig. 10, 2), but they are known to be anomourous by the small size and dorsal position of the posterior legs, and by the little plates intercalated between the last joints of the tail, as seen also in the Dromilites (fig. 10, 1) from the London clay.
Class IV.— IN SECT A.
Char. — Body cliitinous, articulated, with articulated and unci- nated limbs ; head provided with jointed antennae ; respiratory system tracheal.
The fossil insects hitherto examined have afforded no new types or forms of unusual interest. The oldest known, those from the lower coal measures, resemble the Curculionidce and Blattidce or Locustidce of the present day. The lias limestones have afforded a greater variety to the persevering skill of Mr. Brodie : species of the genera Berosus, Elctter, Gyrinus, Lacco- philus, and Melolontha, and undetermined genera of the fami¬ lies Cardbidce, Buprestidce, Chrysomclidce, and Telephoridce ; Panorpa-like insects of the genus Orthophlcbia ; dragon-flies, Nepadce and Cimicidce, Cicada, and the dipterous genus Asilus. Next in age is the insect depository of the Stonesfield slate, which affords the large wing-covers of Buprcstis Bucklandi, species of Prionus and Coccindla, and the great neuropteran Hemerobioides. The Purbeck limestone has supplied, in addi¬ tion, species of Ccrylon and Colymbetcs, Cyphon, Hclophorus, and Limnius ; and examples of Staphylinidce, Cantharidce, Harpalidce, Hydrophilidce, and Tcnebrionidce, Libdlula and Phryganea, A cheta and Blattci, Aphis, Ccrcopis, and other Homoptera, and ten dipterous genera. I11 the newer pliocene fresh-water formations the recent Copris luna/ris has been de¬ tected, and the elytra of Donacia and Harpcdus. I he principal
48
PALAEONTOLOGY
foreign sources of fossil insects have been the lithographic slates of Solenhofen, and the tertiary deposits of Aix in Pro¬ vence, and (Eningen, near Constance, on the Rhine. Remains of species of Tinea and Sphinx are said to have been found in the lower Jura, and of a diurnal Lepidopteran in the Molasse. Numerous examples of insects in true amber have been ob¬ tained, and much more abundantly in “ gum animi,” a more modern fossil resin. These are all unknown to entomologists, and are probably extinct, since no department of recent na¬ tural history has been so closely worked, although the fossil insects have been comparatively neglected. It has been sug¬ gested by Mr. Westwood that the has insects have a sub- alpine character, and may have been brought down by torrents from some higher region. But no attempt has been made to show whether these or any other group of fossil insects most nearly resemble those of any particular zoological province of the present day.
Much has been said of the “ indusial limestone ” of Au- \ eigne, supposed to be built up of the fossilized cases of caddis- worms ( Phryganeidce) ) ; but Mr. Waterhouse, the only entomo¬ logist who has visited the country and examined the formation, entertains doubts of the correctness of this interpretation.
Of the Myriapoda, 17 fossil species have been found, com¬ mencing hi the oolitic system. And of the Arachnida, 131 species are catalogued ; the earliest and most interesting of these is the fossil scorpion (Cyclopthalmus senior ) oAlie Bohemian coal measures (figured in Buckland’s Bridgewater Treatise). Fossil spiders are found in the Solenhofen slates and in the tertiary marls of Aix.
Province III.— MOLLUSC A.
Remains of the Testacea, or shell-bearing molluscous ani¬ mals, are the most common of all fossils, and afford the most
BRACHIOPODA
49
complete series of “ medals,” or characteristic signs for the identification of strata. The duration of types and species, as a general rule, is inversely proportional to rank and intelli¬ gence. The most highly organized fossils have the smallest range, and mark with greatest exactitude the age of the deposit from whence they have been derived. But the evidence afforded by shells, if less precise, is more easily and constantly obtained, and holds good over larger tracts of country.
Class I. — BRACHIOPODA.
The lamp-shells ( Brachiopoda ), more than any other group, have suffered with the lapse of time. Of 1300 known species, only 75 are living ; and of the 34 genera, the larger part (21) are extinct. The number of generic forms is greatest in the Devonian period and least in the upper oolites, after which a second set of new types gradually appears. The preponder¬ ance of fossil Brachiopoda is contrasted with the scarcity of the recent shells even more strongly by the abundance of indi¬ viduals than by the number of species ; for the living shells mostly inhabit deep water and rocky situations inaccessible to the dredger, and are seldom obtained in large numbers.
The genus Terebratula, as now restricted to shells with a short internal loop, musters above 100 fossil species, of which only one survives ( T . vitrea ), an inhabitant of the Lusitanian province. The Waldheimias, or Tcrcbratulce with long loops, are widely distributed in our present seas, although only nine living species are known ; individuals of one or more of these are found on the coast of Spitsbergen and Labrador, at Cape Horn, and most abundantly in New South Wales and New Zealand : there are sixty fossil species dating from the trias. The Terebratellce, having the loop fixed to a mid ridge, com¬ menced in the lias, and occur in small numbers throughout the cretaceous and tertiary periods, and are the only lamp-shells
E
50
PALAEONTOLOGY
which attain their climax inrecent seas. Five species o i Argiope occur in the greensand, chalk, and tertiaries. The allied genus Thecidivm is represented by one species in the carboniferous and one in the triassic system, becomes comparatively common in the secondary period, and dwindles again to a single species in the newer tertiary ; this species survives within still narrower limits in the Mediterranean Sea. The sub-genus Terebratu- lina is represented by twenty species in the secondary and
Fig. 11.
Brachiopoda.
1. Trigonosemus Palissyi, Woodw. ; U. Cretaceous , Ciply.
2. Stririgocephalus Burtini, Defr. ; Devonian , Eifel.
3. Spirifera striata; Carboniferous, Britain.
4. Cyrtia trapezoidalis ; U. Silurian, Dudley.
5. Athyris Roissyi, Ler. ; Carboniferous, Ireland.
6. LTncites gryphus, Schl. ; Devonian, Belgium
7. Atrypa reticularis, L. ; U. Silurian, Malvern.
8. Pentamerus laevis; Caradoc S., Salop.
tertiary formations. T. striata of the chalk is so like the recent T. caput serpcntis as to be with difficulty distinguished from it. Several extinct sub-genera occur in the cretaceous strata, of which the most remarkable are Trigonosemus (fig. 11, 1) and Lyra , shaped like a violin. The genus Stringocephalus (fig. 11, 2) is peculiar to the Devonian strata, and has a large
BRACHIOPODA
51
internal loop, and a very prominent cardinal process, forked
at the end, and fitting over the central plate of the opposite valve.
The shell of Terebratula and some of its allies (Argiope, ThecicLium, Cyrtia, and Spiriferina ) is dotted with minute quincuncial perforations, sometimes visible to the naked eye, as in T. lima, but usually requiring a lens of low power. They are smallest in T. carnea.
The lamp-shells with sharp beaks and plaited valves have been separated from the Terebratulce under the name Rhyn- chonella (Fisch.) Their shells do not exhibit the punctate structure under a magnifying-glass, and they have no internal skeleton to support their arms, which in the recent species are coiled up spirally, and directed towards the concavity of the smaller valve, like the spires of the extinct Atrypa (fig. 11, 7). Of the three living species of Rhynchonella, one is found throughout the Arctic Seas, a second in Flew Zealand, and the third at the Feejees (?). The fossil species exceed 250, and are found in all parts of the world ; those from the palaeozoic strata may prove distinct frojn the rest, since the permian species are known to be provided with large internal processes ( Camarophoria , King). Casts of these shells are frequently impressed with the narrow and angular pallio-vascular impres¬ sions. The extinct genus Atrypa differs from Rhynchonella solely in having calcareous spires, which are preserved in many instances, and may be cleared to some extent by the application of acid. The foramen is separated from the hinge¬ line by a deltidium ; and the interior of the valve is marked by ovarian and vascular spaces exactly as in RTiynchonella. The lower Silurian rock contains another genus, Porambonites (Pander), as yet imperfectly understood, but having the valves marked externally by impressed dots, which are not perfora¬ tions. The genus Pentamerus occurs in all the strata below the carboniferous limestone, and is remarkable for its great
52
PALAEONTOLOGY
internal partitions, causing the shell to split readily across the middle ; and giving rise to deep incisions in those casts of the interior which are so common in the Caradoc sandstone (fig. . 11, 8).
The extinct Spiriferidce are a family characterized by the possession of internal calcareous spires extending from the centre of the shell outwards (fig. 11, 3). These spires, like the shell itself, are frequently silicified, and may be disengaged from the matrix by the action of acid. At other times the shell is imbedded in soft marl, removeable by careful washing, so as to show the calcareous lamina of the spire fringed with hair-like processes, formerly the support of cirri. In the genus Spirifera the shell has a long straight hinge-line, and the flattened area of the larger valve has a deltoid byssal notch* The typical species are characteristic of the palaeozoic strata, and have a shell-structure like Rhynchonella. The liassic spe¬ cies (Spiriferina, d’Orb.), have punctate shells, and the byssal opening is closed (at least in the adult) by a thin arched plate or “ pseudo-deltidium.” In the sub-genus Cyrtia (fig. 11, 4), the hinge-area is ultimately as long as it is wide, and the del- tidium is perforated in the centre by a byssal tube ; some of the species have a punctate shell. The genus Athyris (Dal- man), not always easily distinguished from Terebratula, has usually a smooth and rounded shell, ornamented with concen¬ tric lamellae or wing-like expansions (fig. 11, s) ; the beak is truncated by a round foramen ; the hinge-area is obsolete ; and the spires are as in Spirifera, with the addition of some further complications near the hinge. There are twenty-five species, mostly from the Devonian and carboniferous rocks. The species of Retzia (King) are still more like plaited Terebra- Mce, but have lateral spires; they range from the Silurian
The term deltidium, applied by Von Buch to this foramen, has by miscon- chfseh °f hIS meaning’ beC°me conRtantly URed & r the plates which partially
BRACHIOPODA
53
strata to tlie trias. Uncites gryphus (fig. 11, 6), a peculiar De¬ vonian fossil, has a prominent beak, perforated in the young- shell by a minute apical foramen ; the hinge-area is filled up by a deeply concave deltidium, on each side of which (but only in some specimens) there is a lateral pouch formed by an inflection of the margin of both valves.
Fig. 12.
Brachiopoda.
1. Orthis hysterita, L. (cast) ; Devonian , Rhine.
2. Davidsonia Verneuili, Bouch. ; Devonian , Eifel.
3. Strophomena rhomboidalis, Wahl. ; U. Silurian , Dudley.
4. Producta semireticulata, Martin ; Carboniferous, Derbyshire.
5. Chonetes striatella, Dalm. ; V. Ludlow rock, Herefordshire.
6. Calceola sandalina, Lam. ; Devonian, Eifel.
7. Obolus Apollinis, Eichw. ; L. Silurian, Northern Europe.
8. Siphonotreta unguiculata, Echw. ; U. Silurian, Britain.
The family Orthidce consists of shells with a straight hinge- line, bordered by a flat, narrow area, with a central notch in each valve ; the ventral valve is furnished with articulating hinge-teeth, and the dorsal valve has short processes lor the support of the oral arms, which appear to have been horizon¬ tally spiral (as in Atrypa). Between the oral processes there is a central projection for the attachment of the cardinal muscles. Internal moulds of the Orthis (fig. 1 2, 1) exhibit on
54
PALEONTOLOGY
the ventral side the single attachment of the adductor muscles in the centre, and on each side of it the cardinal muscles ; these are surrounded by the punctate ovarian spaces and impressions of the large pallial sinuses. The genus Orthis includes 100 species, ranging upwards to the Permian, but it is most abundant in the Silurian rocks. Some of the lower Silurian species have a round foramen in the “ pseudo-delti- dium,” and are called OrthisincB (d’Orb.) Other species in the upper palaeozoic rocks have the beak twisted or deformed, probably owing to the attachment of the shell when young (= Streptorhynclius, King). In Strophomena, PLafin (= Leptcena, Kalm.), there is a minute byssal foramen when young, of which no trace exists in the adult ; and the deltoid notch is also closed, except the space required to receive the divided cardinal pi’ocess of the dorsal valve. The oral processes appear to be shifted to the centre of the valve. The shell, when young, is plano-convex, but when it has attained a certain size the valves are bent over to one side or the other, and more or less suddenly. The pallial impressions are the same as in Orthis.
The genus Davidsonict, peculiar to the Devonian limestones, lesembles an Orthis attached, like Thccidiuvi , by the ventral valve to corals, and sometimes taking the markings of the body on which it grows, like the oyster and Anomice. The pallial impressions are like those of Orthis, and the form of the spiral arms is indicated by prominences which almost fill up the interior of the shell in aged examples. Some indica¬ tions have been obtained of slender calcareous spires for the support of the arms in this genus ; and also in Koninclcia, a small shell fiom the trias of St. Cassian, in which there are always spiral grooves in the interior of the valves crossed by the impressions of the pallial sinuses.
Tiie anomalous fossil called Calceola sandalina (Lam.) is also peculiar to the Devonian limestones. In shape it resembles
BRACHIOPODA
55
Cyrtia, but lias no hinge, and neither foramen nor internal processes, except a row of small projections along the hinge¬ line, and two small lateral groups of ridges in the smaller valve. The interior is punctato-striate, but has no recognisable muscular markings.
The Productidce are altogether palaeozoic fossils, and most abundant in the carboniferous limestones. Their valves are concavo-convex, the liinge-line straight, and the interior marked with distinct impressions of the muscles for opening and closing the valves, and simple vascular spaces. There are (30 species of Producta found in the upper palaeozoic rocks, and having a very wide range in North and South America, and from Spitzbergen to Thibet and Tasmania. Some of them are extremely variable in form ; many are armed with long tubular spines, and others completely clothed with short, hair-like processes ; they have no hinge-teeth, and the hinge- area is extremely narrow, except in the sub-genus Aulosteges of the Russian zechstein. Producta proboscidea has its convex- valve prolonged into a tube, as if for the constant supply of respiratory currents. The Permian genus Stroplialosia has its valves articulated by hinge-teeth, and covered with long and slender hollow spines ; the shell is attached when young by the umbo of the large valve. Chonetes is distinguished from Producta by a row of spines along the hinge-margin of the convex-valve ; it also has a narrow hinge-area with a covered notch, and small hinge-teeth. There are 25 species in the Silurian and carboniferous, usually of small size, and finely striated.
Crania is one of the oldest living types, ranging upwards from the lower Silurian. One of the earliest species appears to have been unattached, and another to have had hinge-teeth. Crania Ignabergensis, of the chalk of Sweden, has the valves externally alike, being attached only when very young. The internal markings of C. antiqua, and other fossil species, are
56
PALAEONTOLOGY
remarkably grotesque. Lower valves of this genus and The- cidium are not uncommon, attached to the tests of sea-urchins, in the chalk ; but upper valves are scarce, either detached or
in situ.
The Discinidce are also ancient fossils, few in number, but appearing in every period. Some of the palaeozoic Discince (— Orbiculoidea , d’Orb.) cannot be generically distinguished from the recent species by any characters with which we are as yet acquainted ; but others (= Trematis, Sharpe) are orna¬ mented with quincuncial punctures, and the casts exhibit indications of diverging internal plates, which imply very considerable difference in the organization of the animal. The genus Sijilionotreta (\ erneuil), peculiar to the Silurian forma¬ tions, is covered with moniliform tubular spines.
Lingula, which has given its name to one of the oldest fos-
silifeious rocks, is another form occurring unchanged hi strata of e\ ery period. Only 3d species are known, and none of them are very common. The latest British Lingida is found in the coralline crag (older pliocene) of Suffolk : the nearest living species is as far off as the Philippines. L. Davisii, of the lingula flags in North Wales, has a pedicle groove in the ventral valve, by which the posterior adductor (or cardinal muscle) must have been divided into two elements, as in the genus Obolus ; externally it has all the appearance of an ordi¬ nary existing shell. From the fragments of Lingula in the lower Silurian stiper stones of Shropshire, they appear to belong to a species distinct from L. Davisii. Obolus, Eichw. (= Ungula, 1 ander) is so abundant in the lower Silurian sandstones of Sweden and Eussia as to have given its name to the “ obolite
giit. In England it occurs only in the upper Silurian of Dudley. The shell is horny in texture, and often stained
blue, like the Lingula, by the presence of phosphate of iron. In shape it is regularly oval, and differs from Lingula in the character of the internal muscular impressions.
LAMELLIBRANCHIATA
57
Class II.— LAMELLIBRANCHIATA.
{Bivalve Shells.)
More tlian a third part of the known fossil shells are ordinary bivalves ( Conchifera , Dli.) They amount to nearly 6000, while the recent species scarcely exceed half that number. Nevertheless, it is a group which attains its maxi¬ mum in the present seas. The genera are seven times more numerous in the newer tertiary than in the oldest geological system ; and the number of species found in the entire Silurian series is less than 100, while the chalk contains 500, and the miocene 800. Out of 150 genera, 35 have become extinct,
Fig. 13.
Palaeozoic Bivalves.
1. Aviculopecten, Bp. ; Carboniferous , Belgium.
2. Posidonomya Becheri ; Carboniferous, Hesse.
3. Ambonychia vetusta, Sby.; Carboniferous , Belgium.
4. Myalina Goldfussi, Dkr. ; Carboniferous, Vise.
5. Ctenodonta cuneata, Hall ; L. Silurian, Canada.
6. Lyrodesma plana, Conrad ; L. Silurian, Hudson River.
7. Axinus obscurus, Sby. ; Magnesian limestone, Durham.
8. Conocardium armatum, Pk. ; Carboniferous, Tournay.
9. Pleurophorus costatus, T. Br. ; Magnesian limestone, Durham.
10. Grammysia cingulata, His. ; Ludlow rocks, Kendal.
11. Edmondia, sp. ; Carboniferous, Belgium.
besides numerous sub-genera. The families Gyprinidce, A star- tide*?, and Anatinidce, have passed their maximum , the
58
PALAEONTOLOGY
Trigoniadce are nearly extinct ; and the Hippuritidce have no living representatives.
The monornyary bivalves, and others with an open mantle, attain a degree of importance at an early period ; and with them some of the burrowing families (. Myacidce and Ana- tinidce) ; while the highest organized siphonated shells (e.g., Veneridce and Tellinidce ), unknown in the older rocks, are most abundant now.
The family Ostreidce- , distinguished from the Pectens and Anomice by resting on the left valve, contains two fossil forms. Of these, Exogyra resembles an oyster with spiral umbones, directed backward, or to the left hand ; it is an attached shell, characteristic of the cretaceous strata. The genus Gryphcea (fig. Id, i) abounds in the oolites, and is gregarious, but unattached, the umbo of the larger valve being curved inward like a claw. A single Ostrea occurs in the carboniferous lime¬ stone, after which the species become abundant, and are with difficulty distinguishable from the smooth and plaited, or “ cocks-comb,” oyster of the present day.
Several curious modifications of Anomia and Placuna have been obtained in a fossil state. Limanomia (Bouchard) has ears like Lima, and is attached to shells and corals of the Devonian age. Placunopsis (M. and L.), found in the oolites, has a transverse ligamental groove, which, like the umbo of the upper valve, is some way within the margin of the shell. And Garolia (Cantr.), a tertiary form of Placuna, has a byssal plug passing through a foramen like that of Anomia when young, but closed in the adult.
Fossil Pectinidce are very numerous. Some of them in the carboniferous limestone (e.g., P. Sowerhyi ) cannot be distin¬ guished generically from the living Pectens, and retain diverg¬ ing bands of colour. But the greater part of these old species are somewhat aviculoid in form (fig. 13, i), and their hinge- area is grooved with cartilage-furrows, like those of Area.
L AMELLIBRAN CHIATA
59
The most beautiful forms occur in the chalk and greensand, and resemble the recent scallop ( Janira , Schum.) in the
Fig. 14.
Secondary Bivalves.
1. Gryphtea arcuata, Lam.; Lias, Charaaouth.
2. Pecten (Neithea) quinquecostata, Sby. ; Chalk, Sussex.
3. Pulvinites Adansoni, Defr. (internal mould) ; Corallian, Rochelle.
4. Gervillia anceps, Dh. ; L. Greensand, Isle of Wight.
5. Inoceramus sulcatus, Park. ; Gaidt, Folkestone.
6. Cucullaea (Macrodon) Hirsonensis, D’Arch. ; Great Oolite , Min-
chinhampton.
7. Isoarca cordiformis, Schloth. ; Corallian, Nattheim.
8. Myophoria decussata, Miint. ; Trias, S. Cassian.
inequality of their valves, but are further characterized by the possession of articulating hinge-teeth like Spondylits. These constitute the genus Neithea (fig. 11, 2). Plicatulce exist in the trias and oolites, along with shells referred dubiously to Hinnites and Spondylus. True Hinnites (a sub-genus of Pecten ) are cha¬ racteristic of the miocene. Spondyli appear in the greensand and chalk. Some of them (like the so-called “ Plagiostoma spin- osum”) are unattached ; others resemble the recent deep-water S. Gussonii, and have been called “ Dianchone.” The inner layer, including the hinge of these shells, is seldom preserved. Lima proboscidea first appears in the lower oolite, and reappears in the great oolite, and in the Kelloway rock. Lima duplicate.
60
PALAEONTOLOGY
and some other oolitic species, liave two ranges of little hinge- teeth, hut not like those of the recent species of Limcea. The large and smooth or striated Limas of the oolites have been called Plagiostoma, a name originally given by Llhwyd.
The pearl-oysters ( Aviculidce ) are also very abundant fossils : but owing to the frequent repetition of similar forms, it is difficult to determine the genera with any degree of cer¬ tainty by the aid of external characters alone. The Silurian species mostly belong to the genus Pterinea (Goldfuss), and are broadly winged, and have the hinge-area striated length¬ wise, and a few diverging hinge-teeth. Amboncychia (Hall) resembles Inoceramus, and ranges from the Silurian to the carboniferous strata (fig. 13, 3). The Silurian genus Cardiola is ridged like a cockle ; and Posidonomya, which is found in all the palaeozoic rocks, is very thin and concentrically fur¬ rowed (fig. 13, 2). Many other genera have been proposed whose characters are even more imperfectly understood. Monotis ( Salinarius ), one of the common shells of the trias, lias no anterior ear. Pteroperna (Lycett), an oolitic form, has a winged shell, with numerous small anterior teeth and long posterior laminae. The genus Gervillia (fig. Id, 4), ranging from the carboniferous limestone to the chalk, consists of elon¬ gated shells, with several cartilage-pits in the ligamental area. Balcewellia, found in the Permian, has an anterior muscular impiession like Area. The recent genus Perna commenced m the lias or preceding formation, and exhibits great variety of shape. Pulvinites Adansonii (fig. Id, 3) appears to have been a Perna with a byssal foramen like Anomia ; and Inocc- ramus (fig. Id, 5), characteristic of the cretaceous strata and oolites, differs from Perna chiefly in form, the larger valve being sometimes completely involute, and resembling a Nautilus. The genus Pinna, which appears to belong to this family, although provided with two adductor muscles, occurs fossil in the Devonian and all subsequent strata. Some of the
LAMELLIBRANCHIATA
61
oolitic species, distinguished by the name Trichites, are inequi- valve and irregular, and attain a thickness of more than an inch, resembling mineral masses of fibrous carbonate of lime.
Amongst the Mytilidce are many Silurian species distin¬ guished by their large, round, anterior muscular scar (. Modio - lopsis, Hall), and others which have a straight hinge-line and plaited valves ( Orthonotus , Conrad). Mycdina has the cartilage-groove repeated (fig. 13, 4), and is found in the upper palaeozoic rocks. Sometimes the anterior adductor is supported on a shelf, as in the recent Septifera and Dreisscnia. True Mytili and Modiolce abound in the oolitic strata. Dreissenia, now confined to the rivers of the Aralo-Caspian region, or only naturalized in Western Europe, was represented by many species, and some of large size, in the eocene of Hampshire and miocene of Vienna.
Fossil Arcadce are far more numerous than the recent shells, and mostly belong to the division Gucullcea, of which a single species survives in the Coral Sea. The palaeozoic Arks have anterior teeth like Area, and posterior teeth like Cucullcea, and differ from both in the reduction of the hinge- area to a narrow tract corresponding with the posterior half only in the recent shells. The casts of Ark-like shells in the Silurian rocks are further distinguished by a deep furrow behind the front muscular impression. These constitute the genus Ctenodonta (Salter), which has liinge-teeth like Nucula, and a prominent external ligament (fig. 13, 5). Some of the oolitic Arks, with a byssal sinus, and the posterior teeth very long and parallel, form a sub-genus called Macrodon (fig. 14, 6). Others, with prominent umbones, teeth like Nucula, and a striated ligamental area, form the genus Isoarca of Munster (fig. 14, 7). Above 200 species of Nucula and Lcda are known only as fossils, and range through all the rock systems. The palaeozoic species are anomalous in form, and when better understood, will certainly be considered distinct as genera.
62
PALAEONTOLOGY
Yoldia is a newer tertiary form characteristic of high northern latitudes ; and Solenella occurs fossil in Patagonia and New Zealand. The problematic genus Solemya is supposed to have existed in the carboniferous period Pectunculi appear first in the cretaceous strata, being less ancient than Limopsis, which occurs in the Bath oolite. A member of the latter genus found in the Belgian eocene has the ligamental area entirely behind the cartilage-pit, and is called Nucunella by d’Orbigny. The “ Stalagmium” of Conrad ( = Myopara, Lea) is identical with Crenella (T. Br.), a sub-genus of Modiola, found in the cretaceous and tertiary strata.
The Trigoniadce are represented in the lower Silurian strata by Lyrodesma (fig. 13, 6), a shell with several radiating hinge-teeth, striated transversely ; and in the upper palaeozoics by Axinus (fig. 13, 7) and several other imperfectly-known genera. Schizodus occurs in the permian at Garford (with Turbo and Rissoa ), near Manchester. The trias contains true Trigonice associated with the genus Myophoria (fig. Id, s), which has the umbones turned forwards, and a posterior hinge-tooth. The only member of this family which has yet been found in tertiary strata is the little genus Verticordia (Wood) of the crag. No Trigonice have been met with, although 100 species are known in the secondary rocks, and two are still living on the coasts of South Australia.
Fresh-water mussels ( Unionidce), of large size and various form, occur in the Wealden formation, and are not generically distinguishable from recent shells ; but those of the coal measures and older rocks are extremely problematic, and may even belong to marine genera.
Of the genus Chama there is one species in the upper greensand and chalk of England, and another in the London clay. Elsewhere they are more abundant, amounting to thirty species. Closely allied to Chctma is the Diceras (Lam.), of which the remarkable casts attracted attention at an early
LAMELLIBIIANCHIATA
63
period (fig. 14, i). They are found in the coral rag of Trance and Germany, and resemble the horns of some animal. The shell is attached by the umbo of either valve, indifferently, like some of the recent Cliamas. The posterior adductor muscle is supported on a prominent ridge (as in Pacliydesvia, Mega- lodon , and the recent Cctrdilia ), which causes a spiral furrow in each horn of the cast. The shells which succeed Diceras, in the lower cretaceous strata, have the right valve usually much smaller than the left, and in one instance (fig. 14, 2) it is like the operculum of a spiral univalve. The only British species of this group is Requienia Lonsdalii, found in the ironsand of Bowood. In Trance, and also in Texas, another form occurs, with the attached valve simple and conical, like a Hippurite. The ligamental groove is straight, and the umbo of the free valve marginal.
These shells are so intimately allied to the Hippuritidce , that Requienia has been frequently included with them in the apocryphal order “ Rudista.” The members of the Hippu¬ rite group are attached and gregarious, like oysters, often occurring in great numbers, and filling large tracts of rock. Their valves are different in structure and sculpturing, and are articulated by two prominent teeth above and one below ; the cartilage is internal, but there is a conspicuous ligamental furrow outside. There are nearly 100 species characteristic of the cretaceous strata, and especially of the lower chalk, or “ hippurite limestone.” Only one species ( Radiolites Mortoni ) is found in England ; the rest are from the West Indies, Southern Europe, Algeria, and the East. The form which approaches nearest to Chama is the little genus Gaprotina (fig. 15, 7), whose upper valve has a marginal umbo, but is in other respects like a miniature Radiolite. Caprina (d’Orb.) has the free valve perforated by canals which open in the inner margin, and in Caprinella the outer lamina of both valves possesses this structure. One valve is sometimes spiral (fig.
PALEONTOLOGY
64
1 5, 6), and partitioned off internally by numerous septa, like the water-Spondylus, hut so regularly as to resemble the chambered shell of a Nautilus. In the Racliolite (fig. 1 5, 5),
Fig. 15.
Secondary Bivalves.
1. Diceras arietinum, Lam. ; Corallian, France.
Requienia ammonia ; Neocomian, S. France.
3. Monopleura trilobata, d’Orb. ; Neocomian , Orgon.
4. Hippurites Toucasiana, d’Orb. ; L. Chalk, France.
5. Eadiolites angeiodes, Lam. ; L. Chalk, Gosau.
6. Caprinella Boissyi, d’Orb ; L. Chalk, Valley of Alcantara.
7. Caprotina semistriata, d’Orb. ; U. Greensand, Le Mans.
both valves are conical, and the umbo of the free valve (mar¬ ginal in the very young shell) becomes central in the adult. The structure of the hinge is modified by the absence of any spirality in the valves, but is essentially the same as in Capro¬ tina and Diceras; the prominent teeth of the upper valve support curved plates for the attachment of the adductor muscles, which become continually more undercut in the course of their growth. In Hippurites the anterior muscular plate projects horizontally, the posterior vertically, like a third tooth, for which it has been mistaken. In this genus there are two longitudinal inflexions of the outer shell-wall beside the ligamental furrow, one corresponding to the posterior
LAMELLIBRANCHIATA
65
muscular plate, the other (or third) apparently a siphonal inflexion like that in Trigonia and Leda (fig. 15, 4).
The cockle-shells (Cardiadcej, as they have a world-wide distribution now, had a corresponding range in time, and are found in all strata from the Silurian upwards. The com¬ monest fossil type of Cardium is ribbed concentrically on the sides, and radiately 011 the posterior slope, a style of ornament almost unique amongst the 200 recent species. The Caspian cockles, distinguished by a sinus in the pallial line, appear to have inhabited the Aralo-Caspian region almost from the middle tertiary period; the hinge-teeth are reduced to one (. Monodacna ) or two (Didacua) in each valve, and are some¬ times cpiite wanting even in the young shell (Adacna, Eicliw.) Lithocardium aviculare (fig. 16, 7) is a characteristic shell of the Paris basin, and appears to have spun a byssus, like the fry of some recent cockles ; it also resembles the oriental Tridacna, of which a species is found hi the miocene of Poland. The genus Conocar dium (fig. 13, s) of the upper Silurian and carboniferous systems is remarkable for the prismatic cellular structure of its shell, and the truncation of the posterior (?) side of the valves, which are furnished in some species with a slender siphonal process.
The Lucinidce, allied to the cockles in their hinge-structure, are also plentiful in the fossil state, and have as wide a range. They are usually recognisable, even when in the condition of internal casts, by their circular form and the oblique ridge on their disk. Casts of Lucina also exhibit the peculiar narrow outline of the anterior adductor detached from the pallial line. Cryptoclon, Dijolodontci, Kellia, and Pythina are found in the eocene tertiary. Corbis, under the sub-generic form of Sphcera, commences in the trias ; another modification, found in the oolites and chalk ( TJnicardium, d’Orb.), is edentulous ; and Tancredia (Lycett), a compressed triangular shell, with a dentition like Corbis, is frequent in the lias and oolite.
F
GO
PALAEONTOLOGY
Tlie fresh-water Gycladidce are represented in the Wealden and eocene, by many species of Gyrena, mostly of small size. The recent Gorbicula fluminalis of eastern rivers is a common fossil of the pliocene tertiary in England and Sicily.
The Gyprinidce and A stcirtidce are more abundant as fossil shells, and had a wider range of old than at the present day. Nearly 100 species of Gyprina have been catalogued, com¬ mencing in the trias ; the dentition of the older species is, however, somewhat peculiar. The Isocardice are almost as numerous, and have the same range, but many of the fossil Isocardia-looking shells are really related to the Anatinidce. A yet higher antiquity has been assigned to Gypricardia, a genus now very scarce and difficult to obtain, on account of its habit. The palaeozoic Pleurophorus (fig. 13, 9) is dis¬ tinguished by the prominent ridge behind the anterior muscular impression ; and Megalodon (J. Shy.), by the plate supporting the posterior adductor. This genus is represented in the oolites by Pachyrisma (fig. 1 G, 1), and in the tertiaries and modern seas by Gardilia.
The genus Astarte, now limited to a dozen species in the North Atlantic and Arctic seas, has an almost world-wide geological distribution, and counts 200 species in d’Orbigny’s catalogue, commencing with the lias period. Grcissatella, now almost a southern form, is common in the cretaceous and tertiary strata of Europe. Closely allied to Astarte is the extinct genus Opis (fig. 1G, 3), of which there are 42 species in the secondary series ; and Cardinia (fig. 16, 2), characteristic of the lias and oolites. The so-called Unios of the coal measures ( Anthracosia, , King) are probably members of this group.* One hundred species of Gardita (including Vcneri- cardia ) are found in the secondary and tertiary strata ; of the
* “ They occur in the valuable layers of clay-ironstone called ‘ mussel- bands,’ associated with Nautili , Discince , etc. In Derbyshire the mussel-band is wrought, like marble, into vases.” — Woodward.
LAMELLIBRANCHIATA.
67
50 recent forms, one only is Arctic, and this occurs in the glacial deposits of England. The allied genus Myoconcha is characteristic of the older secondary rocks, and Hipjio- podimn of the lias.
Fig. 16.
Secondary and Tertiary Bivalves.
1. Pacbyrisma septiferum, Bur.; Corallian, Meuse.
2. Cardinia hybrida, Sby. ; Lias, Gloucester.
3. Opis tumulatus, Mill. ; Inf. Oolite, Bayeux.
4. Tancredia secariformis, Dkr. ; Lias, Saxony.
5. Sowerbya crassa, d’Orb. ; Oxfordian, Ardennes.
6. Goniomya scripta, Sby. ; Kelloway rock, Wilts.
7. Litbocardium aviculare, Lam. ; Eocene, Paris.
8. Grateloupia irregularis, Bart. ; Miocene, Bordeaux.
9. Teredina personata, Lam. ; Eocene, Bognor.
The Venevidce are pre-eminently characteristic of the tertiary and present period. Some obscure species of Venus are found in the oolites : Cytherea occur in the greensands ; Artemis, Trigonci, Lucinopsis, Venerupis, and Tapes appear in the middle tertiary ; Petricola in the eocene. The only extinct form is Grateloupia (fig. 16, 8), which differs but little from Trigona.
The Mactras and Tellens are also comparatively modern groups ; most of the supposed oolitic species belong to Luci- nidce, except Sowerbya (fig. 16, 5), which has a pallial sinus, and is found in the oolites of Malton and Portland. Psam-
08
PALAEONTOLOGY
mobice and Mesodesmce occur in tlie greensand j Donax and Syndosmya in the eocene ; Gastrana, (= Venerupis, Lam.) and Lutraria in the miocene. Lutraria rugosa, still living on the coast of Portugal, is fossil in the raised beaches of Sussex.
The oldest forms of razor-fish ( Solenidce ) are those with the transverse internal rib ( Solccurtus ), which occur in the neocomian, whilst true Solens and Glycimeris appear first in the eocene strata. The genus Mya, as now restricted to the species resembling M. armaria , are only met with in the newer tertiary. Corbula ranges upwards from the lower oolites ; Necera appears in the upper greensand ; and Thetis (= Poromya, Forbes) in the neocomian.
Above 100 species of Panopcea (a genus essentially like Mya) have been obtained from oolitic and tertiary strata in all parts of the world. They are with difficulty distinguished from those equally numerous forms of Anatinidce which have been associated with Pholadomya on account of the tenuity of their finely-granulated valves ; they constitute the genus Myacites (Bronn), and occur in all the palaeozoic and secondary rocks ; some of the oolitic and cretaceous species are distin¬ guished by Y-shaped furrows (fig. 16, 6). Still more numerous are the fossil forms of Pholadomya, which range upwards from the lias, but are reduced to a single species now living in the Caribbean seas. Shells with the umbones fissured like Anatina also occur in the oolites. Pandora first appears in the older tertiary. Amongst the extinct genera referred to this family are the Silurian Grammy sia (fig. 13, io), with valves folded transversely ; the carboniferous Edmondia (fig. 13, n), with large oblique cartilage plates ; and Cardiomorpha, shaped like Isocardia ; and the oolitic Geromya (Ag.), which also resembles the lieart-cockle in form. Gercomya is an oolitic A natina, with the posterior end of the valves much attenuated.
The genus Gastrocliccna appears in the lower oolites ; and casts of its burrows are frequently preserved after the decorn-
GASTEROPODA
69
position of the coral in which they were made. Glavagella dates from the upper greensand, and Aspergillum from the miocene. Saxicava is found in the newer tertiary and raised beaches of Northern Europe ; and the great species commonly called “ Panopwea” Korwegica is a characteristic fossil of the newer pliocene of Britain and Greenland.
The Pholades and ship-worms appear first in the oolitic strata. Forms resembling the recent Martesia striata have been discovered in fossil wood of the lias and Speeton clay. Jouannetia (Desm.) was first known as a miocene fossil ; and Pholas occurs in the older tertiary. Extinct species of Teredo are found in the silicified wood of the greensand of Blackdown and in the fossil palm-fruits of Brabant and Sheppy. The drift-wood of the London clay is usually perforated by the ship-worm, and also by an extinct form ( Teredina , fig. 16, 9), which resembles Martesia in possessing an umbonal shield : when adult it not only closes the anterior pedal opening, but also cements its valves to the shelly lining of its burrow, like an Aspergillum. Specimens have been obtained in which the whole interior of the valves and tube had been excessively thickened towards the close of life by successive layers of shell.
Class III.— GASTEROPODA.
Fossil univalves — the remains of spiral and limpet-like shells — are not wanting in any but the very oldest fossili- ferous rocks (“lingula flags”). From the lower Silurian, where less than 100 species, referable to scarcely more than ten genera, are found, they increase in number and variety slowly and regularly up to the newer tertiaries, which have afforded ten times as many genera and twenty times as many species. The total number of fossil marine univalves is less than 6000 ; the recent exceed 8000 ; and although we may expect to discover more new fossil species than recent, yet it
70
PALAEONTOLOGY
is evident that, in comparison with past conditions, the group of univalves has only now attained its maximum development,
Between the extinct and living air-breathers the numerical discrepancy is still greater. About 300 land-snails, and half as many fresh-water Pulmoniferco, are enumerated in the fossil catalogues ; but the greater part of these are recent species, and the whole bears no proportion to the number of living land-snails, which exceeds 4000. That many more have formerly existed is indicated by the fact, that the fossil land- snails of the older tertiaries of Europe are entirely different from their living successors, and most nearly represented at the present time in the West Indies and Brazil. The generic forms peculiar to oceanic islands (remains of old continents) are more numerous than those of the mainlands, as if this order had once been more important. But the circumstances favourable to their petrifaction must have been of such rare occurrence as to preclude the probability of attaining more than the scantiest information concerning them.
From the large and proportional number of living Gas- teropods, and the great amount of information which has been obtained of late years respecting their structure and habits, it might be expected that the affinities of the fossil univalves would be easily worked out, and their indications fully interpreted. Such, however, is not the case. Univalve shells present no internal markings, easily accessible like those of bivalves, and exhibiting the essential characters of the soft parts ; and their external forms are often so overlaid with ornament, and disguised by mimetic characters, as to mislead upon a first examination. Shells of any family may be limpet-shaped, or turreted, or discoidal, plain or ornamented. It is more desirable to ascertain whether they have been nacreous or porcellanous ; whether the apex (or nucleus ) presents any peculiarities ; and if operculated, whether the operculum was pauci- or multi-spiral.
GASTEROPODA.
71
The earlier describers of fossil univalves unhesitatingly recognised many familiar recent genera, even in the older rocks. But their Melania} were marine shells ; the sup-
Fig. 17.
Palceozoic Univalves.
1. Loxonema Lefeburei, L6v. ; Carboniferous, Touraay.
2. Macrochilus Scblotlieimi, d’Arcli. ; Devonian, Eifel.
3. Scoliostoma expansilabrum, Sdgr. ; Devonian, Nassau.
4. Euomphalus sculptus, Sby. ; Wenlock Limestone, May Hill.
5. Murchisonia angulati, Ph. ; Devonian, Eifel.
6. Porcellia Puzosi, L6v . ; Carboniferous, Tournay.
7. Bellerophon bi-carinatus, L6v. ; Carboniferous, Tournay.
8. Tubina armata, Barr. ; U. Silurian, Bohemia.
9. Maclurea Peachii, Salter; L. Silurian, Sutherland.
10. Conularia quadrisulcata, Sby. ; Carboniferous, Lanark.
posed Buccinum had no notch ; the Solarice were pearly , the Neritce assumed, when adult, the irregular aperture of Piler opsis ; the Naticce had non-spiral opercula ; and the Maclurea was figured upside down.
The more closely palaeozoic univalves are examined, so much the more do they appear to differ from ordinary recent types ; and the search for allied forms has to be conducted amongst the rare and minute and least understood of recent shells.
Pteropoda.— The fragile shells of Hyalea and Cleodora are
72
PALAEONTOLOGY
found iu tlie newer tertiary of Italy, with Vaginella (fig. 19, 12), a form allied to Cuvieria. But the occurrence of Pteropoda in the older rocks is attended with considerable obscurity. Eccu- liomphalus is like an incompletely convoluted Euomphalus ; Madurea is like Euomphalus with a depressed spire ; the shells called Theca are slender and conical ; Pterotheca has a wing¬ like expansion; and Conularia (fig. 17, 10) is a four-sided sheath, with the apex partitioned off, as in the recent Cuvieria, If really pteropodous, these shells are the giants of the order.
Nudeohranchiata. — Those fossil univalves, which in their symmetry resemble the Nautilus, but are unfurnished with air-chambers, have been compared to the recent Heteropoda (or Nudeohranchiata, BL), and especially to that division typified by the tiny Atlanta, in which the animal can with¬ draw itself completely into its shell, and close the aperture with an operculum. The genus Porcellia, characteristic of the carboniferous age, has a discoidal shell, with a spiral nucleus projecting, as in Atlanta, from the right side ; the whirls are exposed, and marked with a narrow band along the back, ending in a deep slit (fig. 17, 6). Another genus (. Belter optlion ) resembles the recent Oxygyrus in its more globose form, with a similar narrow umbilicus on either side (fig. 17, 7) ; some¬ times the shell is thin and the aperture expanded, like a trumpet, whilst other species are globular and solid ; the for¬ mer may have been tenanted by large animals living at the surface of the open sea, the latter seem to have been more adapted to protect their owners crawling over the bottom, for it can scarcely be insisted that all were necessarily floaters on account of their organization. The species of Bdlerophon are numerous in all the palaeozoic rocks, and some of the smaller kinds appear to have been gregarious : those with disconnected whirls have been called Cyrtolitcs (Conrad.) The Bdlerophma of d’Orbigny (fig. 18, u), is a minute shell found in the gault. The other division (Firolidce) consists of Mollusks in which
GASTEROPODA
73
the shell is wanting or rudimentary, and small compared with the hulk of the animal. A single species of the genus C uri¬ naria has been found in the middle tertiary of Turin.
Strombidce. — The Strombs with their massive shells, never¬ theless, resemble the fragile Heteropods in some respects. They have the same lingual dentition, and the same carnivo¬ rous habits ; and though living on the sea-bed, they rather leap than glide, having a narrow sole and a deeply-divided opercu- ligerous lobe. Characteristic of the warmer zones of existing seas, they are only found fossilized in the newer tertiary strata of countries south of Britain ; but there is a group of little shells related to the recent Strombus fissurellus in the older tertiaries of London, Paris, and America, to which Agassiz has given the name Rimdla. The allied genus of scorpion-shells ( Pterocera ), now peculiar to eastern seas, has been described as occurring fossil in the secondary strata of Europe ; but the extinct species appear to be more nearly related to Aporrhais. This genus, now confined to the western shores of Europe, occurs in all the tertiaries, and is represented in the secondary rocks by many remarkable forms. Some have been separated under the name A laria ; and to this group the so-called Pterocera Bentleyi may perhaps be referred (fig. 18, z). Rostellaria and Serapis (or Terebellum ), now peculiar to the Red or eastern seas, are conspicuous fossils of the European eocene, at which time their range extended to America. Some of the ancient Eostellarias have the outer lip enormously expanded, as in the R. ampla, ( Hippocrend ) of the London clay. In the oolites and chalk there are slender fusiform shells ( Spinigera , d Orb., fig. 18, 1) with spines on the sides of the whirls, as in some recent Ranellce.
Muricidcc. — The great family of whelks, by far the most important group of living sea-shells, is scarcely of higher anti quity than the eocene tertiary. The Purpurina of the oolites (fig. 18, 3), and Oolumbellina of the chalk, are extinct genera,
74
PALAEONTOLOGY
somewhat resembling Purpura and Columbella. But since the so-called “ cones ” of the oolites have proved to be Tornatellce,
Fig. 18.
Secondary Univalves.
1. Spinigera, sp. ; Oxford Clay , Chippenham.
2 . Alaria Bentleyi, M. and L. ; Great Oolite , Collyweston.
3. Purpurina Morrisii, Buv., Great Oolite, Minchinhampton.
4. Nerinaea Bruntrutana, Thurm. ; Corallian, Poland.
5. Crossostoma Pratti, M. and L. ; Great Oolite, Minchinhampton.
6. Trochotoma conuloides, Desl. ; Great Oolite, Minchinhampton.
7. Neritoma bisinnata, Buv. ; Oxfordian, Ardennes.
8. Pileolus plicatus, Shy. ; Great Oolite, Ancliff.
9. Cinulia incrassata, J. Sby. ; U. Greensand, Blackdown.
10. Acteonina concava, Desl. ; Lias, Normandy.
11. Bellerophina minuta, Sby. ; Gault, Folkestone.
it may not be unreasonable to distrust these other presumed affinities. The huge univalve of the chalk, which Sowerby called a Dolium, has been described as a Pterocera by d’Orbigny. I11 the tertiaries siphonated univalves abound, and are mostly referable with certainty to recent genera. The only marked change consists in the comparative abundance of some scarce existing forms, and the absence or rarity of many now most conspicuous. Moreover, the geographical distribution of the genera has undergone a great change since the close of the eocene period. This change is most noticeable in the cold- temperate zone, and is evidently the result of altered climate.
GASTEROPODA.
( 0
The northern seas must ever have been inclement, and the tropical seas always tropical ; but the latitude of England being most liable to vicissitudes of climate, might be expected to show the greatest variety, and the most complete and rapid alterations of organic life. In the London clay are found many
Fig. 19.
Tertiary Univalves.
1. Nautilus (Aturia) zic-zac, Sby. ; Eocene , Britain.
2. Nautilus zic-zac, front view of a septum.
3. Conorbis dormitor, Sol. ; Eocene , Britain.
4. Borsonia lineata, T. Edw. ; M. Eocene, Hants.
5. Volutilithes luctator, Sol. ; Eocene, Britain.
6. Natica (Deshayesia) cocblearia, Brongn. ; Eocene, N. Italy.
7. Turritella (Proto) cathedralis, Brongn. ; Miocene, Bordeaux.
8. Nerita (Velates) perversa, Gm. ; Eocene, France.
9. Helix (Lychnus) Matberoni, Req. ; Eocene, S. France.
10. Ferussina tricarinata, M. Br. ; Miocene, Ploddieim.
11. Volvaria bulloides, Lam.; Eocene, Grignon.
12. Vaginella depressa, Bast. ; Miocene, Bordeaux.
species of Clavdlct, Typhis, Mitra , Psmdoliva , Oliva, and Ancil- laria ; and some extinct forms (. Leiostoma and Strepsidura ) related to Fusus. The middle tertiary, wanting in England, but largely developed in Central and Southern Europe, also contains many genera belonging now to warmer latitudes, and many species still living in the south. In the newer tertianes of Europe these southern forms disappear, and are gradually
7G
PALAEONTOLOGY
replaced by others of an opposite character (Tr ophon, Neptunia, and Trichotropis), now inhabiting the Arctic and boreal coasts. The entire number of fossil Muricidce amounts to 1 000, or about half as many as the recent. The older tertiaries of Eng¬ land also contain species of Triton, Cassidctria, Cancellaria, and Pyrula, shells (now foreign to our seas), which have formerly been included in this family. As regards bulk, there are no fossil species of Fusus, Triton, and Cassis (or S trombus and Voluta) to compare with those of the present day.
Conidce. — The Cones and Pleurotomas appear first in the chalk, and are abundant in the eocene, accompanied by an intermediate form ( Conorbis , fig. 19, 3), and another extinct sub¬ genus ( Borsonia , fig. 19, 4), in which the column is plaited, as in Mitra. The genus Tcrebra is more common in the miocene.
Volutidce. — The Volutes also appear as cretaceous fossils in Europe and Southern India ; they are very abundant in the London clay, and one occurs in the English crag. The ancient species are mostly distinguished by their spires being acute, as in Mitra (fig. 1 9, 5), a peculiarity only found in one very rare living (!) species, dredged from a bed of dead shells in 132 fathoms water (792 feet) off the Cape. The crag Volute resembles the Magellanic form. Cymba olla, the only living European Volute, is a fossil in th q pliocene of Majorca.
Cyprceidce. — I he Cowries form another group of subtro¬ pical shells once common in the temperate zone. Several laige species are found in the London clay, most nearly related to the southern Cyprovula; whilst the crag contains only members of the sub-genus Trivia, one of which still lives on our coast.
The round-mouthed shells ( Holostomata ), whether animal- feeders or vegetarians, make a conspicuous figure amongst the fossils of an eailier period than that in which the last group began to flourish. The carnivorous Katicidce and Pyramidel- lidce are represented in the palaeozoic strata by Naticopsis,
GASTEROPODA
77
Loxonema (fig. 17, i), and Macrochilus (fig. 17, 2). The violet- snail ( Ianthina ), so unlike any other existing shell-fish, seems related to the Silurian Scalites, Eaphistoma, and Pfolopea. Shells like Scalaria and Solarium occur in the trias and oolites associated with Chemnitzice ( V ) of extraordinary size, and species of Eulima and Niso. These families of shells and the Ceri- thiaclce are more abundant fossil than recent, the known num¬ bers being 1500 extinct and 900 living forms. Solaria, with disconnected whirls and pyramidal opercula ( Bifrontia , Dli.), are common in the eocene tertiary, and a single living species ( B . zanclcea ) has been discovered by M‘Andrew.
Amongst the tertiary Eaticas are many with an oblique aperture and peculiar perforation ( Globulus , J. Sby., = Ampul- lina, Bl.), and others with prominences on the pillar ( Desliaye - sia, fig. 19, 6.) The Nerinceas of the oolites are remarkable for the spiral ridges (like the “ worm” of a screw) winding round their interior, and giving rise to the variety of singular pat¬ terns seen in sections (fig. 18, 4). A similar structure exists in the recent “ telescope-shell” ( Terebralia ). The fresh-water univalves of the Wealden and older tertiaries differ but little from their recent congeners of the genera Paludina, Potamides, Melania, and Melanopsis. Fossil Turritellce are of doubtful occurrence before the tertiary ; the Silurian species have the peristome complete ( Holopella , M‘C.) ; another form (Proto, fig. 19, 7) is characteristic of the miocene.
The bonnet-limpets (Calyptrceidce) are common in the old rocks, which also contain a few species of Chiton and shells like Dentalium. Fossil Trochidce are very numerous, but hitherto many Litorinidcc have doubtless been included with them. Perhaps no true Turbo is known from strata before the cretaceous. The Euomphali (fig. 17, 4), which characterize the older rocks, have multispiral calcareous opercula, like the recent Cyclostrema ( = Adeorbis ). The genus Maclurea (fig. 17, 9), which has been regarded as a “ left-handed Euovipha-
78
PALAEONTOLOGY
lus, is probably very different ; it lias a thick shelly operculum, sinistrally spiral, and furnished with an internal process, as the Nerites are ; the spire is sunk and concealed, whilst the whirls are exposed on the flattened under-side ; it occurs in the older Silurian rocks of Scotland and North America. One common feature of the paleeozoic spiral shells is their ten¬ dency to become irregular towards the conclusion of their growth : in Scrpulctria {= Phccnerotinus, Sby.), the whirls are all disunited ; in Scoliostoma (fig. 17, 3) and (Jatantostoma the aperture is expanded. Some small oolitic shells have a thick¬ ened peristome ( Grossostoma , fig. 18, 5), like the recent Lietia, which commences in the older tertiary. A large proportion of the trocliiform fossil shells have their whirls, whether round or angular, marked by a peculiar band, terminating in a deep slit at the aperture ; most of these were solid nacreous shells belonging to the genus Pleurotomaria, of which but a single species survives ; others in their slenderness resemble Turri- tellce, and have been named Murchisonia (fig. 17, 5). The car¬ boniferous shell called Polytremaria has a row of holes in place of a slit ; and the Silurian Tubina (fig. 17, b) has three rows of tubular spines. The Cirrus of the inferior oolite is a reversed shell with one row of similar ornaments ; and Tro- chotoma (fig. 1 8, 6) has a perforation near the margin of the aperture, which is carried onward as the shell grows. Scissur- ella, which is always diminutive and not pearly, makes its first appearance only in the newer tertiary. PLcdiotis occurs in the miocene oi Malta. The Neritidca appear in the oolites ] besides true Nerites, there are Neritomce (fig. 18, 7), with a channeled outer lip ; Pileolus, which is perfectly limpet-like above (fig. 18, b) ; and Ncritopsis, with its angular columellar notch most distinctly marked. Key-hole limpets (. Fissurcllidcc ) occur as early as the carboniferous period, but are very scarce at first, and never become numerous. The oolitic Rimula is a minute shell supposed to be related to a very rare living
GASTEROPODA.
79
species. Ordinary limpets (Patellidce) of unequivocal form are found in the Bath oolite, but are afterwards less plentiful, and almost disappear from the tertiaries ; M. d’Orbigny regarded them as generically distinct, but employed for them a name (Helcion, Mont.) synonymous with Patella.
Puhnonifera. — The existence of air-breathing snails in the palaeozoic rocks is shown by a small “chrysalis-shell, with a round, not toothed, aperture, ( Dendropupa ), discovered by l)r. Dawson and Sir C. Lyell in a hollow coal tree of Nova Scotia.” Upwards of 40 species of Pupa have been found fossil in eocene strata. The Purbeck limestone contains a modern-looking Physa ; and other species of extraordinary size are found in the older tertiary of France, and also in Central India, where the genus does not exist at the present day. The fresh-water eocene of the Isle of Wight and Paris has afforded many spe¬ cies of Limncea and Planorbis ; a Glandina rivalling in size the G. truncata of South Carolina ; a Cyclostoma, with a sculp¬ tured operculum like the Cyclotus J amaicensis ; and an elon¬ gated species of the section Megalomastoma, which is now liv¬ ing in both East and AVest Indies. At Hordle has been found the little Helix labyrinthicus, still living in Texas ; and in the south of France occur representatives of the Brazilian genera Megaspira and Anastoma (fig. 19, 9). In the mioccne is found another genus ( Ferussina , fig. 19, 10) resembling the lamp-snail, but supposed to be operculated. The Pulmonifera of the Eng¬ lish pliocene are in a few instances extinct, at least in England ; nearly all are still living here, but more or less abundant now than they were in the times of the mastodon and elephant. The extinct land-snails of the Atlantic islands Madeira and Porto Santo are associated with remains of many recent species occurring in numbers which have relatively altered, telling the same tale of gradual changes, affecting some species prejudici¬ ally, but favourable to the increase of others. The fossil land- snails of St. Helena were supposed by Mr. Darwin to have become
80
PALAEONTOLOGY
finally extinct only in tlie last century, owing to tire destruction of the native woods by tlie instrumentality of goats and swine.
Tectibranchiata. — The families typified by Tornatella, Ringi- cula, and Bulla played a more important part in the secondary and tertiary periods, but their affinities have been seldom un¬ derstood. The cone-like Adeonina appeared in the carbonifer¬ ous rocks, and attained a remarkable development in the lias («g. 18, 10V They were succeeded by the A cteonellcc, with a plaited columella, in the cretaceous strata ; and by Volvaria (fig- ii) in the eocene. Tlie diminutive Ringiculce of our seas were preceded by large species of the same genus in the tertiaries, and by Cinulia (fig. 18, 9), GlobiconcJia, and Tylo- stoma, in the cretaceous strata. The genus Varigcra has varices recurring twice in each whirl, like Eulirna ; and Pterodonta is winged like S trombus.
Class IV.— CEPHALOPODA.
Order 1. — Tetrabranchiata.
( Nautiloid Cephcdapoda.)
Of the lower group of Ceplialopods, possessing chambered shells similar to the pearly Nautili, there are 1400 extinct species, belonging to above 30 genera, while 3 or 4 species alone exist in modern seas. These fossils resemble the Nauti¬ lus, and differ from the dibranchiate Spirula in the structure of their shell, which is composed of two layers, the outer por- cellanous, the inner pearly ; whereas the Spirula — an internal shell — is entirely nacreous. They also agree with the Nauti¬ lus in the relative capacity of their last chamber, which seems obviously large enough to contain the whole animal. More¬ over, it appears, from the position of the siphuncle and the form of the aperture, that these shells were revolutely spiral, or coiled over the back of the animal, and not involute like the Spirula. No traces of fossil ink (sepia) or horny claws have been found associated with them, nor any indications of
CEPHALOPODA
81
dense muscular tissue, even in the same matrix which has pre¬ served so completely the mummy cuttle-fish. By their form and size they were ill adapted for rapid locomotion, and must have depended for safety on the shelter afforded by their solid shell. The discoidal A mmonites attained a diameter approach¬ ing 3 feet, and the straight-shelled Orthocerata were sometimes not less than 6 feet in length. These latter must have lived habitually in a position nearly vertical ; whilst the discoidal genera would creep over the sea-bed with their air-chambers above them, like a snail-shell reversed. The Ammonites ap¬ pear to have been provided with an operculum, more secure than the “hood” of the Nautilus, composed, like it, of two elements, not, however, fibrous and confluent, but calcified and united by a straight suture. These opercula, which have been mistaken for bivalve shells, have a porous structure altogether peculiar, and are frequently sculptured on their outer convex surface ; whilst their concavity exhibits only lines of growth (fig. 21, 7). Special forms are associated, in all localities, with particular species of ammonite ; and their size is adapted exactly to the specimens in which they are found. Calcareous mandibles occur in all the secondary strata, but not, hitherto, in such numbers or circumstances as to imply that they belonged to any other genus beside the true Nautilus. They are of two forms : those corresponding to the upper mandible (fig. 21, b) have been called “ Rhyncholit.es” ( Palceo - teuthis and Rynchoteuthis of d’Orbigny) ; whilst the lower man¬ dibles constitute the genus Concliorliynclius of De Blainville (fig. 21, 9). The arms of the extinct Tetrabranchs may have been organized like those of the Nautilus, but were probably less numerous in the genera with slender shells, and in those early forms with a small many-lobed aperture. The length of the body-chamber is greatest when its diameter is least ; and the prominent spines which ornament the exterior are par¬ titioned off internally by a nacreous lamina, indicating con-
G
82
PALEONTOLOGY
siderable motion of tlie animal in its shell. When the outer shell of the fossil is removed by decomposition or the ham¬ mer, the margins of the internal septa (or partitions of the air-chambers) are exposed : these marginal lines are called “ sutures.”
The chambered shells may be divided into two principal groups, viz., those with simple sutures, like the recent Nauti¬ lus ; and those in which the margins of the septa are lobed and foliaceous, the Ammonites. In the former the siphuncle is central or internal ( i.e ., at the margin next the spire) ; in the latter it is external (i.e., at the back of the shell, but ventral as regards the animal). There are, however, Nautili with lobed sutures ( Aturia , Bronn, fig. 19, i) ; and some with an exter¬ nal siphuncle ( Cryptoceras , d’Orb.) And on the other hand, the sutures of the Ammonite are at first very slightly lobed, and become progressively more complex ; so that specimens of the same species have been referred to three genera — Goni- atites, Ceratites, and Ammonites — according to their age.
With the exception of Goniatites, the Ammonitidce are peculiar to, and co-extensive with, the secondary strata ; while the Nautilidce, with the exception of Nautilus and Aturia, are confined to the palaeozoic rocks. But the palaeozoic so-called Nautilidce exhibitpeculiarities suggesting very wide differences from the modern pearly Nautilus. It has been proposed to associate the greater part of them with the Orthocerata as a distinct family, but at present the data are defective. Like the Ammonitidce, their shells assume almost every conceivable form and curvature, and the genera founded on these charac¬ ters are very ill defined.
The simplest form of Orthoceras is like a Nautilus unrolled ; and Lituites (fig. 20, 2) is the same with the apex spiral. Some of the carboniferous Nautili have a square back, and the whirls either compact or open in the centre (fig. 20, 1) ; whilst the last chamber is more or less disunited. The species with the
CEPHALOPODA.
83
whirls quite disunited constitute the genus Trigonoceras, M‘C. (— Nautiloccrcis, d'Orb.) The Silurian genus Trochoceras, Barr, is a spiral Nautilus. Clymenia, a characteristic Devonian fossil, has angular sutures and an internal siphuncle ; it may perhaps he coiled up ventrally like the Spirilla. The tertiary shell called Nautilus zic-zac ( Aturici , Br., fig. 19, i, 2), which is so widely distributed in Europe, America, and India, has a siphuncle nearly marginal when young, hut gradually becom¬ ing more central in the adult : it has no special relation to Clymenia.
Those species of Orthocerata in which the aperture is con¬ tracted form the genus Apioccras, Fischer ( = Poterioceras, M‘C.), or when also curved, the Oncoceras of Hall. In Bar- rande’s genus Ascoccras (fig. 20, 9), the shell is flask-shaped, the chambered and siphunculated apex being apparently deciduous ; the aperture is contracted, and the air-chambers occupy only the dorsal half of the shell. In Phragmoceras (fig. 20, 7), the shell is slightly curved to the ventral side, and the aperture is remarkably contracted, the opening for the respiratory funnel being nearly distinct from the cephalic aperture. In Cyrtoceras the curvature is dorsal.
In some other members of this family the siphuncle attains a remarkable size or extraordinary complexity.
In Camaroceras (fig. 20, 4), the siphuncle is lateral, quite simple, and equal to half the diameter of the shell. Casts of these great siphuncles were called “ Hyolites ” by Eichwald ; they frequently contain small shells of Orthoceras, Bcllerophon, and other genera. In some species the siphuncle is strength¬ ened internally by repeated layers of shell, or partitioned off by a succession of funnel-shaped diaphragms ; these constitute the genus Endoccras of Ilall. The same author has given the name Discosorus to a fossil which is evidently the siphuncle of some very delicate and perishable chambered shell (fig. 20, 6). In those Orthocerata with siphuncles most nearly resembling
PALAEONTOLOGY
84
the Discosorus they diminish rapidly towards the last chamber. Perhaps the most remarkable fossil of this group is the Huronia (fig. 20, 5), found in the upper Silurian limestone of Drum¬ mond Island. Siphuncles 6 feet in length and H inch in diameter, were seen by Dr. Bigsby in the cliffs ; they are sili- cified, and stand out in hold relief from the matrix, hut are un¬ accompanied hy any vestige of the shell, except in one or two instances, where the septa are faintly indicated by coloured lines. They are sometimes overgrown with coral, and were
Fig. 20.
1. Nautiloceras Omalii, de Kon.; Carboniferous, Belgium.
2. Lituites (Breynius), TJ. Silurian, Sweden.
3. Section of Clymenia, showing internal siphuncle ; Devonian, Petlierwin.
4. Section of Camaroceras duplex, Wahl. ; L. Silurian , Russia.
5. Sipliuncle of Huronia Bigsbyi, Stokes ; with outline of shell, and septa.
6. Sipliuncle of Discosorus, Hall ; U. Silurian, Lake Huron.
7. Phragmoceras ventricosum, Shy.; L . Ludlow rock, Herefordshire.
8. Gyroceras Eifeliense, d’Arch. ; Devonian, Prussia.
9. Ascoceras Bohemicum, Barr. ; U. Silurian, Prague.
10. Goniatites, Henslowi, Shy. ; Carboniferous, Asturias.
evidently so durable as to remain on the sea-bed long after the shell itself had decayed. The joints of the sipliuncle are swollen at the upper part, and the interior is filled with an irregularly-radiated structure, apparently produced by the plaiting and calcification of the lining membrane. This struc-
CEPHALOPODA
85
tiire also exists and is very regular in the siphuncle of the Devonian Orthoceras trigonale, and in the shells referred to Gyroceras by d’Orhigny (fig. 20, 8) ; also in Actinoceras, a sub- genus of Orthoceras, discovered by Dr. Bigsby, and described by Stokes ( Gcol . Trans., vol. i., 1825). The plication of this in¬ terior structure takes place in segments corresponding to the septa, and meeting in the centres of the sipliuncular beads, leaving spaces or foramina for the passage of blood-vessels to the lining membrane of the air-chambers.* The vascularity of the latter is well shown in the impression of septa on the fine mudstones of the Ludlow rock, often mistaken for Spon- garia, which they somewhat resemble.
Towards the conclusion of its growth the air-chambers of the Orthoceras frequently become shallower, and the siphuncle diminishes in size. These indications of changed or diminished energies are accompanied by a diminution or disappearance of the internal radiated structure in the last part of the siphuncle.
In Orthoceras bisiphonatum ( Tretoceras , Salter) the body- chamber is prolonged in the form of a marginal lobe, simulat¬ ing a second siphuncle.
The genus Bactrites of Sandberger also resembles an Ortho¬ ceras with single-lobed sutures.
Ammonitidce. — In the second division or family of cham¬ bered shells — those with lobed sutures and a marginal si- phuncle — we find a similar series of forms, straight, spiral, and discoidal, but more varied and more highly ornamented.
One large genus ( Goniatites , fig. 20, io) is found in the Devonian, carboniferous, and triassic strata, and permanently resembles the youngest form of the Ammonites, having the su¬ tures lobed but not foliated. They seldom exceed G inches in diameter and are usually very much smaller. The whiils aie
* In the carboniferous species of Actinoceras (ex/., A. giganteum), these for- amina form a cross on the ventral side of the siphuncle*
86
PALAEONTOLOGY
most frequently concealed to some extent, and often marked by cross furrows or “ periodic mouths.”
The Ceratites are distinguished by having the lobes of the sutures serrated, while the intervening “ saddles” (or curves directed towards the aperture) are simple. They are found in the trias of Europe, Thibet, and South America ; and again, though rarely, in the cretaceous strata of France and Syria — a circumstance quite anomalous in the history of the geological
Fig. 21.
1 . Ceratites nodosus ; Muschellcalk, Bavaria.
2. Ammonites Duncani (spinosus, Sby.) ; Oxford Clay , Wilts.
3. Turrilites. 5. Hamites.
4. Baculites. 6. Ancyloceras.
7. (Trigonellites or Aptyclius), operculum of Ammonites.
8. (Rhyncholites hirundo), upper mandible of Nautilus arietis, Rein. Mus-
chellcalh.
• Lower mandible (Conchorynchus avirostris).
distribution of life. Many Ammonites, perhaps all, are like Ceratites when young.
A bisected specimen of the Ammonites ol>tusus, in the Hunterian collection (No. 188), shows well the extent of the last, or inhabited, chamber of the shell, and the effects of the influence of the animal matter of the decaying cephalopod
CEPHALOPODA
87
upon tlie petrifactive processes after death. The liassic clay has penetrated as far as the retracted soft parts of the ammonite permitted : the decomposing mollusk had been partially replaced by crystals of silex, discoloured by the pigmental or carbonized parts of the animal. The silex, which has more slowly infiltrated through the pores of the shell into the air-chambers, is of a much lighter colour. In the same col¬ lection may be seen exemplifications of injury and repair of the shell. In No. 195, Ammonites Goliathus, from “ Oxford clay,” a portion of the shell, at the period when it formed the dwelling-chamber, “had been broken away during the life¬ time of the animal, and repaired by fresh nacreous material, wanting the ribbed structure of the originally formed shell.”
The species of Ammonite exceed 500 ; and their range is co-extensive with that of the secondary rocks. They are found throughout Europe, and at the Cape, in Kamtschatka, Thibet, and S. India. They are absent from a large area of the United States, but are found in the cretaceous strata of New Jersey, Missouri, and the West Indian Islands ; also in Chili and Bogota.
The sections into which, for the sake of convenience, this extremely natural group has been broken up, are very ill-defined, and have no pretension to be considered sub¬ generic. The group (called Cctssiani ) characterising the triassic period, is remarkable for many-lobed and elaborately- foliated sutures — a circumstance more important because it is the oldest group, and associated with Ceratites and the last-surviving Goniatites and Orthocerata. They abound in the “ alpine limestone” of St. Cassian, and IJallstatt in Austria. A second group ( Arietes ), having the back keeled,
* Catalogue of Fossil Invertebrata, Mus. College of Surgeons, London, 4to, p. 43, in wliich work the writer has described upwards of 350 specimens, illustrative of the different sections of Ammonitidse, collected by John Hunter in the last century.
88
PALAEONTOLOGY
with a furrow on each side of tlie keel, as in the great Ammo¬ nites called Bucklandi and Coneybearei, mark the lias period ; they are less plentiful in the oolites, and are represented in the greensands by the Cristati, which are keeled, but not furrowed, and develope a “beak,” or process, from the keel when adult. The Arietes pass by many intermediate forms into the Falciferi (e. g., A . serpentinm), also characteristic of the upper lias, and these are represented by a few quoit-shaped species [Disci), with sharp backs, in the oolites.
Ammonites with serrated keels ( Amalthei ), exemplified by A. spinatus and margaritatus, abound in the middle and upper lias, and again in the oolites (e. g., A. cordatus and excavatus). They are succeeded by the Rothomagenses in the chalk — thick Ammonites with a line of tubercles in the place of the keel.
Ammonites with channelled backs (Colliciati) are repre¬ sented in the lias (A. anguliferus), inferior oolites [A. Parkin- soni), and middle oolite (A. (incepts) , and in the cretaceous strata by numerous species (e. g., A . serratus , lautus, and fal- catus), remarkable for their elegance.
Of the species with backs more or less squared, armatus and capricornus occur in the lias, cithlctci and p&vciTmcitus in the Oxfordian. But the oolitic forms which have the back square, and ornamented with two rows of spines when young, like Goweri, Duncani (fig. 21, 2), and Jason, become rounded and unarmed in their old age.
Bound-backed Ammonites abound in the lias and oolites. Ihc snake-like annulcitus, the spine-bearing covonatus, and Jimbriatus with its ornamented fringes, have been regarded as types of small groups. A more important division ( Ligati ) is distinguished by nearly smooth whirls, constrictions recur¬ ring at regular intervals. These are seen in A. tatricus, and others related to Hefarophyllus ; in many neocomian Ammo¬ nites, and in A. plcinulatus of the lower chalk.
CEPHALOPODA
89
These constrictions, often accompanied by a prominent rib, undoubtedly indicate periods of rest, when the Ammo¬ nite ceased for a while to grow. They may be traced in species belonging to other groups, as well, e.g., in Mplex and triplicatus, as in the Ligciti; but most frequently all indications are obli¬ terated by subsequent growth. It has been a question whether the lateral processes of Ammonites Duncani (fig. 21, 2), are formed and removed periodically, or whether they are pecu¬ liar to the adults, and mark the close of their outward growth. The first conclusion is more probable from analogy ; and they are commonly found with small and apparently young shells, but not (any more than the lateral spines of the living Argo¬ naut) in those of adult size and condition.
It was remarked by the elder Sowerby that Ammonites were most beautiful when of middle growth, the ornamental characters being less developed in the young, and lost in the adult. The ribs and spines, and even the keel or furrow of the back disappear, in many instances, from the body-whirl of the full-grown shell.
Varieties of form, such as marked the palaeozoic Nautilidce, are met with in the Ammonitidce, chiefly towards the close of their reign. The Baculite (fig. 21, 4), with its straight shell, is characteristic of the upper chalk ; and the TurriliU, which is spiral, and usually a left-handed spiral, abounds in the lowest beds of the same formation. In Hamites the shell is straight, returning upon itself after a certain space, and forming a simple or complex hook. In Btychoce/rcis these limbs of the hook-like shell are in close contact. The Toxoceras is curved like a bow ; in Crioceras the discoidal whirls are separate ; and in Scaphites (including Ancyloceras ) the shell, at first compact like an Ammonite, or open- whirled like Crioceras, lengthens out finally, and returns upon itself like the crozier of the Hamite. Hcli- coceras, again, connects the last with the Tun tide by its elevated spire terminating in a prolonged crozier.
90
PALAEONTOLOGY
Of these forms, Ancyloceras alone is found in the oolites ; all the rest are cretaceous ; and most abound in the alpine districts of the south of France.
Order 2. — Djbranchiata.
( Cuttle-fishes.)
Of the two great divisions of ceplralopodous Mollusca, that which is represented at the present day by the pearly Nautilus was developed in the greatest profusion and variety in the palaeozoic and secondary periods ; whilst the more active and intelligent cuttle-fishes and scpiids have not been (certainly^ found in rocks older than the lias, and scarcely above 100 are found in the whole secondary and tertiary series, while twice as many have been obtained in existing seas.
The Sepiadce are represented in the middle and upper oolites by the genus Coccoteuthis (fig. 22, 6^, whose strong and granulated bone is furnished with broader lateral expansions than the recent cuttle-fishes. In the older tertiaries of London and Paris, many species of Sepia appear to have existed, but only the solid mitcro (fig. 22, s) of the shell is usually pre¬ served. In the miocene tertiary of Malta, a diminutive cuttle-bone is not rare ; and at Turin a remarkable form (Spirulirostra, fig. 22, 7) has been discovered, in which the apex is provided with a chambered and siphonated cavity like the shell of the Spirula. Two other genera, Beloptera (fig. 22, 8) and Belemnoris, very imperfectly known by rare and fragmentary examples, occur in the eocene tertiary.
Remains of the Calamaries (. Tmthidce ) are often found in the fine-grained and laminated argillaceous limestones of the lias and Oxford clays, as at Lyme Regis, and Boll of Solenhofen. Some of these are slender, like the pens of the recent Ovima- strephes, and furnished with a small conical appendix, as in that genus , whilst others are broad, and pointed at each end (Beloteuthis). The most common form has the shaft wide
CEPHALOPODA
91
and longer than the wings, and is truncated posteriorly. It has a nacreous lining, and is usually accompanied by a large and well-preserved ink-hag (fig. 22, 4). These were called Belemnosepia by Agassiz and Buckland, who supposed them to belong to the same animal with the Belemnite. They have also been called Loligo-sepice and Loliginites ; but the name Geoteuthis, given by Count Munster, appears less objection¬ able. One species ( Mastigophora h'evipinnis *\ is of frequent occurrence in the Oxford clay near Chippenham, which retains not only the horny (chitinous) pen and ink-bag, but also the muscular mantle, the rhombic terminal fins, and at least the bases of the arms, with the minute hooks, and traces of the mandibles. Horny claws, like those of the uncinated Calamary ( Onychoteuthis ), have been observed arranged in double series in the lias of Watchett, and they sometimes occur in great numbers in the coprolitic remains of the Enctlio- sauri. The most remarkable examples of this kind are pre¬ served in the lithographic limestones of Solenliofen, and show that the extinct Calamary had ten nearly equal arms, the tentacles, in their retracted condition, being undistinguish- able from the rest — each furnished with 20 to 30 pairs of formidable hooks. What further evidence was needed respecting the nature of this creature has been supplied by the Chippenham fossils, which in all probability are iden¬ tical in genus, if not in species, with the Accinthoteuthis described by Munster. One of these extraordinary fossils — the mummy of a cuttle-fish more ancient than the chalk for¬ mation and the upper oolites — is represented in (fig. 22, 2,) reduced to one-sixth from the original in the British Museum. Nine of the arms are preserved, the sclerotic plates of the eyes, the bases of the large lateral fins, the small ink-bag, and the conical shell. This shell, which is chambered internally,
* Catalogue of Fossil Invertebrata, in the Museum of the College of Surgeons, London. 4to, 1856, p. 1.
92
PALEONTOLOGY
like the phragmocone of the Belemnite (fig. 22, i), has an outer sheath of fibrous structure, one-fourth of an inch thick at the
1. Belemnites Oweni ; Oxford Clay, Chippenham, p. Phragmocone exposed by the removal of the fibrous guard from one side ; s, septum, showing the marginal sipliuncle.
2. Acanthoteuthis antiquus (Cunnington) Oxford Clay, Chippenham ; dorsal aspect.
3. Conoteuthis Dupinii ; Gault, Folkestone.
4. Geoteuthis.
5. Sepia.
6. Coccoteuthis.
7. Spirulirostra.
8. Beloptera anomala.
apex, and furnished with two converging ridges on its dorsal side ; the external surface, however, is horny (or chitinous), like the pen ot the Calamary. These chambered shells occur in great numbers, and are so like the phragmocones of the associated Belemnites, both in structure and proportions, that, they were originally described by me as such,* and 1 still view them as evidences of the close affinity of the cephalopod possessing them to the true Belemnite : hitherto they have only been noticed in the laminated Oxford clay of Wilts, and the equivalent lithographic shales of Solenhofen.
* Philosophical Transactions, 1844; and Cat. Fossil Invert., Mus. Coll, of Surgeons. 4to, p. 5.
CEPHALOPODA
93
Species of Belemnite are found in all the oolitic and cre¬ taceous strata, from the lowest lias to the upper chalk. In its ordinary imperfect state, it is a cylinder pointed at one end (fig. 22, i), and truncated or excavated by a funnel- shaped cavity ( alveolus , ib. p) at the other, and has a radiating fibrous structure, with less distinct concentric laminae of growth. But even this “guard,” which corresponds simply to the “mucro” of the cuttle-hone (ib. 5), exhibits such remarkable modifications of form, thatnearly 100 species have been founded upon no higher evidence. In some Belemnites of half an inch diameter, the guard is scarcely an inch longer than the pliragmocone, whilst in others it attains a length of ten inches, and is tubular, as in B. acuarius. Some are fusiform, others laterally compressed ; some have a longitudinal groove extending from the apex along the upper or under side, and in others the apex is furrowed laterally as well. The Belem¬ nites of the chalk have been called Belemnitellce (d’Orb.), because they have a slit in the ventral side of the alveolar border of the guard ; their external surface also exhibits more distinct traces of vascular impressions.
Specimens of Belemnite have been discovered in which the guard had been broken during the lifetime of the animal ; but the broken portions, being held together by the investing orga¬ nised integuments, had been re-united by the deposition ol new layers of the fibrous structure peculiar to the guard. Several examples of Belemnites, with the apex injured and healed during life, are preserved in the British Museum. In all perfect Belemnites, the alveolus is occupied by a pliragmo¬ cone (fig. 22, p), with tender nacreous walls and septa, terminating in a minute globular apex, and perforated by a ventral siphuncle (fig. 22, i). The last chamber is larely preserved, and appears to have thinned oft into a mere horny sheath, with sometimes two pearly bands like knife-blades on the dorsal side. It must have been sufficiently capacious to
PALEONTOLOGY
94
contain all the viscera. The ink-bag has been very rarely found, and is even smaller than in the last genus, as if in relation to the more greatly developed shell.
The Gonoteutliis (fig. 22, 3) of the Gault has an oblique phragmocone, with a very thin shell, and seems to have been attached to a slender style, like the funnel-shaped appendix of the gladius in the recent sagittated Calamary.
Mr. Dana has described, under the name Hclicerus Fugi- ensis, a belemnitoid fossil from the “slate” rock of Cape Horn. It is half an inch in diameter, has a thick fibrous guard, and the slender pliragmacone terminates in a fusiform spiral nucleus.*
Subjoined is a table of the extinct genera of the mollus¬ cous province : —
Brachiopoda. — Trigonosemus, Lyra, Magas, Rhynchora, Zel- lania, Stringoceplialus, Meganteris ; Spirifera, Cyrtia, Suessia, Athyris, Merista, Retzia, Uncites; Camaro- phoria, Porambonites, Pentamerus, Atrypa, Anoplotheca ; Orthis, Orthisina, Strophomena, Koninckia, Davidsonia, Calceola ; Products, Clionetes, Aulosteges, Strophalosia ; Trematis, Siplionotreta ; Obolus.
Conchipera.— Gryphsea, Exogyra, Limanomia, Carolia, Placu- nopsis, Neithea, Eligmus ; Pteroperna, Aucella, Am- bony chia, Cardiola, Eurydesma, Pterinea, Monotis,
I osidonomya, Aviculopecten, GerviPia, Streblopteria, Pulvinites, Inoceramus, Trichites ; Megalina, Orthonotus, Modiolopsis, Iloplomytilus ; Macrodon, Isoarca, Bake- wellia, Uuculina, Nucinella, CucuPeUa, Ctenodonta ; Myophoria, Axinus, Lyrodesma ; Diceras, Monopleura, Pequienia ; Hippurites, Padiolites, Caprinella, Caprina,
* For the drawings and most of the facts, or their verification, relating to invertebrate fossils, the writer is indebted to his experienced colleague in charge of that department of the British Museum, Mr. S. P. Woodward, F.G.S.
VERTEBRATA
95
Caprotina ; Lithocardium, Conocardium, Corbicella, Sphsera, Unicardium, Tancredia, Volupia ; Pleuropborus, Myoconcha, Anthracosia, Megalodon, Pacbydomus, Pachyrisma, Cleobis, Mseonia, Opis, Cardinia, Hippopo- diiun, Megaloma ; Gratekmpia, Sowerbya, Quenstedtia, Goniophora, Eedonia ; Cercomya, Myacites, Goniomya, Grammyria, Ceromya, Cardiomorpba, Edomondia, Bi- beiria.
Gasteropoda. — Belleroplion, Porcellia, Cyrtolites, Ecculiom- pbalus ; Bimella, Hippocrena, Alaria, Spinigera, Ani- berlya ; Leiostomus, Strepsidura, Purpurina, Columbel- lina, Borsonia, Conorbis ; Euspira, Eaticopsis, Globulus, Desliayesia, Loxonema,Macrocbilus; Diastoma, ISTerinsea, Bracbytrema, Ceritella, Vicarya, Scoliostoma, Proto, Holopella, Catautostoma, Xaticedla ; Platyceras, Metop- tonra, Hypodema, Deslonchampsia ; Euomphalus, Opbi- leta, Plianerotinus, Serpularia, Discolielix, Platystoma, Crossostoma, Pleurotomaria, MurcMsonia, Polytremaria, Cirrus, Trochotoma, Platyscbisma, Scalites, Eliaphi- stoma, Holopea, Maclurea ; Neritoma, Yelates, Pileolus ; Helmintbocliiton ; Lyclmus, Dendropupa, Ferussina ; Cylindrites, Acteonina, Acteonella, Ciuulia, Globiconcba, Yarigera, Tylostoma, Pterodonta, Volvaria, Cbilostoma; Vaginella, Tlieca, Pterotbeca, Conularia.
Cephalopoda. — Aturia, Discites, ISTautiloceras, Trigonoceras, Temnocbilus, Lituites, Trocbolites, Trochoceras, Cly- menia; Ortlioceras, Camaroceras, Huronia, Actinoceras, Discosorus, Gouioceras, Tretoceras, Apioceras, Gompho- ceras, Phragmoceras, Cyrtoceras, Gyroceras, Ascoceras; Goniatites, Bactrites, Ceratites, Ammonites, Crioceras, Toxiceras, Ancyloceras, Scapliites, Iielicoceras, Tur- rilites, Hamites, Ptychoceras, Baculites; Mastigophora, Teudopsis, Beloteuthis, Geoteutliis, Leptoteuthis, Bel-
9G
PALAEONTOLOGY
emnites, Acanthoteuthis, Helicerus, Conoteuthis, Cocco- teutliis, Belosepia, Spirliurostra, Beloptera, Belemnosis.
Province IV.— VEETEBEATA.
There is an enormous series of subaqueous sediment, originally composed of mud, sand, or pebbles, the successive bottoms of a former sea, derived from pre-existing rocks, which has not undergone any change from heat, and in which no trace of organic life has yet been detected. These non- fossiliferous, non-crystalline, sedimentary beds form, in all countries where they have yet been examined, the base-rocks on which the Cambrian or oldest Silurian strata rest.
Whether they be significative of ocean abysses never reached by the remains of coeval living beings, or whether they truly indicate the period antecedent to the beginning of life on this planet, are questions of the deepest significance, and demanding much farther observation before they can be authoritatively answered.
It has been shown that every type of invertebrate animal is represented in the superimposed stratified deposits called Cambrian and lower Silurian.
An important work* embodying the labours of the accomplished naturalist and acute observer, Dr. Christian H. Pander, has recently been published by the Russian govern¬ ment, descriptive of the fossil fishes of the Silurian formations ot that empire. Of some hundred fossils described and beautifully figured in this work, and referred to different genera and species of fishes, from lower Silurian rocks, the writer, after the closest comparison and consideration of the evidence, is disposed to regard only those referred by Pander to the genera Ctenognathus, Cordylodus, and Gnathodns, as
* Monographic der Fossilen Fische ( Untersilwrische Fische Conodonten, etc.), 4to, Petersburg!!, 185G.
VERTEBRATA
97
having any probable claims to vertebrate rank ; and to this admission must be appended the remark, that the parts referred to jaws and teeth may be but remains of the dentated claws of Crustacea. With regard to the fossils called “ Conodonts * on which the main part of M. Pander’s evidence of lower Silurian fishes rests, the following remarks, penned after microscopic examination of original specimens, are applicable to them.
Minute, glistening, slender, conical bodies, hollow at the base, pointed at the end, more or less bent, with sharp opposite margins, might well be lingual teeth of Gastropods, acetabular hooklets of Cephalopods, or teeth of cartilaginous fishes. Against the latter determination is the minute size of the “ Conodont ’’ bodies. Their basal cavity doubtless contained a formative pulp, but the proof that the product of such pulp was “ dentine ” is wanting : the observed structure of the hooklet presents concentric conical lamellae of a dense structureless substance, containing minute nuclei or cells.
In some specimens the base is abruptly produced and divided from the body of the hooklet by a constriction — a form unknown in the teeth of any fishes, but presented by certain lingual teeth of Gastropods — e.g., the lateral teeth of Sparella. In other Conodonts the elongated base is denticulate or serrate, as in the lateral teeth of Buccinum and Chrysodomm. It is improbable, however, that they belong to any conchiferons toothed Mollusk, the shells of such being wanting in the deposit where the Conodonts are most abundant.
The more minute hooklets have a yellowish, transparent, horny appearance ; the larger, perhaps older ones, present a harder whitish appearance. Their analysis by Pander yielded “ carbonate of lime,” carbonic acid being evolved by application of dilute nitric acid, and oxalic acid producing an obvious pre¬ cipitate. Some English analysts have believed that the Cono¬ donts yielded a trace of phosphate of lime.
H
98
PALAEONTOLOGY
The detached condition of the booklets, and the integrity of the thin border of the basal pulp-cavity, indicate that they have not been broken away from any of those kinds of attachment to a bone which the minute villiform teeth of osseous fishes would show signs of. The Oonodonts have been supported upon a soft substance, such as the skin of a mollusk or worm, the mucous membrane of a mouth or throat, or the covering of a proboscis ; hut to select the teeth of cyclostomous or plagiostomous fishes as the exclusive illus¬ tration of the above condition, would he to take a partial and limited view of the subject.
In comparing the Conodonts with the teeth of fishes, they present most resemblance to the minute conical recurved teeth of the genus Rliinodon of Smith : they more remotely resemble the conical, pointed, horny teeth of Myxinoids and Lampreys in that class : and the absence of any other hard part in the strata containing the Conodonts tallies with the condition of the cartilaginous skeleton ; but not more than it does with the like perishable soft condition of annelidous worms and naked mollusks. Rliinodon has very small teeth, “ en brosse,” of a simple conical recurved form : there are 12 or 13 teeth in each vertical row, and about 250 such rows in each jaw : so that each fish may have from 6000 to 7000 teeth. But the teeth of Rliinodon have not the basal extensions and processes of many of the Conodonts ; and the teeth of all known Cyclostomes are much less slender and are less varied in form than in the Conodonts. Certain lingual plates of Myxinoids are serrate, but not with a main denticle of much greater length — such as shown in the form of the Conodont called Machairodus by Pander. Most cyclostomous teeth are simple, thick cones, with a subcircular base ; and every known tooth of a cyclostomous fish is much larger than any of the forms of Conodon, which rarely equal half a line in length. This minuteness of size, with the peculiarities of
PLAGIOSTOMI
99
form, supports a reference of the Conodonts rather to some soft invertebrate genus. Certain parts of small Crustacea — e.g., the pygidium or tail of some minute Entomostraca — resemble in shape the more simple Conodonts ; but when we perceive that these bodies occur in thousands, detached, with entire bases, and that any part of the carapace, or shell of an Entomostracan or other Crustacean, has been rarely detected in the lower Silurian Conodont beds, it is highly improbable that they can have belonged to an organism protected by a substance as susceptible of preservation as their own substance. Much more likely is it that the body to which the minute hooklets were attached was as soluble and perishable as the soft pulp upon which the Conodont was sheathed. The writer finds no form of spine, denticle, or booklet in any Eckinoderm, and especially in any soft-bodied one, to match the Conodonts ; and concludes that they have most analogy with the spines, or hooklets, or denticles of naked Mollusks or Annelides. The formal publication of these minute ambiguous bodies of the oldest fossiliferous rocks, as proved evidences of fishes, is much to be deprecated.
Class L— PISCES.
Order 1. — Plagiostomi.
[Sharks, Rays.)
Char. — Endo-skeleton cartilaginous or partially ossified ; exo¬ skeleton placoid ; gills fixed with five or more gill- apertures ; no swim-bladder ; scapular arch detached from the head ; ventrals abdominal ; intestine with spiral valve.*
The earliest good evidence which has been obtained of a vertebrate animal in the earth’s crust is a spine, of the nature
* For an explanation of the technical terms in these characters, see the article Ichthyology, especially of the scales, Enc. Brit. vol. xii., p. 21b.
100
PALAEONTOLOGY
of the dorsal spine of the dog-fish (. Acanthias ), and a buckler like that of Cephalaspis. Both have been found in the most recent deposits of the Silurian period, in the formation called “ upper Ludlow rock.” The discovery of the first is due to Murchison ;* its determination to Agassiz, who assigns it to a genus of plagiostomous cartilaginous fishes called Onchus. The buckler was discovered by Mr. Banks, in the “ passage- beds ” of Kington, Herefordshire, and is referred to the genus Ptcraspis, Ivnerr, with microscopic evidence of its piscine nature, by Huxley.
The Onclius spines from the upper Ludlow bone-beds are compressed, slightly curved, less than two inches in length, with no trace at their base of the joint characteristic of the dorsal spines of the “ sheat-fishes ” (Ganoids of the family Siluridce), or “ file-fishes ” ( Balistidce ). The sides of the spine are finely grooved lengthwise, with rounded ribs between the grooves. They are referred to two species — Onchus Murchisoni, and 0. semistriatus. Sir P. Egerton has lately figured another species from the argillaceous beds near Ludlow, which is more curved, and is armed along the posterior edge ; the longitudinal ribs are fine and numerous, but are constricted at intervals, as in the genus Ctenacanthus, and become subtuberculate at the base. He deems them significant of a distinct genus of shark¬ like fishes, t
With the dorsal spines of Onchus are found petrified por¬ tions of skin, tubercular and prickly, like the shagreen of shark’s skin, and referred to a genus called Sphagodus ; also coprolitic bodies of phosphate and carbonate of lime, including recognisable parts of the small Mollusks and Crinoids which
* Silurian System, ch. xlv., p. 606.
t In a formation in Indiana, United States of America, referred by Messrs. Norwood and Dale Owen to the Silurian formation, a badly-preserved fossil, considered as an Ichthyolite, and referred to a genus allied to Pterichlhys, has been discovered, and called Macropetalichthys raphiidolaMs. (Silliman’s Journal, 1846, p. 367.)
PLAGIOSTOMI
101
inhabited the sea-bottom in company with the Onchus-fish. No vertebrae, or other parts of the endo-skeleton of a fish, have been discovered, unless the fragments of a calcified bar, with tooth-like processes, called Plectrodus, be truly jaws with teeth. They resemble, however, parts of the pincer claws of Crustaceans, as well as of the jaws and teeth of fishes, and do not indicate that class so satisfactorily as the Onchus spines and Sphagodus shagreen. Yet the denticles are confluent with an outer ridge of the bone, according to the “ pleurodont ” type, and consist of separated large teeth, with minute serial teeth in the interspaces ; and the large teeth are grooved longitudinally.*
If the Plectrodonts be jaws with anchylosed teeth, they belong to an order distinct from the Plagiostovii. If they should belong to any of the fishes indicated by the dorsal spines and shagreen skin, a combination of characters would be exemplified not known in other formations or in any exist¬ ing fishes.
No detached teeth unequivocally referable to a plagi- ostomous genus, nor any true ganoid scale of a fish, have yet been found in the formations that have revealed these earliest known evidences of vertebrate animals. What, then, it may be asked, were the conditions under which so immense an extent, as well as amount, of sediment was deposited — including chambered Cephalopods, Gastropods, Lamellibranchs, Bracliio- pods, various and large trilobitic and entomostracous Crustace¬ ans, with Crinoids, Polypes, and Protozoa — that precluded the preservation of the fossilizable parts of fishes, it that class of vertebrate animals had existed in numbers, and under the variety of forms, comparable to those that people the ocean at the present day 1 Bonitos now pursue flying-fishes through the upper regions of an ocean as deep as any known pait of the Silurian seas of which the deposits afford an idea of greatest * Egerton, Proc. Geol. Soc., March 1857, p. 288, pi. x., figs. 2-4.
102
PALAEONTOLOGY
depth. If fishes of cognate habits with the present deep-sea fishes, under whatever difference of form such Silurian fishes may have been manifested, had really existed, we might reasonably expect to find the remains of some of the countless generations that succeeded each other during that vast and indefinite period, sufficing for the gradual deposition of sedi¬ mentary beds of thousands of feet in deptli or vertical thickness.
The evidences of plagiostomous fishes afforded by fossil spines will be here pursued. In most of the existing cartila¬ ginous fishes of this order the defensive spine which stands erect in front of the dorsal fin is smooth ; such is the case in the dog-fishes (Spinacid.ee) in which each dorsal fin is fronted with a spine. In the Port-Jackson sharks ( Cestrciciontidce ) the spine in front of each dorsal is bony, and is armed along its hinder or concave border with bent spines. The fin is connected with this border, and its movements are regulated by the elevation or depression of the spine during the peculiar rotatory action of the body of the shark. This action of the spine in raising and depressing the fin, resembles, Dr. Buckland has remarked, that of the moveable or jointed mast, raising and lowering backwards the sail of a barge. But their more obvious use, in the small Plagiostomes possessing such spines, is as defensive weapons against the larger and stronger voracious fishes. The spine of the Onchus indicates its danger from some larger, and as yet unknown, predatory fish.
Certain bony fishes are similarly armed — e.g., sticklebacks (G aster ostei), sheat-fishes ( Siluridw ), trigger-fishes (Balistcs), and some species of snipe-fishes (. Fistularidcc ). In the latter family the Centriscus humerosus (fig. 23) shows a dorsal spine, denticulated behind, as in the Cestracionts ; but the base of the spine in bony fishes is peculiarly modified for articulation with another bone. In the Plagiostomes the base of the spine is hollow, becomes thin and smooth when the body of the spine is sculptured, and is in the recent fish implanted in the flesh.
PLAGIOSTOMI
103
The following genera of plagiostomous fishes have been founded on the fossil spines, or “ ichthyodorulites,” which have been discovered in the “ Devonian,” or “ Old Red Sandstone
Fig 23.
Centriscus humerosus.
series.” Onchus (represented by 0. semistriatus, 0. heterogyrus), Dimer acanthus, Haplacanthus, Narcodes, Naulas, Byssacanthus, Gosmacanthus, Homacanthus (fig. 2d), Gtenacanthus, Ptyacan- thus, GUmatius, Parexus, Odontacanthus, and Pleuracantlius.
The genus Homacanthus is founded on small compressed spines, with fine recurved teeth on the back edge, and longitudinal striae on the sides. Specimens of Homacanthus arcuatus (fig. 2d) have been found in Devonian formations near St. Petersburg.
The carboniferous series of formations includes the mountain limestone, millstone grit, and the coal measures (see fig. 1). In this series the genus Onchus is still represented by the 0. sul- catus, O. rectus, and 0. subulatus ; and the genus Homacanthus, by H. macrodus and II. microdus, from the carboniferous limestone of Armagh.
Ptyacanthus, Gtenacanthus, and Pleuracantlius are also forms common to the Devonian and carboniferous periods. The spine of the latter genus is denti¬ culated along both margins, a structure which is presented, in existing Plagiostomes, only by species of the ray family ,
Fig. 24.
Homacanthus
arcuatus.
(Devonian,
Russia.)
104
PALAEONTOLOGY
Plewracanthus, therefore, as Agassiz concludes, may offer the earliest example of the flat, form of cartilaginous fish which is represented by the sting-rays ( Trigon , Myliobcites ) in the present seas. The ichthyodorulite (ichthys, a fish ; dor a, a spear ; lithos, a stone) here selected to illustrate this fossil, is a portion of the spine of the Pleicracanthus levissimus (fig. 25), from the carboniferous beds near Dudley. The other plagiostomous genera based upon fossil spines from the coal formations are, — Oraccmthus, Gyra- canthus, Nemacanthm, Cosmacanthus, Leptacan- thus’ Homacanthus, Trystichius, Aster optery chins, (Coal, Dudley.) Physonmms, Sphenacanthus, Platyacanthus, Dip- riacanthus, Erismacanthus, Orthcicanthus, Cladacanthm, Lepracanthus.
Immediately above the coal measures lie a variable series of sands and clays of different colours, including the coal plants ; above this, a marl slate in thin layers, containing scanty evidences of fishes ; but these are more abundant and
Fig.'25.
instructive in the superincumbent magnesian limestone, in which formation, near Belfast, ichthyodorulites of the genus Gyropristis (Ag.) have been found. Above this are the penean red sandstones, in which, at Westoe, have been found fossil spines closely allied to, if not identical with, the Gyracanthus formosus (Ag.) The foregoing formations constitute the upper¬ most of the palaeozoic series called “Permian,” from the Russian province in which these strata are most extensively developed. Their relative position is known by the term “ magnesian limestone ” in the “ Table of Strata,” fig. 1.
The superimposed strata, marked “new red sandstone,” includes also a varied series of red and white sands, marls, and conglomerates, forming collectively the system called “ triassic.” The ichthyodorulites of this system are referable to the genera Nemacanthus, Leiacanthus, and Hybodus. In
PLAGIOSTOMI
105
•lit
w
the “ lias,” which is the oldest or lowest of the great “ oolitic ” system, the dorsal spines of the genus Hybodus (fig. 26), are the largest and most abundant ; this genus, however, is represented by detached teeth in the keuper and musehelkalk members of the “ trias.” The lias formations give evidence that the dorsal spines and fins of Hybodus were two in number ; and the genus is shown, both by the structure of the spine and the form of the teeth, to have had its nearest affinities with the Cestracion amongst existing Plagiostomes. Hybodus continued to be represented by successive and varying specific forms up to, and including, the cretaceous period.
Hybodus is therefore a genus of cartilaginous fishes eminently characteristic of the secondary or mezozoic period in pakeontology, and ranges through every formation of that period. The specimen selected for the illustration of the dorsal spine of Hybodus is that of the H. sub- carinatus, from the Wealden of Tilgate Forest.
Large fossil spines, longitudinally grooved, have been found associated with the teeth of the extinct cestraciont genus ( Ptychodus ) of the chalk formations.
In the tertiary formations, the fossil spines present for the most part the generic characters of those of existing Plagiostomes — e. g., Spinax,
Trigon, and Myliobates ; but one form, found in tire eocene beds near Paris, is the type of the extinct genus A-ulcicctnthus
Fig. 26.
Hybodus sub- car in atus. (Wealden.)
of Agassiz.
The teeth of the plagiostomous fishes — viz., sharks (Sgua- lidce ), rays ( Raiidce ), and Cestracionts, are very numerous, and, being attached only by ligament to the membrane ot the mouth, they must soon fall of! in the decomposition ot
106
PALAEONTOLOGY
the dead fish, become scattered abroad by the movements of the body through the action of the waters, and sink into the sediment.
Family I.— Cestraciontida?.
(Port- Jackson Shark.)
The existing genus which has thrown most light upon the fossil teeth which have thus become imbedded in the oceanic deposits of the pakeozoic and mezozoic periods, is the Cestracion, now restricted to the Australian and Chinese seas, where it is represented by two or three species, and suggests the idea of a form verging towards extinction. It formerly flourished under a great number of varied generic or family modifications, re¬ presented by species, some of which attained dimensions far exceeding the largest known living Cestracions. The denti¬ tion ot these fishes is adapted to the prehension and mastica¬ tion of crustaceous and testaceous animals ; they are of a harmless, timid character ; and have the before-described den¬ ticulate dorsal spines given to them as defensive weapons. Fig. 27 gives a side view of the upper and lower jaws of
the “Port Jackson shark,” showing the oblique disposi¬ tion of the large crushing teeth, which cover like a pavement the working borders of the mouth. The anterior teeth were small and pointed. Behind the cuspidate teeth the five consecutive rows of teeth progressively increase in all their dimensions, but principally in their antero-posterior extent. The sharp point is converted into a longitudinal ridge traversing a con¬ vex crushing surface, and the ridge itself disappears in the
Cestracwn Philippi (recent).
PLAGIOSTOMI.
107
largest teeth. As the teeth increase in size, they diminish in number in each row. The series of the largest teeth includes from six to seven in the upper, and from seven to eight in the lower jaw. Behind this row the teeth, although preserving
Fig. 27 a.
Upper jaw and teeth of Port-Jackson Shark ( Cestracion ), half nat. size.
their form as crushing instruments, progressively diminish in size, while at the same time the number composing each row decreases. From the oblique and apparently spiral disposi¬ tion of the rows of teeth, their symmetrical arrangement on the opposite sides of the jaw, and their graduated diversity of form, they constitute the most elegant tesselated covering to the jaws which is to be met with in the whole class of fishes.
The modifications of the form of the teeth above described, by which the anterior ones are adapted for seizing and re¬ taining, and the posterior for cracking and crushing alimentary substances, are frequently repeated, with various modifications
108
PALAEONTOLOGY
and under different conditions, in the osseous fishes. They indicate, in the present cartilaginous species, a diet of a lower organized character than in the true sharks ; and a correspond¬ ing difference of habit and disposition is associated therewith. The testaceous and crustaceous invertebrate animals constitute most probably the principal food of the Cestracion, as they appear, by their abundant remains in secondary rocks, to have done in regard to the extinct Cestracionts, with whose fossil teeth they are associated.
From their mode of attachment, these teeth would become detached from the jaws of the dead fish, and dispersed in the way above described ; and it is by such detached fossil teeth that we first get dental evidence of the Cestraciont family in former periods of the earth’s history.
The teeth of the Hybodonts are conical, but broader and less sharp than those of true sharks. The enamel is strongly marked by longitudinal grooves and folds. One cone is larger than the rest, and called the “principal the others are “ second¬ ary.” In one genus ( Clctdodus , Ag.), the secondary cones go on enlarging as they recede from the principal cone ; and teeth of this genus, referred by Eichwald to the Hybodus longi- conus, have been discovered in the old red sandstone in the vicinity of Petersburg.
In the Orodus, the cones are more compressed, trenchant,
and distinct from the body of the tooth than in Hybodus ; but they present a principal and secondary cones. Fig. 28 is a tooth of the Orodus cinctus (Ag.), from the car¬ boniferous beds near Bristol. The
Fig. 28.
Orodus cinctus (tooth), (Carboniferous.)
0. porosus and 0. conypressus are from deposits of similar age near Armagh.
If fig. 29 be compared with fig. 27 a, it would seem as if the several teeth of each oblique row in Cestracion had been
PLAGIOSTOMI
109
welded into a single dental mass in Cochliodus, the proportions and direction of the rows being closely analogous. Whether in Cochliodus, there were any small anterior prehensile teeth, is hypothetical ; the large crushing dental plates must have been admirably adapted to crack and bruise the shells of mollusks and crus¬ taceans. The Cochliodus contortus (Ag.) (fig. 29) has been found in the carboniferous formations near Bristol and Armagh, and the genus is peculiar to that geological period.
Teeth referable to the genus Hy- bodus occur in all the secondary rocks from the trias to the chalk inclusive.
A form of tooth which more closely resembles the crush¬ ing-teeth of Cestracion, is that on which the genus Acrodus is founded, and which also ranges from triassic strata to the upper chalk of Maestricht. The species here selected (fig. 30) is the Acrodus nobilis, from the lias of Lyme Begis. The upper figure shows the grinding surface, which, from its finely and transversely striated character and dark colour, has suggested to the quarrymen the name of “ fossil leeches.” The older fos- silists regarded these teeth as petrified Vermes ; but the struc¬ ture, as shown by the microscope, is closely similar to that of the teeth of Cestracion* Portions of the jaw of the Acrodus have been discovered which show that these teeth were ar¬ ranged, as in Cestracion, in oblique rows, wTith at least seven teeth in each row. Acrod.us lateralis is a muschelkalk fossil, A. hirudo a Wealden fossil, and A. transversus a cretaceous
'* See Owen’s Odontography, vol. i., p. 54, pis. 14 and 15.
Fig. 30.
Acrodus nobilis (tooth). (Lias.)
Fig 29.
Cochliodus contortus, Ag. (Carboniferous.)
110
PALAEONTOLOGY
fossil. No tootli referable to the genus lias been found in any tertiary stratum.
The genus Ptychodus is founded on teeth usually of large size, and of a more or less square form (fig. 31). The crown is deeper than the root, which is obtuse and truncate. The enamelled summit of the crown is granulate at the margin, and raised in the middle into an obtuse emi¬ nence, disposed in large transverse, parallel, sometimes wavy and rather sharp ridges. With teeth of this form are sometimes found others of smaller size, with more convex rounded crowns, doubtless forming the ex¬ tremes of the multiserial pavement which, as in modern sharks and rays, covered Ptychodus latissimm. the broad jaws of the Ptychodonts. Large (Chalk). dorsal spines have been found so associa¬ ted with the above-described teeth as to indicate the affinity of the Ptychodus to the Cestraciont family of sharks. All the specimens and species referable to this genus have been found in the cretaceous strata.
Family II. — Squalidae.
(Sharks.)
The well-marked, saw-shaped tooth (fig. 32), so closely re¬ sembles the lower jaw-teeth of the sharks, called “ grisets ” by the French (Kotidanus, Cuv.), as to be referred to that genus by Agassiz. Such teeth nevertheless occur in strata of oolitic age (Kotidanus Miinsteri, Ag., fig. 32). Other species — e. g., K. pedinatus — are found in the chalk of Kent ; and K. serra- tissimus, in the eocene clay at Slieppy.
The tooth (fig. 33) on which Agassiz has founded the genus Corax, indicates by its close resemblance to those of Carcharias, its relationship with the true sharks ( Squalidce ). Most of the
PLAGIOSTOMI
111
species of Corcix, including C. falcatus, are cretaceous ; a few are tertiary : all are extinct.
Fig. 32.
Notidanus Miinsteri. (Upper Oolite.)
Fig. 33.
Corax falcatus. (C'lialk.)
Fig. 34.
Galeocerdo aduncus. (Miocene.)
Another form of shark’s tooth, deeply notched at one mar¬ gin, and with the rest of the border finely denticulate, resembles more that of the “topes” or gray sharks ( Galeus , Cuv.), and is referred by Agassiz to the genus Galeocerdo. The species are found in both the cretaceous and tertiary forma¬ tions ; Galeocerdo aduncus (fig. 34) is from the miocene of Europe and America. In the same tertiary series are found the teeth of the Hemi- pristis serra, Ag. (fig. 35).
Odontaspis (Ag.), presents a form of tooth most like that in the blue sharks ( Lamna ) of the pre- Fig. 35. sent seas. Species of Odontaspis occur in the ere- Hemipristis
serra.
taceous and tertiary beds. The 0. Hopei (fig. 36) (Miocene.) is from the London clay of Sheppy. It indicates a very destructive and formidable species of shark.
Teeth shaped like those of the white sharks (Carcliarias), but solid and usually of large size, are referred to the genus Carcliarodon. One of these teeth, from miocene beds, Malta, in the Hun¬ terian Museum, London, measures 5 inches 10 lines at its longest side, and 4 inches 8 lines across the base. By the side of it is placed a tooth of an Fig. 36. existing Carcharias, 2 inches 3 lines at its “ longest 0c^^esHs side,” from a shark which measured 20 feet in (Eocene.) length. If the tooth of the fossil Carcliarodon bore the same
PALAEONTOLOGY
1 12
proportion to the body of the fish, this must have been
about sixty feet in length.* Teeth of Garcharodon have been obtained from the Bed Crag of Suffolk, mea¬ suring upwards of six inches in length. The microscopic structure of the teeth in sharks is illustrated by the longitudinal section of a fossil from Sheppy, showing the outer hard layer of “vitrodentine,” and the “vaso-dentine” forming the body of the tooth. With these fossil teeth of sharks are found, though
Fig. 36 a.
Magn. section of a tootli of a fossil Shark ( Lamna ).
Side view and back view of the body of a vertebra of a Shark, Lamna or Odontaspis. (London clay, Sheppy.)
sparingly, in both the cretaceous and tertiary beds, petrified
* See the Author’s Catalogue of Fossil Reptilia and Pisces, in Mus. R. Lond. 4to, 1854, p. 124.
Coll, of Surgeons.
PLAGIOSTOMI
113
bodies of vertebrae, showing by their extreme shortness in com¬ parison with their breadth, by their bi-concavity, and the fissures on the external surface (as shown on the lower figuie oi cut 3/), that they belonged to a shark closely allied to the Porbeagle ( Lamna , Cuv.)
Family III. — Raiidze.
[Rays.)
Fossil evidences of this peculiar family of cartilaginous fishes have been discovered in oolitic (Spathobatis Belem- nobatis ), cretaceous, and tertiary formations, and consist of defensive spines, dermal tubercles, and teeth, but chiefly the latter. The most peculiar and distinctive modifications of the dental system, presented by the eagle-rays (Myliobatidce) are unequivocally shown by fossils of the tertiary formations, and have not been found in earlier strata.
The teeth of the rays are in general more numerous than those of the sharks ; they have less mobility, are more closely impacted, and in some cases are laterally united together by fine sutures, so as to form a kind of mosaic pavement on both the upper and lower jaws. The Myliobates, or eagle-rays, which present the last-mentioned condition, unique in the ver¬ tebrate sub-kingdom, have large and massive teeth (fig. 38) ; but in the rest of the present family of cartilaginous fishes, the teeth (fig. 38) are remarkable for their small size as compared with those of the sharks. The teeth in some species of rays are adapted for crushing, but in others they have the middle or one of the angles of the crown produced into a sharp point. In all genera of the ray tribe, whatever the diversity of size and shape of the teeth, they are placed in several rows, and succeed each other uninterruptedly from behind.
The modification of the plagiostomous type of teeth, for the purpose of crushing alimentary substances, is most complete in the genus Myliobates. A view of this armature of the mouth,
i
114
PALAEONTOLOGY
as seen from behind in the Myliobates aguila, is given in fig. 38. Both jaws are covered with a pavement of broad teeth,
Fig. 38.
Jaws and teeth of an Eagle-Ray ( Myliobates aquila).
having a flat grinding surface. To the genus Myliobates , as now restricted, certain fossils from the London clay of Sheppy ( Myliobates toliapicus, Ag., fig. 39) belong.
In Zygobates (fig. 40), the middle series of teeth is less
Fig. 39. Fig. 40.
Myliobates toliapicus Zygobates Woodwardi
(Eocene, Sheppy). (Miocene).
broad ; and a narrower series is interposed between the mid¬ dle and the small lateral teeth. Existing rays showing this modification are found in Brazilian seas ; fossil teeth of this genus, e. g., Zygobates Woodwardi, Ag. (fig. 40), occur in the
PLAGIOSTOMI
115
tertiary crag (probably miocene) of Norfolk, and in the mio- cene mollasse of Switzerland.
When the teeth form broad transverse undivided plates, as in fig. 41, they characterize the genus jEtobcites. Fossils of this genus occur in the English eocenes and the Swis smol- lasse.
In the “crag” of Norfolk and Suffolk, and in marine plio¬ cene beds, fossils have been found which closely resemble
Fig. 41.
Fig. 41 a.
Raia clavata Dermal spines).
JEtobates subarcuatus ^Eocene, Bracklesham).
the osseous and spinigerous plates that beset the skin of the kind of ray called “thornback” (fig. 41 a), and which indicate the existence of a pliocene species allied to the Raia clavata.
Thus we obtain evidence of fishes of tire plagiostomous order in the marine deposits of every formation from the upper Silurian beds to the present period. But none of the pakeozoic fossils are referable to any existing genus. A few only of the mezozoic Plagiostomes, and those chiefly from the chalk, are so determinable : but most of them belong or are allied to a family ( Gestraciontidce ), now nearly extinct. The evidence of the generic forms of Plagiostomes characteristic of the present time become common only in the tertiary periods. No fossil species is the same with any existing one.
JIG
PALAEONTOLOGY
Order II. — IIOLOCEPH ALL
( Chimceroid Fishes.)
(Jlmr. — Jaws bony, traversed and encased by dental plates ; endo-skeleton cartilaginous ; exo-skeleton as placoid gran¬ ules ; most of the fins with a strong spine for the first ray ; ventrals abdominal ; gills laminated, attached by their margins ; a single external gill aperture.
To judge from the paucity of existing representatives of this order of cartilaginous fishes, it would seem, like the Cestracionts, to be verging towards extinction. One genus ( Chimcera , Linn.) is founded on a single known species of the northern seas called “ king of the herrings” ( Chimcera monstrosa ) ; another genus ( Callorhynchus of Gronovius) is represented by two known species in the Australian and Chinese seas. The only parts of chimseroid fishes likely to be fossilized are the jaws and spines. The bony and dental substances are so combined in the more or less beak-shaped jaws, that they characterize the order, and are never found separate. It is chiefly on such fossil mandibles, and portions of them, that the evidence of the Iloloccphali in former geological periods rests. These singular fishes ranged, under different generic and specific modifications, from the bottom of the oolitic series to the present period.
Genus Ciilvlera. — The premaxillary teeth, one in each bone, are oblong, about twice as high as they are broad, and terminate below in a transverse trenchant edge ; they present, exteriorly, vertical columns of alternately harder and softer substance, occasioning a notched margin when worn by use ; interiorly, they have oblique laminae which do not extend to the margin. The maxillary dental plates, one in each bone, are triangular, and present a broad surface to the lower jaw.
Genus Iacmonus, Egerton.-— Each upper maxillary has four dental columns ; the lower jaw is less produced and
HOLOCEPHALI
117
deeper than in Edaphodus. Of this genus, I. Johnsoni is from the lias of Dorsetshire ; I. Egertoni from the Kimmeridge of Shotover ; and I. Townshendi, a magnificent species, from the Portland stone. Two species (/. Agassizii and I. brevirostris) are from the cretaceous beds ; at which period the genus appears to have perished.
Genus Ganodus, Egerton (including Ganodus and Psit- tacodus of Agassiz). — This genus is exclusively represented by species from the oolitic slate of Stonesfield — e. g., G. Buck- landi, G. Colei, G. Owenii.
Genus Edaphodus, Egerton (including Edaphodon and Passalodon of Buckland). — Each upper maxillary has three dental columns ; the lower jaw is more produced, but less deep, than in Ischiodus : the premaxillary dental mass consists of five vertical and slightly bent series of oblicpie and curved transverse plates ; the median and longest series being strength¬ ened by a supplementary dental column behind : it represents the genus Passalodon of Buckland. The large E. Sedgwickii is from the greensand near Cambridge ; the still larger E. gigas from the chalk of Kent and Sussex. The ichthyodorulite called Psittacodus Mantelli by Agassiz may be the dorsal spine of this species. Three species, including the E. Bueklandi, are found in the eocene of Bagsliot and Bracklesham ; and one species ( E . helveticus ) is from the mollasse of Switzerland.
Genus Elasmodus, Egerton. — Each upper maxillary has three dental columns, but the dentine is confluent, “being- rolled round like a scroll on the substance of the bone, one edge forming the margin of the tooth, the other buried deep in its centre.* The premaxillary has a thin incurved scal- priform tooth, rounded at the cutting edge, of a lamellate struc¬ ture, with a columnar arrangement of the plates, which are juxtaposed. This genus is exclusively represented by species — e. g., E. Ilunteri- — from the London clay of Sheppy.
* Egerton, Proc. Geol. Soc., Mot 12, 1S47.
118
PALAEONTOLOGY
Order III. — GANOIDEI.
Char. — Endo-skeleton in some osseous, in some cartilaginous, in some partly osseous and partly cartilaginous ; exo¬ skeleton formed by enamelled bones ; fins usually with the first ray a strong spine.
Sub- Order 1 . — PLACOGANOIDEI.
( Ostracostei , Ow. Cat. Mus. Coll, of Surgeons, 4to, 1854, p. 166.)
Char. — Endo-skeleton cartilaginous, or retaining the noto¬ chord ; head and more or less of the trunk protected by large ganoid, often reticulated, plates ; heterocercal.
The last term signifies a form and structure of tail illus¬ trated by fig. 42, and to be seen in the sharks, dog-fishes, and sturgeons of the present day : it results from a prolongation
Fig. 42.
Heterocercal tail ( Lepidosteus osseus).
of the vertebral column into the upper lobe dn, producing an unsymmetrical form of the caudal fin, which is contrasted with the symmetrical form of the same fin presented by most fishes of the present day, and illustrated by the Leptolepis spratti- formis (fig. 5G, p. 144), in which the vertebral column termi¬ nates at the middle of the base of the caudal fin. There are a few exceptional intermediate forms and structures of this fin.
Earn. Placodermata. — The fossil remains of the singular
PLACOGANOIDEI
119
fishes of the extinct order Placoganoiclei were first discovered about 1813, in formations of the “ old red” or Devonian age in Eussia, and are preserved in museums at St. Petersburg and Dorpat. The relation of these specimens to the class of fishes was first announced by Professor Asmuss,* and shortly after, the generic names Aster olepis and Bothriolepis were invented by Professor Eichwald,t to express certain modifications of the external surface of portions of the ganoid plates, subse¬ quently recognised as constituting the buckler of the fore-part of the extinct fishes. In September 1840 Mr. Hugh Miller submitted to the geological section of the British Association at Glasgow the first discovered specimens, affording a recog¬ nizable idea of the form of one of these “old red” fishes, and for this form Professor Agassiz assigned the generic name Pterichthys {goteron, a wing, ichthys, a fish). Although, there¬ fore, the term Aster olepis had been attached to a fragment of the cuirass of this fish a few months previously, yet, as no recog¬ nizable generic characters were associated with such name, and as Asterolepis has been applied also to other genera — e.g., Homosteus and Heterostius of Asrnuss — the example of British paleontologists will be here followed, in retaining the name Pterichthys for the present genus. “ Of all the organisms of the system,” wrote the lamented Hugh Miller in his work on the Old Red Sandstone, “ one of the most extraordinary, and the one in which Lamarck would have most delighted, is the Pterichthys, or winged fish, an ichthyolite which the writer had the pleasure of introducing to the acquaintance of geolo¬ gists nearly three years ago (1840), but which he first laid open to the light about seven years earlier” (1833).
Genus Pterichthys (fig. 43). — The head and the anterior
* Bulletin Scient. par l’Acad. Imp. cles Sciences de St. Petersburg, 1840,
t. vi., p. 220. .
f Ibid, t. vii., p. 78, communicated March 13, 1840. Dr. Fleming had recognized certain fossil scales as those of fishes in the “Old Red” of Fife- shire, in 1827.
120
PALAEONTOLOGY
half of the trunk are defended by ganoid plates — i. e., plates composed of a hard hone coated with enamel ; those of the trunk forming a buckler composed of a back plate (fig. 43) and breast-plate (fig. 44), articulated together at the sides. The rest of the trunk was defended by small ganoid scales, flexible, like scale-armour, and bore a small dorsal fin (fig. 43, cl), and a terminal heterocercal fin, very rarely displayed in fossil specimens. The pectoral spines, c, are formed of ganoid material, like the buckler. The armour of the head, or helmet, appears to have been articulated by a movable joint to the trunk-buckler. One of the few existing ganoid fishes (. Lepidosteus ) is remarkable for the degree in which the head moves upon the trunk. The component dermal plates of the helmet correspond in some measure with the position of the cranial bones in osseous fishes, but not sufficiently to sanction the application to them of corresponding names. They are indicated by figures in the cut 43 : z is the front terminal or rostral plate ; it is followed in the median line by four other pl'ates in the following order : — 4, premedian ; 6, me¬ dian ; 8, postmedian ; 10, nuchal ; 3 is the marginal, and 7 the postmarginal ; 5 is the prelateral, and 9 the postlateral. The dorsal shield of the trunk-cuirass is composed of two mid¬ plates and two on each side. 12 is the “ dorsomcdian,” 14 the post-dor somedian ; n is the dorsolateral, 13 the post-dorso- lateral. The ventral shield (fig. 44) consists of one mid-plate and two side-plates : 15 is probably a part of the cephalic shield or of the mandible : 19 is the ventrolateral, n the gwstventrolateral ; the small supplementary plate marked 17 is usually confluent with 19 ; 16 is the ventromedian plate ; its margins are bevelled oft' and overlapped by the lateral plates.
The pectoral spines (fig. 43, c) are long and slender, and consist of two principal segments, both defended by finely tuberculated ganoid plates, like those of the head and trunk. F fom their form, they would seem to have served to aid the
PLACOGANOIDEI
121
fish in shuffling along the sandy bottom or bed, if left dry at low-water. The fins attached to the flexible part of the body
Fig. 43.
Pterichthys Milleri, dorsal surface (Devonian), after Pander.
indicate a certain power of swimming, though not with an) great rapidity ; they include a small dorsal and a pair of
122
PALAEONTOLOGY
ventrals — these latter were first observed by Sir P. Egerton. The jaws are small, and possess confluent denticles.
The type-species is the Ptericlithys Millcri ; others have been based upon proportions of the cuirass, of the pectorals, and the tail ; all are from the “ old red sandstone,” and the
great majority have been
found in the Devonian strata of Boss-shire, Caith¬ ness, and other Scotch localities.
Cephalaspis head ; aspis,
In this genus
Genus (kephale, buckler).
the posterior angles of the shield-shaped helmet are produced backward in a pointed form, giving to the head the form of a “ saddler’s knife;” in other respects the genus closely resembles Ptericlithys.
Mr. D. Page has re¬ cently acquired specimens of Cephalaspis from Lan- arkshire tile-stones, form¬ ing the base of the Devo¬ nian system, which show a dorsal fin, pectoral fins, and a large heterocercal fin, besides a well-marked capsule of the eye-ball. Cephalaspis Murchisoni occurs in the passage beds from the Silurian to the Devonian systems.
Genus Pteraspis. — -The buckler of Pteraspis truncatus has been found in a Silurian stratum below the Ludlow bone bed ;
Pig. 44.
Ptericlithys ; Plastron or Ventral Shield. (Devonian), after Pander.
PLACOGA.NOIDEI
123
it is the earliest known indication of a vertebrate animal. Pteraspis Lloydii occurs in the lower “ old red ” of Britain.
Genus Coccosteus (kokkos, berry ; osteon, bone). — If a heterocercal fin were added in outline to the restoration of the fish of this genus, given in fig. 45, a correct idea would be given of the “ old red” fossil, which, in the progress of its reconstruction, has suggested so many strange notions of its nature and affinities.
The helmet and cuirass are firmly united, and there is no trace of the jointed appendages, like pectoral fins, which characterize Pterichthys. The unprotected part of the trunk shows an ossification of the neural and haemal spines, and of their appendages, the rays of a “ dorsal ” and “ anal ” fin ; and, by the analogy of Cephalaspis, the tail was most probably terminated by an unequal-1 obed fin. The lower jaw is com¬ posed of two rami, loosely connected at the symphysis ; so that, when displaced, as they commonly are in crushed fossil specimens, they gave the notion of the fish being provided with laterally- working jaws, like those of the lobster. But, in reality, the jaw worked vertically upon a fixed upper jaw ; both jaws being provided with from ten to twelve teeth on each side, anchylosed to the bone.
An under-view of the cephalothoracic buckler of Coccosteus, according to Dr. Pander’s restoration, is given in fig. 46, showing the sutures of most of the cephalic plates, and the external surface of the plates of the plastron. 9, rostral plate; 7, premedian; 5, median; 8, prelateral ; 6, lateral; 16 and 24, the suborbital bone; 15, prevcntromedian ; behind the lozenge-shaped ventromedian, and on each side, are (22) the preventrolateral and (20) the post-ventrolateral. The same figures mark the above plates in the side view (fig. 45), with the addition of (12) the dorsomedian and (14) the post-dorsomcdian.
The blank space between the neural (n) and haemal (b) spines of the fossil endo-skeleton indicates the position of the
124
PALEONTOLOGY
soft “notochord” (c), which lias been dissolved away. The cylindrical gelatinous body, so called (in Latin chorda dorsalis ) pre-exists to the formation of the bony bodies of the vertebrae in all vertebrate animals ; and the development of those bodies seems never to have gone £ beyond this embryonal phase U in any palaeozoic fish ; such j> fishes are accordingly termed
t-»— i
“ notochordal,” as retaining g the notochord.
-t-j
(fi
T There are but two genera * of existing fishes which
Q
^ manliest, when full grown, 3 such a structure, associated J with ossified peripheral ele- '8 ments of the vertebrae — viz., g the Protoptcrus of certain § rivers of Africa, and the Lepidosircn of certain rivers of South America. Those fishes alone would, if fossi¬ lized, present the appearance of the vertebral column shown in fig. 45, and which characterizes all the oolitic fossil ganoid fishes (see figs.
* See Linnsean Transactions, vol. xviii. ; and Proceedings of the Lin- nrean Society, April 2, 1830.
PLACOGANOIDEI
125
54? and 55).
This persistence in palaeozoic and most mezozoic
Fig. 46.
Cephalothoracic buckler, ventral aspect, Coccosteus decipiens (Devonian).
iishes of an embryonic vertebral character, transitory in nearly
12G
PALAEONTOLOGY
all existing fishes, significantly testifies to a principle of “ pro¬ gression.”
The external “ ganoid ” surface of the buckler-plates of Coccostcus is ornamented with small hemispherical tubercles ; whence the generic name, signifying “berry-bone.” The similarity of this ornamentation to that of the plates of the buckler in some tortoises, led to the belief, when the coccos- teal plates were first found, of their being evidence of the clielonian genus Trionyx in Devonian beds. Passing notions also got into print of the crustaceous affinities of Coccosteus ; whence the trivial name of the type-species decipiens, or the “ deceiving ” Coccosteus.
Strange as seem the forms and structure of the placo- ganoid fishes of the “ old red ” period, there are not wanting existing species which throw much truer light on their nature than any existing Chelonia or Crustacea. The singular little family of “ trunk-fishes ” ( Ostracionidce ) shows species in which the body is inclosed in a more or less quadrangular cuirass, composed of suturally-articulated ganoid plates, which are usually tuberculated on the external surface, and with the angles prolonged into spines in some species, like those of the helmet of Cephalaspis. The caudal part of the trunk protrudes from the back opening of the cuirass, as in Coccos¬ teus and Pterichtliys, and ossification of the endo-skeleton is incomplete. The species of this family are for the most part natives of seas of tropical or warm temperate latitudes.
In another family of existing fishes, called “Siluroids,” there are species in which the broad cranial bones, connate with dermal ossifications, form a helmet to the head, whilst one or two dermal spine-bearing bones combine to form the part called “ buckler ” by Cuvier * In the genus Doras, the lateral line is armed with bony ganoid plates ; and in Callich- thys, these biserial plates are developed so as to incase the
* !Iistoire des Poissons, tom. xii.
PLACOGANOIDEI
127
whole body. But generally, as in Pimelodus, the hinder muscular part of the trunk is undefended, as in Goccosteus. The ganoid plates of the head and hack shields are fretted with rows or ridges of confluent tubercles, radiating from the centre to the circumference of the plate, whilst the inner surface is smooth, as in Coccosteus (fig. 46) ; and, moreover, the dorsal plate in existing Siluroids sends down a median ridge from its inner surface, like that from the “ dorso-median ” plate in Coccosteus. The point of resemblance to be mainly noticed, however, is the contrast furnished by the powerful armature of the head and back with the unprotected naked¬ ness of the posterior portions of the creature — a point specially noticeable in Coccosteus, and apparent also, though in a lesser degree, in some of the other genera of the old red, such as the Ptericlithyes and Asterolepides. “ From the snout of the Coccosteus down to the posterior termination of the dorsal plate the creature was cased in strong armour, the plates of which remain as freshly preserved in the ancient rocks of the country as those of the Pimelodi of the Ganges on the shelves of the Elgin museum ; but from the pointed termination of the plate immediately over the dorsal fin to the tail, com¬ prising more than one-half' the entire length of the animal, all seems to have been exposed, without the protection of even a scale ; and there survives in the better specimens only the internal skeleton of the fish and the ray-bones of the fins. It was armed, like a French dragoon, with a strong helmet and a short cuirass ; and so we find its remains in the state in which those of some of the soldiers of Napoleon’s old guard, that had been committed unstripped to the earth, may be dug up in the future on the fatal field of Borodino, or along the banks of the Dwina or the Wap. The cuirass lies still attached to the helmet, but we only find the naked skeleton attached to the cuirass. The Pterichthys to its strong helmet and cuirass added a posterior armature of comparatively
128
PALAEONTOLOGY
feeble scales, as if, while its upper parts were shielded with plate-armour, a lighter covering of ring or scale armour sufficed for the less vital parts beneath. In the Asterolepis the arrangement was somewhat similar, save that the plated cuirass was wanting. It was a strongly-helmed warrior in slight scale-armour ; for the disproportion between the strength of the plated head-piece and that of the scaly coat was still greater than in the Pterichtliys. The occipital star-covered plates are, in some of the larger specimens, fully three- quarters of an inch in thickness, whereas the thickness of the delicately-fretted scales rarely exceeds a line.
“ Why this disproportion between the strength of the armature in different parts of the same fish should have obtained, as in Pterichtliys and Asterolepis , or why, while one portion of the animal was strongly armed, another portion should have been left, as in Coccosteus, wholly exposed, cannot of course be determined by the mere geologist. His rocks present him with but the fact of the disproportion, without accounting for it. But the natural history of existing fish, in which, as in the Pimelodi, there may be detected a similar peculiarity of armature, may perhaps throw some light ou the mystery. In Hamilton’s Fishes of the Ganges, the habitats of the various Indian species of Pimelodi, whether brackish estuaries, ponds, or rivers, are described, but not their charac¬ teristic instincts. Of the Silurus, however, a genus of the same great family, I read elsewhere that some of the species, such as the Silurus Glanis, being unwieldy in their motions, do not pursue their prey, which consists of small fishes, but lie concealed among the mud, and seize on the chance stragglers that come in their way. And of the Pimelodus gulio, a little strongly-helmed fish with a naked body, I was informed by Mr. Dub, on the authority of the gentleman who had presented the specimens to the Museum, that it burrowed in the holes of muddy banks, from which it shot out its
LEPIDOGANOIDEI
129
armed head, and arrested, as they passed, the minute animals on which it preyed. The animal world is full of such com¬ pensatory defences ; there is a half-suit of armour given to shield half the body, and a wise instinct to protect the rest. Now it seems not improbable that the half-armed Coccosteus, a heavy fish, indifferently furnished with fins, may have burrowed, like the recent Silurus Glcinis or Pimelodus gulio, in a thick mud, oi the existence of which in vast quantity, during the times of the old red sandstone, the dark Caithness flagstones, the foetid breccia of Stratbpeffer, and the gray stratified clays of Cromarty, Moray, and Banff unequivocally testify ; and that it may have thus not only succeeded in capturing many of its liglit-winged contemporaries, which it would have vainly pursued in open sea, but may have been enabled also to present to its enemies, when assailed in its turn, only its armed portions, and to protect its unarmed parts in its burrow.” *
Sub-Order 2.— LEPIDOGANOIDEI.
Family I. — DiPTERim-E.
This family includes a few heterocercal fishes with a double anal as well as dorsal fin. The head is large and flattened ; the teeth subequal ; the scales perforated by small foramina ; the notochord persistent.
Fig. 47.
Dipterus macrolepidotus (Devonian).
In the genus Dipterus (fig. 47), the two dorsals, d 1, d 2, are opposite the two anals, a 1, a 2 : the ventrals, v, are in
* Hugh Miller, Rambles of a Geologist, p. 288.
K
130
PALAEONTOLOGY
advance of the first anal and first dorsal. The Dipterus macrolepidotus is characterized by the large size of its scales. Its remains are found in the old red sandstone of many localities of Scotland and England.
In the allied genus Diplopterus the vertical fins are oppo¬ site, hut the dorsals are wider apart, and the teeth are larger and fewer. Four species have been recognised in the middle “ old red” of Gamrie, Orkney, and Lethenbar, Eoss-shire. Two species occur in the carboniferous series.
In the genus Osteolepis the vertical fins are alternate in position, the first dorsal being near the middle of the back. The teeth are sharp ; not any of the species exceed a foot in length : they are all from the middle “ old red.”
Family II. — Acanthodii.
The species of this family are characterized by their very small scales : they are heterocercal and notochordal. There is a strong spine in front of each fin. The head is large ; the orbits approximate ; the mouth wide, formed chiefly by the maxillaries, and opening obliquely upwards, so that they
Fig. 48.
Diplacanthus striatus.
have somewhat the aspect of the Uranoscopi. They have many branchiostegal rays. The principal genera are from the old
LEPIDOGANOIDEI
131
led sandstone, and are as follows : — Cheir acanthus, with a single dorsal situated in front of the anal; Acanthodes, in which the dorsal is situated behind the anal ; and Dipla- canthus (fig. 48), in which there are two dorsals.
The Diplacanthus striatus is found in the “ old red” of Cromarty. In fig. 48, as in the other figures, p is the pectoral fin, cl the dorsal, v the ventral, a the anal, and c the caudal. In this species the upper lobe of the caudal is much prolonged. The fin-spines in the Acanthoclii were, like those of the recent dog-fish (, Spinax ), simply imbedded in the flesh, with their base, as it were, unfinished ; not provided, as in the Siluroids and other modern bony fishes, with a joint-structure.
Cheirolepis, with the minute scales of the family, has the dorsal behind the anal, but has no spine in any fin : the mouth is large, the teeth small and uniserial. Some species of the present family, Acanthodes Bronnii, Ac. sulccdus, existed in the seas of the carboniferous period.
Family III. — Ccelacanthi.
The species of this family are characterized by the hollow¬ ness of the rays or spines ; whence the name. The caudal fin has a peculiar structure, the vertebral column being continued into and beyond its middle part, supporting a kind of slender appendage between the two normal lobes. The species of the genus are most abundant in the Devonian and carboniferous formations ; but some occur in oolitic and even, if Mcicropoma be a true Ccelacanth, in cretaceous beds ; but all became extinct before the tertiary epoch.
Glyptolepis had a heterocercal tail, with rounded scales, smooth exter-
nally, and with radiating compart- Glyptolepis microlepidotus ments internally. The G. microlc- (Devonian).
piclotus, of which a magnified view of the inner side of some
132
PALAEONTOLOGY
scales is given in fig. 49, occurs in the middle old red sandstone of Scotland and England.
Phyllolepis is, as yet, known only by its large smooth or concentrically furrowed scales, some of which are six inches in diameter. Ph. conccntncus occurs in the upper old red of Clashbinnie \ Asterolepis in the middle “ old red of Elgin , Bothriolepis in the upper “ old red ” of Scotland and Russia , and Glyptopomus, with the cranial hones sculptured externally, in the upper “ old red” of Dura Den.
Family IV. — Holoptychidjs.
The type-genera of this family were first recognized and characterized by the fossil scales, under the name Holoptychius (Ag.), and by the fossil teeth, under the name Rhizodus (Ow.) They include species which have left their remains in the “old red” and the coal measures. They are nearly allied to the Coelacantliians, having, like them, but partially ossified bones and spines, the interior of which retained their primitive gristly state, and appear hollow in the fossils. The head was defended by large externally sculptured and tuberculate ganoid plates. The teeth consist of two kinds — small serial teeth, and large laniary teeth — at long intervals ; both kinds show¬ ing the “ labyrinthic” structure* at their base, which is anchylosed to the jawbone.
The generic term Rhizodus is now retained for the Iloloptychians of the coal measures which have Scaieoi 'iioiop- more robust and obtuse serial teeth, and longer, tychius nobil- sharper, and more slender laniaries, exemplified by vonTan)/haif the R- Hibberti .j- Species of true Holoptychius — nat. size. Ctg^ jp gigantcus (Ag.), Id. ndbilissimus (Ag.), occur in the old red sandstone. A noble specimen of the latter species, 2 feet C inches in length, discovered in the old red sandstone at Clashbinnie, near Perth, is now in the pakeonto- * Owen’s “Odontography,” Plate 63 n, fig. 1. f lb., Plates 35 and 36.
LEPIDOGANOIDEI
133
logical series of tlie British. Museum. It is chiefly remarkable for the size and hold sculpturing of the ganoid scales (fig. 50).
Large fossil teeth, with the more complex “ dendritic” disposition of the tissues, charac¬ terize a genus ( Dendrodus ), most pro¬ bably of the Holoptychian family.
The complexity is produced by numerous fissures radiating from a central mass of vasodentine, which more or less fills up the pulp-cavity of the seemingly simple conical teeth of this genus. Fig. 50 a is one of these fossil teeth of the natural size — a, a Fig- 50 a.
transverse section ; and fig. 50 b, a Tooth of Dendrodus Uporcatus
reduced view of a portion of the
same section enlarged twenty diameters. Thus magnified, a central pulp-cavity of relatively small size, and of an irregular lobulated form, is discerned, a poition of which is shown at p ; this is immediately surrounded by transverse sections of large cylindrical vascular or pulp canals of different sizes ; and beyond these there are smaller and more numerous medullary canals, which are processes of the central pulp-cavity. In the transverse section these processes are seen to be connected together by a net-work of smaller vascular canals belonging to a coarse osseous texture, into which the pulp has been con¬ verted, and this structure occupies the middle half of the sec¬ tion. All the vascular canals were filled up by the opaque matrix. From the circumference of the central net-work straight pulp-fissures radiate at pretty regular intervals to the periphery of the tooth ; most of these fissures divide once, rarely twice, in their course — the division taking place some¬ times at their origin, in others at different distances from their terminations, and the branches diverge slightly as they pro¬ ceed. Each of the above pulp-canals or fissures is continued
PALAEONTOLOGY
134
from a short process of the central structure, which is con¬ nected by a concave line with the adjoining process, so that the whole periphery of the transverse section of the central
Fig. 50 b.
Magn. section of part of Dendrodus biporcatus.
coarse reticulo-vascular body of the tooth presents a crenate outline. From each ray and its primary dichotomous divi¬ sions short branches are sent off at brief intervals, generally at right angles with the trunk, or slightly inclined towards the periphery of the tooth. These subdivide into a few short ramifications like the branches of a shrub, and terminate in irregular and somewhat angular dilations simulating leaves, but which resolve themselves into radiating fasciculi of minute dentinal tubes. There are from fifteen to twenty-five or thirty-
LEPIDOGANOIDEI
135
six of these short and small lateral branches on each side of the medullary rays. The teeth of Dendrodus occur in the corn-stone beds of the “ Old Red ” at Scat-crag, near Elgin.
Such are some of the forms and structures of fishes that swam in the seas from which were deposited the sediment that has hardened into the “ old red sandstones” of Great Britain, Russia, and other parts of the world. And in this process of consolidation the carcases of the fishes entombed in the primaeval mud have had their share. For, just as a plaster- cast boiled in oil derives greater density and durability from that addition, so the oily and other azotized and ammoniacal principles of the decomposing fish operated upon the imme¬ diately surrounding sand so as to make it harder and more compact than the sediment not reached by the animal princi¬ ples. Accordingly it has happened that in the course of the upheaval and disturbance of old red strata, parts of it, broken up and exposed to the action of torrents, have been reduced to detritus, and washed away, with the exception of certain nodules, generally of a flattened elliptic form, which are harder than the surrounding sandstone. Such nodules form the bed of many a mountain stream in “ old red sandstone ” districts of Scotland. If one of these nodules be cleft by a smart and well-applied stroke of the hammer, the cause of its superior density will be seen in a more or less perfect speci¬ men of the fossilized remains ol some animal, most commonly a fish.
But the placoganoid and lepidoganoid, heterocereal and notochordal, fishes of the Devonian epoch existed in such vast shoals in certain favourable inlets, that the whole mass of the sedimentary deposits has been affected by the decomposing remains of successive generations of those fishes. The De¬ vonian flagstones of Caithness are an instance. Ihey owe their peculiar and valuable qualities of density, tenacity, and durability wholly to the dead fishes that rotted in their pi imitfv c
136
PALAEONTOLOGY
constituent mud. From no other part of the world, perhaps, can a large flagstone he got, which a builder could set on its edge with assurance of its holding long together in that position. A great proportion of the county of Caithness formed, before its upheaval, the bottom of what may truly he termed a “ piscina mirabilis.” Yet there are minds, who, cognizant of the won¬ derful structures of the extinct Devonian fishes — of the evi¬ dence of design and adaptation in their structures — of the altered nature of the sediment surrounding them, and its dependence on the admixture of the decomposing and dissolved soft parts of the old fish — would deliberately reject the conclu¬ sions which healthy human reason must, as its Creator has constituted it, draw from such proofs of His operations. There are now individuals, one at least,* who prefer to try to make it be believed that God had recently, and at once, called into being all these phenomena ; that the fossil bones, scales, and teeth, had never served their purpose — had never been recent— were never truly developed, but were created fossil ; that the creatures they simulate never actually existed ; that the superior hardness of the inclosing matrix was equally due to primary creation, not to any secondary cause ; that the geological evidences of superposition, successive stratification, and upheaval were, equally with the palaeontological evidences, an elaborate design to deceive and not instruct !
Family Y. — Pal^eoniscidal
The Tlacoganoids, so richly represented in the Devonian epoch, disappear in the carboniferous one ; the Lepidoganoids increase in number. In the present family they combine with rhomboid scales, a heterocereal tail, and jaws armed with numerous, minute, close-set, rather blunt teeth. The type- genus is Palceoniscus (fig. 51 j , species of which range through¬ out the carboniferous and Permian beds : it is characterized by
* See Omphalos, by T. II. Gosse, 8vo, 1858.
LEPIDOGAEOIDEI
137
moderate-sized fins, the dorsal, D, being single, and opposite the interval between the anal, A, and ventral, V, fins : each fin has an anterior spine ; the fore-part of the head is obtuse.
TJ
Fig. £1.
Palceoniscus (Permian).
In the Palceonisci from the coal formations at Burdie House, near Edinburgh, the outer surface of the scales is striate and punctate, e.g., in P. ornatissimus, P. striatus ; but in the Palceonisci of other British localities, and of the continental and American coal formations, the scales are smooth, e.g., in P. fultus, from North America, P. Duvernoyi and P. minutus, from the coal beds of Munster Appel. In the Palceonisci from the Permian copper schales and zechstein, the scales are striate or punctate : the Palceoniscus Freieslcbeni is the most common in these beds, and was the first recognized species of the genus. Of this there are now forty known species, chiefly from carboniferous and Permian eras : one from the Keuper beds at Rowington, Warwickshire, appears to be the last representative of the genus : it is the Palceoniscus superstes of Egerton.
Amblypterus, with a geological
range like that of Palceoniscus, differs
in its shorter and deeper tail, and
x # Fig. 52.
larger body-fins, which are devoid of Scales of AmUypterus striatus anterior spines. In fig. 52, a indi- (Carboniferous),
cates the outer surface of parts of two series of the rliomboidal nano id scales ; and b the inner surface of two scales, showing the ridge produced at one end into a projecting peg, which fits
138
PALAEONTOLOGY
into a notch of the next scale, in the way that tiles are pegged together in the roof of a house. The species affording the above structure is the A mblypterus striatus from the coal- formations at Newhaven.
Several species of Amblypterus have left their remains in the musclielkalk, at which triassic period the genus seems to have passed away.
Family VI. — Saurichtiiyidae.
Magnificent species of lieterocercal rhomb-scaled Ganoids, with large dispersed laniary teeth, sometimes of a size rivalling those of great Saurians, for which they have been mistaken, have left their remains in the coal strata at Carluke, near Glasgow, and other localities, and constitute the genus Mega- lichthys of Agassiz. The head is defended by strong ganoid plates, of a beautiful polish ; the trunk-scales are usually granulate exteriorly. In this genus, as in the type of the family, the fulcra of the fin-rays are in two rows : all the known species of Saurichthys are triassic.
Pygopterus and Acrolepis, with fin-fulcra in a single row ; Eurynotus, Elonichthys, Plectrolepis , Graptolepis, Orognathus, Pododus, Acantliodes, and Diplopterus, are carboniferous genera of Ganoids, with rhomboid scales. Ccelacanthus, Isodus, Phyl- lolepis, Hoplopygus, Uronemus, Colo7iodus, Centrodus, Asterolepis, Psammosteus, and Osteoplax, are genera of Ganoids with rounded scales, represented by species in carboniferous strata.
01 the above-named genera, Acrolepis, Pygopterus, Palceo- niscus, and Goslacanthus, continue to be represented in Permian beds ; in which also are found species of the ganoid genera Doryptcrus, Holacanthodus, and Globulodus, if the teeth on which the latter is based be not those of Platysomus, a pycno- dont genus which is both Permian and carboniferous.
The formations of tire mezozoic or secondary periods give
LEPIDOGANOIDEI
139
evidence of tlie full development of the ganoid order. In the lowest or “triassic” division this order is still represented by heterocercal and notochordal species belonging to some of the genera of the Permian period, as, e. g., (Jcelacanthus, Amblyp- terus, and Paloeoniscus. The genus Placodus, a supposed pycnodont fish of the muschelkalk, has been shown to be a conchivorous Saurian.*
In the oolitic division the heterocercal Ganoids are almost completely superseded by liomocercal genera, which now, for the first time, appear on the stage of life ; but the ossification of the endo-skeleton is still incomplete. In the cretaceous series the Teleostian, or well-ossified, bony fishes, are nume¬ rous ; and here also first are seen fishes with the flexible “cycloid” or “ctenoid” scales, and of genera which continue to be represented by living species.
Of 33 genera of fishes in the lias, I only were represented in older strata, while the rest extend into the upper oolitic beds. Of these, 19 genera are Ganoids with rhomboid scales, and two (Leptolepis and Gyrosteus ) have rounded scales.
Family VII. — Caturidte.
Homocercal rhombo-ganoids, with a short dorsal fin, and some of the teeth much larger than the rest and laniariform.
Germs Caturus.— In this genus the jaws are armed with
close-set, large, conical teeth ; the scales are delicate ; the (ins * Owen, in Phil. Trans. 1858, p. 169.
140
PALAEONTOLOGY
are of moderate size ; all the species are sub-homocercal * and notochordal (fig. 53). The dorsal, d, is opposite the ventral, v. One species of CcUurus (G. Buchlandi ) is from the lias , but the majority, like G. furcatus, are from the lithographic slates of Solenhofen. The most recent known species ( G . similis) is from the chalk of Kent.
P achy cor mus, Saurostomus, Sauropsis, Thryssonotus, and Eugnathus, are liassic genera of the present family. It is deemed by some Palaeontologists to be represented at the present day by the North American genus Lepiclosteus ; but in this fish the notochord is converted into bony vertebral bodies, united by ball-and-socket joints, and the tail is hetero- cercal.
Family VIII.— Pycnodontes.
The name of this group of ganoid fishes refers to the blunt rounded form of the greater proportion of the teeth, especially those attached to the palate and hind alveolar part of the
lower jaw : the few anterior teeth are small and sub-prehen¬ sile ; but the whole dentition bespeaks fishes adapted to feed on small testaceous and crustaceous ani¬ mals. In the modern “ Sea Breams ” (Spa- riatysomus gibbosus (zechstein of Mansfield). roids), with an analo¬ gous dentition, the two premaxillaries oppose the two pre- mandibulars, but in the extinct Pycnodonts the vomer, as in Anarhichas, opposes its pavement of teeth to that of the two
* By this term is meant a symmetrical shape of the tail fin, with an unsym- metrical development of the supporting spines, the terminal vertebrae inclining to the upper lobe.
LEPID0GAN01DEI
141
closely approximated premandibular or dentary elements of the under jaw.
The Pycnodonts were for the most part deep-bodied fishes, symmetrically compressed from side to side. They were notochordal ; a few of the earlier forms were heterocercal, hut the majority of the family were liomocercal.
The pycnodont type was first manifested in the carboni¬ ferous strata by the heterocercal genus Platysomus, and by the species P. parvulus, which has been found in that formation at Leeds : but this earliest pycnodont genus is chiefly repre¬ sented by Permian species, of which Platysomus gibbosus (fig. 54) is a fine example.
In the lias, most beautiful fossil fishes of this group are found, which were referred by Bronn to the genus Tdragono- lepis, and by Agassiz to the lepidoid sub-order. Sir P. Egerton has, however, shown that the dentition is truly “pycnodont,” having a very close resemblance to that of Microdon, but with the masticatory apparatus smaller in proportion to the size ot the fish. The scales, moreover, instead of being articulated by interlocking pegs and sockets, as in fig. 52, are joined in a peculiar way, which Sir P. Egerton describes as follows : — “ Each scale bears upon its inner anterior margin a thick solid bony rib, extending upwards beyond the margin of the scale, and sliced off obliquely above and below, on opposite sides, for forming splices with the corresponding processes of the adjoining scales. These splices are so closely adjusted, that without a magnifying power, or an accidental dislocation, they are not perceptible. When in situ, and seen internally, these continuous lines decussate with the true vertebral apophyses, and cause the regular lozenge-shaped pattern so characteristic of the pycnodont family.” * These decussating “ pleurolepidal ” lines are, however, confined to the space between the skull and the dorsal fin, as in fig. 55.
* Proceedings of the Geological Society, May 1853, p. 270.
142
PALAEONTOLOGY
The Pycnodonts so characterized are further distinguished from the closely-resembling lepidoid genus Dapedius, by having the small anterior teeth conical and single-pointed, instead of being bifurcate ; and although this character is subject to occasional variations, nevertheless, on taking a comprehensive view of all the dapedioid species, it seems to have been suffi¬ ciently constant to warrant the continuance of the separation of the group into the unicuspid and bicuspid species. And Sir P. Egerton has accordingly proposed to apply the generic terms JZchmodus (from ar/jD,, a point, and odovg, a tooth),* for the unicuspid and pycnodont species, formerly termed Tetra- gonolepis, and to continue the name Bcipedius for the bicuspid and unequivocally lepidoid homocercal deep-bodied Ganoids, many beautiful species of which are found in the lias.
Fig. 55.
Pycnodus rhombus (Upper Oolite).
Genus Pycnodus (fig. 55).— The type-genus of this sub¬ order is characterized by the large size of the round flat crowned teeth, which cover the broad jaws as by a pave¬ ment of from three to five rows ;f at the fore-part of the jaws are two or more trenchant incisive teeth both above and
* Proceedings of the Geological Society, May 1854, p. 367. f For the disposition of these teeth on the palate, see Owen’s Odontography, \ol. i., pi. 34, figs. 1 and 2 ; and for their microscopic structure, ibid, p. 71, pi. 33
LEPIDOGANOIDEI
143,
below. The oblique inner processes of the scales appear as distinct dermal ossicles decussating the neural spines in the space between the occiput and the dorsal fin (fig. 55).
The species of Pycnodus abound in the oolitic formations above the lias : the one figured (P. rhombus ) is from a cal¬ careous deposit, so charged with animal remains as to be foetid, at Torre d’Orlando, near Naples. Species of Pycnodus (P. cretaceous, e. y.) occur in the chalk of Kent ; and one species (P. toliapicus ) has left its remains in the eocene clay of Sheppy. Some teeth from German miocene have been referred to this genus ; but at this period, if not at the earlier tertiary one, Pycnodus became extinct.
Family IX. — DAPEDiDiE.
Notochordal rliombo-ganoids, with front teeth conical or bifurcate, back teeth obtuse, vertebral column and side scales continued into the upper lobe of an almost sym¬ metrical tail-fin.
The type-genus, Dapcclms, is a compressed deep-bodied fish, with a single dorsal, and a single series of fin-fulcra ; the front teeth are commonly notched. All the species are from liassic strata. Amblyurus, with a similar form, and also liassic, has a very narrow anal, and a wide mouth with small pointed teeth. Semionotus and Pholidophorus are long-bodied fishes, the species of which range from the lias upwards to the Purbecks ( Pholidophorus ornatus), and to the chalk (, Semionotus Bcrgeri ).
Family X. — Lepidotid^e.
Homocercal rhombo-ganoids, with obtuse teeth and well ossi¬ fied vertebrae.
The type-genus of this family, Lepidotus, is remarkable for the density and polish of its full-sized imbricated rhomboid
144
PALAEONTOLOGY
scales ; it lias a short dorsal fin opposite the anal, and has two rows of fulcra to the anterior rays of all the fins. The species range from the lias to the chalk ; one species, indeed (. Lepidotus Maximiliani), lingers, after the commencement of the tertiary period, in the “ calcaire grossier ” of Paris.
In Nothosomus and Ophiopsis the fin-fulcra are in a single row, and the dorsal fin is very long. Notagogus and Propterus have the dorsal fin almost cleft into two.
Family XT. — Leptolepidul
The Ganoids of this family are homocercal, and have rounded scales. In the type-genus ( Leptolepis , fig. 56), the
Fig. 56.
Leptolepis sprattiformis (Oolite, Solenhofen).
scales are extremely thin, yet a fine layer of ganoin may he discovered on them. The teeth are minute and en brosse, with two of larger size in front of the mouth. It has not been determined whether the notochord is ossified ; but traces of distinct vertebral bodies appear to the writer to be discernible in some specimens. Species of Lcptolepis range from the lias to the calcareous slates of Eichstadt. They are very common in the lithographic slates of Solenhofen and Pap- penheim.
Family XII. — Macropomidte.
Genus Macropoma. — Fine specimens of homocercal ganoid fishes, with rounded scales, sculptured externally, as in fig. 57,
sturionim:
145
have been discovered in the chalk formations of Kent and Sussex. They have been referred by Agassiz to the genus called Macropoma, significative of the large size of the gill-cover, and to the coelacanthal family. Casts of the “ interior” of the alimentary canal, showing impressions of a broad spiral ,,
° L x Macropoma
valve, are preserved in certain specimens in the MantelU British Museum. One species (if. Egertoni) is (Chalk), from the Speeton clay ; the other (if. Mantdli ) from the chalk.
Family XIII. — Sturionidul
The family Shirionidce, represented by the sturgeons of the present seas, makes its first appearance in the lias, under the generic form of Chondrosteus, which has recently received a full description and illustration in a memoir communicated by Sir P. Egerton to the Eoyal Society of London* In this it is shown “ that Chondrosteus, though essentially sturionian, yet evidences a transitional form between the sturgeons and more typical Ganoids ; that its food was similar to that of the existing members of the family, but that it was procured in a tranquil sea, rather than in the tumultuous waters frequented by sturgeons at the present time.”
In the tertiary division of geological time the ganoid order rapidly diminishes, and its place is taken by fishes with better ossified internal skeletons, and with thinner, more flexible, and usually soluble scales. The gills are supported on bony arches, and are protected by branchiostegal rays, and by an operculum or gill-cover. The aortic bulb is provided with but two valves , and the optic nerves decussate. For this group, including the majority of existing fishes, and of those which made their appearance during the tertiary period, Muller proposed the name “ Teleostei,” which almost corresponds with the “ osseous fishes ” of Cuvier.
* Proceedings of the Royal Society, April 20, 1858.
1 46
PALAEONTOLOGY
Order IV.— ACANTHOPTERI.
Char. — Endo-skeleton ossified ; fins with one or more of the first rays unjointed or inflexible spines ; ventrals in most beneath or in advance of the pectorals ; swim-bladder without air-duct.
Sub-Order 1. — CTENOIDEI. Exo-skeleton as ctenoid scales (fig. 58).
Of this sub-order may be given two genera, both of which
are now extinct. One ( Semiopho - ms) belongs to the chetodont
Fig. 58.
Scale of Perea (Recent).
family ; the other ( Smerdis ) to the Percoids.
The genus Sewiiophorus,
Ag. (fig. 59), is represented ex¬ clusively by ex¬ tinct species pe¬ culiar to the tertiary deposits at Monte Bolca.
It is character¬ ized by the ex¬ treme height or prolongation of the anterior part of the dorsal
Fig. 59.
Semiophorus velicans (Monte Bolca).
CYCLOIDEI
147
tin, d, and lor the correlative elongation of the slender pointed ventral tins. The anal tin, A, is much shorter than the dorsal. Owing to the soluble nature of the scales, and to the well- ossified skeleton, the fossils of this, as of most other tertiary fishes, are exemplified by the vertebral column and skull more than by the skin.
Genus Smerdis. — The species composing this genus are of small size, and are wholly extinct ; they likewise are chiefly
Fig. 60.
Smerdis minutus (Gypsum of Provence).
met with in the tertiary ichthyolite beds of Monte Bolca ; but some (e.y., the Smerdis minutus, fig. 60) are from eocene depo¬ sits in France. In all the species the first suborbital or lacry- mal bone is strongly dentate, as is also the preoperculum ; but this has no spine at the angle. The operculum terminates behind by a rounded prominence. There are two dorsals. The scales are minute, but are occasionally preserved.
Sub- Order 2.— CYCLOIDEI.
This sub-order includes the teleostian fishes with undivided and unjointed spines at the fore part of the dorsal, and with smooth flexible circular or elliptical scales (fig. 61). It is not represented by any species of older date than the cretaceous epoch ; and both here and in the eocene tertiaries by extinct
Fig- 62.
148
PALAEONTOLOGY
species, mostly of extinct genera. It is most richly represented at the pre¬ sent day by the Sphyrenoid,
Scomberoid, and Xiphioid families.
There are two kinds of ex¬ isting sword-fish, Xiphias and Histiophorus ; in the former FJrr f;i the sword-like prolongation of Scaies 0f a Scom- the confluent premaxillaries is teroid fish, flattened, in the latter it is rounded.
Fossil remains of a rounded rapier-like “ sword,” but much longer and more slender than in the existing Histiophorus, have been found hi the eocene clay at Sheppy and Bracklesham. They are referred to an ex¬ tinct genus of the xiphioid family by Agassiz, called Coslorhynchus, or “ hollowbeak.” The most perfect specimen hitherto found is figured in fig. 62, of half the natural size. It forms part of the instructive collection of Captain Le Hon at Brussels. The upper transverse section shows the single cavity at the middle of the rostrum ; and the lower section shows the double or divided cavity near its base.
Order V.— ANACANTIIINI.
Char. — Endo-skeleton ossified ; exo-skeleton in some as cycloid, in others as ctenoid scales ; fins supported by flexible or jointed rays ; ventrals beneath the pectorals, or none ; swim-bladder with¬ out air-duct.
ANACANTHINI
149
Family. — Pleuronectida:.
( Flat-Fishes .)
In this family the symmetrical form is lost, and both eyes are on one side of the head. Species of still existing genera of this much-modified family have been found in tertiary deposits. The little turbot (Rhomb usminimus, e. g., fig. 63) occurs in the tertiary deposits of Monte Bolca. An equally extinct species of sole (>' Solea antique i) has been found in ter¬ tiary marls near Ulm.
Fig 63.
PJiombus minimus (Monte Bolca).
Fossil fishes of the cod, mullet, carp, salmon, and herring genera, are found in the tertiary formations, but are distinct from all known species. The Ganoids in these formations are reduced to the genera Lepidosteus and Acipcnser ; but may have been represented by the palates with crushing teeth, from the Sheppy clay, to which the names Pisodus* and Pliyllodus t have been given.
With respect to the fishes of the tertiary period, “ they are so nearly related,” says Agassiz, “ to existing forms, that it is often difficult, considering the enormous number (above
* See Owen’s Odontography, p. 138, pi. 47, fig. 3. f Ibid, p. 139, pi. 47, figs. 1 and 2.
150
PALAEONTOLOGY
8000) of living species, and the imperfect state of preservation of the fossils, to determine exactly their specific relations. In general I may say that I have not yet found a single species which was perfectly identical with any marine exist¬ ing fish, except the little Capelin (Mallotus villosus ), which is found in the nodules of clay of unknown geological age in Greenland.” These nodules are mostly veiy recent, and ex¬ emplify the operation of the dissolving soft parts of the fish in consolidating the surrounding matrix.
We cannot, from present knowledge, assign to any past period of the earth’s history a characteristic derived from a fuller and more varied development of the entire class of fishes than has since been manifested, nor predicate of the present state of the class that it has degenerated in regard either to the number, bulk, powers, or range of modifications of the piscine type. A retrospect of the genetic history of fishes imparts an idea rather of mutation than of development, to which the class has been subject in the course of geolo¬ gical time. Certain groups, now on the wane, have existed in plenary development, as, e. g., the ganoid order in the rnezo- zoic period, and the cestraciont form of Plagiostomes in both palaeozoic and mezozoic times.
As to the variety of the forms of fishes, seeing that the earth yields no indisputable evidence of Ctenoids or Cycloids anterior to the cretaceous epoch, yet still retains living repre¬ sentatives ot both Ganoids and Placoids, the present would appear to be the culminating period in the development of fishes, in respect of the number of ordinal forms or modifica¬ tions of the class. It represents, however, rather a period of mutation ol the piscine character, depending upon the pro¬ gressive assumption of a more special piscine type, and pro¬ gressive departure from a more general vertebrate type. The Scomberoids, as fishes, are at the head of the piscine modifica¬ tion of the vertebrate type. But as the retention of general
ANACANTHINI
151
vertebrate characters implies closer affinity with the proximate cold-blooded class, so a higher character of organization may be predicated of the palaeozoic Placoids and Ganoids than of the Ctenoids and Cycloids forming the great bulk of the class at the present day. The comparative anatomist dissecting a shark, a Polypterns, or a Lepidostens, would point to the structures of the brain, heart, generative organs, and in the last two genera to the air bladder, as being of a higher or a more reptilian character than the corresponding parts would present in most other fishes. But the palaeontologist would point to the persistent notochord, and to the heterocercal tail in palaeo¬ zoic and many mezozoic fishes, as evidence of an “ arrest of development,” or of a retention of embryonic characters in those primaeval fishes.
Ho class of animals is more valuable in its application to the great point now mooted by the Uniformitarians and Pio- gressionists of the present day than that of fishes , foi they are exempt from the attack of the Uniformitarian on the score of the defective nature of negative evidence, to which attack conclusions from the known genetic history of air-breathing animals are open. Many creatures living on land may ne\ei be carried out to sea ; but marine deposits may be expected to yield adequate grounds for general conclusions as to the character of the vertebrate animals that swarmed in the seas precipitating such deposits.
One -other conclusion may be drawn from a general retro¬ spect of the mutations in the forms of the fishes at different epochs of the earth’s history,— viz., that those species, such as the nutritious cod, the savoury herring, the rich-flavoured sal¬ mon, and the succulent turbot, have greatly predominated at the period immediately preceding and accompanying the advent of man ; and that they have superseded species which, to judge by the bony Garpikes (Lepidostens), were much less fitted to afford mankind a sapid and wholesome food.
PALAEONTOLOGY
152
ICHNOLOGY.®
In entering upon the genetic history of the class of reptiles, we have to inquire, as in that of fishes, in what period of the earth’s history the class was introduced, and under what forms ; at what period it attained its plenary development, in regard to the size, grade of structure, number and diversities ol its representatives ; and the relations which the existing members of the class bear to its past condition. Fifteen years ago, the oldest known reptilian remains were those of the so- called “ Thuringian Monitor, ’ from the Permian copper-slates ol Germany. Five years ago, the batraehian Apateon, or Ar- chegosaurus was discovered in a Bavarian coal-field ; and about the same period, footprints in carboniferous sandstones of North America, had been recognized as evidence of the com¬ mencement of reptilian existence at that period of the earth’s history. Air-breathing ambulatory animals may leave other evidence of their former presence upon earth than their fossil¬ ized remains.
There are several circumstances under which impressions made on a part of the earth’s surface, soft enough to admit them, may be preserved after the impressing body has perished. When a shell sinks into sand or mud, which in course of time becomes hardened into stone, and when the shell is removed 'A any solvent that may have filtered through the matrix, its place may become occupied by crystalline or other mineral matter, and the evidence of the shell be thus preserved by a cast, for which the cavity made by the shell has served as a mould. If the shell has sunk with its animal within it, the plastic matrix may enter the dwelling-chamber as far as the retracted soft parts will permit ; and as these slowly melt away, their place may become occupied by crystallized deposits of
* I x»os, a footstep, and Ao-yot.
1CHN0L0GY
153
any silicious, calcareous, or other crystallizable matter that may have been held in solution by water percolating the matrix, and such crystalline deposit may receive and retain some colour from the soft parts of which it thus becomes a cast.
Evidences of soft-bodied animals, such as Actiniae and Medusae, and of the excremental droppings of higher animals, have been thus preserved. Fossil remains, as they are called, of soft plants, such as sea- weeds, reeds, catamites, and the like, are usually casts in matrix made naturally after the plant itself has wholly perished.
Even where the impressing force or body has been removed directly or shortly after it has made the pressure, evidence of it may be preserved. A superficial film of clay, tenacious enough to resist the escape of a bubble of gas, may retain, when petrified, the circular trace left by the collapse of the burst vesicle. The lightning flash records its course by the vitrified tube it may have constructed out of the sandy par¬ ticles melted in its swift passage through the earth. The hailstone, the ripple wave, the rain-drop, even the wind that bore it along and drove it slanting on the sand, have been registered in casts of the cavities which they originally made on the soft sea-beacli ; and the evidence of these and other meteoric actions, as sun-cracks and frost-marks, so written on imperishable stone, have come down to us from times incal¬ culably remote. Every form of animal life that, writhing, crawling, walking, running, hopping, or leaping, could leave a track, depression, or foot print, behind it, might thereby leave similar lasting evidence of its existence, and also to some extent of its nature.
The interpretation of such evidences of ancient life has much exercised the sagacity of naturalists since Dr. Duncan, in 1828, first inferred the existence of tortoises at the period of the deposition of certain sandstones in Dumfriessliiie, fiom the impressions left on those sandstones, and the casts after-
154
PALAEONTOLOGY
wards formed in those impressions. The faculty of interpreting has been still more racked by similar evidences of more extra¬ ordinary footprints, probably of large batrachian reptiles, first noticed in 1834 at Hildberghausen in Saxony, in sandstones of the same geological age as those in Scotland.
The vast number and variety of such impressions, due either to physical or meteoric forces, to dead organic bodies, parts or products, or to the transitory actions of living beings, have at length raised up a distinct branch of palaeonto¬ logical research, to which the term “ I ch oology” has been given.
In this class of evidences the impressions called “ protich- nites”* (fig. 64), left upon the “Potsdam sandstones”-)- of the older Silurian age in Canada, are the most ancient ; but the footprints of birds surpass all others in regard to their num¬ ber, distinctness, and variety of sorts.
But how, it may be asked, are such footprints preserved ? A common mode may be witnessed daily on those shores where the tide runs high, and the sea-bottom is wTell adapted to receive and retain the impressions made upon it at low- water.
Dr. Gould of Boston, U. S., first called the attention of natu¬ ralists to this interesting operation on the shores of the Bay of .1 undy, where the tide is said to rise in some places seventy feet in height. The particles deposited by that immense tidal wave are derived from the destruction of previously existing rocks, and consist of silicious (flinty) and micaceous (talcky) particles, cemented together by calcareous (limy) or argillaceous (clayey) paste, containing salts of soda, especially the muriate (common salt), and coloured with various shades of the oxide or rust of iron, of which the red oxide predominates. The perfection of the surface for receiving and retaining an impression depends
See Owen, “ Description of the Impressions and Footprints of the Pro- tichnites from the Potsdam Sandstone of Canada,” Quarterly Journal of the Geological Society, 1852, p. 214. t Logan, ibid, p. 2.
ICHNOLOGY
155
much upon the micaceous element. Vast are the numbers of wading and sea birds that course to and fro over the extensive tract of plastic red surface left dry by the far retreat of the tide in the Bay of Fundy. During the period that elapses between one spring tide and the next, the highest part of the tidal deposit is exposed long enough to receive and retain many impressions ; even during the hours of hot sunshine, to which, in the summer months, this so-trodden tract is left exposed, the layer last deposited becomes baked hard and dry, and before the returning tidal wave, turbid with the same commi¬ nuted materials of a second stratum, has power to break up the preceding one, the impressions left on that stratum have received the deposit. A cast is thus taken of the mould pre¬ viously made, and the sediment superimposed by each suc¬ ceeding tide, tends more and more surely to fix it in its place. Then, let ages pass away, and the petrifying influences conso¬ lidate the sand layers into a fissile rock : it will split in the way it was formed, and the cleavage will expose the old moulds on one surface and the casts on the other.
Another condition for fixing the impressions on a sandy shore is the following : — When an extensive level tract is left dry by the retreating tide, as at the estuary of the small rivers entering the Bay of Morecombe, on the Lancashire coast, those rivers occasionally overflow the sands at low-water, and deposit in the footprints made previous to such overflow the fine mud which sudden heavy rains have brought down from the surrounding hills. Again, those sudden “ freshets,’ as they are locally called, sometimes as quickly subside, and the thin layer of argillaceous mud is left dry on the sand before the returning tide. Such layer of mud readily receives and retains the footprints of the many birds that course over the flat expanse ; and as the tide returns, it deposits in such footprints a layer of the fine sand which the rising waters hold in suspension.
156
PALAEONTOLOGY
The best-defined footprints in the new red sandstone quarries at Stourton, on the Cheshire coast, are found where strata of sandstone are separated by a thin layer of argil¬ laceous stone, which, when exposed, soon breaks up and crumbles away. This layer has, however, received the im¬ pressions when it was plastic, and the superincumbent deposit of sandstone retains those impressions in relief upon its under surface. The observations which have just been recorded, of the circumstances that produce an interposition of a thin layer of claystone between thicker beds of sandstone, and which circumstances the writer has witnessed in the Bay of More- combe, explain the formation and the preservation of the best “ ichnites” of the labyrinthodont and other reptiles in the new red sandstone of Stourton.
There is a third condition under which impressions, and casts of impressions, on a sandy beach may be preserved. On a dry windy day clouds of fine sand are drifted along the surface exposed at low-water, are spread lightly over all its little inequalities, and fill up every impression that may have been made on it since it was left bare by the retreating waves. On the return of the tide, the fine sand filling the impressions is moistened, and more wet fine sand is added to it , and a cast is thus fixed in the moulds, to be more and more firmly fixed by each deposition from successive tidal waves.
Thus may be witnessed the actual conditions and the cir¬ cumstances daily occurring that tend to preserve footprints and other impressions made on the sea-shore, and which have operated in past time to similarly preserve the impressions then made on tracts alternately exposed and covered by the tidal wave. The merit of having first discerned the nature and cause of the numerous small hemispheric pits and tuber¬ cular casts in relief on the surface of certain sandstone slabs, is due to John Cunningham, Esq., F.G.S., architect, of Liver-
ICHNOLOGY
1
lo7
pool* Since that light was thrown on their nature, they have been recognized under various modifications, as impres¬ sions of soft rain, of the big-dropped thunder-shower, of rain driven obliquely by the gale, and making impressions with the side of the cup highest opposite the point whence the wind blew, of frozen rain or hail, etc. Dr. Deane, in 1845, after witnessing the first exposure and raising of the red sand slabs, near Greenfield, Mass., IT. S., writes, “ They were characters fresh as upon the morning when they were im¬ pressed ; ‘ on that morning gentle showers watered the earth,’” etc. Whenever a stratum is proved to be a “ sedimentary” one — i.e., to be due to the precipitation of its constituent particles from water, in which they had been previously sus¬ pended — we have evidence of some expanse of water, — proof, in fact, of the existence of that element, with all its properties of condensation by cold, and expansion and vaporization by heat and exposure. Evaporation makes the raw material of rain. iSTo wonder, then, that impressions of rain-drops should be seen on the oldest sedimentary rocks. Conditions are co¬ ordinated in meteoric as in organic phenomena ; one being given, the rest may be deduced.
The oldest rocks in which rain-drop impressions have been observed are those of the Cambrian age at Longmynd, Wales, described and figured by Mr. Salter Many of the micaceous flags of the same formation are covered with ripple, or current marks. They show borings of worms, and a trace of a trilobite ( Palceopyge ) nearly allied to the Dikelocephalus — the oldest known trilobite of America (Lower Silurian or Cambrian at St. Croix, Minnesota).
It is in “ Potsdam sandstones” of the same geological anti¬ quity that the impressions have been discovered which the
* Communicated by Dr. Buckland to the meeting of the British Association at Newcastle, 1838; and subsequently by Mr. Cunningham to the Geol. Soc. (Proc. of the Geol. Soc., vol. iii., 1839, p. 99.)
j- Quar. Jour, of the Geol. Soc., vol. xii., 1856, p. 250, pi. iv., fig. 4.
PALAEONTOLOGY
1 58
writer has interpreted to be those of a large entomostracous Crustacean ;* in evidence of which the following sample, appli¬ cable to a single species, may be given, in illustration of the ichnologist’s mode of work.
Pkotichnites.
Proticlinites septem-notatus (fig. 64).
The subject so named consists of a series of well-defined impressions, continued in regular succession along an extent of 4 feet ; and traceable with an inferior degree of definition, along a further extent of upwards of 2 feet.
In the extent of 4 feet there are thirty successive groups of footprints on each side of a median furrow, which is alter¬ nately deep and shallow along pretty regular spaces of about 2i inches in extent. The number of prints is not the same in each group ; where they are best marked, as in fig. 64, 1 L, we see 3 prints in one group, a, a, a ", 2 prints in the next, 6, V, and 2 in the third, c, o', which is followed by a repetition of the group of 3 prints, a, a, a, making the numbers in the three successive groups 3, 2, 2 ; the three groups of impres¬ sions being recognizably repeated in succession along the whole series of tracks on both sides of the median groove.
The principal footprints are disposed in pairs, placed with different degrees of obliquity, in each of the three groups towards the median track ; the innermost print in the second, B, and third, C, pairs, which are best marked, being usually rather more than half the size of the outer print, V and c.
The two footprints of the same pair are a little further apart from each other, in the three succeeding pairs, as at a, a, k V, c, c, especially in the second and third groups of each set ; the two forming the pair a', a", again approximating in the next series, and the pairs 5, V and c, c, diverging in the same direction and degree ; and this alternate approximation
* Quarterly Journal of the Geological Society, vol. viii., p. 214, 1852.
ICHNOLOGY
159
and divergence is repeated throughout the entire series of the present tracks.
But what strikes the iclmologist, heretofore conversant chiefly with the footprints of bipeds or quadrupeds, is the occurrence in the present series of the third impression a ,
Fig. 64.
Protichnites 7-notatus (Cambrian).
which complicates the most approximated pair A, being placed in front and a little to the inner side of the hindmost impres¬ sion, a", of that pair. The superadded impression a, is about the same size as the innermost in each pair, the average diameter of that impression being 5 lines.
Taking this view of the impressions, it appears that whilst the innermost in each pair, a', b, c, are of equal size, the outei- most, a ", b\ c, 1 L, progressively increase in size, from the most
160
PALAEONTOLOGY
approximated to the most divergent of the three pairs ; that of the first, a, being narrow in proportion to its length, that of the second b', as broad as long, and the outermost, c, c", of the third pair being oblong, but larger than that in the first pair. In some places where the most approximated pair of impressions, a, a", are deeply marked, they are complicated by a fourth shallow and very small pit, cc", 2 L, midway between the third, a, and the outermost, a”, of the pair of impressions.
There are no clear or unequivocal marks of toes or nails on any of the impressions which form the lateral pairs or triplets. Their margins are not sharply defined, but are rounded off, and sink gradually to the deepest part, which is a little behind the middle of the depression. There is a slight variation in the form and depth of the answerable impressions, but not such as to prevent their correspondence being readily appreciable through the whole of the extent here described ; that is to say, the innermost of each of the three pairs here described as first, A, second, B, and third, C, may be identified with the corres¬ ponding innermost impression on the opposite side, and with the same impression of the same pair in the three preceding and the three succeeding pairs.
The impressions selected for fig. 61 clearly demonstrate that the animal, progressing in an undulating course, made at each action of its locomotive members, answering to the single step of the biped and the double step of the quadruped, not fewer than, in Protichnites 7- notatus , fourteen impressions, seven on the right and seven on the left ; and in Protichnites 8 -notatus, sixteen impressions, eight on the right and eight on the left ; these seven and eight impressions respectively being- arranged in three groups — viz., in Protichnites 7 -notatus, three, two, and two ; in Protichnites 8-notatus, three, two, and three — the groups being re-impressed, in successive series, so similarly and so regularly as to admit of no doubt that they were made by repeated applications of the same impressing
ICHNOLOGY
161
instruments, capable of being moved so far in advance as to clear the previous impressions and make a series of new ones at the same distance from them as the sets of impressions in the series are from each other. What then was the nature of these instruments 1 To this four replies may be given, or hypotheses suggested : — They were made either, first, as in the case of quadrupedal impressions, each by his own limb, which would give seven and eight pairs of limbs to the two species respectively ; or, secondly, certain pairs of the limbs were bifurcate, as in some insects and crustaceans, another pair or pairs being trifurcate at their extremities ; and each group of impressions was made by a single so subdivided limb, in which case we have evidence of a remarkably broad and short, and, as regards ambulatory legs, hexapod creature ; or, thirdly, three pairs of limbs were bifurcate, and the supplementary pits were made by small superadded limbs, as in some crustaceans ; or, fourthly, a single broad fin-like member, divided at its impress¬ ing border into seven or into eight obtuse points, so arranged as to leave the definite pattern described, must have made the series of three groups by successive applications to the sand.
The latter hypothesis appears to be the least probable, — first, as being most remote from any known analogy ; and, secondly, because there are occasional varieties in the groups of footprints which would hardly accord with impressions left by one definitely subdivided instrument or member. Thus in the group of impressions marked 1 L in fig. 61, the outer impression, c', is single, but in the preceding set it is divided ; whilst the impressions, a, a, are confluent in that set, and are separate in 1 L. The same variety occurs in the outer pair, c, c", in Protichnites S-notatus.
Yet, with respect to the hypothesis that each impression was made by its own independent limb, there is much diffi¬ culty in conceiving how seven or eight pairs of jointed limbs could be aggregated in so short a space of the sides of one
M
1G2
PALAEONTOLOGY
animal. So that the most probable conception is, that the creatures which have left these tracks and impressions on the most ancient of known sea-sliores belonged to a crustaceous genus —either with three pairs of limbs employed in locomotion, and severally divided to accord with the number of prints hi each of the three groups, — or bifurcated merely, the supplemen¬ tary and usually smaller impressions being made by a small and simple fourth, or fourth and fifth pah of extremities.
The great entomostracous king-crab ( Limulus ) which has the small anterior pair of limbs near the middle line, and the next four lateral pairs of limbs bifurcate at the free extremity, the last pair of lateral limbs with four lamelliform appendages, and a long and slender hard tail, comes nearest to the above idea of the kind of animal which has left the impressions on the Potsdam sandstone.
The shape of the pits, so clearly shown in the ice-rubbed slabs, impressed by Protichnites 8-notatus, accords best with the hard, subobtuse, and subangular terminations of a crusta¬ ceous ambulatory limb, such as may be seen in the blunted legs of a large Palinurus or Birgus ; and it is evident that the animal of the Potsdam sandstone moved directly forwards after the manner of the Macroura and Xipliosura, and not sideways, like the brachyurous Crustaceans.
The appearances in the slab impressed by the Protichnites multi-notatus favour the view of the median track having been formed by a caudal appendage, rather than by a prominent part of the under surface of the trunk.
The imagination is baffled in the attempt to realize the extent of time past since the period when the creatures were in being that moved upon the sandy shores of that most ancient Silurian sea : and we know that, with the exception of certain microscopic forms of life, all the actual species of animals came into being at a period geologically very recent in comparison with the Silurian epoch.
ICHNOLOGY
163
The deviations from the living exemplars of animal types usually become greater as we descend into the depths of time past ; of this the Archegosaur and Ichthyosaur are instances in the reptilian class, and the Pterichthys and Coccosteus in that of fishes. If the vertebrate type has undergone such inconceivable modifications during the Secondary and Devo¬ nian periods, what may not have been the modifications of the articulate type during a period probably more remote from the secondary period than this is from the present time % In all probability no living form of animal bears such a resemblance to that which the Potsdam footprints indicate as to afford an exact illustration of the shape and number of the instruments, and of the mode of locomotion, of the Silurian Protichnites.
Since the foregoing interpretation of the Silurian Ichnites of North America was published, similar impressions have been observed in rocks of the like high antiquity in Scotland, as at Binks, Eskdale, which have received the name of Proticli- nites Scoticus *
Amphibichnites.
Genus Cheirotherium. — Fig. 68 gives a reduced view of a portion of new red sandstone, with three pairs of footprints in relief : the first and third of the left, the second of the right, side. Consecutive impressions of such prints have been traced for many steps in succession in quarries of that forma¬ tion in Warwickshire and Cheshire, more especially at a quarry of a whitish quartzose sandstone at Storton Hill, a few miles from Liverpool. The footmarks are partly concave and partly in relief ; the former are seen upon the upper surface of the sandstone slabs, but those in relief are only upon the lower surfaces, being in fact natural casts, formed on the subjacent footprints as in moulds. The impressions of the
* Harkness and Salter “ On the Lowest Rocks of Eskdale, Quarterly Journal of the Geological Society, vol. xii., pp. 238, 243, fig. 2.
164
PALAEONTOLOGY
liind foot are generally 8 inches in length and 5 inches in width ; near each large footstep, and at a regular distance — about an inch and a half — before it, a smaller print of the fore foot, 4 inches long and 3 inches wide, occurs. The footsteps follow each other in pairs, each pair in the same line, at intervals of about 14 inches from pair to pair. The large as well as the small steps show the thumb-like outermost toe alternately on the right and left side, each step making a print of five toes.
Footprints of corresponding form, but of smaller size, have been discovered in the quarry at Storton Hill, imprinted on five thin beds of clay, lying one upon another in the same quarry, and separated by beds of sandstone. From the lower surface of the sandstone layers the solid casts of each impres¬ sion project in high relief, and afford models of the feet, toes, and claws of the animals which trod on the clay.
Similar footprints were first observed in Saxony, at the village of Hessburgh, near Hillburghausen, in several quarries of a grey quartzose sandstone, alternating with beds of red sandstone, and of the same geological age as the sandstones of England that had been trodden by the same strange animal. The German geologist who first described them (1834) pro¬ posed the name of Cheirotherium (cheir, the hand, therion, beast) for the great unknown animal that had left the foot¬ prints, in consequence of the resemblance, both of the fore and hind feet, to the impression of a human hand ; and Dr. Kaup conjectured that the animal might be a large species of the opossum kind ; but in Didelphys the thumb is on the inner side of the hind-foot. The fossil skulls, jaws, teeth, and a few other bones, in the sandstones exhibiting the footprints in question, and corresponding in size with those impressions, belong to labyrinthodont or huge extinct batrachian reptiles.
The impressions of the Gheirothermm resemble those of the footprints of a salamander, in having the short outer toe of the hind foot projecting at a right angle to the line of the
ICHNOLOGY
1G5
mid toe, but are not identical with those of any known Batrachian or other reptile. They show a papillose integu¬ ment as in some mammals, but also like that on the sole of certain Geckos, and which may be another mark of sauroid departure from the modern batrachian type. The proximity of the right and left prints to the median line indicates a narrower form of body, or its greater elevation upon longer and more vertical limbs, than in tailless Batracliia. In the attempt to solve the difficult problem of the nature of the animal which has impressed the new red sandstone with the cheirotherian footprints, we cannot overlook the fact, that we have in the Labyrinthodons also batrachoid reptiles, differing as remarkably from all known Batracliia, and from all other reptiles, in the structure of their teeth ; both the footsteps and the fossils are, moreover, peculiar to the new red sandstone ; the different size of the footprints referred to different species of Cheiro- theria correspond with the different size of ascertained species of Labyrinthodon ; and the present facts best support the hypothesis, that the footprints called “ cheirotherian,” are those of labyrinthodont reptiles.
Genus Otozoum. — The footprints in the red sandstones, probably of liassic age, in Connecticut, described by Prof. Hitchcock under the above name, equalled in size the largest of those of the Chcirotherium (Oh. Hercules ), but the hind foot had but four toes, whilst the fore foot had five toes. It would seem that the hind foot, which was larger than the fore foot, obliterated the print of that foot, by being placed upon it in walking. In the few instances of the fore foot print the toes are turned outward, and the fourth and fifth seem to have been connate at their base. An impression of a web has been clearly discerned in the hind foot. Only one toe on this foot shows a claw, the rest are terminated by “ pellets,” as in the Batracliia, to which family Dr. Hitchcock refers these footprints, though with a surmise of the possibility of their marsupial nature.*
* Ichnolog)- of Massachusetts, 4to, 1858, p. 123.
1GG
PALAEONTOLOGY
Genus Batrachopus ( Batrachopus primcevus. King.) — In 18-M, Dr. King of Greensburg, Pennsylvania, discovered fossil footmarks, which he announced as being those of a reptile, in the sandstone of the coal measures, near that town. No reptilian footprints had previously been found lower in the series than the New Eed sandstone. Dr. King states the impressions to be “ near 800 feet beneath the topmost stratum of the coal formation.”
Sir C. Lyell, in Sillimaris Journal, July 1846, describes his visit to Greensburg, where he examined these footmarks, and confirmed Dr. King’s description of them. He considered them to be allied to the labyrinthodont footprints which have been referred to the genus Cheirotherium. He says — “ They consist, as before stated, of the tracks of a large reptilian quad¬ ruped, in a sandstone in the middle of the carboniferous series, a fact full of novelty and interest ; for here in Pennsylvania, for the first time, we meet with evidence of the existence of air-breathing quadrupeds capable of roaming in those forests where the Sigillaria, Lepidodendron, Caulopteris, Catamites, ferns, and other plants flourished.”
These footmarks were first observed standing out in relief from the lower surface of slabs of sandstone resting on thin layers of fine unctuous clay, which also exhibited the cracks due to shrinking and drying. Now these cracks, where they traversed the footprints, had produced distortion in them, for the mud must have been soft when the animal walked over it and left the impressions ; whereas, when it afterwards dried up and shrunk, it would be too hard to receive such indentations, and could only affect them in the way of subsequent dislocation.
No less than twenty-three footsteps, the greater part so arranged as to imply that they were made successively by the same animal, were observed in the same quarry.
Everywhere there was a double row of tracks, and in each row they occur in pairs, each pair consisting of a hind and
ICHNOLOGY
167
fore foot, and each being at nearly equal distances from the next pair. The hind foot-print is about one-third larger than the fore foot-print : it has five toes, but the front one only four ; some of them exhibit a stunted rudiment of the innermost toe or “ pollex,” which is the undeveloped one. The outermost toe in the hind footprint is shorter and rather thicker than the rest, and stands out like a thumb on the wrong side of the hand.
With this general resemblance to the footprints of Laby- rinthodon, from the new red sandstones of Europe, there are well-marked distinctions. In the first place, the right and left series of impressions are wider apart, indicative of a broader-bodied animal. The front print in Batrachopus has only four well-developed toes instead of five, as in Labyrin- thodon ; it is also proportionably larger, — the fore foot in Labyrmtliodon being less than half the size of tire hind foot. The distance between the fore and hind print of each pair, and of one such pair from the next on the same side, is nearly the same in Batrachopus and Lcibyrinthodon.
Genus Sauropus, Bogers. — Very similar footprints were discovered and described by Mr. Isaac Lea in a formation of red shales, at the base of the coal measures at Pottsville, 78 miles 1ST.E. of Philadelphia. These are of older date than the preceding, inasmuch as a thickness of 1700 feet of strata intervenes between the footprints at Greensfield and the Potts¬ ville impressions.
Professor H. D. Bogers, in 1851, announced his discovery in the same red shales, between the Devonian and carboniferous series, of three species of four-footed animals, which he deems to have been rather saurian than batrachian, seeing that each foot was five-toed ; one species, the largest of the three, pre¬ sented a diameter for each footprint of about two inches, and showed the fore and hind feet to be nearly equal in dimensions. It exhibits a length of stride of about nine inches, and a breadth between the right and left footsteps of nearly four inches. The
1G8
PALAEONTOLOGY
impressions of the hind feet are but little in the rear of the fore feet. With these footmarks were associated shrinkage cracks, such as are caused by the sun’s heat upon mud, and rain-drop pittings, with the signs of the trickling of water on a wet beach, — all confirming the conclusions derived from the footprints, that the quadrupeds belonged to air-breathers, and not to a class of animals living in and breathing water.
Class II.— REPTILIA.
Order I.— Gangcephala.*
The name of this order has reference to the sculptured and externally polished or “ ganoid ” bony plates with which the entire head was defended. These plates include the “post-orbital” and “super-temporal” ones, which roof over the temporal fossae. There are no occipital con¬ dyles. The teeth have converging inflected folds of cement at their basal half. The notochord is persistent ; the vertebral arches and peripheral elements are ossified ; the pleurapophyses are short and straight. There are pectoral and pelvic limbs, which are natatory and very small ; large median and lateral “throat-plates scales small, narrow, sub-ganoid ; traces of branchial arches. The above combination of characters gives the value of an ordinal group in the cold-blooded Vertebrata.
Genus Apateon, Yon M. ; ARCHEGOSAunus,t Goldf.
The extinct animals which manifest the above ordinal characters were first indicated by certain fossils, discovered in the sphserosideritic clay-slate forming the upper member of the Bavarian coal measures ; and also in splitting spheroidal con¬ cretions from the coal-field of Saarsbruck, near Treves. They were originally referred to the class of fishes ( Pygoptcrus Lucius, Agassiz) : but a specimen from the Brandschiefer of Miinster-
* Vavos, lustre; KMpaAr), head, f Airareur, a cheat; apxvyos, beginning; aavpos, lizard.
GANOCEPHALA
169
Appel presented characters which were recognized by Dr. Gergens to be those of a salamandroid reptile.* Dr. Gergens placed his “ sala¬ mander” in the hands of II. von Meyer for description, whoconunnnicated the result of his examination in a later number of the under-cited journal. t In this notice the author states that the sala¬ mandroid affinities of the fossil in question, for which he proposes the name of Apateon pedestris, “ are by no means demonstrated.” \ “ Its head might be that of a fish as well as that of a lizard, or of a Batraclxian.” “ There is no trace of bones or limbs.” M. von Meyer concludes by stating that, in order to test
* Mainz, Oktober 1843. “ In
dem Brandschiefer von Miinster- appel in Bhein-Baiern habe ich in vorigen Jahre einen Salamander aufgefunden. Gebort dieser Schiefer der Kohlen-formation ? in diesem falle ware der Fund aucb in anderen Hinsicht interessant.” (Leonbard und Bronn, Neues Jahrbuch fur Mineralogie , etc., 1844, p. 49.)
f Ibid, 1844, p. 336.
I “Ob das — Apateon pedestris — ein Salamander - artiges Gescbopf war, est keinesweg ausgemacbt.” (Ibid.)
170
PALAEONTOLOGY
tlie hypothesis of the Apateon being a fossil fish, he has sent to Agassiz a drawing with a description of it.
Three years later, better preserved and more instructive specimens of the problematical fossil were obtained by Pro¬ fessor von Dechen from the Bavarian coal-fields, and were submitted to the examination of Professor Goldfuss of Bonn : he published a quarto Memoir on them, with good figures, referring them to a saurian genus which he calls Archego- saurus, or primaeval lizard, deeming it to be a transitional type between the fisli-like Batraeliia and the lizards and crocodiles.*
The estimable author, on the occasion of publishing the above Memoir, transmitted to me excellent casts of the originals therein described and figured. They are in the museum of the Boyal College of Surgeons, and are described in my Catalogue of the Fossil Pteptiles, 4 to, 1854, p. 1 1 7.f One of the specimens appeared to present evidence of persistent branchial arches. The osseous structure of the skull, especially of the orbits, through the completed zygo¬ matic arches, indicated an affinity to the Labyrintliodonts ; but the vertebra: and numerous very short ribs, with the indications of stunted swimming limbs, impressed me with the conviction of the near alliance of the Arcliegosaurus with the Proteus and other perennibranchiate reptiles.
This conclusion of the affinity of Arcliegosaurus to existing types of the reptilian class has been confirmed by subse¬ quently-discovered specimens, some of which have been acquired by the British Museum, others have been described and figured by H. von Meyer in his Palceontographica (Bd. vi., 2to Lief. 1857) ; more especially by his discovery of the embryonal condition of the vertebral column — i. e., of the persistence of the notochord, and the restriction of ossification
* “Arcliegosaurus, Fossile-Saurier aus dem Stein kohlengebirge die den Uebergang der Icktkyoden zu den Lacerten und Krokodilen bilden,” p. 3. ( Beitrage zur vorweltlichen Fauna cles Steinhohlengebirges, 4to, 1847).
f See also, Quarterly Journal of the Geological Society, vol. iv., 1848.
GANOCEPHALA
171
to the arches and peripheral vertebral elements * In this structure the old carboniferous reptile resembled the existing Lepidosiren, and affords further ground for regarding that remarkable existing animal as one which obliterates the line of demarcation between the fishes and the reptiles.
Coincident with this non-ossified state of the basis of the vertebral bodies of the trunk (fig. 65, c), is the absence of the ossified occipital condyles which characterize the skull in better developed Batrachia. The fore part of the notochord has extended into the basi-splienoid region, and its capsule has connected it by ligament to the broad flat ossifications of expansions of the same capsule, forming the basi-occipital or basi-splienoid plate. In fig. 65 are represented the chief modifications of the vertebrae, as shown in the neck, thorax, abdomen, sacrum, and tail. The vertebrae of the trunk in the fully-developed full-sized animal present the following stage of ossification : —
The neurapophyses (fig. 65, n\ coalesce at top to form the arch, from the summit of which was developed a compressed, sub-quadrate, moderately high spine, witli the truncate or slightly convex summit expanded in the fore-and-aft direction so as to touch the contiguous spines in the back ; the spines are distinct in the tail. The sides of the base of the neural arch are thickened and extended outwards into diapophyses, having a convex articular surface for the attachment of the rib, pi ; the fore-part is slightly produced at each angle into a zygapophysis looking upwards and a little forwards ; the hinder part was much produced backwards, supporting two- tliirds of the neural spine, and each angle developed into a zygapophysis, with a surface of opposite aspects to the anterior one. In the capsule of the notochord three bony plates were developed, one on the ventral surface, and one on each side,
* Reptilien aus der Steinkolilen Formation in Deutchland, Sechster Band, p. 61.
172
PALAEONTOLOGY
at or near the back part of the diapophysis. These bony plates may be termed cortical parts of the centrum, in the same sense in which that term is applied to the element which is called “body of the atlas” in man and Mammalia, and “ sub- vertebral wedge-bone” at the fore-part of the neck in Enaliosauria.
As such neural or inferior cortical elements co-exist with seemingly complete centrums in the Ichthyosaurus, thus affording ground for deeming them essentially distinct from a true centrum, the term “hypopophysis” has been proposed for such independent inferior ossifications in ■ and from the notochordal capsule ; and by that term may be signified the sub-notochordal plates in Archegosaurus, which co-exist with proper hsemapophyses ( h ) in the tail. In the trunk they are flat, subquadrate, oblong bodies, with the angles rounded off ; in the tail they bend upwards by the extension of the ossifi¬ cation from the under to the side parts of the notochordal capsule ; sometimes touching the lateral cortical plates. These serve to strengthen the notochord and support the interverte¬ bral nerve in its outward passage. The ribs (pi) are short, almost straight, expanded and flattened at the ends, round and slender at the middle. They are developed throughout the trunk and along part of the tail, co-existing there with the haemal arches, as in the Menopome.* The haemal arches (h), which are at first open at their base, become closed by exten¬ sion of ossification inwards from each produced angle, con¬ verting the notch into a foramen. This forms a wide oval, the apex being produced into a long spine ; but towards the end of the tail the spine becomes shortened, and the haemal arch reduced to a mere flattened ring,
O
The size of the canal for the protection of the caudal blood¬ vessels indicates the powerful muscular actions of that part,
* “Principal Forms of the Skeleton,’’ Orr’s Circle of the Sciences, p. 187 fig. 11.
GANOCEPHALA
173
as the produced spines from both neural and haemal arches bespeak the provision made for muscular attachments, and the vertical development of the caudal swimming organ.
The skull of the Archegosaurus appears to have retained much of its primary cartilage internally, and ossification to have been chiefly active at the surface ; where, as in the com¬ bined dermo-neural ossifications of the skull in the sturgeons and salamandroid fishes — e. g., Polypterus, Amici, Lepidosteus — these ossifications have started from centres more numerous than those of the true vertebral system in the skull of saurian reptiles. This gives the character of the present extinct order of Bcctrachia.
The skull is much flattened or depressed, triangular, with rounded angles, and the front one more or less produced according to the species ; and in some species according to the age of the individual. The base is concave ; the sides nearly straight, or slightly concave. The basi-occipital appears to have retained its primordial soft, unossified state. Of the ex-occipitals, in a distinctly ossified state, no clear view has yet been had. The super-occipital (fig. 65, 4), is represented, as in the salamandroid fishes, by a pair of flat bones, more probably developed in the epicranial membrane and integu¬ ment than in the cartilaginous protocranium. The pair of bones external to these, and forming the prominent angles of the occipital region, represent the “ par-oceipitals.” The lower peripheral surface of the basi-splienoidal cartilage is ossified with a concave border towards the notochord behind, to the capsule of which it seems to have been attached. The ali- sphenoids were doubtless cartilaginous, and the protocranium there unaltered, as it was apparently in the ex-occipital region. The peripheral ossifications above representing the “parietal” (7), form a pair of oblong flat bones, with the “foramen parietale ” in the mid-suture. External to these, and wedged between the parietals,. « the super- and par-occipitals, are
174
PALEONTOLOGY
the pair of hones answering to the “mastoids” (s). They give attachment externally and below to the tympanic (28), and to a subsidiary bony plate, holding the position of that development of the mastoid and squamosal, which roofs over the temporal fossa in the Chelonia : it may be termed “ supra- sqnamosal ” (the bone between 8 and 27 in fig. 65). The frontal bones (n), divided by a mid-snture, like the parietals, increase in length, and are continued far in advance of the orbits. The bone (12) which occupies the position of the post¬ frontal in Clielonia is ossified from two centres, one articulating with the mastoid ( 8 ), the other, which is external to it, with the supra-squamosal. This other bone may be termed the “post- orbital,” as proposed by Yon Meyer. The post-frontal extends forward above the orbit to meet the pre-frontal, separating the frontal (u) from the orbit, as in the sturgeon ( Acipenser ), Polypterus, and Lepidosteus, and also in some Chclones. The pre-frontal extends far forward, terminating in a point between the nasal (15) and lacrymal. The nasals (15), divided by the median suture, extend to the external nostrils, their prolonga¬ tion varying with the species and age of the individual.
Thus far the ossification of the superficies of the skull of Archegosaurus closely conforms to that of the salamandroid ganoid fishes above cited ; and the homologous bones are determinable without doubt. The lacrymal bone obviously answers to the front large suborbital scale-bone in fishes ; its large size and forward extension in Archegosaurus is a mark of that affinity.
The upper jaw consists of pre-maxillary (22), maxillary (21), and palatine bones. The pre-maxillaries are divided by a median suture, as in Lepidosteus and Crocodilus, and are short bones, the breadth exceeding the length in A. latirostris, and also in the young of A. Decheni ; but in the old animal opposite proportions prevail. 1 n A . Decheni each pre-maxillary contains eight teeth ; in A. latirostris not less than eleven.
GANOCEPHALA
175
Tlie maxillary (21) which extends from the pre-maxillary to beneath and beyond the orbit, presents a great length, varied according to species and age ; it is of small vertical extent, and terminates in a point, which reaches the tympanic. An¬ teriorly it unites with the pre-maxillary, and enters into the formation of the back boundary of the nostril; mesially it unites above with the lacrymal and suborbital, and below forms the outer boundary ol the choanal aperture, joining the vomer anteriorly, and the palatine posteriorly. The palatine is a long narrow bone, rather expanded at both extremities ; it forms anteriorly the hinder border of the choanal aperture, and mesially throughout a great part of its extent the outer boundary of the great palatal vacuity. It supports a row of teeth, of which one or two at the fore part are of large size.
Between the orbit and the maxillary extends an oblong flat bone (26), forming the lower or outer border of the orbit, uniting with the pre-frontal and lacrymal anteriorly, with the maxillary below, and with the tympanic ( 9 ) and another bone behind. In this position, and in its connections, it agrees with the malar of the crocodile, and also with the suborbital bone or bones of fishes. The latter are unequivocally muco- dermal bones, and may not be the homologues of the endo- skeletal malar bone of saurians, birds, and mammals. To which of the bones, therefore, — suborbital or malar, — the one in question of the Archegosaurus answers, may be doubtful. The writer inclines to view it as a dermal ossification, and to conclude that, as in the higher Batracliia, the true malar and the zygomatic arch are not developed. Admitting the doubt on this point, the bone (26) may be termed the “ suborbital.”
With regard to the next bone (27), the same question, whether it answers to the squamosal in the crocodile, or whether it is a dermal ossification, applies. If a homology with a determinate endo-skeletal bone in the crocodile and higher vertebrates were to be predicated, it would be the
176
PALEONTOLOGY
“squamosal.” Above 27, between it and 8, is the “supra- squamosal.” Essentially it indicates the tendency to excessive dermal ossification of tlie skull, like that which extends into the superficial temporal fascia from the squamosal and mastoid in the Ghelonia ; this separate ossification in Archegosaurus roofs over the temporal fossa. It is the homologue of the supernumerary surface-bone called “ supersquamosal ” in the Labyrinthodonts ; and both this and the “ postorbital” corre¬ spond in position with the posterior suborbital scale-bones in Amia and Lepiclosteus.
The hinder angles of the skull are formed by the tympanic ; in young individuals the tympanic does not extend backward beyond the par-occipital, but as age advances it projects further backward. It appears to abut internally against the pterygoid.
The two rami of the mandible were loosely united at a short symphysis, not exceeding the breadth or depth of the jaw at that point ; the depth gradually augments to near the articular end, but never exceeds a sixth, and is usually only an eighth of the length of the jaw, no definite coronoid process being developed ; the upper and lower borders are nearly straight as far as the deepest part. The lower border behind this part rises rather abruptly to an angle, which is just below the articular pit. The angular element (30) presents a con¬ vexity answering to the point of ossification whence some faint ridges radiate upon its outer surface. The dentary (32), if it does not form the articular surface, begins very near it, and each ramus appears to be composed of these two bones. The dentary developes the coronoid rising. Neither articular nor splenial element has been clearly demonstrated. If an articu¬ lar element has existed, it has been very small.
From fishes the lower jaw of Archegosaurus differs in the great length or forward extension of the angular piece (30) ; but it resembles the piscine type in the simplicity of its com¬ position. The angular piece is, however, longer in the Ganoids
GANOCEPHALA
177
—e.g., Amia, Polypterus, Lepidosteus, — than in other fishes; in Lepidosirm its proportions are almost those of the Arche- gosaurus ; and it offers similar proportions in the mandible of the Axolotl and Proteus (fig. 65).
The teeth in Archegosaurus have the simple conical pointed shape. They are implanted in the premaxillary, maxillary, mandibular, and vomerine bone, and in a single row in each. In the short premaxillaries there are from 8 (A. Decheni ) to 12 (A. latirostris ) ; they are rather larger than the maxillary teeth. These follow in an unbroken series to beneath and beyond the orbit, and are about 30 in number ; but their in¬ terspaces are such as would lodge double that number in the same extent of alveolar border. The vomerine teeth are in a single row, parallel with and near to the maxillary row ; one or two behind the clioane are much larger than the rest, which resemble the maxillary teeth in size. The mandibular teeth extend backward to the coronoid rising, and decrease in size, the front ones being the largest. Each tooth is implanted by a simple base in a shallow cup-shaped socket, with a slightly raised border, to which the circumference of the tooth becomes ancliylosed. The tooth is loosened by absorption and shed to make way for a successor. These are developed on the inner, hind, and fore part of the base of the old tooth. The teeth are usually shed alternately. They consist of osteodentine, dentine, and cement. The first substance occu¬ pies the centre ; the last covers the superficies of the tooth, but is introduced into its substance by many concentric folds extending along the basal half. These folds are indicated by fine longitudinal, straight striae along that half of the crown. The section of the tooth at that part (see fig. 65, tootli-section) gives the same structure which is shown by a like section of a tooth of the Lepidosteus oxyurus.*
The same principle of dental structure is exemplified in
* Wyman, American Journal of the Natural Sciences, Oct. 1843.
N
178
PALAEONTOLOGY
the teeth of most of the ganoid fishes of the carboniferous and Devonian systems, and is carried out to a great and beautiful degree of complication in the “old red” Dendrodonts.
The repetition of this structure in the teeth of one of the earliest genera of Reptilia , associated with the defect of ossifi¬ cation of the endo-skeleton and the excess of ossification in the exo-skeleton of the head and nape, instructively illustrates the true affinities and low position in the reptilian class of the so-called Archegosauri.
Resting upon and protected by the throat-plate in the middle line, there is a longish slender bone, which must belong to the median series of the hyoid system, either basi- or uro- liyal ; it is most probably homologous with the uro-kyal of Amphiuma and other Perennibranchiates. That two pairs of slender bones projected outward and backward from the median series, is shown by more than one specimen of Arclie- goscturus in the British Museum. The anterior pair is the longest ; these are situated as if they had been attached, one to each side of the broad “throat-plate,” which may have represented a basi-hyal. The anterior pair are homologous with the corresponding longer pair of appendages to the broad basi-hyal of Amphiuma, and are cerato-hyals. The shorter posterior pair answer to the branchi-hyals in Ampliiuina and other Perennibranclis. There is no such pair in the lxyoidean arch of any known Saurian.
External to the ends of the above lateral elements of the hyoid apparatus, feeble traces of arched series of bony nuclei were detected by Goldfuss, and interpreted by him as remains of partially ossified branchial arches. In all those specimens possessing them they present the outline of two or three arches in dots, or slightly curved series of dots or points. In the small relative size of these indications of branchial arches, the Archegosaurus agrees with the Amphiuma.
No doubt, in the fully-grown Archegosaurus, the lungs
GANOCEPHALA
179
ould be equal to the performance of the required amount of respiration ; but the retention of such traces of the embryonal water-breathing system in the adult leads to the inference that the animal must have affected a watery medium of exist¬ ence for as great a proportion of its time as is observed to be the case m the existing perennibranchiate reptiles ; in which, notwithstanding the degree of development of the lungs, the respiratory function seems to be mainly performed by the gills.
The additional marks of affinity to fishes which the Arche- gosaurus presents in its persistent notochord, cartilaginous basi-occipital, dermal ossifications on the head, and minute body-scales (fig. 65, scales), remove it further from the saurian reptiles, and exhibit it more strongly in the light of an osculant form between the Batrachians and the Ganoids.
The under surface of the body between the head and trunk is defended by broad bony plates, three in number. One is median and symmetrical, of an elongate lozenge shape, with the angles rounded off ; slightly convex externally, a little produced along the middle of the anterior half into somethin0,
O
like a low guasi- keel. The outer surface is sculptured by radiating furrows, except at so much of the marginal part as is overlapped by the lateral pieces, and by the scapular arch. The lateral throat-plates are attached to the anterior half of the sides of the median one, are shaped like beetles’ elytra, and converge forwards. Their centre of ossification is towards their outer and back part, from which the external ridges and grooves radiate towards the inner border.
Yon Meyer* compares these dermal shields to the ento- and epi-sternal elements of the plastron of Chelonia ; their truer homology seems to the writer to be with the median and lateral large throat-plates or scales of Megalichthys and Sudis
“Die kehlbrust platten konnte man der unpaarigen Platte und dem ersten Platten-paar im Bauchpanzer der Schildkroter vergleichen.” {Op. cit., p. 100.)
180
PALAEONTOLOGY
gig as. The ento-sternal element is the only endo-skeletal piece uncombined with a dermal ossification in most Chelonia. 1 he epi-sternal, like the hyo- and hypo-sternals, appear to be abdo¬ minal ribs, with snperadded dermal ossifications in Chelonia.
The scapulae (fig. 65, 51) are instructively exhibited in the very young specimen of the Archcgosaurus figured in t. xiv., fig. 4, of Yon Meyer’s treatise. The coracoids being doubtless wholly cartilaginous at that stage, are not discernible in the specimen referred to. The upper slender end of the scapula is opposite the side of the vertebral column, about the fifth neurapopliysis from the head, and it curves gently downward and forward, expanding at its humeral end. This expansion is more sudden in the fully-developed animal, giving the bone the shape of a rudder, and the direction of the scapula is changed. At least in the specimens (the great majority) in which the skeleton is seen from above, the slender dorsal end of the scapula is seen overlying, or near the hinder border of the lateral throat-plate, and it extends outward and backward to its expanded humeral end. The coracoids (52) are repre¬ sented by a pair of flat reniform plates, with the convex border turned forward, the concave one backward ; they seem to have overlapped the smooth margins of the posterior half of the median throat-plate. It is most probable that, as in Amphiuma, a portion of the broad coracoid remained in the cartilaginous state, and that the full reniform plate answers to the ossified part of that coracoid which it resembles in shape and relative position. The position of the slender scapuke, styliform and rib-like, as in the Perennibrancliiates, is instructively shown in t. xviii., figs. 1 and 2, of M. von Meyer’s treatise. The coracoids, as in Amphiuma, form the chief part of the articular cavity for the humerus.
The perennibranchiate affinities of Archec/osaurus are shown as clearly by the scapular as by the hyoidean arch. The fore- limi) does not exceed half the length of tire head. The humerus
GANOCEPHALA
181
(53) is a short thick hone, slightly constricted at the middle, expanded and rounded at both ends, the proximal one being the largest. For some time the bone is hollow and open at each end ; when ossification finally closes the terminal apertures, it shows that the ends were connected to the coracoid and to the fore-arm by interposed ligamentous matter, — not, as in true Saurians, by a synovial joint. Of the two bones of the fore¬ arm the ulna is a little longer and larger than the radius (54). Both bones present the simplest primitive form, gently con¬ stricted in the middle, with the proximal ends a little concave, the distal ones a little convex. The space between the anti- brachium and the metacarpus plainly bespeaks the mass of cartilage representing, as in Amphmma, the carpal segment (56) in Archegosaurus. ISTo trace of a carpal bone is found save in the largest and oldest examples, in which five or six small roundish ossicles are aggregated near the ulnar side of the carpus. Four digits are present ; and considering the pollex to be, as usual, wanting, the second digit answering to the medius of pentadactyle feet, is the largest, and includes at least four phalanges (58) ; these, with the metacarpals (57), are long, slender, terminally expanded, and truncate. They obvi¬ ously supported a longish, narrow, pointed paddle. The outer¬ most or little finger was the shortest, and has the shortest metacarpal and first phalanx.
It is true that in Mystriosaurus the fore limbs are relatively almost as short as in Archegosaurus ; and the oolitic crocodile recalls the arrest of development of the same limbs in the marsupial Potoroos ; but in Archegosaurus, not only is the small size of the fore limbs, but also their type of structure, especially that of their scapular arch, closely in accordance with that in the Permnibranchiata, as shown in the tridactyle fore-limb of the Proteus anguinus, of which a figure is added to that of the Archegosaurus in fig. 65.
The ilium (62), like the scapula, is expanded at its articular
182
PALAEONTOLOGY
or femoral end. It is less long and slender ; one border is straight, the other concave, by the expansion toward that border of the femoral end. Two shorter bones on each side complete tlie pelvis below. One is of a simple form, straight, thicker in proportion to its length than in the ilium : it may be ischium.
The other bone is shown, with its fellow, in t. xiii., fig. 6, and xviii., figs. 8 and 9, of Yon Meyer’s treatise. That author compares the pair of bones to the Aptyclius in shape ; they may be the pubic bones. On this hypothesis, they are restored to their true position at 64 (pubis) in fig. 65. The femur (65) is slightly expanded, and truncate at both ends ; it is not longer than the ilium. The tibia (66) and fibula are separate bones, like those of the fore-arm ; the margins, which are turned toward each other, are most concave. They are rather more than half the length of the femur.
The foot-bones are separated by a fibro-cartilaginous tarsal mass (68) from those of the leg. The form of the phalanges, expanded and truncate at both ends, bespeaks their simple ligamentous joints, and that they supported, like the fore-limb, a fin or limb adapted simply for swimming. The argument for the saurian affinities of Archegosaurus, based by V. Meyer on the short fore-limbs of Mystriosaurus, already invalidated by the difference of structure, is controverted by the fact, that the hind limbs of Archegosaurus, like those of the Perenni- branchs, are not only as simple in structure, but also as short, as the fore-limbs.
Genus Dendrerpeton. — In 1852 Sir Charles Lyell and Mr. Dawson, in the course of their investigations of the coal strata of Nova Scotia, remarkable for the erect fossil trees in certain parts, discovered in the hollow of the trunk of one of these trees ( Sigillaria , 2 feet in diameter), which was wholly con¬ verted into coal, some small bones, which Professor Wyman of Boston surmised to have belonged to a batrachian reptile.
LABYRINTHODONTIA
183
By the professor’s advice they were brought to England and submitted to the writer, who has described and figured them* as batrachian, under the name Dendrerpeton Acadianum, and with close affinities, from the plicated structure of the teeth, the sculpturing of some broad cranial plates, and the structure and proportions of certain limb-bones, to the genus Archego- saurus. The subsequent discovery of carinate scales with bones of the Dendrerpeton adds to the probability of its apper¬ taining to the Gfanocephalous order.
Genus Raxiceps. — In about the centre of the great car¬ boniferous basin of Ohio, United States, at the mouth of the “ yellow creek,” is a seam of coal 8 feet in thickness, the lower four inches of which is “ cannel coal.” In this has been found the skull, part of the vertebral column, scapular arch, and fore limbs of a reptile referred by Professor Wyman f to the batra¬ chian sub-class, under the name of Raniceps. Two closely- allied fossils, also referred to Batrachia, have been found in the same formation and locality.
Order II. — Labyrinthodontia.
Head defended, as in the Ganocephala, by a continuous casque of externally sculptured and unusually hard and polished osseous plates, including the supplementary “ post-orbital” and “ super-temporal” bones, but leaving a “ foramen parietale.” Two occipital condyles. Vomer divided and dentigerous. Two nostrils. Vertebral bodies, as well as arches, ossified, biconcave. Pleur- apophyses of the trunk, long and bent. Teeth rendered complex by undulation and side branches of the con¬ verging folds of cement, whence the name of the order.
The reptiles presenting the above characters have been divided into genera, according to minor modifications exempli-
* Quarterly Journal of the Geological Society, vol. ix., 1853.
-f- American Journal of Science and Arts, March 1857.
184
PALAEONTOLOGY
fiecl by the form and proportions of the skull, and by the relative position and size of the orbital, nasal, and temporal cavities.
Gemis Baphetes, Ow.
Sp. Baphetes planiceps. — In January 1854 the writer com¬ municated to the Geological Society of London a description of part of a fossil cranium of an animal, from the Pictou coal, Nova Scotia, measuring 7 inches across the orbit. Prom the characters then specified, the fossil was determined to be the fore part of a skull of a sauroid Batrachian of the extinct family of the Labyrinthodonts. It agreed with them in the number, size, and disposition of the teeth ; in the proportions and mode of connection of the premaxillaries, maxillaries, nasals, pre- frontals and frontals ; and in the resultant peculiarly broad and depressed character of the skull, the bones of which also present the same well-marked external sculpturing as in the Labyrinthodonts : and amongst the genera that have been established in that family, the form of the end of the muzzle, or upper jaw, in the Pictou coal specimen, best accorded with that in the Gapitosaurus and Metopias of Yon Meyer and Burmeister. But the orbits had been evidently larger and of a different form than in the reptiles so called ; and, for the convenience of distinction and reference, it was proposed to name the fossil Baphetes planiceps (‘Sdirru, I dip or dive), in reference to the depth of its position and the shape of its head.
Being thus introduced at the carboniferous period to the labyrinthodont order, which attained its full development in the triassic period, the more decisive evidences and typical illustrations of that extinct group of reptiles will next be described.
Genus Labyrinthodon, Ow.
At the period of the deposition of the new red sandstone, in the present counties of Warwick and Cheshire, the shores of the ancient sea, which were then formed by that sandy
LABYRINTIIODONTIA
185
deposit, were trodden by reptiles having the essential bony characters of the modern Batrachia, but combining these with other bony characters of crocodiles, lizards, and ganoid fishes ; and exhibiting all under a bulk which, as made manifest by the fossils and footprints, rivalled that of the largest crocodiles of the present day. The form of the largest Labyrintliodonts, if we may judge by the great breadth and flatness of the skull, and the proportions of certain bones, seems to have been something between that of the toad or land-salamander.
The smooth-skinned Batrachians have no fixed type of exter¬ nal form like the existing higher orders of reptiles, but some, as the broad and flat-bodied toads and frogs, most resemble the Chelonians, especially the soft-skinned mud-tortoises ( Trionyx ); other Batrachians, as the Ccecilice, resemble Ophidians ; a third group, as the newts and salamanders, represent the Lacertians ; and among the perennibranchiate reptiles there are species (Siren) which combine with external gills the mutilated con¬ dition of the apodal fishes.
Thus it will be perceived that, even if the entire skeleton of a Labyrinthodont had been obtained, there is no fixed or characteristic general outward form in the Batrachian order whereby its affinity to that group could have been determined.
The common characters by which the Batrachians, so di¬ versified in other respects, are naturally associated into one
group or sub-class of reptiles,
6 . , . ,1 Fig. 65 a.
besides being taken from the Cranium and upper jaw and teeth of
condition of the circulating and the Menopome (. Menopoma
generative systems, and other alieghanmense).
perishable parts, are manifested in modifications of the skeleton,
186
PALAEONTOLOGY
and principally in the skull. This is joined to the atlas by the medium of two tubercles, developed exclusively from the ex-occipitals ; the bony palate is formed chiefly by two broad and flat bones (fig. 65 a, c ), called “ vomerine,” and generally supporting teeth. It is only in the Batrachians among existing
Fig. 6G.
reptiles that examples are found of two or more rows of teeth on the same bone, especially on the lower jaw (C cecilia, Siren). With re¬ gard to vertebral characters, no such absolute batrachian modifications can be ad¬ duced as those above cited from the anatomy of the cranium. Some Batrachians have the vertebrae united by ball-and-socket joints, as in most recent reptiles ; others by biconcave joints, as in a few recent and most extinct Saurians. Some species have ribs, others want those appendages ; the possession of ribs, there¬ fore, even if longer than those of the Ccecilia, by a fossil reptile combining all the essential batrachian
Canine tooth of the Ldbyrintliodon Jcujaeri characters of the skull, 'H'1*' ' would not be sufficient
ground for pronouncing such reptile to be a Saurian. Much less could its saurian nature be pronounced from the circum¬ stance of its possessing large conical striated teeth : the ordi-
LABYRINTIIODONTIA
187
nary characters of size, form, number, and even of presence or absence of teetli, vary much in existing Batrachians ; and the location of teeth on the vomerine bones is the only dental character in which they differ from all other orders of reptiles.
The writer’s acquaintance with the remarkable fossils under consideration was begun by the examination, in 1840, of portions of teeth from the new red sandstone of Coton End quarry, Warwickshire. The external characters of these teeth corresponded with those (fig. 66) which had previously been discovered by Professor Jaeger in the German Iveuper forma¬ tion in Wirtemberg, and on which the genus Mastodonsaurus had been founded.
The results of a microscopic examination of the teeth of the Mastodonsaurus from the German Keuper, and of those from the new red sandstone of Warwickshire, proved that the teeth from both localities possessed in common a very remarkable and complicated structure (fig. 67), to the principle of which,
_ viz., the convergence of numerous inflected folds of the
external layer of cement towards the pulp-cavity, a very slight approach was made in the fang of the tooth of the Ichthyosaurus, whilst a closer approximation to the labyrinthic structure in question was made by the teeth of several species of ganoid fishes, and by those of Archegosaurus.
Thus, inasmuch as the extinct animals in question mani¬ fested in the intimate structure of their teeth an affinity to fishes, it might be expected that, if they actually belonged to the class of reptiles, the rest of their structure would manifest the characters of the lowest order, — viz., the Batrachia, the existing members of which pass, though not by the dental cha¬ racter alluded to, yet by so many other remarkable degrada¬ tions of structure, towards fishes.
In the same formation in Wirtemberg from which the laby¬ rinthic teeth of the so-called Mastodonsaurus had been derived, a fragment of the posterior portion of the skull has been obtained,
188
PALAEONTOLOGY
showing tlie development of a separate condyle on each ex- occipital hone ; whence Professor Jaeger, recognizing the identity of this structure with the batrachian character above mentioned, founded upon the fossil a new genus of Batrachia which he called “ Scdamandroides giganteus Subsequent dis¬ coveries, however, satisfied the Professor that the bi-condylous fragment of skull, representing the genus Salamandroides, belonged to the same reptile as the teeth on which he had founded the genus Mastodonsaurus. The following fossils, from the new red sandstone of Warwickshire, gave additional proof of the batrachoid nature of the genus to which those
Fig. 67.
Transverse section of a tootli of the Labyrinthodon (magn.)
fossils belong, with the establishment of five distinct species, one of which is most probably identical with the Mastodon¬ saurus salamandroides of Professor Jaeger. In reference to the generic denomination Mastodonsaurus, it unavoidably re¬ calls the idea of the mammalian genus Mastodon, or else a mam-
LABYRINTHODONTIA
189
milloid form of tooth, whereas all the teeth of the reptile so called are originally, and most of them are permanently, of a cuspidate and not of a mammilloid form ; secondly, because the second element of the word, saurus, indicates the genus to belong to the saurian or lacertian order of reptiles. For these reasons, the writer has proposed to designate the genus in question Labyrinthodon, in allusion to the peculiar and cha¬ racteristic structure of the teeth (fig. 67).
The specimens from British localities are referable to five species — viz., 1. Labyrintlioclon salamandroides ; 2. L.leptogna- thus ; 3. L. pachygnatlius ; 4. L. ventricosus ; and 5. L. scutu- latus ; and we shall here briefly notice the characters exhi¬ bited by the bones assignable to the second, third, and fifth species.
Labyrinthodon leptognathus. — The remains of this species consist of fragments of the upper and lower jaws, two vertebrae, and a sternum. They were found in the new red sandstone quarries at Coton End near Warwick.
A dorsal vertebra from Coton End presents further evidence of the batrachian nature of the Labyrinthodon. It has con¬ cave articular cavities at the extremities of the body,— a con¬ dition now known among existing reptiles only in the Geckos, and in the lower or perennibranchiate division of Batrachians. It is a common structure in extinct Saurians, but the depth of the vertebral articular cavities in the Labyrinthodon exceeds that in the amphicoelian Crocodiles and in most Plesiosauis. The body of the vertebra is elongate and sub-compressed, with a smooth but not regularly curved lateral surface, terminating below in a slightly-produced, longitudinal, median ridge ; and it exhibits the same exceptional condition in the reptilian class as do the vertebrae of existing Batrachians, in having the superior arch or neurapophysis ancliylosed with the centrum. From each side of the base of the neural arch a thick and stiong transverse process extends obliquely outwards and upwards.
190
PALAEONTOLOGY
A symmetrical bone, resembling the episternum of the Ich¬ thyosaurus was associated with the preceding remains. It consists of a stem or middle, which gradually thickens to the upper end, where cross pieces are given off at right angles to the stem, and support on each a pretty deep and wide groove indicating strongly the presence of clavicles, and thus pointing out another distinction from crocodiles, in which clavicles are wanting. Most Batrachians possess these bones.
The modifications of the jaws, and more especially those of the bony palate of the Labyrintliodon leptognathus , prove the fossil to have been essentially Batrachian, but with affinities to the higher Sauria, leading, in the form of skull and the sculp¬ turing of the cranial bones, to the crocodilian group, in the collocation of the larger fangs at the anterior extremities of the jaws to the Plesiosaurus , and in one part of the dental structure, in the form of the episternum, and the bi-concave vertebrae, to the Ichthyosaurus. Another marked peculiarity in this fossil is the anchylosis of the base of the teeth to dis¬ tinct and shallow sockets, by which it is made to resemble the Sphyrsena and certain other fishes. From the absence of any trace of excavation at the inner side of the base of the func¬ tional teeth, or of alveoli of reserve for the successional teeth, it may be concluded that the teeth were reproduced, as in the lower Latiacliians and in many fishes, in the soft mucous membrane which covered the alveolar margin, and that they subsequently became fixed to the bone by anchylosis, as in the pike and Lophius.
Labyrintliodon pachygnathus. — The remains of this species, which have been obtained, consist of portions of the lower and upper jaws, an anterior frontal bone, a fractured humerus, an ilium with a gieat part of the acetabulum, the head of a femur, and two ungual phalanges. A portion, nine and a half inches long, of a right ramus of a lower jaw, in addition to the charac¬ ters common to it and the fragment of the lower jaw of the
LABYRINTHODONTIA
191
L. leptognathus, in the structure of the angular and dentary pieces, shows that the outer wall of the alveolar process is not higher than the inner, as in frogs and toads, the salamanders and menopome, in all of which the base of the teeth is anchy- losed to the inner side of an external alveolar plate. The smaller serial teeth are about forty in number, and gradually diminish in size as they approach both ends, but chiefly so towards the anterior part of the jaw. The sockets are close together, and the alternate ones are empty. The great laniary teeth were apparently three in each symphysis, and the length of the largest was one inch and a half. The base of each tooth is anchylosed to the bottom of its socket, as in scomberoid and sauroid fishes ; but the Labyrintliodon possesses a still more ichthyic character in the continuation of a row of small teeth anterior and external to the two or three larger tusks. The premaxillary bone presents the same peculiar modification as in the higher organized Batrachia, the palatal process of the premaxillary extending beyond the outer plate both externally and, though in a less degree, internally, where it forms part of the boundary of the anterior palatal foramen, whence the outer plate rises in the form of a compressed process from a longitudinal tract in the upper part of the palatal piocess , it is here broken off near its margin, and the fractured surface gives the breadth of the base of the outer plate, stamping the fossil with a Batrachian character conspicuous above all the saurian modifications by which the essential nature of the fossil appears at first sight to be masked.
In the pre-frontal bone there are indications of crocodilian structure. Its superior surface is slightly convex and pitted with irregular impressions ; and from its posterior and outer part it sends downwards a broad and slightly concave process, which appears to be the anterior boundary of the orbit. This process presents near its upper margin a deep pit, from which a groove is continued forwards ; and in the corresponding
192
PALAEONTOLOGY
orbital plate of the crocodile there is a similar hut smaller foramen.
From these remains of the cranium of the L. jpacliygnathus it is evident that the facial or maxillary part of the skull was formed in the main after the crocodilian type, hut with well- marked batracliian modifications in the premaxillary and inferior maxillary hones. The most important fact which they show is, that this sauroid Batrachian had subterminal nostrils, leading to a wide and shallow nasal cavity, separated by a broad and almost continuous palatal flooring from the cavity of the mouth ; indicating, with their horizontal posi¬ tion, that their posterior apertures were placed behind the anterior or external nostrils, whereas in the air-breathing Batracliia the nasal meatus is short and vertical, and the inter¬ nal apertures pierce the anterior part of the palate, suitable to their mode of breathing by deglutition. It may be inferred, therefore, that the apparatus for breathing by inspiration must have been present in the Labyrinthodon as in the crocodile ; and that the skeleton of the Labyrinthodon will be found to be provided with well-developed costal ribs, and not, as in most of the existing Batracliians, with merely rudimentary styles. Since the essential condition of this defective state of the ribs of Batracliians is well known to be their fish-like mode of generation and necessary distension of the abdomen, it is probable that the generative economy of the Labyrinthodonts, m which the more complete ribs would prevent the excessive enlargement of the ovaria and oviducts, may have been similar to that of saurian reptiles.
01 the few bones of the extremities which have come under the writer’s inspection, one presents all the characteristics of the corresponding part of the humerus of a toad or frog, viz., the convex, somewhat transversely extended articular end, the internal longitudinal depression, and the well-developed del¬ toid ridge. The length of the fragment is two inches, and the
LABYRINTHODONTIA
193
breadth is thirteen lines. The ridges are moderately thick and compact, with a central medullary cavity. In its structure, as wrell as in its general form, the present bone agrees with the batrachian, and differs from the crocodilian type.
In the right ilium, about six inches in length, and in the acetabulum, there is a combination of crocodilian and batra¬ chian characters. The acetabular cavity is bounded on its upper part by a produced and sharp ridge, as in the frog, and not emarginate at its anterior part, as in the crocodile.
As the fragment of the ilium was discovered in the same block as the two fragments of the cranium and the portion of the lower jaws, it is probable that they may have belonged to the same animal ; and if so, as the portions of the head corres¬ pond in size with those of the head of a crocodile six or seven feet in length, but the acetabular cavity with that of a crocodile twrenty-five feet in length, then the hinder extremities of the Labyrintliodon must have been of disproportionate magnitude compared with those of existing Saurians, but of approximate magnitude with some of the living anourous Batrachians. That such a reptile, of a size equal to that of the species whose remains have just been described, existed at the period of the formation of the new red sandstone, is abundantly mani¬ fested by the remains of those singular impressions to which the term Cheirotherium has been applied. Other impressions, as those of the Cheirotherium Hercules, correspond in size with the remains of the Lcibyrinthodon salamandro'ides, which have been discovered at Guyl s Cliff. The head of a femur from the same quarry in which the ilium was found is shown to corres¬ pond in size with the articulate cavity of the acetabulum. The two toe-bones, or terminal phalanges, resemble those of Batrachians in presenting no trace of a nail, and from their size they may be referred to the hind feet of the L. pachygnathus.
An entire skull of the largest species discovered in the new red sandstones of Wurtemberg ; a lower jaw of the same
o
194
PALAEONTOLOGY
species found in the same formation in Warwickshire ; some vertebrae, and a few fragments of bones of the limbs, have served, with the indications of size and shape of the trunk of the animal yielded by the series of consecutive footprints, as the basis of the restoration of the Ldbyrinthodon salaman- dro'ides, at the Crystal Palace. It is to be understood, how¬ ever, that, with the exception of the head, the form of the animal is necessarily more or less conjectural.
Ldbyrinthodon scutulatus. — The remains to which this specific designation has been applied compose a closely and irregularly aggregated group of bones imbedded in sandstone, and manifestly belonging to the same skeleton ; they consist of four vertebrae, portions of ribs, a humerus, a femur, two tibiae, one end of a large flat bone, and several small osseous externally sculptured dermal scutes, which show that the crocodilian nature of a fossil reptile is not determinable by scutes only. The mass was discovered hr the new red sand¬ stone at Leamington, and was transmitted to the writer in the summer of 1840.
The vertebrae present bi-concave articular surfaces similar to those of the other species. In two of them the surfaces slope in a parallel direction obliquely from the axis of the vertebrae, as in the dorsal vertebrae of the frog, indicating a habitual inflexion of the spine, analogous to that in the humped back of the frog. The neurapophyses are anchylosed to the vertebral body. The spinous process rises from the whole length of the middle line of the neurapophysial arch, and its chief peculiarity is the expansion of its elongated summit into a horizontally-flattened plate, sculptured irregularly on the upper surface. A similar flattening of the summit of the elongated spine is exhibited in the large atlas of the toad. The body of the vertebra agrees with that of the L. leptog- nathus. The humerus is an inch long, regularly convex at the proximal extremity, and expanded at both extremities, but
LABYKINTHODONTIA
195
contracted in the middle. A portion of a somewhat shorter and flatter hone is bent at a subacute angle with the distal extremity, and resembles most nearly the anchylosed radius and ulna of the Batrachia.
The femur wants both the extremities ; its shaft is sub- trihedral and slightly bent, and its walls are thin and compact, including a large medullary cavity. The tibiae exhibit that remarkable compression of their distal portion which charac¬ terizes the corresponding bone in the Batrachia ; they likewise have the longitudinal impression along the middle of the flattened surface. Were more of the skeleton of the above- defined species of LabyrintTiodon known, they might present differences of subgeneric value. Such differences in the forms and proportions of the skull, and in the form and relative position of the orbits, of specimens that have been discovered subsequently in the triassic sandstones of Germany, have been so interpreted.
In the Labyrintliodon ( Mccstodonsaurus ) Jaegeri — the largest of the species — the skull is triangular, the two condyles projecting from the middle of the base ; the sides are straight, and converge to the obtuse apex. The orbits are oval, nar¬ rowest anteriorly, and are situated nearly midway between the fore and back part of the skull. The nostrils are very small, and are as wide apart as the orbits.
Labyrintliodon {Trematosaurus) Braunii, Yon Meyer. — The name Trematosaurus was given by Braun to a labyrin- thodont reptile, in reference to the parietal foramen, at that time deemed to be peculiar to it, but now known to be com¬ mon to all the family. The genus was founded on an unusually perfect skull discovered in the richly fossiliferous bunter- sandstein of Bernburg. It is about one foot long, and, lela- tively to its basal breadth, it is longer and narrower than in L. Jaegeri, the sides converging at a more acute angle. The orbits are elliptical, situated in the middle of the skull, and
19G
PALEONTOLOGY
wider apart than in L. Jaegeri ; the nostrils are relatively nearer together, their interspace being only half that in the L. Jaegeri.
Lahyrinthodon ( Metopias *) diagnosticus, H. von M. — In this species the skull is broader in proportion to its length than in the foregoing ; the sides are convex as they converge to the obtuse muzzle. The orbits are small, of a vide elliptical form, situated in the anterior third of the skull ; they are twice as wide apart as are the nostrils. The parietal foramen is near the occipital ridge. The remains of this species are from the upper beds of the keuper sandstone in Wirtemberg.
The Lahyrinthodon ( Capitosaurus ) arena ceus, Munster, is distinguished by a much broader and almost truncate muzzle. The orbits are elliptic, and situated almost wholly in the hinder third of the cranium ; their interspace is the same as that between the nostrils, which are relatively as large as in L. Braunii.
The name Zygosaurus appears to have been applied with better grounds, by Eichwald, to a labyrintliodont reptile from the Permian cupriferous beds at Orenburg. It has the para¬ bolic skull of L. J acgeri and L. diagnosticus ; the orbits large, and divided by an interval less than their own diameter. The temporal fossae are relatively larger, and bounded by stronger zygomatic arches, and seem not to have been roofed over by bone. The dentition is strictly labyrinthodont.
Odontosaurus Voltzii is a genus and species founded by Yon Meyer on a portion of a lower jaw, containing fifty teeth lodged in rather a deep groove, but apparently presenting the labyrinthic structure. The specimen is from the hunter sand¬ stone of Soultz-les-Bains.
Xestorrhytias Perrini. — By this name M. von Meyer would indicate certain flat cranial bones, sculptured like those of
* This generic term has been applied to another fossil by Eichwald.
L AB Y RINTHOD ONTI A
197
Labyrinthodon, but with a peculiarly polished ganoid-like surface, from the muschelkalk of Luneville.
In all the foregoing forms of Labyrinthodonts, represented by complete crania, with the exception perhaps of Zygosaurus, the supplemental osseous plates roofing over the temporal fossae are present, as in Archegosaurus, viz., the “post-orbital” and the “ super-squamosal ” bones. In all of them the occipital condyles are distinct, forming a pair ; and in all the vomer is divided and bears teeth. The structure and disposition of the entire dental system is strictly labyrinthodont.
The relation of these remarkable reptiles to the saurian order has been advocated to be one of close and true affinity, chiefly on the character of the extent of ossification of the skull, and of the outward sculpturing of the cranial bones. But the true nature of some of these bones appears to have been overlooked, and the glance of research for analogous structures has been too exclusively upward. If directed down¬ ward from the Labyrinthodonts to the Archegosauri and certain ganoid fishes, it suggests other conclusions.
The conformity of pattern in the dermal, semidermal, or neurodermal bones of the outwardly well-ossified skull of Polypterus, Lepidosteus, Sturio, and other salamandroid-ganoid fishes, with well-developed lung-like air-bladders, and of the same skull-bones in the Archegosaurus and the Labyrintho¬ donts ; the persistence of the notochord ( chorda dorsalis) in Archegosaurus, as in Sturio ; the persistence of the notochord and branchial arches in Archegosaurus, as in Lepidosiren; the absence of occipital condyle or condyles in Archegosaurus, as in Lepidosiren ; the presence of labyrinthic teeth in Archego¬ saurus, as in Lcpidosteics and Labyrinthodon ; the large median and lateral throat-plates in Archegosaurus, as in Megalichthys, and in the modern Arapaima and Lepidosteus ; — all these characters point to one great natural group, peculiar for the extensive gradations of development, linking and blending
PALAEONTOLOGY
198
together fishes and reptiles within the limits of such group. The salamandroid (or so-called “sauroid”) Ganoids — Lepi- dosteus and Polyptcrus — are the most ichthyoid, the true Labyrinthodonts are the most sauroid, of the group. The Lepidosiren and Arclicgosaurus are intermediate gradations, one having more of the piscine, the other more of the reptilian characters. The Archegosaurus conducts the march of develop¬ ment from the fish proper to the labyrinthodont type ; the Lepidosiren conducts it to the perennibranchiate batrachian type. Both illustrate the artificiality of the supposed class distinction between fishes and reptiles, and the naturality of the “ Heematocrya,” or cold-blooded Vertebrata, as the one unbroken progressive series. There is nothing in the known structure of the so-named Archegosaurus or Mastodonsaurus that truly indicates a belonging to the saurian or crocodilian order of reptiles. The exterior ossifications of the skull and the canine-shaped labyrintliic teeth are both examples of the salamandroid modification of the ganoid type of fishes.
The small proportion of the fore limb of the Mystriosaurus in nowise illustrates this alleged saurian affinity ; for though it be as short as in Archegosaurus , it is as perfectly constructed as in the crocodile, whereas the short fore limb of Archego¬ saurus is constructed after the simple type of that of the Proteus and Siren. But the futility of this argument of the sauroid affinities is made manifest by the proportions of the hind limb of Archegosaurus. As in Proteus and Amphiuma, it is as stunted as the fore limb ; whereas in Mystriosaurus, as in other 1 eleosaurians, the hind limbs are relatively larger and stronger than in the existing crocodiles.
Order 3. — Ichtiiyopterygia.*
The bones of the head still include the supplementary “ post- orbitals” and “ supra-temporals,” but there are small
* a fsh; n repv£, a fin.
ICHTHYOPTERYGIA
199
temporal and other vacuities between the cranial bones : a “ foramen parietale ” a single convex occipital condyle, and one vomer which is edentulous. Two antorbital nostrils. Vertebral centra, ossified, biconcave. Pleur- apophyses of the trunk long and bent, the anterior ones with bifurcate heads. Teeth with converging folds of cement at their base ; implanted in a common alveolar groove, and confined to the maxillary, premaxillary, and premandibular bones. Premaxillaries much exceeding the maxillaries in size. Orbit very large ; a circle ot sclerotic plates. Limbs natatory ; with more than five multi-articulate digits ; no sacrum. With the retention of characters which indicate, as in the preceding orders, an affinity to the higher Ganoid fishes, the present ex¬ clusively marine Eeptilia more directly exemplify the iclithyic type in the proportions of the premaxillary and maxillary bones, in the shortness and great number of the biconcave vertebrae, in the length of the pleur- apopliyses of the vertebrae near the head, in the laige proportional size of the eyeball and its well-ossified sclerotic coat, and especially in the structure of the pectoral and ventral fins.
It has been usual to unite the present with the following order in the same group, called Encdiosauria or sea-lizaids. They were adapted for marine life, but breathed the air like the Cetacea : they were, however, “ cold-blooded,” or of a low temperature, like crocodiles and other reptiles. The proof that the Enaliosaurs respired atmospheric air immediately, and did not breathe water by means of gills like fishes, is afforded by the absence of the bony framework of the gill apparatus, and by the presence, position, and structure of the air-passages leading from the nostrils to the mouth, and also by the bony mechanism of the capacious chest or thoracic-
200
PALAEONTOLOGY
abdominal cavity ; all of which characters have been demon¬ strated by their fossil skeletons. With these characters the sea-lizards combined the presence of two pairs of limbs shaped like fins, and adapted for swimming.
The group of reptiles so termed includes all those which have any part of the thoracic-abdominal cavity encompassed by moveable ribs. The first character distinguishes them from the Batrachia and Chelonia with fin-shaped limbs.
The Enaliosauria, however, do not form a strictly natural group ; for this is based upon a single character relating to merely the medium of life and locomotion. Some of the labyrintliodont reptiles may have had their limbs in structure and shape as paddles ; but more important modifications of structure would keep them apart, like the lower Batrachia and the Chelonia , from the more lizard-like reptiles called Enaliosauria.
In this group there are two divisions, — one characterized by having five digits in the fin, the other by having more than that typical numbet. The pentadactyle division may be sub-divided into those in which the ilio-pubic arch is attached to a sacrum and those on which it is freely sus¬ pended or not so attached. The polydactyle division presents a general type of structure more conformable with that of which the Archegosaurs and Labyrintliodonts manifest two phases of development, and in which the ascent from the gano-salamandroid fishes reaches its culminating point in Ichthyosaurus.
Genus Ichthyosaurus.— The name (from the Greek ichthys, a fish, and sauros, a lizard) was devised to indicate the closer affinity of the Ichthyosaur, as compared with the Plesiosaur, to the class of fishes. The Ichthyosaur (fig. 68) is remark¬ able for the shortness of the neck and the equality of the width of the back of the head with the front of the chest, impressing the observer of the fossil skeleton with a conviction
ICHTHYOPTERYGIA
201
that the ancient animal must lu and the fishes, in the absence of any intervening constriction or neck.
This close approximation in the Ichthyosaurs to the form of the most strictly aquatic verte¬ brate animals of the existing creation, is accompanied by an important modification of the surfaces forming the joints of the back-bone, each of which surfaces are hollow, leading to the inference that they were originally connected together by an elastic bag or “ capsule” filled with fluid — a structure which prevails in the class of fishes, in the Labyrinthodonts and a few extinct aquatic rep¬ tiles, in the existing perenni- branchiate Batrachia, but not in any of the whale or porpoise tribe.
With the above modifica¬ tions of the head, trunk, and limbs, in relation to swimming, there co-exist corresponding modifications of the tail. The bones of this part are much more numerous than in the Plesiosaurs, and the entire tail is consequently longer ; but it does not show any of those
resembled the whale tribe
202
PALEONTOLOGY
modifications that characterize the bony support of the tail fin in fishes. The numerous caudal vertebrae of the Ichthyosaurus, gradually decrease in size to the end of the tail, where they assume a compressed form, or are flattened from side to side, and thus the tail, instead of being short and broad as in fishes, is lengthened out as in crocodiles.
The very frequent occurrence of a fracture of the tail, about one-fourth of the way from its extremity, in well preserved and entire fossil skeletons, is owing to that proportion of the end of the tail having supported a cutaneous and perishable caudal fin.* The only evidence which the fossil skeleton of a whale would yield of the powerful horizontal tail-fin characteristic of the living animal, is the depressed or horizontally-flattened form of the bones supporting such fin. It is inferred, therefore, from the corresponding bones of the Ichthyosaurus being flattened in the vertical direction, or from side to side, that it possessed a tegumentary tail fin expanded in the vertical direction. The shape of a fin composed of such perishable material is of course conjectural, as is the outline in fig. 68. Thus, in the construction of the principal swimming organ of the Ichthyosaurus we may trace, as in other parts of its structure, a combination of mammalian (beast-like), saurian (lizard¬ like), and piscine (fish-like) peculiarities. In the great length and gradual diminution of the tail we perceive its saurian character ; in the tegumentary nature of the fin, unsustained by bony fin-rays, its affinity to the same part in the mammalian whales and porpoises is shown ; whilst its vertical position makes it closely resemble the tail fin of the fish.
The horizontality of the tail fin of the whale tribe is essen¬ tially connected with their necessities as warm-blooded animals breathing atmospheric air ; without this means of displacing a mass of water in the vertical direction, the head of the whale * Trans. Geol. Soc., 2d series, vol. v., p. 511.
ICHTHYOPTERYGIA
203
could not be brought with the required rapidity to the surface to respire ; but the Ichthyosaurs, not being warm-blooded or quick breathers, would not need to bring their head to the surface so frequently or so rapidly as the whale ; and more¬ over, a compensation for the want of horizontality of their tail fin was provided by the addition of a pair of hind paddles, which are not present in the whale tribe. The vertical fin was a more efficient organ in the rapid cleaving of the liquid element, when the Ichthyosaurs were in pursuit of their prey, or escaping from an enemy.
The general form of the cranium of the Ichthyosaurus resembles that of the ordinary cetaceous dolphin ( Delphinus tursio ) ; but the I. tenuirostris rivals the DelgMnus gangeticus in the length and slenderness of the jaws. The essential difference in the sea-reptile lies in the restricted size of the cerebral cavity, and the vast depth and breadth of the zygomatic arches, to which the seeming expanse of the cranium is due ; still more in the persistent individuality of the elements of those cranial bones which have been blended into single though compound bones in the sea-mammal. The Ichthyosaurus further differs in the great size of the premaxillary, and small size of the maxillary bones, in the lateral aspects of the nostrils, in the immense size of the orbits, and in the large and nume¬ rous sclerotic plates, which latter structures give to the skull of the Ichthyosaurus its most striking features.
The true affinities of the Ichthyosaur are, however, to be elucidated by a deeper and more detailed comparison of the structure of the skull ; and few collections now afford richer materials for pursuing and illustrating such comparisons than the palaeontological series in the British Museum* The two supplemental bones ol the skull, which have no homologues
* The anatomical reader is referred to the writer’s “ Report, on British fossil Reptiles,” Trans Brit. Assoc. 1839, and to the Annals and Magazine of Natural
History, 1858, p. 388.
204
PALAEONTOLOGY
in existing Crocodilians, are the post-orbital and super- squamosal ; both, however, are developed in Archcgosaurus and the Labyrinthodonts. The post-orbital is the homologue of the inferior division of the post-frontal in those Lacertians — e. g.. Iguana, Tejus, Ophisaurus, Anguis, in which that bone is said to be divided. But in Ichthyosaurus the post-orbital resembles most a dismemberment of the malar. Its thin obtuse scale-like lower end overlaps and joins by a squamous suture the hind end of the malar : the post-orbital expands as it ascends to the middle of the back of the orbit, then gradually contracts to a point as it curves upward and forward, articu¬ lating with the super-squamosal and post-frontal. The super- squamosal may be in like manner regarded as a dismember¬ ment of the squamosal; were it confluent therewith, the resemblance which the bone would present to the zygomatic and squamosal parts of the mammalian temporal would be very close ; only the squamosal part would be removed from the inner wall to the outer wall of the temporal fossa. The super-squamosal, in fact, occupies the position of the temporal fascia in Mammalia, and should be regarded as a supplemental sclero-dermal plate, closing the vacuity between the upper and lower elements of the zygomatic arch, peculiar to certain air- breathing Ovipccra. In the Ichthyosaurus it is a broad, thin, flat, irregular-shaped plate, smooth and slightly convex exter¬ nally, and wedged into the interspaces between the post-frontal, post-orbital, squamosal, tympanic, and mastoid.
The principal vacuities or apertures in the bony walls of
the skull of the Ichthyosaurus are the following : _ In the
posterior region the “ foramen magnum,” the occipito-parietal vacuities, and the auditory passages ; on the upper surface the parietal foramen and the temporal fossa; ; on the lateral surfaces the orbits and nostrils, the plane of the aperture in both being vertical ; on the inferior surface the palato-nasal, the pterygo-sphenoid, and the pterygo-malar vacuities. The
ICHTHYOPTERYGIA
205
occipito-parietal vacuities are larger than in Crocodilia, smaller than in Lacertilia ; they are hounded internally by the basi-, ex-, and super-occipitals, externally by the parietal and mastoid. The auditory apertures are hounded by the tympanic and squamosal. The tympanic takes a greater share in the forma¬ tion of the “ meatus auditorius ” in many lizards ; in crocodiles it is restricted to that which it takes in Ichthyosaurus.
The orbit is most remarkable in the Ichthyosaurus, amongst reptiles, both for its large proportional size and its posterior position ; hi the former character it resembles that in the lizards, in the latter that in the crocodiles. It is formed by the pre- and post-frontals above, by the lacrymal in front, by the post-orbital behind, and by the peculiar long and slender malar bar below. In crocodiles and in most lizards the frontal enters into the formation of the orbits, and in lizards the maxillary also. The nostril is a longish triangular aperture, with the narrow base behind ; it is bounded by the lacrymal, nasal, maxillary, and premaxillary bones. It is proportionally larger than in the Plesiosaurus, and is distant from the orbit about half its own long diameter. Like the orbit, the plane of its outlet is vertical.
The pterygo-palatine vacuities are very long and narrow, broadest behind, where they are bounded, as in lizards, by the anterior concavities of the basi-sphenoid, and gradually narrow¬ ing to a point close to the palatine nostrils. These are smaller than in most lizards, and are circumscribed by the palatines, ecto-pterygoid, maxillary, and premaxillary. The pterygo- malar fissures are the lower outlets of the temporal fossae ; their sudden posterior breadth, due to the emargination of the pterygoid, relates to the passage of the muscles for attachment to the lower jaw. The parietal foramen is bounded by both parietals and frontals ; its presence is a mark of labyrinthodont and lacertian affinities ; its formation is like that in Iguana and Rhynchocephalus. The temporal fossae are bounded above
206
PALEONTOLOGY
by the parietal internally, by the mastoid and post-frontal externally ; they are of an oval form, with the great end forward. In their relative size and backward position they are more crocodilian than lacertian.
In the Ichthyosaurus communis there are seventeen sclerotic plates forming the fore part of the eyeball. In a well-preserved example, the pupillary or corneal vacuity, as bounded by those plates, is of a full oval form, li inch in long diameter, the length of the plates (or breadth of the frame) being from 8 to 1 0 lines. In the same skull the long diameter of the orbit is 4 inches. The deep position of the sclerotic circle in this cavity showed how they had sunk, by pressure of the external mud, as the eyeball became collapsed by escape of the humours in decomposition.
Whenever the antecedent forms of an extinct genus of any class are known, the characters of such genus should be com¬ pared with those of its predecessors in such class, rather than with its successors or with existing forms, in order to gain an insight into its true affinities.
We derive a truer conception of the affinities of the Ichthyosaurus by comparison with the Labyrinthodonts and other triassic reptiles, as we do of the Plesiosaurus by com¬ parison with the muschelkalk Sauropterygia, than of either by comparison with modern Lacertians and Crocodilians. It is commonly said that the Ichthyo- or the Plesiosaurus resembles more the lizards in such and such characters, and in a less degree the crocodiles, as in such a character. The truer expression would be that the lizards, which are the predo¬ minating form of Saurians at the present day, have retained more of the osteological type of the triassic and oolitic reptiles, and that the crocodiles deviate further from them or exhibit a more modified or specialized structure. The posterior position of the nostrils, the small size and position of the palato-pterygoid foramen, are marks of affinity to Plesiosaurus,
ICHTHYOPTERYGIA
207
in common with, which genus the cranial structure of the Ichthyosaurus exhibits a majority of lacertian characters.
In comparing the jaws of the Ichthyosaurus tenuirostris with those of the gangetic Gharrial, an equal degree of strength and of alveolar border for teeth result from two very different proportions in which the maxillary and premaxillary bones are combined together to form the upper jaw. The prolonga¬ tion of the snout has evidently no relation to this difference ; and we are accordingly led to look for some other explanation of the disproportionate development of the premaxillaries in the Ichthyosaurus. It appears to me to give additional proof of the collective tendency of the affinities of the Ichthyosaurus to the lacertian type of structure. The backward or antorbital position of the nostrils, like that in whales, is related to their marine existence. But in the Lacertians in which the nostrils extend to the fore paid of the head, their anterior boundaries are formed by the premaxillaries : it appears, therefore, to be in conformity with the lacertian affinities of the Ichthyosaur that the premaxillaries should still enter into the same relation with the nostrils, although this involves an extent of anterior development proportionate to the length of the jaws, the forward production of which sharp-toothed instruments fitted them, as in the modern dolphins, for the prehension of agile fishes.
That the Ichthyosaurs occasionally sought the shores, crawled on the strand, and basked in the sunshine, may be inferred from the bony structure connected with their fore fins, which does not exist in any porpoise, dolphin, grampus, and whale ; and for want of which, chiefly, those warm-blooded, air-breathing, marine animals are so helpless when left high and dry on the sands. The structure in question in the Ichthyosaur is a strong osseous arch, inverted and spanning across beneath the chest from one shoulder-joint to the other ; and what is most remarkable in the structure of this “scapular
208
PALAEONTOLOGY
arch is, that it closely resembles, in the number, shape, and disposition of its bones, the same part in the singular aquatic mammalian quadruped of Australia, called Qrnithorynchus, and Platypus, or duck-mole. The Ichthyosaur, when so visiting the shore either for sleep or procreation, would lie or crawl prostrate, or with its belly resting or dragging on the ground.
The most extraordinary feature of the head was the enor¬ mous magnitude of the eye : and from the quantity of light admitted by the expanded pupil, it must have possessed great powers of vision, especially in the dusk. It is not uncommon to find in front of the orbit in fossil skulls, a circular series of petrified thin bony plates, ranged round a central aperture, where the pupil of the eye was placed. The eyes of many fishes are defended by a bony covering consisting of two pieces ; but a compound circle of overlapping plates is now found only in the eyes of turtles, tortoises, lizards, and birds. This curious apparatus of bony plates would aid in protecting the eye-ball from the waves of the sea when the Ichthyosaurus rose to the surface, and from the pressure of the dense element when it dived to great depths ; and they show, writes Dr. Buckland ( Bridgewater Treatise), “that the enormous eye of which they formed the front, was an optical instrument of varied and prodigious power, enabling the Ichthyosaurus to descry its prey at great or little distances, in the obscurity of night, and in the depths of the sea.”
Of no extinct species are the materials for a complete and exact restoration more abundant and satisfactory than of the Ichthyosaurus ; they plainly show that its general external figure must have been that of a huge predatory abdominal fish, with a longer tail and a smaller tail fin ; scaleless, more¬ over, and covered by a smooth or finely wrinkled skin, analo¬ gous to that of the whale tribe.
The mouth was wide, and the jaws long, and armed with
SAUROPTERYGIA
209
numerous pointed teeth, indicative of a predatory and carni¬ vorous nature in all the species ; hut these differed from one another in regard to the relative strength of the jaws, and the relative size and length of the teeth.
Masses of masticated hones and scales of extinct fishes, that lived in the same seas and at the same period as the Ichthyosaurus, have been found under the ribs of fossil speci¬ mens, in the situation where the stomach of the animal was placed ; smaller, harder, and more digested masses, containing also fish-bones and scales, have been found, bearing the impres¬ sion of the structure of the internal surface of the intestine of the great predatory sea-lizard. One of these “ coprolites ” is figured beneath the skeleton in fig. 68.
In tracing the evidences of creative power from the earlier to the later formations of the earth’s crust, remains of the Ichthyosaurus are first found in the lower lias, and occur more or less abundantly through all the superincumbent secondary strata up to, and inclusive of, the chalk formations. They are most numerous in the lias and oolite, and the largest and most characteristic species have been found in these formations.
More than thirty species of Ichthyosaurus are known to the writer, many of which have been described or defined.
Order 4.— Sauropterygia.*
.No post-orbital and supra-temporal bones : large temporal and other vacuities between certain cranial bones ; a foramen parietale ; two antorbital nostrils ; teeth simple, in distinct sockets of premaxillary, maxillary, and pre- mandibular bones, rarely on the palatine or pterygoid bones ; maxillaries larger than premaxillaries. Limbs natatory ; not more than five digits. A sacrum of one or two vertebrae for the attachment of the pelvic arch in some, numerous cervical vertebrae in most. Pleura-
* 'S.avpos, a lizard ; irrtpv^ a fin.
P
PALAEONTOLOGY
pophyses with simple heads ; those of the trunk long and bent.
Genus Nothosaurus, Mun¬ ster.
Sp. Nothosaurus mirabilis, Munster. — In fig. 69 is given an analysis of the chief charac¬ ters as yet ascertained of the species which may be regarded as the type of its family ; by comparing this diagram with that of the Archegosaurus (fig. 65), the advance in the orga¬ nization of the aquatic reptiles will be readily traced and understood.
The skull is no longer de¬ fended by a continuous covering of sculptured plate-bones ; the vacuities behind the orbits for the temporal muscles are large and widely open. These vacui¬ ties are fenced externally by two long and slender horizontal bony bars ; the upper one is formed by the mastoid (fig. 69, 8), and the post-frontal (12) ; the lower one by the malar (27), and squamosal (28) ; the latter answering to the true zygomatic arch in Mammals. The squa¬ mosal abuts by its hinder ex-
SAUROPTERYGIA
211
paneled end against the almost vertical tympanic pedicle, which gives attachment to the lower jaw. This shows the reptilian compound structure : 29 marks the surajigular ele¬ ment, 30 the angular one, 32 the dentary. In the side-view of the skull in fig. 69, 22 is the premaxillary, 21 the maxillary, 1 s the nasal — the cavity below being the nostril, 10 is the pre¬ frontal — between which and 21 is the lacrymal, n the frontal above the orbit. The premaxillary teeth and corresponding premandibular ones are unusually long, strong, and sharp ; there are two similar teeth in each maxillary ; the remaining serial teeth are smaller, but equally acute. There are no teeth on the palate.
The almost entire and undisturbed vertebral column, from the musclielkalk of Bayreuth, figured by Yon Meyer in pi. 23 of his work on musclielkalk Saurians, and attributed by him to Nothosciurus mircibilis, gives the earliest indication of that modification of the trunk-bones which reaches its maximum in the Plesiosaurus (fig. 71), in which it was first detected by the sagacity of Conybeare.*
Twenty of the anterior vertebrae of this series, in Notho- saurus, which begins with the atlas, have the whole or part of the rib-pit situated on the centrum as in the first vertebra in fig. 09 ; the pit is wholly there on fourteen vertebrae ; it begins to ascend upon the neural arch in the fifteenth, as in the second vertebra, given in fig. 69, and is wholly placed there on the twenty-first vertebra.
According, therefore, to the characters by which the writer has proposed f to distinguish the cervical from the dorsal vertebrae, Nothosaurus has twenty of the former. In the specimen referred to, nineteen consecutive vertebrae show the rib-pit supported wholly on an outstanding diapophysis from the neural arch, as in the third vertebra in fig. 69 ; these are
* Trans. Geol. Soc., vol. vi., 1822, and vol. i., 2d series, p. 381, 1824.
-j- Report of British Fossil Reptiles, 1839, pp. 50, 58.
212
PALAEONTOLOGY
to be reckoned therefore as dorsal vertebrae. In the cervical vertebrae the rib-pit is large, vertically reniform, not divided by a groove ; its circumference slightly projects in Notho- saurus.
There is no clear evidence of any of the cervical ribs being terminally expanded and liatcliet-shaped, as in Plesiosaurus ; those of the back are vertically longer than in Plesiosaurus, and more convex.
In the sacral vertebrae, fourth in fig. 69, the rib-pits again begin to sink upon the centrum.
There are two distinct sacral vertebrae in Nothosaurus. They are known by their long, straight, terminally-bent, and convergent pleurapopliyses, the first of which overlaps a little the second. To the convergent ends of these riblets, the ilium (fig. 69, 62, pi) was doubtless ligamentously affixed. In the first caudal vertebra the par- and di-apophyses stand out much farther than in the sacrum ; but rapidly shorten in the second and third caudals. The compound process in each supports a short stiliform straight riblet, as in the fifth figured vertebra (fig. 69) ; the anterior and succeeding caudals support haemal arches and spines, after the disappearance of the pleur- apopliyses. The haemal arch disappears in about the eighth vertebra from the end, and finally the neural arch. The terminal centrums are subelongate and subcompressed. Both Nothosaurus and Pistosaums had abdominal ribs, of which the median piece (fig. 69, hs) was subsymmetrical, the two rays diverging at a very open angle, and terminating in a point or a fork ; the side-pieces (p) seem not to have been so numerous as in Plesiosaurus.
The scapula (fig. 69, 51) is a short and strong bone, its blade appearing as a short and narrow sub-compressed process extending from the subquadrate, thick and expanded end which affords the articular surfaces for the coracoid, clavicle, and humerus.
SAUROPTERYGIA
213
The clavicle, which is an exogenous process in Plesiosaurus, is here united by a strong oblique suture to the scapula. It expands into, or sends off from its outer part, a broad, flat, obtuse process, near the suture ; then contracts and bends inwards to the episterniun, to which it is articulated also by suture.
The coracoid (fig. 69, 52) sends forward a broad and short flattened process, separated by a narrow notch from the scapular part of its head ; it then contracts and soon expands into a broad, fiat, sub-triangular plate, the broad and straight border of which articulates with that of the opposite coracoid. A wide unossified interval separates the coracoid from the episternum. The ossification of the coracoid in the direction of this interval gives the peculiar longitudinal or fore-and-aft extent to those bones in the Plesiosaur, in which they unite with the episternum.
The pelvic arch presents a closer correspondence with that in the Plesiosaurus (fig. 71). The ischium (fig. 69, 63), con¬ tracting beyond its articular head, there expands into a fiat subtriangular plate. The pubis (fig. 69, 64) is a subcircular flat bone, with a notch near the articular end.
The bones of the limbs, although evidently those of fins or paddle-shaped extremities, are better developed than in Plesiosaurus, and more resemble the corresponding bones in the turtle ( Chelones ). The tuberosities or processes for muscu¬ lar attachment near the head of the humerus (omitted in the diagram) are better marked, especially that on the concave side of the shaft ; the distal end is thicker and less expanded. The whole bone is more curved than in any Plesiosauri. The femur (fig. 69, 65) is relatively longer and less expanded at its distal end. The bones of the fore arm, like those of the leg (ib. 66 and 67), are longer than in Plesiosaurus. The articular surfaces present the foramina with raised borders, which characterize those in Plesiosauri, and which indicate the fibro¬ cartilaginous nature of the joints.
214
PALAEONTOLOGY
There is a ligamentous or unossifiecl space at the back part of both carpus and tarsus (fig. G9, 68). At present there is evidence of hut four digits in both the fore and hind paddles of Nothosaurus ; the metapodial and phalangeal bones are of the elongate flattened simple form, characteristic of supports of a tegumentary fin.
One species of Nothosaurus (N. Schimjperi, Yon. M.) is from the lower division of the trias, called “ gres bizarre” of Soulz- les-Bains ; the other representatives of the genus (V. giganteus, N. venustus, N. Munsteri, Ar. Andriani, N. angustifrons, and Ar. mirabilis ), are from the musclielkalk of Bayreuth and Luneville.
Genus Pistosaurus, Yon Meyer.
Sp. Pistosaurus longcevus. — In this genus the facial part of the skull contracts abruptly in front of the orbits ; so that, viewed from above, it resembles a long-necked bottle ; the orbits are situated in the posterior half of the skull, and the nostrils are lateral, from the musclielkalk of Bayreuth.
Genus Conchiosaurus, Von Meyer.
Sp. Conchiosaurus clavatus. — The facial part of the skull is less prolonged than in Pistosaurus , and the nostrils are terminal. The teeth are twelve in number on each side, are subequal, with a pyriform crown, and are placed at widish intervals. From the musclielkalk at Laineck, near Bayreuth.
Genus Simosaurus,* Yon Meyer.
Sp. Simosaurus Gaillardoti.— The fossils, chiefly cranial, on which this genus is founded, occur in the dolomitic musclielkalk near Ludwigsberg, and in the musclielkalk of Luneville. The skull presents the large temporal fossa?,, the divided nostrils, and the general depressed form and compo¬ sition of that of Nothosaurus and Pistosaurus. But its facial part is much shorter; the muzzle is neither prolonged nor terminally expanded, but forms the obtuse end of the short
* 5i juor, snub-nosed, fiat-nose.
SAUKO PTERYGIA
215
depressed face, of wliicli the premaxillary part is the narrowest. The nostrils, consequently, although distant from the orbits by half the diameter of the latter, are yet nearer the fore end of the skull than in the above-cited Sauropterygian genera. The nostrils are relatively nearer to each other, the intervening- bony tract being due to the premaxillaries, which, relatively to the breadth of the skull, are much narrower in Simosaurus
than in Notho- or Pistosaurus.
The profile of the skull rises from the internasal to the interorbital regions much more than in the Nothosaur, and the depth of the skull behind the orbit is greater in propor- tion to its length. The post-frontals are most clearly produced backwards, along the upper border of the zygoma to the mas- toids. The malars are co-extended, and connected with the post-frontals, but terminate freely and obtusely a little beyond the co-prolonged hind part of the maxillary, without being
met by or joining a squamosal.
Most complete and extensive is the ossification of the roof of the mouth in this genus. The pterygoids are expanded into one broad unbroken imperforate flat expanse of bone, from about one-third of the distance from the snout to the occipital condyle ; they are united by a median suture, and underlap the whole of the sphenoid. The teeth, compared with Nothosaurus, are few and large, and are subequal, save one or two at the fore and hind extremity of the series. The crown expands a little above the fang, is conical, sub-bifurcate, and impressed by a few coarse longitudinal ridges ; some are obtuse, others acute ; but all are shorter and thicker than in Notho- or Pisto-saurus.
The vertebrae have flat or very slightly concave articular surfaces on the body ; the neural arch articulates therewith by suture. In these characters, and in their general propor¬ tions, they resemble those of Notlio- and Plesiosaurus. It is significant of some difference in respect of the arrangement of
216
PALAEONTOLOGY
tlie vertebrae in the same column, that although specimens from the tail, and from different parts of the hack, have been obtained, no cervical vertebra with any probability belonging to this genus has yet been found. The caudal centrum presents two well-defined, rather prominent, liypapophyses for the haemal arch.
The coracoid in the contraction of the body reminded Cuvier of that of the Ichthyosaurus , but its expanded median part was differently shaped. The pubis, like that of the Plesiosaurus, resembles to a certain degree the pubis in Ghelonia. The few bones of the limbs which have been found still more resemble, as do those of Pistosaurus, the corresponding bones of marine Ghelonia. Accordingly, there have been entered in palaeonto¬ logical catalogues an Ichthyosaurus Lunevillensis (De la Beche), a Plesiosaurus Lunevillensis (Munster), and a Ghelonia Lunevil¬ lensis (Gray and Keferstein) ; but all these are parts of one and the same genus of Enaliosaurian, the “ Saurien des environs de Luneville ” of Cuvier, the “ Simosaurus ” of H. von Meyer.
Genus Placodus. — The cranial structure in this genus of muschelkalk reptile is closely similar to that in Simosaurus, but its proportions are different ; it is as broad as long ■ the greatest breadth being behind, whence the sides converge to an obtuse muzzle ; the entire figure viewed from above being that of a right-angled triangle, with the corners rounded off. Hie temporal fossae are the widest, and zygomatic arches the strongest, in the whole class Reptilia ; the lower jaw presents a like excessive development of the coronoid processes. These developments, for great size and power of action of the biting and grinding muscles, relate to a most extraordinary form and size of the teeth, which resemble paving-stones, and were evidently adapted to crack and bruise shells and crusts of marine Invertebrata.
The teeth of the upper jaw consist of an external or maxillary series, and an internal or palatal series. The
SAUROPTERYGIA
217
maxillary series are supported in a marginal row of alveoli by the premaxillary and maxillary bones ; the palatal series are implanted in the palatine and pterygoid bones. The maxillo- premaxillary teeth are five in number on each side, two implanted in the premaxillary, and three in the maxillary. The premaxillary teeth are subequal, smaller than the maxillary teeth ; their crowns are subhemi spheric in P. laticeps, but in P. Andriani they present a bent, pointed, prehensile character. In P. laticeps the first maxillary tooth has a full oval crown, lines by 4 in diameter ; the second measures 5i lines by 4^ lines in diameter ; the third is subcircular, 8 lines hr diameter, on the right side. The palatal series begins on the inner side of this tooth, and consists of two teeth on each side. The first tooth has a full elliptical crown, 10 lines by 8 ; the second tooth, developed in the broad pterygoid bone, presents a full oval shape, 1 inch 9 lines by 1 inch 3 lines in diameter. In Placodus gig as and P. Andriani the palatal teeth, three in number on each side, are all of large size, slightly increasing from before backwards ; they are situated close together, forming on each side a series a little curved with the convexity outwards, and the interspace between the two series is very narrow. The first tooth is triangular, the second and third are quadrangular; each with the angles rounded, and the transverse diameter exceeding the fore and aft or longitudinal one. The maxillary teeth are much smaller than the palatal ones, have a rounded or subquadrate crown, are four in num¬ ber, and of subequal dimensions. The premaxillary teeth, three in number on each side, are more remote and distinct from the maxillary teeth than in Placodus rostratus and P. laticeps ; their crowns are more elongated and conical than m P. laticeps ; the prehensile power of the prolonged premaxil¬ lary part of the jaw being obviously greater in Placodus gigas than in P. laticeps or P. rostratus. The size of the last tooth in P. laticeps surpasses that of any of the teeth in the previ-
218
PALAEONTOLOGY
ously discovered species. In proportion to the entire skull, it is the largest grinding tooth in the animal kingdom, the elephant itself not excepted.
All these teeth are implanted by short simple bases in distinct hollow sockets, subject to the same law of displace¬ ment and succession as in other reptiles. By some it may be deemed requisite to separate generically the Placodi with two teeth from those with three teeth in each palatal series ; but the Placodus rostratus offers a transitional condition in the small relative size of the first two palatal teeth, and in the rounded form of all the teeth, from the P. Andriani to the P. laticeps.
We cannot contemplate the extreme and peculiar modifi¬ cation of form of the teeth in the genus Placodus without a recognition of their adaptation to the pounding and crushing of hard substances, and a suspicion that the association of the fossils with shell-clad Mollusks in such multitudes as to have suggested special denominations to the strata containing
. o
Placodus {e.g., muschelkalk, terebratulitenkalk, etc.), is indi¬ cative of the class whence the Placodi derived their chief subsistence.
No doubt the most numerous examples of similarly-shaped teeth for a like purpose are afforded by the class of fishes, as, e.g., by the extinct Pycnodonts, and by the wolf-fish (Anar- rhichas lupus ^ and the Oestracion of the existing seas. But the reptilian class is not without its instances at the present day of teeth shaped like paving-stones, of which certain Australian lizards exhibit this peculiarity in so marked a degree that the generic name Gyclodus has been invented to express that peculiarity. Amongst extinct reptiles, also, a species of lizard from the tertiary deposits of the Limagne in France presents round obtuse teeth, of which the last, in
the lower jaw, is suddenly and considerably larger than the rest.
SAUROPTERYGIA
219
Nothosaurus, Simosaurus, and Pistosaurus present the same evidences of lacertian affinities in the division of the nostrils by the median extension of the premaxillary backwards to the nasals, the same thecodont dentition, and the same circum¬ scription of the orbits and temporal fossae as in Placodus : there is also a general family likeness in the upward aspect of these apertures, accompanying an extreme depression of the skull. The muzzle, though varying greatly in length in these genera, presents the same obtuseness ; and the alveolar border of the jaws the same smooth outward convexity which we observe in the Placodus. The peculiar confluence of the elements of the upper and lower zygomatic arches, — i.e., of post-frontal and malar, — forming the broad wall of bone behind the orbit, is continued still farther backwards in the Simosaurus. In Pistosaurus the elongated post-frontal, malar, and squa¬ mosal are united together in one deep zygomatic arch, which has the mastoid and tympanic for its hinder abut¬ ment.
It is remarkable that hitherto no vertebras or other bones of the trunk or limbs have been found so associated with the teeth of Placodus , as to have suggested their belonging to the same species. Usually, after the indication of a reptile by detached teeth, the next step in its reconstruction is based upon detached vertebrae. The twelve or more evidences of Placodus, afforded by bone as well as tooth, are all portions of the skull. It is possible that some of the singularly modified vertebrae from the muschelkalk, next to be described, may belong to the Placodus ; and the same surmise suggests itself in reference to some of the limb-bones from the muschelkalk that cannot be assigned to other known saurian genera.
The obvious adaptation of the dentition of Placodus to the crushing of very hard kinds of food, its close analogy to the dentition of certain fishes known to subsist by breaking the shells of whelks and other shell-clad Mollusks, and the cha-
220
PALEONTOLOGY
racteristic abundance of fossil shells in the strata to which the remains of Placodus are peculiar, concur in producing the belief that the species of this genus were reptiles frequenting the sea-shore, and probably good swimmers. But as at present we have got no further than the head and teeth in the recon¬ struction of this mezozoic form of molluscivorous reptile, the present notice will conclude with a remark suggested by the disposition and form of the teeth. In all the species, under the rather wide range of specific varieties of the dentition, there are two rows of the crushing teeth in the upper jaw, and only one row in the lower jaw, on each side of the mouth ; and the lower row plays upon both upper rows, with its strongest (middle) line of force directed against their inter¬ space. Thus the crushing force below presses upon a part between the two planes or points of resistance above, on the same principle on which we break a stick across the knee ; only here the fulcrum is at the intermediate point, the moving powers at the two parts grasped by the hands. It is obvious that a portion of shell pressed between two opposite flat sur¬ faces might resist the strongest bite, but subjected to alternate points of pressure its fracture would be facilitated*
Genus Tanystropheus.
Sp. Tanystrophceus conspicuus, H. von Meyer. — Certain long, slender, hollow bones (fig. 70, a), from the German muschel- kalk, were referred by Count Munster to the class Reptilia, under the name of Macroscelosaurus, under the impression that they were bones of the limbs. H. von Meyer subsequently, in more perfect specimens, observing that each slightly ex¬ panded extremity of the long bone was terminated by a sym¬ metrical oval concave articular surface, surmounted by a pair of symmetrical lateral incurved plates, resembling confluent
* Previous to the writer’s Memoir on Placodus in the Philosophical Trans¬ actions (1858), all paLeontologists had referred the genus to the pycnodont order of fishes.
SAUROPTERYGIA
221
neurapophyses, with articular surfaces, and with their some¬ times confluent bases arching over a neural canal (as in figure b, in cut 70), recognized their vertebral character ; and, adopt-
Fig. 70.
a, b, Tanystrophaius (Trias) ; c, Ichthyosaurus.
ing the determination of their reptilian nature, hut repudiating the idea of their being limb-bones, he discarded Munster’s name, and substituted for it that of Tanystrophceus* indicative of their peculiar proportions as vertebrae. Although the articular ends are for the most part symmetrical, the long intervening body is not so. It is subcompressed, usually broader and flatter below than above ; sometimes more flat¬ tened on one side than on the other, giving an irregular, verti¬ cally oval, or triangular cross section. A low median ridge is not uncommon on the lower surface towards the ends of the vertebra ; and similar less regular ridges project from the sides of the otherwise smooth outer surface. The centrum is excavated by a canal, resembling a medullary one, but more probably filled, in the recent state, as in the long caudal style of the frog, with unossified cartilage. The walls of this cavity are compact, and in thickness about one-sixth of the diameter of the bone. The terminal neural arches support each a low median ridge or rndimental spine, which soon subsides. The trace of neural canal in like manner disappears, or is continued by two distinct slender canals, which traverse lor a certain extent the substance of the thicker upper wall of the cavity of the vertebral body. A single large vascular canal opens on the wider surface midway between the two ends of the body.
* From Tcivvw, to elongate, <rrp«po>, verto.
222
PALAEONTOLOGY
There is no trace of transverse processes, rib-surfaces, or haem- apophyses ; this, and the absence of the continuous neural canal, indicate these singular vertebrae to belong to the tail. From the long cau do- vertebral style of anourous Batrachia the vertebrae of Tanystroplueus differ in having distinct articular surfaces at both ends. The difference of shape and size in the few that have been found also indicates that there were more than two such vertebrae in the tail of the extraordinary animal to which they have belonged. Caudal vertebrae of the normal proportions and structure, from musclielkalk of the same localities with Tanystrophceus have been referred to Nothosaurus. It is possible, however, that one or other of the remarkable genera — Simosaurus, Placodus, e.y. — may have possessed the peculiar structure in the tail, or some part of it, which the tanystrophaean vertebrae indicate. The first four vertebrae of the neck or trunk of the Fistularict tabaccaria are those which most resemble in their proportions the vertebrae above described ; but none of the tistularian vertebrae have the articular concavity and the zygapopliyses at both ends ; the first presents them at the fore end, and the last at the hind end, and the modifications of both these finished articular ends pretty closely correspond with those of Tanystrophceus ; but the second and third vertebrae of Fishdaria are united with the first and fourth by sutural surfaces with deeply-inter¬ locking pointed processes.
Genus Sphenosaurus.
Sp. Sphenosaunts Sternbcrgii, Yon. M, — The fossil vertebrae on which this genus is founded are imbedded in a sandstone, most like the hunter, from Bohemia or the south of Germany. Of the twenty-three vertebrae so preserved in nearly their natural position, and with their under surface exposed, five belong to the tail, the rest to the trunk. Of these, two are sacral, two lumbar, the rest are dorsal or thoracic, with long and slender ribs connected with them. The neural arch
SAUROPTERYCilA
223
appears to have been suturally united to the centrum with large zygapophyses. The articular end of the centrum is vertical to its axis ; both are slightly concave. Between each centrum is a transversely oval, depressed ossicle, homologous with the cervical wedge-hones or hypapopliyses in Enaliosaurs. This is the chief peculiarity in Sphenosaurns, and recalls a character in the vertebral column of Archegosaurus.
Genus Plesiosaurus. — The discovery of this genus forms one of the most important additions that geology has made to comparative anatomy. Baron Cuvier deemed the structure of the Plesiosaur “ to have been the most singular, and its cha¬ racters the most anomalous that had been discovered amid the ruins of a former world.” “ To the head of a lizard it united the teeth of a crocodile, a neck of enormous length, resembling the body of a serpent, a trunk and tail having the proportions of an ordinary quadruped, the ribs of a chameleon, and the paddles of a whale” (fig. 71). “Such,” writes Dr. Buckland, “are the strange combinations of form and structure in the Plesiosaurus, a genus, the remains of which, after interment for thousands of years amidst the wreck of millions of extinct inhabitants of the ancient earth, are at length recalled to light by the re¬ searches of the geologist, and submitted to our examination, in nearly as perfect a state as the bones of species that are now existing upon the earth.”
The first remains of this animal were discovered in the lias of Lyme Ptegis about the year 1822, and formed the subject of the paper by the Bev. Mr. Conybeare (afterwards dean of Llandaff), and Mr. (afterwards Sir Henry) De la Beche, in which the genus was established, and named Plesiosaurus (“ approximate to the Samians ”), from the Greek words plcsios and sauros, signifying “ near ” or “ allied to, and lizard, because the authors saw that it was more nearly allied to the lizard than was the Ichthyosaurus from the same formation.
The entire and undisturbed skeletons of several individuals,
224
PALAEONTOLOGY
of different species, have since been discovered, fully confirm¬ ing the sagacious restorations by the original discoverers of the Plesiosaurus.
Vertebral Column. — The vertebral bodies have their ter¬ minal articular surfaces either flat or slightly concave, or with the middle of such cavity a little convex. In general the bodies present two pits and holes at their under part. The cervical vertebrae consist of centrum, neural arch, and pleur- apophyses. The latter are wanting in the first vertebra ; hut both this and the second have the liypapophyses. The cervical ribs are short, and expand at their free end, so as to have suggested the term “ hatchet-hones ” to their first discoverers. They articulate by a simple head to a shallow pit, which is rarely supported on a process, from the side of the centrum ; hut is commonly bisected by a longitudinal groove, a rudi- mental indication of the upper and lower processes which sustain the cervical ribs in Crocodilia.
The body of the atlas articulates with a large hypapopliysis below, with the neurapopliysis above, with the body of the axis behind, and with part of the occipital condyle in front ; all the articulations save the last become, in Plesiosaums pachyomus, and probably with age in other species, obliterated by anchylosis. The hypapopliysis forms the lower two-tliirds, the neurapopliysis contributes the upper and lateral parts, and the centrum forms the middle or bottom of the cup for the occipital condyle. The second hypapopliysis is lodged in the inferior interspace between the bodies of the atlas and axis ; it becomes ancliylosed to these and to the first hypapopliysis. The first pleurapopliysis, or rudimental rib, is developed from the centrum of the axis.
As the cervical vertebras approach the dorsal, the lower part of the costal pit becomes smaller, the upper part larger, until it forms the whole surface, gradually rising from the centrum to the neurapopliysis (fig. 7l).
S AUROPTERY GI A
225
The dorsal region is arbitrarily commenced by this vertebra, in which the costal surface begins to be supported on a di¬ apophysis, which progressively increases in length in the second and third dorsal, continues as a transverse process to near the end of the trunk ; and on the vertebra above or between the iliac bones, it subsides to the level of the neurapophysis. In the caudal vertebra the costal surface gradually descends from the neurapophysis upon the side of the centrum ; it is never divided by the longitudinal groove which, in most Plesiosauri , indents that surface in the cervical vertebrae. The neural arches remain long unanchylosed with the centrum in all Plesiosauri, and appear to be always distinct in some species. The pleurapophyses gain in length, and lose in terminal breadth, in the hinder cervicals ; and become long and slender ribs in the dorsal region, curving outwards and downwards so as to encompass the upper two-thirds of the thoracic abdominal cavity. They decrease in length and curvature as they approach the tail, where they are reduced to short straight pieces, as in the neck, but are not terminally expanded ; they cease to be developed near the end of the tail. The haemapophyses in the abdominal region are subdivided, and with the haemal spine or median piece, form a kind of “ plastron ” of trans¬ versely-extended, slightly bent, median and lateral, overlapping, bony bars, occupying the subabdominal space between the coracoids and pubicals. In the tail the haemapophyses are short and straight, and remain re-united both with the centrum above and with each other below. The haemal spine is not developed in this region. This modification has been expressed by the statement that there were no chevron-bones in the Plesiosaur. The tail is much shorter in the Plesio- than in the Ichthyosaurus.
The skull is depressed ; its length is rather more than thrice its breadth ; but the proportions somewhat vary in different species. The cranial part, or that behind the orbits,
Q
226
PALAEONTOLOGY
is quadrate ; thence it contracts laterally to near the maxillo- premaxillary suture, where it continues either parallel or with a slight swelling before rounding into the obtuse anterior termination.
The orbits are at or near the middle of the skull : estimat¬ ing the length of this by that of the lower jaw, they are in advance of the middle part in Plesiosaurus Hawkinsii. The orbits are rather subtriangular than round, being somewhat squared off behind, straight above, and contracted anteriorly. No trace of sclerotic plates has yet been discerned in any specimen. The temporal fossae are large subquadrate apertures. The nostrils, which are a little in advance of the orbits, are scarcely larger than the parietal foramen. Beneath them, upon the palate, are two similar-sized apertures, probably the palatal nostrils.
The lower jaw presents an angular, surangular, splenial, and dentary element, in each ramus ; the dentary elements being confluent at the expanded symphysis. There is no vacuity between the angular and surangular or any other element of the jaw. The coronoid process is developed, as in Placodus, from the surangular, but rises only a little higher than in crocodiles. The alveoli are distinct cavities, and there is a groove along their inner border in both jaws.
When the successional teeth first project hr that groove, they give the appearance of a double row of teeth. All the teeth are sharp-pointed, long, and slender, circular in cross section, with fine longitudinal ridges on the enamel ; the anterior teeth are the longest.
The scapula is a strong triradiate bone, the longest ray being formed by the acromial or clavicular process, which arches forward and inward to abut against the sternum or epicoracoid.
The proper body of the scapula* is short and straight,
* This is omitted in most of the published restorations of the Plesiosaurus.
SAUROPTERYGIA
227
somewhat flattened ; the thick articular end, which forms shortest ray, is subequally divided by the articular surface for the coracoid, and that for the head of the humerus.
The coracoids are chiefly re¬ markable for their excessive ex¬ pansion in the direction of the axis of the trunk, extending from the abdominal ribs forward, so as to receive the entosternum, which is wedged into their anterior inter¬ space. The median borders meet and unite for an extent deter¬ mined by their degree of curvature or convexity, which is always slight. The coracoids unite an¬ teriorly with the clavicles, as well as with the episternum ; laterally they articulate with the scapula, combining to form the glenoid cavity for the humerus.
The episternum has the same general form as the median pieces of the abdominal ribs, being, like those pieces, a modified haemal spine, only more advanced in position ; the lateral wings or prolongations are broader and flatter ; the median process is short ; a longitudinal ridge pro¬ jects from the middle of the in¬ ternal surface. The humerus is a moderately thick and long bone,
the
228
PALAEONTOLOGY
witli a convex head, suh-cylindrical at its proximal end, becoming flattened and gradually expanded to its distal end, where it is divided into two indistinct surfaces for the radius and ulna. The shaft in most species is slightly curved backwards, or the hind border is concave, whilst the front one is straight. The radius and ulna are about half the length of the humerus ; the former is straight, the latter curved or reniform, with the concavity towards the radius ; both are flattened ; the radius is a little contracted towards its carpal end, and in some species is longer than the ulna. The carpus consists of a double row of flat rounded discs, — the largest at the radial side of the wrist ; the ulnar or hinder side appear¬ ing to have contained more unossified matter. The meta- carpals, five in number, are elongate, slender, slightly expanded at the two ends, flattened, and sometimes a little bent. The phalanges of the five digits have a similar form, hut are smaller, and progressively decrease in size ; the expansion of the two ends, which are truncate, makes the sides or margins concave. The first or radial digit has generally three phalanges, the second from five to seven, the third eight or nine, the fourth eight, the fifth five or six phalanges. All are flattened ; the terminal ones are nailless ; and the whole were obviously included, like the paddle of the porpoise and turtle, in a com¬ mon sheath of integument. The pelvic arch consists of a short but strong and straight narrow moveable ilium, and of a broad and flat pubis and ischium ; the former subquadrate or subcircular, the latter triangular ; the fore-and-aft expanse of both bones nearly equals that of the coracoids. All concur in the formation of the hip-joint. The ischium and pubis again unite together near their mesial borders, leaving a wide elliptic vacuity, or “ foramen ovale,” between this junction and their outer acetabular one. The pelvic paddle is usually of equal length with the pectoral one, but in P. mctcrocephahts it is longer. The bones closely correspond, in number, arrange-
SAUROPTERYGIA
229
ment, and form, with, those of the fore limb. The lemur has the hind margin less concave, and so appears more straight. The fibula, in its reniform shape, agrees with its homotype the ulna. The tarsal bones are also smallest on the tibial side. Of existing reptiles, the lizards, and amongst these the old world Monitors ( Varanus, Fitz.b by reason of the cranial vacuities in front of the orbits, most resemble the Plesiosaur in the structure of the skull. The division of the nostrils, the vacuities in the occipital region between the exoccipitals and tympanies, the parietal foramen, the zygomatic extension of the post-frontal, the palato-maxillary, and pterygo-splienoid vacuities in the bony palate, are all lacertian characters, as contradistinguished from crocodilian ones.
But the antorbital vacuities between the nasal, pre-frontal, and maxillary bones are the sole external nostrils in the Plesiosaurs ; the zygomatic arch abuts against the fore part of the tympanic, and fixes it. A much greater extent of the roof of the mouth is ossified than in lizards, and the palato¬ maxillary and pterygo-sphenoid fissures are reduced to small size. The teeth, finally, are implanted in distinct sockets. That the Plesiosaur had the “head of a lizard” is an emphatic mode of expressing the amount of resemblance in their cranial conformation. The crocodilian affinities, however, are not confined to the teeth, but extend to the structure of the skull itself.
In the simple mode of articulation of the ribs, the lacertian affinity is again strongly manifested ; but to this vertebral character such affinity is limited ; all the others exemplify the ordinal distinction of the Plesiosaurs from known existing reptiles. The shape of the joints of the centrums ; the num¬ ber of vertebrae between the head and tail, especially of those of the neck ; the slight indication of the sacral vertebrae ; the non-confluence of the caudal haemapophyses with each other, are all “ plesiosauroid.” In the size and number of abdominal
230
PALAEONTOLOGY
ribs and sternum may perhaps be discerned a first step in that series of development of the hsemapophyses of the trunk which reaches its maximum in the plastron of the Chelonia.
The connation of the clavicle with the scapula is common to the Chelonia with the Plesiosauri ; the expansion of the coracoids — extreme in Plesiosauri — is greater in Chelonia than in Crococlilia, but is still greater in some Lacertia. The form and proportions of the pubis and ischium, as compared with the ilium, in the pelvic arch of the Plesiosauri, find the nearest approach in the pelvis of marine Chelonia; and no other existing reptile now offers so near, although it be so remote, a resemblance to the structure of the paddles of the Plesiosaur. Amongst the many figurative illustrations of the nature of the Plesiosaur in which popular writers have indulged, that which compares it to a snake threaded through the trunk of a turtle is the most striking ; but the number of vertebra? in the Plesiosaur is no true indication of affinity with the ophidian order of reptiles.
The reptilian skull from formations underlying the lias, to which that of Plesiosaurus has the nearest resemblance, is the skull of the Pistosaurus ; in this genus the nostrils have a similar position and diminutive size, but are somewhat more in advance of the orbits, and the premaxillaries enter into the formation of their boundary : the premaxillary muzzle and the temporal fossae are also somewhat longer and narrower. The post-frontals and mastoids more clearly combine with malars and squamosals in forming the zygomatic arch, which is of greater depth in Pistosaurus ; the parietal foramen is larger ; there is no trace of a median parietal crest. On the palate, besides the vacuities between the pterygoids and pre¬ sphenoids, and the small foramina between the palatines, pre¬ maxillaries, and maxillaries, there is in Pistosaurus a single
o
median foramen in advance of the latter foramina, between the pointed anterior ends of the pterygoids and the premaxil-
SAUROPTERYGIA
231
laries. In Nothosaurus the pterygoids extend hack, under¬ lapping the basi-splienoid, as far as the basi-occipital, the median suture uniting them being well marked to their ter¬ mination ; and there is no appearance of vacuities like the pterygo-sphenoid ones in Plesio- and Pisto-saurus. The tym¬ panies are relatively longer, and extend farther back in Pisto- than in Plesio-saurus. There is no trace of lacrymals in Pistosaurus ; and its maxillaries are relatively larger than in Plesiosaurus. In Pistosaurus there are 18 teeth on each the upper jaw, including the 5 premaxillary teeth ; in Plesiosaurus there are from 30 to 40 teeth on each side. In Pistosaurus the teeth are relatively larger, and present a more oval trans¬ verse section : the anterior teeth are proportionally larger than the posterior ones than they are in Plesiosaurus. The dis¬ proportion is still greater in Nothosaurus, in some species of which the teeth behind the premaxillary and symphysial terminal expansions of the jaws suddenly become — e.g., in Nothosaurus mirabilis (fig. 68) — very small, and form a straight, numerous, and close-set single series along the maxillary and corresponding part of the mandibular bone.
Both Nothosaurus and Pistosaurus had many neck-verte¬ brae, and the transition from these to the dorsal series was effected, as in Plesiosaurus, by the ascent of the rib-surface from the centrum to the neurapophysis j but the surface, when divided between the two elements, projected further outwards than in most Plesiosauri.
In both Notho- and Pisto-saurus the pelvic vertebra develops a combined process (par- and di-apophysis), but of relatively larger, vertically longer size, standing well out, and from near the fore part of the side of the vertebra. This process, with the coalesced riblet, indicates a stronger ilium, and a firmer base of attachment of the hind limb to the trunk, than in Plesiosaurus. Both this structure, and the greater length of the bones of the fore arm and leg show that the
232
PALAEONTOLOGY
muschelkalk predecessors of the liassic Plesiosauri were better organized for occasional progression on dry land.
More than twenty species of Plesiosaurus have been de¬ scribed by, or are known to, the writer ; their remains occur in the oolitic, Wealden, and cretaceous formations, ranging from the lias upwards to the chalk, inclusive. A comparison of remains of various Plesiosauri has led to a conviction, that specific distinctions are accompanied with well-marked dif¬ ferences in the structure and proportions of answerable verte¬ brae, but are not shown in small differences of number in the cervical, dorsal, or caudal vertebrae.
When any region of the vertebral column presents an unusual excess of development in a genus, such region is more liable to variation, within certain limits, than in genera where its proportions are more normal. The differences of the number of cervical and dorsal vertebrae, ranging between 29 and 31 in the Plesiosaurus Hawkinsii, e.g. — as noted in the description of that species in the writer’s Beport on British Fossil Beptiles, 1839 — indicate the range of variety observed in the only species of which, at that time, the vertebral column of different individuals could be compared.
Genus Pliosaurus, Ow. — hi. von Meyer regards the num¬ ber of cervical vertebrae and the length of neck as characters of prime importance in the classification of Reptilia, and founds thereon his order called Macrotrachelen, in which he includes Simosaurus, Pistosaurus, and Nothosaurus, with Plesiosaurus. No doubt the number of vertebrae in the same skeleton bears a certain relation to ordinal groups : the Ophidia find a common character therein ; yet it is not their essential character, for the snake-like form, dependent on multiplied vertebrae, characterizes equally certain Batrachians (C cecilia) and fishes ( Murcena ). Certain regions of the vertebral column are the seats of great varieties in the same natural group of Reptilia. We have long-tailed and short-tailed lizards ; but
SAUROPTERYGIA
233
do not therefore separate those with numerous caudal vertebrae, as “ Macroura ” from those with few or more. The extinct Dolichosaurus of the Kentish chalk, with its procoelian vertebrae, cannot be ordinarily separated, by reason of its more numerous cervical vertebrae., from other shorter-necked procoelian lizards. As little can we separate the short-necked and big-headed amphiccelian Pliosaur from the Macrotrachelians with which it has its most intimate and true affinities.
There is much reason, indeed, to suspect that some of the muschelkalk Saurians, which are as closely allied to Notho- saurus as Pliosaurus is to Plesiosaurus, may have presented analogous modifications in the number and proportions of the cervical vertebrae. It is hardly possible to contemplate the broad and short-snouted skull of the Simosaurus, with its proportionally large teeth, without inferring that such a head must have been supported by a shorter and more powerful neck than that which bore the long and slender head of the Nothosaurus or Pistosaurus. The like inference is more strongly impressed upon the mind by the skull of the Placodus, still shorter and broader than that of Simosaurus, and with vastly larger teeth, of a shape indicative of their adaptation to crushing molluscous or crustaceous shells.
Neither the proportions and armature of the skull of Placodus, nor the mode of obtaining the food indicated by its cranial and dental characters, permit the supposition that the head was supported by other than a comparatively short and strong neck. Yet the composition of the skull, its proportions, cavities, and other light-giving anatomical characters, all bespeak the close essential relationship of Placodus to Simo¬ saurus and other so-called “ macrotrachelian ” reptiles of the muschelkalk beds. I still, therefore, regard the fin-like modi¬ fication of the limbs as a better ordinal character than the number of vertebrae in any particular region of the spine. Bu( by those who would retain the term Enalioscturia tor the
234
PALAEONTOLOGY
large extinct natatory group of saurian reptiles, tlie essential distinctness of the groups Sauropterygii and Ichthyopterygii, typified by the Ichthyosaurus and Plesiosaurus respectively, should be borne in mind.
Sp. Pliosaurus brachydeirus, Ow. — The generic characters of Pliosaurus are given by the teeth and the cervical vertebrae. As compared with those of Plesiosaurus, the teeth are thicker in proportion to their length, are subtrihedral in transverse section, with one side flattened, and bounded by lateral promi¬
nent ridges from the more convex sides, which are rounded off into each other, and alone show the longitudinal ridges of the enamel ; these are there very well defined. The vertebrae of the neck, presenting a flat articular surface of the shape shown in outline below the neck in fig. 72, are so compressed from before backward as to resemble the vertebrae of the Ichthyo¬ saurus (fig. 70, c), and as many as twelve may be compressed within the short neck intervening between the skull and scapular arch, as shown in fig. 72. For the rest, save in the more massive proportions of the jaws and paddle-bones, the bony framework of Pliosaurus closely accords with that of Plesiosaurus ; and, as the vertebras of the trunk resume the plesiosaurian proportions, they give little indication of the genus of reptile to which they truly belong, when found detached and apart. Some individuals of Pliosaurus appear to have attained a length of between 30 and 40 feet. The remains of
ANOMODONTIA
235
this modified form of Enaliosaur are peculiar to the Oxfordian and Kimmeridgian divisions of the upper oolitic system. They have heen discovered in these beds in Russia ( Pliosaurus Worinskii and Spondylosaurus of Fischer), as well as in those counties of England where the Kimmeridge and Oxford clays have heen deposited.
Genus Polyptychodon. — A genus represented by species equalling in size those of Pliosaurus. The teeth have a strong conical crown with a sub-circular transverse section, and the longitudinal ridges of the enamel are set close all round the crown, whence the name of the genus, signifying “many- ridged tooth they may he distinguished from the teeth of Mosasaurus or Pliosaurus by the absence of the smooth almost flattened facet of the crown, which, in those genera, is divided by two strong ridges from the rest of the crown. The teeth are implanted in distinct sockets, as in Plesiosaurus. The vertebrae found in the same strata, corresponding in size with the teeth, present the plesiosauroid type. Bones of a large paddle or natatory limb, from the chalk of Kent, may also belong to Polyptychodon. A portion of the cranium of Polyp¬ tychodon interruptus, from the chalk, shows the “foramen parietale,” and a plesiosauroid type of temporal fossae.
Remains of Polyptychodon have hitherto been met with only in the cretaceous formations : in the green-sand of Kent and Cambridge, also at Kursk, in Russia, and in the chalk of Kent and Sussex.
Order 5. — Anomodontia.
Teeth wanting, or limited to a single maxillary pair, having the form or proportions of tusks : a “ foramen parietale two nostrils ; tympanic pedicle fixed ; vertebrae bicon¬ cave ; trunk-ribs long and curved, the anterior ones with a bifurcate head ; sacrum of more than two vertebrae. Limbs ambulatory.
23G
PALAEONTOLOGY
Fam. — Dicynodontia.
A long ever-growing tusk in each maxillary bone ; pre-maxil- laries connate, forming with the lower jaw a beak- shaped mouth, probably sheathed with horn.
Genus Dicynodon, Ow. — In 1841 Mr. Andrew G. Bain, who had been engaged in the construction of military roads in the colony of the Cape of Good Hope, discovered, in the tract of country extending northwards from the county of Albany, about 450 miles east of Cape Town, several nodules or lumps of a kind of sandstone, which, when broken, displayed in most instances evidences of fossil bones, and usually of a skull with two large projecting teeth. Accordingly these evi¬ dences of ancient animal life in South Africa were first notified to English geologists by Mr. Bain under the name of “ Biden¬ tals and the specimens transmitted by him were submitted to the writer for examination. The results of the comparisons thereupon instituted went to show that there had formerly existed in South Africa, and from geological evidence, probably, in a great lake or inland sea, since converted into dry land, a race of reptilian animals presenting in the construction of their skull (fig. 73) characters of the crocodile, the tortoise, and the lizard, coupled with the presence of a pair of huge sharp-pointed tusks, growing downwards, one from each side of the upper jaw, like the tusks of the mammalian morse ( Trichecus ). No other kind of teeth were developed in these singular animals : the lower jaw appears to have been armed, as in the tortoise, by a trenchant sheath of horn.
The vertebrae, by the hollowness of the co-adapted articular surfaces, indicate these reptiles to have been good swimmers, and probably to have habitually existed in water ; but the construction of the bony passages of the nostrils proves that they must have come to the surface to breath air. The pelvis
DICYNODONTIA
237
consists of a sacrum composed of 5 confluent vertebrae, with very broad iliac bones, and thick and strong ischial and pubic bones.
Some extinct plants allied to the Lepidodendron, with other fossils, render it probable that the sandstones containing the dicynodont reptiles were of the same geological age as those that have revealed the remains of the Ehynchosaurs and Labyrinthodonts in Europe.
The generic name Dicynodon is from the Greek words sig¬ nifying “two tusks or canine teeth.” Four species of this genus, having a rounded profile and less strongly ridged maxillaries, have been demonstrated from the fossils trans¬ mitted by Mr. Bain.
Sp. Dicynodon lacerticeps, Owl — This species is founded on a skull six inches in length, of which a reduced figure is given in cut 73, where c shows the canine tusks.
Sp. Dicynodon testudiceps, Ow. — In this species the skull, and the facial part more particularly, is shorter than in D. lacerticeps.
Sp. Dicynodon strigiceps, Ow. — The shortening ol the jaws and blunting of the muzzle are carried to an extreme in this species, in which the nostrils are situated almost beneath the orbits.
Sp. Dicynodon
tigriccps, Ow.j' _ In Skull and tusks of Dicynodon lacerticeps.
this species the length of the skull is 20 inches, its breadth across the widest part of the zygomatic arches being 1 8 inches. It differs from the D. lacerticeps not only in size, but in the
* Trans. Geological Society, 2d series, vol. vii. (dis, two ; kunodos, canine- tooth.) t Trans. Geol. Soc., 2d series, vol. vii,, p. 233.
238
PALAEONTOLOGY
relatively larger capacity of the temporal fossae, and smaller size of the orbits. These cavities in D. lacerticeps occupy the middle third of the skull, hut in D. tigriceps are wholly in the anterior half of the skull. The profile of the skull in D. lacer- ticeps begins to slope or curve down from a line parallel with the hack part of the orbits, but in D. tigriceps it does not begin to bend down until in advance of the orbits.
Genus Ptychognathus, Ow.— Three other species, showing a remarkable angular contour of the skull, with strongly ridged maxillary and upwardly produced mandibular bones, have been subgenerically separated under the name Ptychognathus. Their remains characterize the same formations as those of Dicynodon. No evidence of the Dicynodont family has yet been met with out of South Africa.
Fam. — Cryptodontia.
Upper as well as lower jaws edentulous, or with inconspicuous teeth.
Genus Oudenodon, Bain.
Sp. Oudenodon Bainii. — The fossils on which the above genus and species are founded are from a bluish argillo-ferru- ginous limestone in South Africa, and form part of a collection transmitted to the British Museum by A. G. Bain, Esq.
One portion of the fossil skull includes all that part in advance of the temporal fossee ; the fore part of the temporal ridges, at the upper and back part of this fragment, curve as they diverge from each other to the back part of the orbit. The upper interorbital part of the cranium is nearly flat, with the orbital margins slightly raised, and terminating anteriorly in a low antorbital prominence ; the least breadth of the inter¬ orbital space is one inch. A slight depression divides the antorbital from the supranasal tuberosities. The nasal bones form an almost flat rhomboid surface, from the contracted fore part of which the broad premaxillary part of the upper jaw
CRYPTODONTIA.
239
inclines downward and forward at an open angle. This part is traversed by a low obtuse median ridge, and terminates below in a trenchant edentulous border.
The nostrils are small, oval, and separated from each other by the broad junction of the ascending branch of the pre¬ maxillary with them.
The maxillary bone presents the chief peculiarity, being traversed obliquely by a strong angular ridge, commencing a little anterior to the orbit, and terminating at the alveolar border, not far from the maxillo-premaxillary suture. The alveolar border gently curves to this termination, and shows no trace of a tooth or alveolus.
The compound structure of the lower jaw is shown at the fractured back part, where an upper (surangidar T) element, thick and rounded above, is received into an outer and lower element, thin above, and thick and bent below, forming a groove for the reception of the ripper element. On the outer side of the jaw, about the middle of the part preserved, there is a longitudinal depression or narrow vacuity, above which there is a low ridge. The symphysis is thick, long, and bent up in the form of a beak, terminating by an edentulous sub- trenchant border ; its fore and outer part is traversed by a low median ridge. The length of this portion of the skull is 6 inches ; its breadth across the maxillary ridges is 2 inches 10 lines ; the extent of the symphysis of the lower jaw is 2 inches 6 lines. Oudenodon is more closely allied to tire African bidental reptiles of the following order than to the English Rhynchosaurus : so closely, in the construction of the skull, as to suggest the surmise that the absence of the two upper teeth may be a sexual character.
Genus Rhynchosaurus, Ow.
Sp. Rhynchosaurus articeps, Ow.* — The fossils in which
* Transactions of the Cambridge Philosophical Society, vol. vii., part iii., 1842, p. 355, plates 5 and 6.
240
PALEONTOLOGY
the above order, genus, and species of reptile have been based are from the new red sandstone (trias) of Shropshire. They occur at the Grinsill quarries, near Shrewsbury, in a fine¬ grained sandstone, and also in a coarse burr-sandstone ; in the latter the writer found imbedded some vertebrae, portions of the lower jaw, a nearly entire skull, fragments of the pelvis and of two femora : in the fine-grained sandstone, vertebrae, ribs, and some bones of the scapular and pelvic arches are imbedded. The bones present a very brittle and compact texture ; the exposed surface is usually smooth, or very finely striated, and of a light blue colour. The sandstones containing these bones occasionally exhibit impressions' of footsteps which resemble those figured in the Memoir by Murchison and Strickland (Geol. Trans., 2d series, vol. v., pi. xxviii. fig. 1) ; but they differ in the more distinct marks of the claws, the less distinct impression of a web, the more diminutive size of the innermost toe, and an impression corresponding with the hinder part of the foot, which reminds one of a hind toe point¬ ing backwards, and which, like the hind toe of some birds, only touched the ground with its point. The footprints are likewise more equal in size, and likewise in their intervals, than those figured in the above-cited Memoir : they measure from the extremity of the outermost or fifth toe to that of the innermost or first rudimental toe, about one inch and a half. They are the only footprints that have as yet been detected in the new red sandstone quarries at Grinsill.
As the fossil bones have always been found nearly in the same bed as that impressed by the footsteps above described, they probably belong to the same animal. In the vertebrae both articular surfaces of the centrum are concave, and are deeper than in the biconcave vertebrae of the extinct Croco- dilians ; the texture of the centrum is compact throughout. The neural arch is anchylosed with the centrum, without trace of suture, as in most lizards ; it immediately expands
CRYPT 0 D 0 N T I A
Ail
and sends outwards from each angle of its base a broad tri- angnlar piocess with a flat articular surface, the two anterior sin-faces look directly upwards, the posterior ones downwards ; the latter are continued backwards beyond the posterior ex¬ tremity of the centrum ; the tubercle for the simple articula¬ tion of the rib is situated immediately beneath the anterior oblique process. So far the vertebrae of the Rhynchosaurus, always excepting their biconcave structure, resemble the vertebrae of most recent lizards. In the modification next to be noticed, they show one of the vertebral characters of the Dinosauria. A broad obtuse ridge rises from the upper convex surface of the posterior articular process and arches forwards along the neural arch above the anterior articular process, and gradually subsides anterior to its base : the upper part of this arched angular ridge forms, with that of the opposite side, a platform, from the middle line of which the spinous process is developed. Nothing of this kind is present in existing lizards ; the sides of the neural arch immediately converge from the articular processes to the base of the spine, without the inter¬ vention of an angular ridge formed by the sides of a raised platform. The base of the spinous process is broadest behind, and commences there by two roots or ridges, one from the upper and back part of each posterior articular process. The anterior margin of the spinous process is thin and trenchant ; the height of the spine does not exceed the antero-posterior diameter of its base ; it is obliquely rounded off. The spinal canal sinks into the middle part of the centrum and rises to the base of the spine, so that its vertical diameter is twice as great at the middle as at the two extremities : this modification resembles in a certain degree that of the vertebrae of the Palceosaurus from the Bristol conglomerate.
The skull presents the form of a four-sided pyramid, com¬ pressed laterally, and with the upper facet arching down in a graceful curve to the apex, which is formed by the termination
PALAEONTOLOGY
242
of the muzzle. The very narrow cranium, wide temporal iossse on each side, bounded posteriorly by the parietal and the mastoid bones, and laterally by strong compressed zygomata ; the long tympanic pedicle, descending freely and vertically from the point of union of the posterior transverse and zygo¬ matic arches, and terminating in a convex pulley for the articular concavity of the lower jaw ; the large and complete orbits, and the short, compressed, and bent down maxillse, all combine to prove the fossil to belong to the lacertian division of the saurian order. The mode of articulation of the skull with the spine cannot be determined in the present specimen, but the lateral compression and the depth of the skull, the great vertical breadth of the superior maxillary bone, the small relative size of the temporal spaces, the vertical breadth of the lower jaw, prove that it does not belong to a reptile of the batracliian order. The shortness of the muzzle, and its compressed form, equally remove it from the Crocodilians. Xo Clielonian has the tympanic pedicle so long, so narrow, or so freely suspended to the posterior and lateral angles of the cranium.
The general aspect of the skull differs, however, from that of existing Lacertians, and resembles that of a bird or turtle, which resemblance is increased by the apparent absence of teeth. The dense structure of the produced ends of the pre- maxillaries indicates an analogy of function to the tusks of Dicynodon ; the premaxillaries are double, as in crocodiles and Chelonians ; but most of the essential characters of the skull are those of the lizard. The rami of the lower jaw are remark¬ able, as in Bathygnathus, for their great depth, but not the least trace of a tooth is discernible in the alveolar border of the dentary element.
The cranium, in my first described Pdiynchosaur, was pre¬ served with the mouth in the naturally closed state, and the upper and lower jaws in close contact. In this state we must
CRYPTODONTIA
243
suppose that they were originally buried in the sandy matrix which afterwards hardened around them ; and since lizards, owing to the unlimited reproduction of their teeth, do not become edentulous by age, we must conclude that the state in which the Rhynchosaurus was buried, with its lower jaw in un¬ disturbed articulation with the head, accorded with its natural condition, while living, so far as the less perishable hard parts of its masticatory organs were concerned. Nevertheless, since a view of the inner side of the alveolar border of the jaws has not been obtained, we cannot be quite assured of the actual edentulous character of this very singular Saurian. The indica¬ tions of a dental system are much more obscure in the Rhyn¬ chosaurus than in any existing Lacertian ; the dentations of the upper jaw are absolutely feebler than in the chameleon, and no trace of them can be detected in the lower jaw, where they are strongest in the chameleon. The absence of the coronoid process in the Rhynchosaurus, which is conspicuously developed in all existing lizards, corresponds with the unarmed condition of the jaw, and the resemblance of the Rhynchosaurus in this respect to the Ghelys ferox, would seem to indicate that the correspondence extended to the toothless condition of the jaws. The resemblance of the mouth to the compressed beak of certain sea-birds, the bending down of the curved and elon¬ gated premaxillaries, so as to be opposed to the deep symphysial extremity of the lower jaw, are further indications that the ancient Rhynchosaur may have had its jaws encased by a bony sheath, as in birds and turtles, the dentinal ends of the pre¬ maxillaries projecting from, or forming, the deflected end of the upper mandible.
There are few genera of extinct reptiles of which it is more desirable to obtain the means of determining the precise modifications of the locomotive extremities than the Rhyncho¬ saurus. The fortunate preservation of the skull has brought to light modifications of the lacertine structure leading towards
244
PALEONTOLOGY
Chelonia and birds wliicli before were unknown ; the vertebrae likewise exhibit very interesting deviations from the lacertian type. The entire reconstruction of the skeleton of the Rhynclio- saurus may be ultimately accomplished, if due interest be taken in the collection and preservation of the fossils of the Grinsill quarries.
The cranium of a Rhynchosaurian reptile with small palatal teeth and obscure maxillary dentations, has been discovered in the problematical sandstones, containing the Leptopleuron, near Elgin ; and adds to the probability of their triassic age.
Order VI.— Pterosauria.
Char. — Pectoral members, by the elongation of the anti- bracliium and fifth digit, adapted for flight, Vertebrae procoslian ; those of the neck very large, not exceeding eight in number ; those of the pelvis few and small. Most of the bones pneumatic. Head large ; jaws long, and armed with teeth.
The species of this order of reptiles are extinct, and peculiar to the mezozoic period. Although some members of the pre¬ ceding order resembled birds in the shape or the edentulous state of the mouth, those of the present order make a closer approach to the feathered class in the texture and pneumatic character of most of the hones, and in the development of the pectoral limbs into organs of flight (fig. 74<). This is due to an elongation of the antibracliial bones, and more especially to the still greater length of the metacarpal and phalangial bones of the fifth or outermost digit (fig. 74-, 5), the last phalanx of which terminates in a point. The other fingers were of more ordinary length and size, and terminated by claws. The number of phalanges is progressive from the first (fig. 74, 1) to the fourth (4), which is a reptilian character. The whole osseous system is modified in accordance with the
PTEROSAURIA
245
possession of wings ; tlie bones are light, hollow, most of them permeated by air-cells, with thin compact outer walls. The scapula and coracoid are long and narrow, but strong. The vertebrae of the neck are few, but large and strong, for the support of a large head with long jaws, armed with sliarp-
Fossil skeleton of Pteroclactylus crassirostris : A, Sketch of living Pterodactyle.
pointed teeth. The skull was lightened by large vacuities, of which one (o, fig. 7-1) is interposed between the nostril n and the orbit l. The vertebrae of the back are small, and grow less to the tail. Those of the sacrum are small, from three to five in number : but the weak pelvis and hind limbs bespeak a creature unable to stand and walk like a bird. The body must have been dragged along the ground like that of a bat. The Pterosauria may have been good swimmers as well as
246
PALAEONTOLOGY
flyers. The vertebral bodies unite by ball-and-socket joints, the cup being anterior, and in them we have the earliest manifestation of the “procoelian” type of vertebra. The atlas consists of a discoid centrum, and of two slender neurapo- pliyses ; the centrum of the axis is ten times longer than that of the atlas, with which it ultimately coalesces ; it sends off from its under and back part a pair of processes, above which is the transversely extended convexity articulating with the third cervical vertebra. In each vertebra there is a large pneumatic foramen at the middle of the side. The neural arch is confluent with the centrum. The anterior ribs have a bifurcate head. The dentition is thecodont.
Genus Dimokphodon, Ow.
Sp. Dimorythodon macromyx , Bkd. — The Pterodactvles are distributed into sub-genera, according to well-marked modifi¬ cations of the jaws and teeth. In the oldest known species, from the lias, the teeth are of two kinds ; a few at the fore part of the jaws are long, large, sharp-pointed, with a full elliptical base \ behind them is a close-set row of short, com¬ pressed, very small lancet-shaped teeth. In a specimen of Dimorphodon macromyx, from the lower lias of Lyme Regis, the skull was 8 inches long, and the expanse of wing about 4 feet. There is no evidence of this species having had a long tail.
Genus Ramphorhynchus, Yon Meyer. — In this genus the fore part of each jaw is without teeth, and may have been encased by a horny beak, but behind the edentulous pro¬ duction there are four or five large and long teeth, fol¬ lowed by several smaller ones. The tail is long, stiff, and slender.
The Ramphorhynchus longicaudns, R. Gemmingi, and R. Munsteri belong to this genus. All are from the lithographic (middle oolitic) slates of Bavaria.
Genus Pterodactylus, Cuv.— The jaws are provided with
PTEROSAURIA
247
teeth to tlieir extremities ; all the teeth are long, slender’ sharp-pointed, set well apart. The tail is very short.
P. longirostris. Ok.— About 10 inches in length ; from lithographic slate at Pappenheim. P. crassirostris, Goldf. — About 1 foot long ; same locality (fig. 74). P. Kochii, Wagn. — 8 inches long ; from the lithographic slates of Kehlheim. P. medius, Must. — 10 inches long; from the lithographic slates at Meulenliard. P. grandis, Cuv.— 14 inches long; from lithographic slates of Solenhofen. Two small and probably immature Pterodactyles, showing the short jaws characteristic of such immaturity, have been entered as species under the names of P. brevirostris and P. Mcycri. The latter shows the circle of sclerotic eye-plates.
The fragmentary remains of Pterodactyle from British oolite — e. g., Stonesfield slate, usually entered as Pterodactylus Bucklandi — indicate a species about the size of a raven.
The evidences of Pterodactyles from the Wealden strata indicate species about 16 inches in length of body. Those ( P. Fittoni and P. Sedgwickii, Ow.) from the greensand forma¬ tion, near Cambridge, with neck-vertebrae 2 inches long, and humeri measuring 3 inches across the proximal joint, had a probable expanse of wing of from 18 to 20 feet. The P. Cuvieri, Ow., and P. compressirostris, Ow., from the chalk of Kent, attained dimensions very little inferior to those of the greensand Pterodactyles.
More evidence is yet needed for the establishment of the pterosaurian genus, on the alleged character of but two phalanges in the wing-finger, and for which the term “ Orni- thopterus” has been proposed by Yon Meyer.
With regard to the range of this remarkable order of flying- reptiles in geological time, the present evidence is as follows : The oldest well-known Pterodactyle is the Dimorphodon macro - nyx, of the lower lias ; but bones ol Pterodactyle have been discovered in the coeval lias of Wirtemberg. The next in point
248
PALEONTOLOGY
of age is the Dimorphodon Banthensis, from the “Posidonomyen- sciiiefer” of Banz in Bavaria, answering to the alum shale of the Whitby lias ; then follows the P. BucTclandi from the Stonesfield oolite. Above this come the first-defined and numerous species of Pterodactyle from the lithographic slates of the middle oolitic system in Germany, and from Girin, on the Rhone. The Pterodactyles of the Wealden are as yet known to us by only a few bones and bone fragments. The largest known species are those from the upper greensand of Cambridgeshire. Finally, the Pterodactyles of the middle chalk of Kent, almost as remarkable for their great size, con¬ stitute the last forms of flying reptile known in the history of the crust of this earth.
Order VII. — Thecodontia.
Char. — Vertebral bodies biconcave : ribs of the trunk long and bent, the anterior ones with a bifurcate head : sacrum of three vertebrae : limbs ambulatory, femur with a third trochanter. Teeth with the crown more or less compressed, pointed, with trenchant and finely serrate margins : implanted hi distinct sockets.
Genus Theoodontosaurus.
Sp. Theoodontosaurus antiquus. — In 1836 certain reptilian remains from the “ dolomitic conglomerate” at Redland, near Bristol, were described by Messrs. Riley and Stutchbury.* The matrix has been referred to the Permian period ; it is now thought by some good observers to be not older than the triassic.
The teeth in these reptilian fossils are lodged in distinct sockets ; they are arranged in a close-set series, slightly de¬ creasing in size towards the posterior part of the jaw ; each ramus of the lower jaw contained twenty-one teeth. These
* Geological Transactions, 2d series, vol. v., p. 344.
THECODONTIA
249
are conical, rather slender, compressed and acutely pointed, with an anterior and posterior finely-serrated edge, the serra- tures being directed towards the apex of the tooth ; the outer surface is more convex than the inner one ; the apex is slightly recurved ; the base of the crown contracts a little to form the fang, which is subcylindrical.
Genus Pal.eosaurus, Eiley and Stutclibury. In the same formation as contained the jaw and teeth of the Thccodontosau- rus two other teeth were separately discovered, differing from the preceding and from each other ; the crown of one of these teeth measuring nine lines in length and five lines in breadth. It is compressed, pointed with opposite trenchant and serrated margins, but its breadth as compared with its length is so much greater than in the Thecodontosccurus, that upon it has been founded the genus Palceosaurus, and it is distinguished by the specific name of platyodon, from the second tooth, which is referred to the same genus under the name of Palceosaurus cylindrodon. The portion of the tooth of the Palceosaurus cylindrodon which has been preserved, shows that the crown is subcompressed and traversed by two opposite finely-serrated ridges, as in the Thecodontosaurus ; its length is five lines, its breadth at the base two lines.
The vertebrae associated with the two kinds of teeth above described are sub-biconcave, with the middle of the body more constricted, and terminal articular cavities rather deeper than in Teleosaurus ; but they are chiefly remarkable for the depth of the spinal canal at the middle of each vertebra, where it sinks into the substance of the centrum ; thus the canal is wider, vertically, at the middle than at the two ends of the vertebra : an analogous structure, but less marked, obtains in the dorsal vertebrae of the Rhyncliosaurus from the new red sandstone of Shropshire.
Besides deviating from existing lizards in the thecodont dentition and biconcave vertebrae, the Saurians of the dolomitic
250
PALAEONTOLOGY
conglomerate also differ in having some of tlieir ribs articulated by a head and tubercle to two surfaces of the vertebra, as at the anterior part of the chest in crocodiles and Dinosaurs. The shaft of the rib was traversed, as in the Protorosaur and Rhynchosaur, by a deep longitudinal groove. Some fragmen¬ tary bones indicate obscurely that the pectoral arch deviated from the crocodilian, and approached the lacertian or enalio- saurian type, in the presence of a clavicle, and in the breadth and complicated form of the coracoid. The sacrum includes at least three vertebrae. The humerus appears to have been little more than half the length of the femur, and to have been, like that of the Rhynchosaurus, unusually expanded at the two extremities. The femur is chiefly remarkable for a third process or trochanter, just above the middle of the shaft, which shows a medullary cavity. The distal condyles are flattened, the outer one being the larger; there is a deep depression between them posteriorly, and a very light one anteriorly.
The tibia, fibula, and metatarsal bones manifest, like the femur, the fitness of the Saurians for progression on land. The ungual phalanges are sub-compressed, curved downwards, pointed, and impressed on each side with the usual curved canal.
The following conclusions may be drawn from the know¬ ledge at present possessed of the osteology of the Thecodonto- saurus and Palceoscmrus : in their thecodont type of dentition, biconcave vertebrce, double-jointed ribs, and proportionate size of the bones of the extremities, they agree with the amphi- coelian crocodiles ; but they combine a dinosaurian femur, a lacertian form of tooth, and a lacertian structure of the pec¬ toral and probably pelvic arch with these crocodilian charac¬ ters ; and they have distinctive modifications, such as the moniliform spinal canal, in which, however, the almost con¬ temporary Rhynchosaur participates. It would be interesting
THECODONTIA
to ascertain whether the caudal vertebras are characterized, as in the Thuringian Protorosaur, by double diverging spinous processes.
Genus Belodon, Yon Meyer.
Sp. Belodon Plieningeri. — The reptile from the upper white keuper sandstone of Wirtemberg, described by Plieninger,* agrees in its essential characters so closely with the thecodont Saurians of the Bristol conglomerate as to add to the proba¬ bility of both belonging to the same lower mezozoic period.
Three vertebrae are modified to afford adequate attachment to the iliac bones in Belodon , and this additional evidence of affinity to Dinosauria may have characterized also the English Thecodonts.
Genus Cladyodon, Ow.
Sp. Cladyodon Lloydii. — In the Memoir on the Triassic Pied Sandstones of Warwick, by Murchison and Strickland, published in 1840, in the 2d series of the Geological Transac¬ tions, vol. v., a tooth, which is an extremely rare fossil in those English formations, was figured in pi. xxviii., fig. 6.
Having had the opportunity of studying the original speci¬ men and fragments of some others of seemingly the same species from the new red sandstones of Warwick and Learning- ton, the writer recognized the affinity of the reptile possessing those teeth to the thecodont reptiles of the Bristol conglomerate, and indicated what appeared to be a generic modification of dental form by the term Cladyodon. f Pie subsequently received other specimens of the teeth characterizing this genus, which may be described as being two-edged, sub-compressed ; the sides more or less convex ; the edges more or less sharp, and
* Wiirtemb. naturf. Jahreshefte, viii., Jahrg. 1857, p. 389. Jaeger’s Pliytosaurus appears to Lave been founded on casts of the sockets of the teeth of Belodon.
f Reports of the British Association, “ Brit. Fossil Reptiles,” 1841, p. 155. (See fuller descriptions, with figures, in Odontography , pi. 62, A, fig. 4, a , 6.)
252
PALAEONTOLOGY
frequently finely serrate j tlie crown slightly bent sideways, the inner side towards the mouth-cavity. The teeth are sometimes lancet-shaped, through convergence of the edges towards point ; sometimes through one edge being convex and the other concave, the crown is slightly curved or sickle- shaped ; sometimes through use, the point is blunted. The enamel is very thin, smooth, showing under the lens a slight longitudinal striation, forming wrinkles. The dentine is dis¬ posed in concentric layers ; it is not labyrintliic ; the base of the tooth shows a conical pulp-cavity. These teeth indicate a Saurian about ten feet in length.
The writer cannot discern any generic, or even good specific distinctions, between the teeth from the Warwickshire keuper, on which in 1840 he founded the genus Chicly odon, and those from the Wirtemberg keuper, on which M. Yon Meyer in 1844 founded the genus Belodon. Both are nearly allied to Palceosaurus.
The two following genera are referred provisionally and with doubt to the present order : —
Genus Bathygnathus, Leidy.
Sp. Batlvygnatlms borealis, Leidy. — Allied to the Cladyodon and Belodon by the shape of the teeth is the Saurian from the new red sandstone of Prince Edward’s Island, North America, the generic and specific characters of which have been deduced by Dr. Leidy* from a portion of lower jaw, containing seven teeth, but with interspaces from which others have been lost. The depth of the dentary bone is five inches ; a peculiarity which suggested the generic name (batlms, deep ; gnathos, jaw). The precise mode of implantation of the teeth is not described.
The fossil was discovered at a depth of 21 feet from the
* Journal of the Academy of Sciences, Philadelphia, vol. ii. , p. 327, pi. xxxiii.
THECODONTIA
253
surface, in a red sandstone supposed to be of the same age as that of Connecticut, so remarkable for the various and singular foot-marks, referable, some to reptiles, and others to large birds.
Genus Protorosaurus, Yon. Meyer.
Sp. Protorosaurus Speneri, Yon M. — The first fossil Saurian on record is that which marks the circumstance by its generic name, and honours its describer by the specific one. The slab of “ copper-slate” from the Permian beds of Eisenach in Thuringia, displaying, either in fossils or impressions, the skull, vertebral column, and bones of the fore foot of the reptile in question, was figured and described by Spener, a physician at Berlin, in 1710.* The original specimen is now in the museum of the Royal College of Surgeons, London, where it forms part of the Hunterian series of fossils. It was obtained from a copper-mine near Eisenach, at a depth of 100 feet from the surface.
A second specimen, showing the two fore limbs, a hind limb, and part of the trunk, was described by Link in I7l8.f Cuvier gives copies of portions of two other specimens in his Ossemens Fossilcs.\
The healthy, honest mind of Spener is shown by the conclusions which he formed from the state of preservation of his specimen (“ omnia, enim, minutissima, etiam apophyses, spinse,” etc.), and from its association with equally well- preserved remains of fishes, and even of the delicate leaves of plants, against the notions of those fossils merely simulating, and never having been, the living organisms which they represented — notions wdiich were then advocated under the sounding phrase of “plastic force,” as they have lately been under that of “ prochronism.” Spener’s only doubt was, whether the reptile had been a crocodile or a lizard ; but lie
* Miscellanea Berolinensia, 4to, i., p. 99, figs. 24 and 25. f Acta Eruditorum, 1718, p. 188, pi. ii.
} Ed. 8vo, 1836, pi. ccxxxvii., figs. 1 and 2.
254
PALEONTOLOGY
inclined to the former view, on account of the proportions ot the head to the trunk. He then enters upon speculations as to how a crocodile could have come into Germany ; and shows the usual effect of a mind biassed by a hypothetical diluvial catastrophe not demonstrated by observation and inductive research, and to the extent of such bias benumbed in the exercise of the faculty for the acquisition of natural truth.
The seven cervical vertebrae are proportionally larger than in any known recent or fossil terrestrial or aquatic Saurian ; they resemble in this respect the cervical vertebrae of Ptero- dactyles ; the tail is long, and its vertebrae differ from those of all other known reptiles, recent or fossil, in having the spinous processes bifurcate, diverging in the direction of the axis of the body.*
The muscular power of the neck is indicated by traces of bone-tendons. The dorsal vertebrae exceed eighteen in number, and have higher spines than in the modern Monitors ; the dorsal ribs are long, and longitudinally impressed. The hind limb is much longer than the fore limb, and the leg is longer, in proportion to the thigh and foot, than in the Moni¬ tors. The teeth are sharp-pointed, slender ; there appear to be at least twenty in both upper and lower jawTs in Speners specimen.
It may be concluded, from the length and strength of the tail and the peculiar provision for muscular attachments in that part,, and from the proportions of the hind limbs, that the Protorosaurus was of aquatic habits, and that the strength of its neck and head, and the sharpness of its teeth, enabled it to seize and overcome the struggles of the active fishes of the waters which deposited the old Thuringian copper-slates.
At Spynie and Cummingstone, in the neighbourhood of Elgin, N. E., in a stratum of a fine-grained whitish sandstone,
* A character first pointed out in the writer’s “Report on British Fossil Reptiles,” Trans, of Brit. Assoc., 1841, p. 155.
THECODONTIA
255
cemented by carbonate of lime, situated between “ Old Red ” and “ Purbeck ” formations, and resting conformably upon the former, evidences of Saurian (Crocodilian and Lacertian) reptiles, characteristic of triassic time, have been discovered. The remains of the large reptile, with pitted bony dermal scales, had been, on their first discovery, referred to a genus of fishes by Agassiz, under the name of Staganolejns, or “ pitted- scale,” probably from the belief that the formation belonged to the “ Old Red System.” I determined the crocodilian nature of the scales, and the affinity of the reptile to the Thecodonts, in the breadth of the coracoid or pubis as shown by the cast of the bone, at the meeting of the British Associa¬ tion at Leeds, in September 1858. I have since been favoured by Mr. Duff with a tooth, assoicated with scales of Stagctnolejns, which is “ thecodont ” in character, and like that of Cladyodon.
In the same sandstone, in the quarry at Cummingstone, near Elgin, a continuous series of thirty-four impressions have been observed. The impressions are in pairs, forming two parallel rows, the hind one being one inch in diameter.
I had some years before determined the true saurian nature of the impression of the skeleton of the trunk and part of the head of a small reptile discovered by Mr. Patrick Duff of Elgin, at Spynie, and noticed by him in the “ Elgin Courant ” of October 10th, 1851, as evidence of an air-breathing vertebrat in “ Old Red Sandstone.” The specimen was submitted by Mr. Duff to my examination, the result of which was given, Dec. 1 5, 1851, in the “ Literary Gazette” of that week, as follows : —
“ It is the impression, in two pieces, of a grey variety of the old red sandstone, of a long and slender four-footed vertebrate animal, four inches and a half in length, clearly belonging, by the form, proportions, and positions of the scapular and pelvic arches, and their appended limbs, to the reptilian class. The osseous substance has disappeared ; the cavities in the sandstone which contained it remain, stained
25G
PALAEONTOLOGY
by a deposit of an oclireous tint. The impressions are so well defined, as clearly to show that there were twenty-six vertebrae between the skull and sacrum, two sacral vertebrae, and thirteen caudal vertebrae, before the tail disappears by dipping into an unexposed part of the matrix. Impressions of twenty-one pairs of ribs are preserved, all very slender, short where they commence near the head, but rapidly gaining length as they are placed further back. The cervical and anterior ribs are expanded, but not bifurcate, at their vertebral end ; all the ribs articulate close to the bodies of the vertebrae. In the crocodilian reptiles the anterior ribs are bifurcate, and the posterior ones, with a simple head, articulate with long diapophyses. The distinctive characters of tire batrachian skeleton are the double occipital condyle ; ribs wanting, or very short and subequal ; a single sacral vertebra, and rib¬ shaped ilium. The first character cannot be determined, the occipital articulation not being preserved in the fossil. Instead of the second character, the fossil shows ribs of varied length, and most of them much longer than in the salamanders, newts, or any known Batrachian. With regard to the third character, the impression in the matrix clearly shows two sacral vertebrae and a short subquadrate pelvis.
“Both the humerus and the femur show the lacertian sigmoid shape, and near equality of length, which distinguish them alike from the crocodilian and batrachian orders ; they are likewise, as in lizards, relatively longer than in the newts and salamanders. Near the imperfect impression of the head may be seen the hollow bases of some large, slightly-compressed, conical teeth, which also tell for the saurian and against the batrachian nature of this ancient reptile. I propose to call it Leptojjleuron lacertinum * Many particulars of minor import, bearing upon the more immediate affinities of this most rare
* Act tt6s, slender ; ir\evp6v, rib; for this compound we have the authority of Poihilopleuron, already applied to an extinct genus of Saurian s.
DINOSAUKIA
and interesting fossil, liave been noted, and will be given, with the figures, in my History of British Fossil Beptiles, for which voik Mi. Hull has kindly consented to place the specimen at my disposal. In the meanwhile, I beg to offer the above precis of the main characters of the fossil. — Bichabd Owen.”
Other palaeontologists regarded the fossil as a batrachian reptile ; but no evidence, osteological or dental, has been pointed out in support of this view.*
With regard to the geological age of the calcareous sand¬ stone containing Staganolepis and Lcptopleuron, the author has remarked, in the article “Palaeontology,” when the belief of some eminent geologists in the Devonian age of the stratum is quoted ■“ As yet, however, no characteristic Devonian or Old Eed fossils of any class have been discovered associated with the foregoing evidences of reptiles, which, according to the determination of strata by characteristic fossils, would belong to the secondary or mezozoic period.”f It is, most probably, of triassic age.
Order VIII. — Dinosauria.
Char. — Cervical and anterior dorsal vertebrae with par- and di-apophyses, articulating with bifurcate ribs ; dorsal vertebrae with a neural platform, sacral vertebrae ex-
The following notice of this determination of the fossil will be found in the Athenceum of Dec. 13, in the title of a paper to he read at the ensuing meeting of the Geological Society “Notice of the occurrence of Fossil Foot- Tracks, and the Remains of a Batrachian Reptile, in the Old Red Sandstone of Morayshire, by Capt. Brickenden and Dr. Mantell.” The belief in the antiquity of the stratum showing the impression of the skeleton— remains of the skeleton there are none — appears to have weighed with these gentlemen in placing the animal at the bottom of the air-breathing series of vertebrals, as well as in pro¬ posing for it the name of Tderpeton, or “last of reptiles;” (reA os, the end or issue of a thing, or reAeioy, having reached its end, and ep-rrerov, a reptile), at least as traced backwards in time. The term Leptopleicron has, however, the priority of publication : being also the result of a truer exposition of the nature and affinities of the fossil, and free from the signification of its appearance in time it will be, probably, preferred.
f Fncyclopsedia Britannica, vol. xxii., p. 130.
S
258
PALAEONTOLOGY
ceeding two in number ; body supported on four stiong unguiculate limbs.
The well-ossified vertebrae, large and liollow limb-bones, and tritrochanterian femora of tlie thecodont reptiles of the Bristol conglomerate, together with the structure of the sacral vertebrae in the allied Belodon, indicate the beginning, at the triassic period, of an order of Reptilicc which acquired its full development and typical characteristics in the oolitic period.
Genus Scelidosaurus, Ow. — By this name is indicated a Saurian with large and hollow limb-bones, with a femur, having the third inner trochanter, and with metacarpal and phalangial bones, adapted for movement on land. The fossils occur in the lias at Charmouth, Dorsetshire.
Genus Megalosaurus, Bkld. — The true dinosaurian cha¬ racters of this reptile have been established by the discovery of the sacrum, which consists of five vertebrae, interlocked by the alternating position of neural arch and centrum. The articular surfaces of the free vertebrae are nearly flat ; the neural arch develops a platform which in the anterior dorsals supports very long and strong spines.
The compressed piercing and trenchant form of tooth which characterises the existing varanian lizards was manifested by the Megalosaurus. The specimen which is most illustra¬ tive of the dental peculiarities of this gigantic reptile is a portion of the lower jaw with a few teeth. The first cha¬ racter which attracts attention in this fossil is the inequality in the height of the outer and inner alveolar walls ; a similar inequality characterizes the jaws of almost all the existing lizards. But in these the oblique groove, so bounded, to which the bases of the developed teeth are ancliylosed, is much more shallow, and is relatively wider ; and the teeth in all the stages of growth are completely exposed when the gum has been removed.
DINOSAURIA
259
In the Megalosaurus the greater relative development of the inner alveolar wall, as compared with the dentigerous part of the jaw m existing Saurians, narrows the dental groove, and covers a greater proportion of the bases of the teeth, besides concealing more or less completely the germs of their suc¬ cessors. Moreover, instead of the mere shallow impressions upon the inner side of the outer alveolar plate to which the teeth are attached in modern lizards, there are distinct sockets formed by bony partitions connecting the outer with the inner alveolar wall in the jaw of the Megalosaurus. These parti¬ tions rise from the outer side of the inner alveolar wall in the form of triangular vertical plates of bone, and from the middle of the outer side of each plate a bony partition crosses to the outer parapet, completing the alveoli of the fully-formed or more advanced teeth ; the series of triangular plates forming a kind of zig-zag buttress along the inner side of those alveoli. The outer parapet rises an inch higher than the inner one.
Fig. 75 exhibits a portion of another jaw of the Megalo¬ saurus, also from Stonesfield oolite, from which the inner wall has been removed to show the germ of a successional tooth c, about to succeed an old tooth a, which has been broken, and near to which is a newly-formed tooth, h, coming into place. These teeth will exemplify the shape of the crown of the tooth, which is subcompressed, slightly recurved, sharp edged, and sharp-pointed, tire edges being minutely serrated ; the edge upon the convex or front border b becomes blunted as it descends about two-thirds of the way towards tire base of the tooth j that upon the concave hinder border a is continued to the base. The lower half of the crown is thicker towards the fore margin than towards the hind one ; so that a transverse section, like that above, a, in fig. 75, gives a narrow oval form pointed behind. At the upper half of the crown the sides slope more equally from the middle thickest part to both margins, and the section is a narrow pointed ellipse. The
2(50
PALAEONTOLOGY
crown is covered by
a smooth and polished enamel, which
Fig. 75.
Section of jaw with teeth of the Mecjciloscturus Bucldcindi , nat. size
T.) IN 0 SAUK I A
261
wholly forms the marginal serrations. The base of the tooth is coated with a smooth, lighter-coloured cement, forming a thin layer, and becoming a little thicker towards the implanted end of the tooth. The remains of the pulp are converted into osteo-dentine in the basal part of the completely formed tooth. Moderately magnified, the surface of the enamel pre¬ sents a finely wrinkled appearance. The marginal serrations show, under a somewhat higher power, that the points are directed towards the apex of the tooth — a structure well adapted tor dividing the tough tissues of the saurian integument,
ilie main body of the tooth consists of dentine, of that hard unvascular kind of which the same part of the teeth of existing crocodiles and most mammals is composed. No part of the dentine is pervaded by medullary canals, as in the Iguanodon.
A series ot teeth from individual Megalosaurs, of different ages, are preserved in the British Museum and in the geological museum at Oxford ; although differing in size, they preserve the characteristic form above described. In one specimen the point of the crown and the trenchant margins have been rubbed down to a smooth obtuse surface ; it seems to have come from the hinder part of the dental series, where the teeth may have been smaller and less sharp, or more liable to lie blunted by a greater share in the imperfect act of mastication, than the teeth in advance.
Successional teeth in different stages of growth are shown in the original portion of jaw of the Megalosaur in the Oxford museum. Some, more advanced, show their crowns projecting from alveoli already formed by the plates extending across from the triangular jirocesses before described : vacant sockets, from which fully formed teeth have escaped, occur, generally in the intervals between these more advanced teeth. The summits of less developed teeth are seen protruding at the inner side of the basal interspaces of the triangular plate,
PALAEONTOLOGY
202
between them and the true internal alveolar parapet. There can he no doubt that, in the course of the development of these teeth, corresponding changes take place in the jaw itself, by which new triangular plates and alveolar partitions are formed, as the old ones become absorbed, analogous to those concomi¬ tant changes in the growth and form ol the teeth, alveoli, and jaws, which take place in so striking a degree in the elephant. The peculiarity of the Megalosaur, as compared with the crocodiles and lizards which have a like endless succession of teeth, is the deeper position of the suceessional tooth (fig. 75, c), in relation to the one (a) it is destined to replace, and the great proportion of the tooth which is formed before it is pro¬ truded. The anterior tooth a hi this specimen shows at the inner side of its base the commencing absorption stimulated by the encroaching capsule of the suceessional tooth c below, the crown of which is completed externally, though not consoli¬ dated. On one of the fractured margins of this piece of jaw, a part of the basal shell of an absorbed and shed tooth remains, with part of the root of the suceessional tooth, which has risen into place, but which shows its base full of matrix, the pulp not having been calcified at that period of the tooth’s growth.
In the proportion of the suceessional teeth which is formed in the formative cavity in the substance of the jaw, the Mega¬ losaur offers a closer resemblance to the mammalian class than do any of the recent or extinct crocodilian or lacertian reptiles. But the evidence of uninterrupted and frequent succession of the teeth in the Megalosaur is unequivocal ; and this part of the dental economy of the great carnivorous reptile is strictly analogous to that which governs the same system in the existing members of the class. The different forms of the teeth at different stages of protrusion did not fail to attract the attention of the gifted discoverer of the great predatory saurian, in whose words this notice of its dentition may be fitly concluded : —
DINOSAUKIA
263
“In the structure of these teeth we find a combination of mechanical contrivances analogous to those which are adopted in the construction of the knife, the sabre, and the saw. When first protruded above the gum, the apex of each tooth presented a double cutting edge of serrated enamel. In this stage its position and line of action were nearly vertical ; and its form, like that of the two-edged point of a sabre, cutting equally on each side. As the tooth advanced in growth, it became curved backwards in the form of a pruning-knife, and the edge of serrated enamel was continued downwards to the base of the inner and cutting side of the tooth, whilst on the outer side a similar edge descended, but a short distance from the point ; and the convex portion of the tooth became blunt and thick, as the back of a knife is made thick for the purpose of pro¬ ducing strength. The strength of the tooth was further increased by the expansion of its side. Had the serrature continued along the whole of the blunt and convex portion of the tooth, it would in this position have possessed no useful cutting power ; it ceased precisely at the point beyond which it could no longer be effective. In a tooth thus formed for cutting along its concave edge, each movement of the jaw combined the power of the knife and saw ; whilst the apex, in making the first incision, acted like the two-edged point of a sabre. The backward curvature of the full-grown teeth enabled them to retain, like barbs, the prey which they had penetrated. In these adaptations we see contrivances which human ingenuity has also adopted in the preparation of various instruments of art.”*
The oldest known beds from which any remains of Mcgalo- saurus have been obtained are the lower oolites at Selsby Hill, and Chipping-Norton, Gloucestershire. Abundant and charac¬ teristic remains occur in the Stonesfield slate, Oxfordshire. Teeth of this genus have been found in tire Cornbrash and Hath oolite ; both teeth and bones are common in the Wealden * Buckland, “ Bridgewater Treatise,” p. 236.
264
PAL.-KONTQLOGY
strata and Rurbeck limestone. Some of these fossils indicate a reptile of at least 30 feet in length.
Genus IIyiaeosaukus, Mtll, — Remains of the Dinosanrian so called have hitherto been found only in Wealden strata, as at Tilgate, Bolney, and Battle. The most instructive evidence is that which was exposed by the quarreymen of the Wealden stone at Tilgate, and was obtained and described by Mantel 1 in 1832. It consisted of a block of stone measuring 4 \ feet by 2J feet (fig. 76), and included the following parts of the
Fig. 76.
] fylceosaurvs (Wealden).
skeleton in almost natural juxtaposition : — io, anterior verte¬ bra, the first supporting part of the base of the skull ; several ribs, 4, 4 ; some enormous dermal bony spines, 5, 6, 6, which supported a strong defensive crest along the back ; two cora¬ coids, 7, 7 ; scapulae, 8, 8 ; and some detached vertebrae and fragments of bones. In 1841 the writer showed that the sacrum was dinosaurian, and included five vertebrae.
The teeth are relatively small, close-set, thecodont in im¬ plantation, with subcylindrical fang and a subcompressed slightly expanded and incurved crown, with the borders straight and converging to the blunt apex. They indicate rather a mixed or vegetable diet than a carnivorous one. The
DINOSAUMA
265
skin was defended by subcircular bony scales. Tlie length of the Hykeosaur may have been 25 feet.
Genus Iguanodon, MtlJ. — Remains of the large herbivorous reptiles of this genus have been found in Wealden and neoco- mian (greensand) strata. Femora, four feet in length, showing the third inner trochanter, have been discovered. The sacrum included five, and in old animals six, vertebrae ; the claw-bones are broad, flat, and obtuse. There were only three well- developed toes on the hind foot ; and singular large tridactyle impressions, discovered by Beccles in the Wealden at Hastings, have been conjectured to have been made by the Jguanodon.
With vertebrae, subconcave at both articular extremities, having, in the dorsal region, lofty and expanded neural arches, and doubly articulated ribs, and characterized in the sacral region by their unusual number and complication of structure ; with a Lacertian pectoral arch, and unusually large bones of the hind limbs, excavated by large medullary cavities, and adapted for terrestrial progression the Ljuanodon was distin¬ guished by teeth, resembling in shape those of the Iguana, but in structure differing from the teeth of that and every other known reptile, and unequivocally indicating the former exis¬ tence in the Dinosaurian order of a gigantic representative of the small group of living lizards which subsist on vegetable substances.
The important difference which the fossil teeth presented in the form of their grinding surface was pointed out by Cuvier,* of whose description Dr. Mantell adopted a condensed view in his Illustrations of the Geology of Sussex, 4to, 1827, p. 72. The combination of this dental distinction with the vertebral and costal characters, which prove the Iguanodon not to have belonged to the same group of Samians as that which includes the Iguana and other modern lizards, rendered it highly desirable to ascertain by the improved modes of investi-
* Ossemens Fost-iles, 1824, vol. v., pt. ii., p. 351.
266
PALAEONTOLOGY
sating dental structure, the actual amount of correspondence
O O
between the Iguanodon and Iguana in this respect. This has been done in the author’s general description of the teeth ol reptiles,* from which the following notice is abridged : — The teeth of the Iguanodon (fig. 77), though resembling most
closely those of the Iguana, do not present an exact magnified image of them, but differ in the greater relative thickness of the crown, its more com¬ plicated external surface, and, still more essentially, in a modification of the internal structure, by which the Igua-
Fig. 77.
Front and side views of a tooth of the lower jaw of the Iguanodon, nat. size.
nodon equally deviates from every other known reptile.
As in the Iguana, the base of the tooth is elongated and contracted ; the crown expanded and smoothly convex on the inner side ; when first formed it is acuminated, compressed, its sloping sides serrated, and one surface, external in the upper jaw, internal in the lower jaw, is traversed by a median longitudinal ridge, and coated by a layer of enamel ; but beyond this point the description of the tooth of the Igua- nodon indicates characters peculiar to that genus. In most of the teeth that have hitherto been found, three longitudinal ridges traverse the ridged surface of the crown, one on each side of the median primitive ridge ; these are separated from each other and from the serrated margins of the crown by four wide and smooth longitudinal grooves. The relative * Odontography, pt . ii., p. 249; Transactions of the British Association, 1838.
DINOSAUWA
267
widtli of these grooves varies in different teetli ; sometimes a fourth small longitudinal ridge is developed on the ridged side of the crown. The marginal serrations which, at first sight, appear to be simple notches, as in the Iguana, present under a low magnifying power (fig. 78), the form of transverse ridges, themselves notched, so as to resemble the mammilated margins of the unworn Plates of the elephant’s grinder ; slight grooves |
lead from the interspaces of these notches upon the sides of the marginal ridges. These ridges Fig 78 or dentations do not extend beyond the expanded Marginal ridges Part of the crown ; the longitudinal ridges are of the iguano- continued farther down, especially the median don> masn- ones, which do not subside till the fang of the tooth begins to assume its subcylindrical form. The tooth at first increases both in breadth and thickness ; then it diminishes in breadth, but its thickness goes on increasing ; in the larger and fully formed teeth, the fang decreases in every diameter, and some¬ times tapers almost to a point. The smooth unbroken surface of such fangs indicates that they did not adhere to the inner side of the maxillae, as in the Iguana, but were placed in separate alveoli, as in the Crocodile and Megalosaur ; such support would appear, indeed, to be indispensable to teeth so worn by mastication as those of the Iguanodon.
The apex of the tooth soon begins to be worn away, and it would appear, by many specimens, that the teeth were retained until nearly the whole of the crown had yielded to the daily abrasion. In these teeth, however, the deep excavation of the remaining fang plainly bespeaks the progress of the successional tooth prepared to supply the place of the worn-out grinder. At the earlier stages of abrasion a sharp edge is maintained at the ridged part of the tooth by means of the enamel which covers that surface of the crown; the prominent ridges upon that surface give a sinuous contour to the middle of the cutting
PALAEONTOLOGY
268
edge, whilst its sides are jagged by the lateral serrations. The adaptation of this admirable dental instrument to the cropping and comminution of such tough vegetable food as the 6 Icitlu ai ice and similar plants, which are found buried with the Iguanoclon, is pointed out by Dr. Buckland, with his usual felicit} oi illustration, in his Bridgewater Treatise, vol. i., p. 210.
When the crown is worn away beyond the enamel, it pre¬ sents a broad and nearly horizontal grinding surface (fig. i 0), and now another dental substance is brought into use, to give an inequality to that surface , this is the ossified remnant of the pulp, which, being firmer than the surrounding dentine, forms a slight transverse ridge in the middle of the grinding surface ; the tooth in this stage has
rig. ii/. ^
A worn tooth of exchanged the functions of an incisor for that the Iguanodon. (y a moiar? and is prepared to give the final
compression, or comminution, to the coarsely divided vege¬ table matters.
The marginal edge of the incisive condition of the tooth and the median ridge of the molar stage are more effectually established by the introduction of a modification into the texture of the dentine, by which it is rendered softer than in the existing Iguanre and other reptiles, and more easily worn away. This is effected by an arrest of the calcifying process along certain cylindrical tracts of the pulp, which is thus con¬ tinued, in the form of medullary canals, analogous to those in the soft dentine of the Megatherium’s grinder, from the central cavity, at pretty regular intervals, parallel with the dentinal tubes, nearly to the surface of the tooth. The medullary canals radiate from the internal (upper jaw) or external (lower jaw) sides of the pulp-cavity, and are confined to the dentine forming the corresponding walls of the tooth. Their diameter is y^tli of an inch. They are separated by pretty regular intervals, equal to from six to eight of their own diameters. They
DIN0SAU1UA
260
sometimes divide once in their course. Each medullary canal is surrounded by a clear space. Its cavity was occupied in the section described by a substance of a deeper yellow colour than the rest of the dentine.
The dentinal tubes present a diameter of T^th of an inch, with interspaces equal to about four of their diameters. At the first part of their course, near the pulp-cavity, they are bent in strong undulations, but afterwards proceed in slight and regular primary curves, or in nearly straight lines to the periphery of the tooth. The secondary undulations of each tooth are regular, and Arery minute. The branches, both primary and secondary, of the dentinal tubes are sent off from the concave side of the main inflections ; the minute secondary branches are remark¬ able at certain parts of the tooth for their flexuous ramifica¬ tions, anastomoses, and dilatations into minute calcigerous cells, which take place along nearly parallel lines for a limited extent of the course of the main tubes. The appearance of interruption in the course of the dentinal tubes, occasioned by this modification of their secondary branches, is represented by the irregularly dotted tracts in the figure. This modifica¬ tion must contribute, with the medullary canals, though in a minor degree, in producing that inequality of texture and of density in the dentine, which renders the broad and thick tooth of the Igucmodon more efficient as a triturating instrument.
The enamel which invests the harder dentine, forming the ridged side of the tooth, presents the same peculiar dirty brown colour, when viewed by transmitted light, as in most other teeth. Very minute and scarcely perceptible undulating fibres, running vertically to the surface of the tooth, form the only discernible structure in it.
The remains of the pulp in the contracted cavity of the completely formed tooth are converted into a dense but true osseous substance, characterized by minute elliptical radiated cells, Avhose long axis is parallel with the plane of the concern-
270
PALEONTOLOGY
trie lamellae, which surround the few and contracted medullary canals in this substance.
The microscopical examination of the structure of the Iguanodon’s teeth thus contributes additional evidence of the perfection of their adaptation to the offices to which their more obvious characters had indicated them to have been destined.
To preserve a trenchant edge, a partial coating of enamel is applied ; and, that the thick body of the tooth might be worn away in a more regularly oblique plane, the dentine is rendered softer as it recedes from the enamelled edge, by the simple contrivance of arresting the calcifying process along certain tracts of the opposite wall of the tooth. When attrition has at length exhausted the enamel, and the tooth is limited to its function as a grinder, a third substance has been prepared in the ossified remnant of the pulp to add to the efficiency of the dental instrument in its final capacity. And if the follow¬ ing reflections were natural and just, after a review of the external characters of the dental organs of the Iguanodon, their truth and beauty become still more manifest as our knowledge of their subject becomes more particular and exact : —
“ In this curious piece of animal mechanism we find a varied adjustment of all parts and proportions of the tooth, to the exercise of peculiar functions, attended by compensations adapted to shifting conditions of the instrument during different stages of its consumption. And we must estimate the works of nature by a different standard from that which we apply to the productions of human art, if we can view such examples of mechanical contrivance, united with so much economy of expenditure, and with such anticipated adaptations to vary¬ ing conditions in their application, without feeling a profound conviction that all this adjustment has resulted from design and high intelligence.”
All trace of dinosaurian reptiles disappears in the lower cretaceous beds.
CROCODILIA
271
Order IX. — Crocodilia.
Char, leetli in a single row, implanted in distinct sockets ; external nostril single and terminal or sub-terminal. Anterior trunk vertebra; with par- and di-apophyses, and bifurcate ribs ; sacral vertebrae two, each supporting its own neural arch. Skin protected by bony, usually pitted plates.
Sub- Order 1. — Amphiccelia.*
Crocodiles closely resembling in general form the long and slender-jawed kind of the Ganges called “ gavial ” or “ gharrial,” existed from the time of the deposition of the lower lias.
Their teeth v ere similarly long, slender, and sharp, adapted for the prehension of fishes, and their skeleton was modified foi more efficient progress in water by the vertebral surfaces being slightly concave, by the hind limbs being relatively laigei and stronger, and by the orbits forming no prominent obstruction to progress through water. From the nature of the deposits containing the remains of the so-modified croco¬ diles, they were marine. The fossil crocodile from the Whitby lias, described and figured in the Philosophical Transactions, 1/58, p. 088, is the type of these amphicoelian species. They have been grouped under the following generic heads \-—Tcleo- saurus, Steneosaurus, Mystriosaurus, Macrospondylus, Masso- spondylus, to which must be added Pccciloplcuron, Pelagosaurus, PEolodon, Sucliosaurus, Goniopholis.
Species of the above genera range from the lias to the chalk inclusive.
Suchosaurus of the Wealden is characterized by the com¬ pressed crown and trenchant margins of the teeth ; Goniopholis, of the Purbeck beds, by some of the dermal scales having the same peg-and-pit interlocking as in the scales of the ganoid fish in fig. 52.
* Ampin, both ; Jcoilos, hollow ; the vertebra being hollowed at both ends.
272
PALAEONTOLOGY
Sub- Order 2.— OpiSTHOCCELlA*
Tlie small group of Crocodilia so called is an artificial one, based upon more or less of the anterior trunk vertebrae being united by ball-and-socket joints, but having the ball in front, instead of, as in modern crocodiles, behind. Cuvier first pointed out this peculiarity f in a Crocodilian from the Oxfordian beds at Ilonfleur, and the Kimmeridgian at Havre. The writer has described similar opisthoccelian vertebrae from the great oolite at Chipping Horton, from the upper lias of Whitby, and, but of much larger size, from the Wealden for¬ mations of Sussex and the Isle of Wight. These specimens probably belong, as suggested by the writer in 1841,t to the fore part of the same vertebral column as the middle dorsal vertebrae, flat at the fore part, and slightly hollow behind, on which he founded the genus Cetiosaums. The smaller opis¬ thoccelian vertebrae described by Cuvier have been referred by Yon Meyer to a genus called Strep tospondylus.
In one species from the Wealden, dorsal vertebrae measur¬ ing 8 inches across are only 4 inches in length, and caudal vertebrae nearly 7 inches across are less than 4 inches in length. These characterize the species called Cetiosaurus brevis.§
Caudal vertebrae measuring 7 inches across and 5 jr inches in length, from the lower oolite at Chipping Horton, and the great oolite at Enstone, represent the species called Cetiosaums medius.
Caudal vertebrae from the Portland stone at Garsington, Oxfordshire, measuring 7 inches 9 lines across and 7 inches
*' Opisthos, behind ; koilos, hollow ; vertebra concave behind, convex or flat in front.
f Annales du Mus6um, tom. xii., p. 83, pi. x. xi.
1 “ Report on British Fossil Reptiles,” Trans. Brit. Assoc, for 1841, p. 9G.
£ They have since been referred to the dinosaurian order under the name of Pelorosaurus, but without any evidence of the true sacral characters of that, order; the cavities of long bones are common to Crocodilians and Dino¬
saurs.
CROCODILIA
273
in length, are referred to the Cetiosaurus longus. The latter must have been the most gigantic whale-like of Crocodilians.
Sub- Order 3. — Proccelia.*
The best and most readily recognizable characters by which the existing Crocodilians are grouped in appropriate genera are derived from modifications of the dental system.
In^tlie _ (genus Alligator ) the teeth vary in number fr°ni 18—18 1° 22—22 ^ the fourth tooth of the lower jaw or canine, is received into a cavity of the palatal surface of the upper jaw’ where it is concealed when the mouth is shut ; in old indi¬ viduals the upper jaw is perforated by these large inferior canines, and the fossa; are con¬ verted into foramina.
In the true crocodiles (genus Orocodilus'j the first tooth in the lower jaw perforates the palatal process of the intermaxillary bone when the mouth is closed ; the fourth tooth in the lower jaw is received into a notch exca¬ vated in the side of the alveolar border of the upper jaw, and is visible externally when the mouth is closed.
In the two preceding genera the alveolar borders of the jaws have an uneven or wavy contour, and the teeth are of unequal size.
In the gavials (genus Gavialis j the teeth are nearly equal in size and similar in form in both jaws, and the first as well as the rl’eeth of the Gaviai. fourth tooth in the lower jaw passes into a groove in the margin of the upper jaw, when the mouth is closed.
The number of teeth is always greater in the gavials than in the crocodiles or alligators. The first five pairs of teeth
* Pros , front; Icoilos, hollow; vertebra with the cup at the fore part and the ball behind.
Fig. 80.
T
274-
PALEONTOLOGY
above are supported by the premaxillary bones ; the first, second, and fourth of the lower jaw are the longest.
The eight or nine posterior teeth are nearly conical, the rest are sub-compressed antero-posteriorly, and present a trenchant edge on the right and left side, between which a few faint longitudinal ridges traverse the basal part of the enamelled crown (fig. 80).
The position of the opposite sharp ridges, and the direction of the flat sides of the crown, are reversed in the extinct crocodile (Croc, cultridms ), which in other respects most nearly resembles the gavial in the form of the teeth.
In most of the extinct species of Crocodilians the teeth are characterized by more numerous and strongly dev eloped longi¬ tudinal ridges upon the enamelled crown, than in the recent species ; and they are commonly longer, more slender, and sharp-pointed. But in one of the crocodiles with sub-biconcave vertebral ( Goniopholis crctssidens ), from the Wealden formation and Purbeck limestone, the teeth have crowns which are as round and as thick in proportion to their length as in the recent crocodiles or alligators.
The more ancient crocodiles, from the Oolite and Lias, called Steneosauri and Teleosauri, had jaws like those of the modern gavials, but sometimes longer and more attenuated, and armed with more numerous, equal, and slender teeth, adapted for the capture of fishes, which appear to have been the only other vertebrate animals existing at those periods in numbers sufficient to yield subsistence to carnivorous marine Saurians.
In all the Teleosauri the teeth are more slender, less com¬ pressed, and sharper pointed than in the gavial ; they are slightly recurved, and the enamelled crown is traversed by more numerous and better defined iddges — two of which, on opposite sides of the crown, are larger and more elevated than the rest. The fang is smooth, cylindrical, and always exca-
CROCODILIA.
275
vated at the base. The teeth of the Steneosauri, or extinct crocodiles with long and slender jaws, and with vertebra sub¬ concave at both extremities, but with subterminal nostrils, differ from those of the Tdeosauri in being somewhat thicker
m proportion to their length, and larger in proportion to the jaws.
The teeth of both the existing and extinct crocodilian reptiles consist of a body of compact dentine, forming a crown covered by a coat of enamel, and a root invested by a moder¬ ately thick layer of cement. The root slightly enlarges or maintains the same breadth to its base (fig. 80, a), which is deeply excavated by a conical pulp-cavity extending into the crown, and is commonly either perforated or notched at its concave or inner side.
The tooth-germ c (figs. 80 and 81) is developed from the membrane covering the angle between the floor and the inner wall of the socket. It becomes, in this situation, completely enveloped by its capsule, and partially calcified, before the young tooth penetrates the in¬ terior of the pulp-cavity of its predecessor.
The matrix of the young
v O
growing tooth affects, by its pressure, the inner wall of the socket, as shown in figs. 80 and Fig. si.
81, and forms for itself a shallow Section of jaw with teeth of the
recess ; at the same time it Alligator.
attacks the side of the base of the contained tooth : then, gaining a more extensive attachment by its basis and increased size, it penetrates the large pulp-cavity of the previously formed tooth either by a circular or semicircular perforation.
276
PALAEONTOLOGY
The size of the perforation in the tooth, and of the depiession in the jaw, proves them to have been in great part caused by the soft matrix, which must have produced its effect by exciting absorbent action, and not by mere mechanical force. The resistance of the wall of the pulp-cavity having been thus overcome, the growing tooth and its matrix recede from the temporary alveolar depression, and sink into the substance of the pulp contained in the cavity of the fully-formed tooth.
As the new tooth grows, the pulp of the old one is re¬ moved ) the old tooth itself is next attacked, and the crown, being undermined by the absorption of the inner surface of its base, may be broken off by a slight external force, wdien the point of the new tooth is exposed.
The new tooth disembarrasses itself of the cylindrical base of its predecessor (fig. 81, a) with which it is sheathed, by maintaining the excitement of the absorbent process so long as the cement of the old fang retains any vital connection wdth the periosteum of the socket ; but the frail remains of the old cylinder, thus reduced, are sometimes lifted out of the socket upon the crown of the new tooth (as in fig. 81, a), when they are speedily removed by the action of the javTs. This is, how¬ ever, the only part of the process wdiich is immediately pro¬ duced by violence ; an attentive observation of the more important previous stages of growth, teaches that the pressure of the growing tooth operates upon the one to be displaced only through the medium of the vital absorbent action wdiich it has excited.
No sooner has the young tooth (fig. 80, b) penetrated the interior of the old one (fig. 80, a) than another germ c, begins to be developed from the angle between the base of the young tooth and the inner alveolar process ; or in the same relative position as that in which its predecessor began to rise, and the processes of succession and displacement are carried on
CROCODILIA 277
uninterruptedly throughout the long life of these cold-blooded carnivorous reptiles.
1 rom the period of exclusion from the egg, the teeth of the crocodile succeed each other in the vertical direction ; none are added from behind forwards like the true molars in Mam¬ malia. It follows, therefore, that the number of the teeth of the crocodile is as great when it first sees the light as when it has acquired its lull size ; and, owing to the rapidity of their succession, the cavity at the base of the fully-formed tooth is never consolidated.
The fossil jaws of the extinct Crocodilians demonstrate that the same law regulated the succession of the teeth at the ancient epochs when those highly-organised reptiles prevailed in greatest numbers, and under the most varied generic and specific modifications, as at the present period, when they are reduced to a single family composed of so few and slightly varied species as to have constituted in the system of Linnaeus a small fraction of the genus Laccrta.
The large, thick, externally ridged or pitted scales, though common to the Crocodilian order, are not peculiar to them. The labyrinthodont Anisopus* the thecodont Staganolepis, the lacertian Saurillus, have left similar petrified scales.
Crocodilians with cup-and-ball vertebrae, like those of living species, first make their appearance in the greensand of North America (Grocodilus basijissus and C. basitruncatusY In Europe their remains are first found in the tertiary strata. Such remains from the plastic clay of Meudon have been referred to G. isorhynchus, G. ccelorhynchus, G. Becquereli. In the calcaire grossier of Argenton and Castelnaudry have been found the C. Rallinati and G. Dodunii. In the coeval eocene London clay at Sheppy Island the entire skull and charac¬ teristic parts of the skeleton of G. toliapicus and G. Champ-
* “ Labyrinth odon scutulatus,” Trans. Geol. Soc , 2d series, vol. ri. p. 53S, pl. 46.
278
PALAEONTOLOGY
su'ides occur. In the somewhat later eocene beds at Brackles- ham occur the remains of the gavial-like G. Dixoni. In the Hordle beds liave been found the C. Hastingsice, with short and broad jaws ; and also a true alligator (G. Hantoniensis). It is remarkable that forms of procoelian Crocodilia, now geo¬ graphically restricted — the gavial to Asia, and the alligator to America — should have been associated with true crocodiles, and represented by species which lived, during nearly the same geological period, in rivers flowing over what now forms the south coast of England.
Many species of procoelian Crocodilia have been founded on fossils from miocene and pliocene tertiaries. One of these, of the gavial sub-genus (G. crassidens ), from the Sewalik tertiary, was of gigantic dimensions.
Order X. — Lacertilia.
( Lizards , Monitors, Ic/uance.)
Ghar. — -Vertebrae procoelian, with a single transverse process on each side, and with single-headed ribs ; sacral verte¬ brae not exceeding two : two external nostrils ; a foramen parietale in most.
Small vertebrae of the lacertian type have been found in the Wealden of Sussex. They are more abundant, and are associated with other characteristic parts of the species, in the cretaceous strata. On such evidence have been based the Raphiosaurus subulidens, the Goniasaurus crassidens , and the DolicJwsaurus longicollis * The last-named species is remark¬ able for the length and slenderness of its trunk and neck, indicative of a tendency to the ophidian form. But the most remarkable and extreme modification of the lacertian type in the cretaceous period is that manifested by the huge species, of which a cranium five feet long was discovered in the upper
* Owen, “ History of British Fossil Reptiles,” 4to, pp. 173-183, pis. 2, 8, 9.
QPHIDIA
279
chalk of St. Peter’s Mount, near Maestricht, in 1780. The vertebrae are gently concave in front, and convex behind ; there are thirty-four between the head and the base of the tail ; a sacrum seems to have been wanting. The caudal vertebrae have long neural and haemal spines, both of which arches coalesce with the centrum, and formed the basis of a powerful swimming tail. The teeth are anchylosed to emi¬ nences along the alveolar border of the jaw, according to the acrodont type. There is a row of small teeth on each pterygoid bone. For this genus of huge marine lizard the name Mosa- saurus has been proposed. Besides the M. Hofmanni of Maestricht, there is a M. Maximilliani, from the cretaceous beds of North America, and a smaller species, M. gracilis, from the chalk of Sussex.* The Leiodon anceps of the Norfolk chalk was a nearly allied marine Lacertian.f
Small pleurodont lizards, known at present only by jaws and teeth, with associated pitted scutes, but which may have had procoelian vertebrae, have been discovered in Purbeck beds, and have been referred to the genera Saurillus, Macel- lodus, etc.J Many small terrestrial Lacertians have left their remains in European tertiary formations.
Order XI. — Ophidia.
[Slow -worms, Serpents.)
Char. — Vertebra3 very numerous, procoelian, with a single transverse process on each side ; no sacrum ; no visible limbs.
The order Ophidia, as it is characterized in the system of Cuvier, requires to be divided into two sections, according to the nature of the food, and the consequent modification of the jaws and teeth. Certain species, which subsist on worms,
* Op. cit, p. 185, pis. 1, 2, 9. t Op. cit., p. 195, pi. 10.
I Quart. Journ, Geol. Soc., No. 40, 1854, p. 420.
280
PALAEONTOLOGY
insects, and other small invertebrate animals, have the tym¬ panic pedicle of the lower jaw immediately and immoveably articulated to the walls of the cranium. The lateral branches of the lower jaw are fixed together at the symphysis, and are opposed by the nsnal vertical movement to a similarly com¬ plete maxillary arch above ; these belong to the genera A m- pMsbcena and Anguis of Linnaeus, the latter represented by our common slow-worm. The rest of the Ophidians, including the ordinary serpents and constrictors, which form the typical members, and by far the greatest proportion, of the order, prey upon living animals of frequently much greater diameter than their own ; and the maxillary apparatus is conformably and peculiarly modified to permit of the requisite distension of the soft parts surrounding the mouth, and the transmission of their prey to the digestive cavity.
The earliest evidence of an ophidian reptile has been obtained from the eocene clay at Sheppy ; it consists of ver¬ tebrae indicating a serpent of 12 feet in length, the Palceophis toliapicus. Still larger, more numerous, and better preserved vertebrae have been obtained from the eocene beds at Brackles- ham, on which the Palceophis typhceus and P. porcatus have been founded.* These remains indicate a boa-constrictor-like snake, of about 20 feet in length. Ophidian vertebrae of much smaller size, from the newer eocene at Hordwell, support the species called Paleryx rhomlnfer and P. depressus ,f Fossil verte¬ brae from a tertiary formation near Salonica have been referred to a serpent, probably poisonous, under the name of Laophis.\ A species of true viper has been discovered in the miocene deposits at Sansans, South of France. Three fossil Ophidians from the CEningen slate have been referred to Coluber arenatus, C. K argii, and C. Oicenii.
* History of British Fossil Reptiles, pp. 139-149, pis. 2 and 3. t Op. cit., p. 149, pi. 2, figs. 29-32.
t “Quarterly Journal of the Geological Society,” vol. xiii , p. 196, pi. iv.
CHELONIA
281
Order XII. — Chelonia.
( Tortoises and Turtles.)
Char. Trunk-ribs broad, flat, suturally united, forming with vertebras and sternum an expanded thoracic abdominal case, into which, as into a portable chamber, the head, tail, and limbs can, usually, be withdrawn. No teeth : external nostril single.
Eefeience has already been made to the impressions in sandstones of triassic age in Dumfriesshire, referred by Dr. Duncan to tortoises. These impressions have been finely illustrated in the great work by Sir William Jardine on the footprints at Corncockle Muir. The earliest proof of chelonian life which the writer has obtained has been afforded by the skull of the Chelone planiceps, from the Portland stone ; and by the carapace and plastron of the extinct and singularly- modified emydian genera Tretosternon and Pleurosternon* (fig. 82). In the first genus the plastron retains the central vacuity , in the second genus an additional pair of bones is interposed between the hyosternals ( hs ) and hyposternals (ps). In the specimen figured (fig. 82), the plastron, and the under surface of the marginal pieces (2 to 12) of the carapace, of Pleurosternon emarginatum are shown. This fine Chelonite is now in the British Museum.
True marine turtles ( Chelone Camperi, C. obovata, C. pulchriceps ) have left their remains in cretaceous heds.f The emydian Protemys is from the greensand near Maidstone. J The eocene tertiary deposits of Britain yield rich evidences of marine, estuary, and fresh-water tortoises. More species of true turtle have left their remains in the London clay at the mouth of the Thames than are now known to exist in the
* Monograph of the Fossil Chelonian Reptiles of the Wealden and Purbeck Limestones, 4to, 1853, Palseontographical Society.
f Owen, “Hist. Brit. Fossil Reptiles,” pp. 155-1(38, pis. 41-46. f Op. cit., p. 1 69, pi. 47.
2S2
PALAEONTOLOGY
whole world ; and all the eocene Chelones are extinct. One of them ( G . gigas, Ow.) attained unusual dimensions ; the skull, now in the British Museum, measures upwards of a foot across its hack part * The estuary genus Trionyx (soft
Fig. 8'2.
Pleurosternon emarginatum (Purbeck).
turtle) is represented by many beautiful species in the upper eocene at Ilordwell ;f the fresh-water genera Emys and Platcmys by as many species, both at Sheppy and Hordwell. In the pliocene of CEningen remains of a species of Chelydra have been discovered ; this generic form is now confined to America.
* The upper end of the femur from Sheppy, in t. xxix. of Monograph of Fossil lieptilia of the London Clay, Falfeontographical Society, 1850, belongs to this species.. See also “ Hist, of Brit. Foss. Reptiles,” pp. 10-40, pis. 1-22. f Op. cit., pp. 50-60, pis. 26-33.
REPTILIA
283
Remains of land-tortoises (. Testudo , Brong.) indicate several extinct species in the ndocene and pliocene formations of continental Europe. Strata of like age in the Sewalik Hills have revealed the carapace of a tortoise 20 feet in length ; it is called by its discoverers, Cautley and Falconer, Colossochelys atlas. The same locality has also afforded the interesting- evidence of a species of Emys (E. tectum, Gray) having con¬ tinued to exist from the (probably miocene) period of the Sivatherium to the present day.
Order XIII. — Batrachia.
[Toads, Frogs , Newts.)
Char. Vertebrae biconcave (Siren), procoelian (Ram), or opisthocoelian (Piym) : pleurapophyses short, straight. Tv o occiiiital condyles ; two vomerine bones, in most dentigerous : no scales or scutes. Lame with gills, in most deciduous.
It is only in tertiary and post-tertiary strata that extinct species, referable to still existing genera or families of this order, have been found. The reptiles with amphibian or batrachian characters, of the carboniferous and triassic periods, combined those characters with others which gave them dis¬ tinctions of ordinal value they illustrated, indeed, rather a retention of the more general cold-blooded vertebrate type, with concomitant piscine and saurian features, than any near- affinity with the more specially modified naked or soft-skinned reptiles to which the name Batrachia is given in zoological catalogues of existing species.
Of the tailless or “anourous” Batrachia, toads of extinct species (. Palceophrynos Gessneri and P. clissimilis ) have been discovered in the (Eningen beds ; and frogs, more abundantly, in both miocene and pliocene deposits of France and Germany. The batracholites from the tertiary lignites of the “ Siebenge-
284
PALAEONTOLOGY
birge,” near Bonn, show different stages of transformation of the Rana diluviana, Gdf. Tertiary shales from Bombay have made known to the author the small fossil Rana pusilla.
Of the salamander family, the most noted fossil is that which was referred, when first discovered at (Eningen in 1726, to the human species, as Homo diluvii testis. Cuvier demon¬ strated its near affinities to the water-salamander (Menopoma) of the United States : more recently a living species of sala¬ mander has been discovered in Japan which equals in size the fossil in question — Andrias Scheuchzeri.
A retrospect of the foregoing outline of the paleontology of the class of reptiles shows that, unlike that of fishes, it is now on the wane ; and that the period when Reptilia flourished under the greatest diversity of forms, with the highest grade of structure, and of the most colossal size, is the mezozoic. The progress of air-breathing vertebrates, graduating by close transitional steps from the water-breathing class, has been checked, as if it had been unequal to the exigencies and life- capacities of the present state of the planet, Reptiles have been superseded by air-breathers of higher types, which cannot be directly derived from the class of fishes. A more general¬ ized vertebrate structure is illustrated, in the extinct reptiles, by the affinities to ganoid fishes shown by the Ganocephala, Ldbyrinthodontia , and Ichthyopterygia ; by the affinities of the Pterosauria to birds, and by the approximation of the Dino- sauria to Mammals. It is manifested by the combination of modern crocodilian, chelonian, and lacertian characters in the Cryptodontia and Dicynodontia ; and by the combined croco¬ dilian and lacertian characters in the Thecodontia and Saurop- terygia. Even the Chelonia of the Purbeck period illustrate the same principle, by the more typical number of modified hiemapophyses, or abdominal ribs, entering into the composition of their plastron.
REPTILIA
285
The diagram (fig. 83) gives a concise view of the geological re¬ lations, or distri¬ bution in time, of the principal groups of the class Reptilia. In the column opposite the right hand, the
dark mark shows '-s
a,
that the ganoce- d-; phalous group re- presented by the -S Archegosaurus be- rg gan, culminated, -s and ended in 5 the carboniferous period. The Lahy- "o rinthodonts, cul- ^ minating in the ^ trias, disappear at ^ the base of the oolitic system. Of the true Batra- chia, those retain¬ ing the tail appear to have been at their maximum during the upper tertiary period, and to have begun to decline after
CO
CO
fcb
K
280
PALAEONTOLOGY
that time ; whilst the tailless genera and species are most numerous and various at the present day. The Ophidia resemble the Anoura, commencing in the older tertiary, and showing their maximum of development at the present day. The true procoelian, and especially the pleurodont, lizards, commencing a little earlier in the chalk, have also gone on increasing in number and variety of forms to the present day. The acrodont group was represented by Mosasaurus, with a maximum of size, during the cretaceous period. The Theco¬ donts have but the partial relationship to modern Lacertilia which the Labyrinthodonts bear to the modern Batrcicliia. The great ordinal groups of Ichthyo - and Sauro-ypterygia, of Pterosauria, and Dinosauria, together with the amphi- and opistho-coelian Crocodilia, passed away ere the tertiary time had dawned. The procoelian crocodiles which culminated in the lower and middle tertiary times, are now on the wane. Perhaps, also, the same might be said of the Clielonia, in regard to the size of individuals and the number of species of certain genera ( 'e.g . Ghclone, Trionyx, Chelydra).
Class III.— AYES.
Long before any evidence of birds from actual or recog¬ nizable fossil remains is obtained in tracing the progress of life from the oldest fossiliferous deposits upwards, we meet with indications of their existence impressed in sandstones of the t.riassic or liassic period.
These earliest evidences of the class are by footprints in some former tidal shore, preserved in one or other of the ways explained in the section “ Ichnology.” The fossil bones of birds have not been found save in strata of much later date than the impressed sandstones ; and they are much more rare than the remains of mammals, reptiles, and fishes, in any formations except the most recent in certain limited localities, — e.g.. New Zealand.
Sir C. Lyell has well remarked, that “ the powers of flight possessed by most birds would insure them against perishing b} numerous casualties to which quadrupeds are exposed during floods.” The same writer further argues, that “ if they chance to be drowned, or to die when swimming on water, it will scarcely ever happen that they will be submerged so as to become preserved in sedimentary deposits.”* It is true that the carcase of a floating bird may not sink where it has died, but be carried far along the stream ; ultimately, however, if not devoured, its bones will subside when the soft parts have rotted, and both the compactness of the osseous tissue, and the facts made known by the ornitholites of the greensand near Cambridge, of the London clay at Sheppy, and of the Montmartre eocene quarry-stone, show that they can be pre¬ served in the fossil state. The length of time during which the carcase of a bird may float, doubtless exposes it the more to be devoured, and so tends to make more scarce the fossil remains of birds in sedimentary strata. Certain it is that the major part of the remains of extinct birds that have as yet been found are those of birds that were deprived of the power of flight, and were organized to live on land.1
The existence of birds at the triassic period in geology, or at the time of the formation of sandstones which are certainly intermediate between the lias and the coal, is indicated by abundant evidences of footprints impressed upon those sand¬ stones which extend through a great part of the valley of the Connecticut Liver, in Connecticut and Massachusetts, North America.
The footprints of birds are peculiar, and more readily dis¬ tinguishable than those of most other animals. Birds tread on the toes only ; these are articulated to a single metatarsal bone at right angles equally to it, and they diverge more from each other, and are less connected with each other, than in
* Principles of Geology, ed. 1847, p. 721.
288
PALEONTOLOGY
other animals, except as regards the web-footed order of birds.
Not more than three toes are directed forward ;* the fourth when it exists, is directed backward, is shorter, usually rises higher from the metatarsal, and takes less share in sustaining the superincumbent weight. No two toes of the same foot in any bird have the same number of joints. There is a constant numerical progression in the number of phalanges (toe-joints), from the innermost to the outermost toe. When the back toe exists, it is the innermost of the four toes, and it has two phalanges, the next has three, the third or middle of the front toes has four, and the outermost has five phalanges. When the back toe is wanting, as in some waders, and most wingless birds, the toes have three, four, and five phalanges respectively. When the number of toes is reduced to two, as in the ostrich, their phalanges are respectively four and five in number ; thus showing those toes to answer to the two outermost toes in tridactyle and tetradactyle birds.
The same numerical progression characterizes the two phalanges in most lizards from the innermost to the fourth ; but a fifth toe exists in them which has one phalanx less than the fourth toe. It is the fifth toe which is wanting in every bird. In some Gallinacea, one or two ( Pavo bicalcaratus ) spurs are superadded to the metatarsus ; but this peculiar weapon is not the stunted homologue of a toe. Dr. Deane of Green¬ field, United States, noticed, in 1835, impressions resembling the feet of birds in some slabs of sandstone from Connecticut River, arid first, in a letter to Dr. Hitchcock, dated March 7, 1835, recorded his belief that they were the footsteps of a bird. He prepared casts of the impressions, some of which he trans¬ mitted, with his opinion of their nature, to Professor Silliman, Editor of the “American Journal of Science,” in April 1835. Dr. Hitchcock, President of Amherst College, United States, first
* Save in the Swift.
AVES
289
made public the fact, based on scientific. comparison, and sub¬ mitted to the geological world his interpretations of those impressions as having been produced by the feet of living- birds, and he gave them the name of OrnitMchnites.
It was a startling announcement, and a conclusion that must have had strong evidence to support it, since one of the lands of the tracks had been made by a pair of feet, each leaving a print 20 inches in length. Under the term Orni- thichniles giganteus, however, Dr. Hitchcock did not shrink from proclaiming the fact of the existence, during the period of the deposition of the red sandstones of the valley of the Connecticut, of a bird which must have been at least four times larger than the ostrich* The impressions succeeded each other at regular intervals ; they were of two kinds, but differing only as a right and left foot, and alternating with each other, the left toot a little to the left, and the right foot a little to the right, of the mid-line between a series of tracks. Each footprint (fig. 84, b and r) exhibits three toes, diverging as they extend forwards. The distance between the tips of the inside and outside toes of the same foot was 1 2 inches. Each toe was terminated by a short strong claw projecting from the mid toe a little on the inner side of its axis, from the other two toes a little on the outer side of theirs. The end of the metatarsal bone to which those toes were articulated rested on a two-lobed cushion which sloped upwards behind. The inner toe (rj showed distinctly two phalangeal divisions, the middle toe three, the outer toe (b'j four. And since, in living birds, the penultimate and ungual phalanges usually leave only a single impression, the inference was just, that the toes of this large foot had been characterized by the same progressively-increasing number of phalanges, from the inner to the outer one, as in birds. And, as in birds also, the toe with the greatest number of joints Avas not the longest ; it
* American Journal of Science for 1836, vol. xxix., pi. i.
U
290
PALAEONTOLOGY
measured, e.g., 12| inches, the middle toe from the same base¬ line measured 16 inches, the outer toe 12 inches. Some of the impressions of this huge tridactylous footstep were so well preserved as to demonstrate the papillose and striated charactei of the integument covering the cushions on the under side of the foot. Such a structure is very similar to that in the ostrich. The average extent of stride, as shown by the distance between the impressions, was between three and four feet ; the same limb was therefore carried out each step from six to seven feet forward in the ordinary rate of progression.
These footprints, although the largest that have been ob¬ served on the Connecticut sandstones, are the most numerous. The gigantic Brontozoum, as Principal Hitchcock proposes to term the species, “must have been,” he writes, “ the giant rulers of the valley. Their gregarious character appears from the fact, that at some localities we find parallel rows of tracks a few feet distance from one another.”
The strata of red sandstone, with the above-described im¬ pressions, occupy an area more than 150 miles hi length, and from 5 to 10 miles in breadth. “ Having examined this series of rocks in many places, I feel satisfied that they were formed in shallow water, and for the most part near the shore ; and that some of the beds were from time to time raised above the level of the water and laid dry, while a newer series, composed of similar sediment, was forming.” “The tracks have been found in more than twenty places, scattered through an extent of nearly 80 miles from N. to S., and they are repeated through a succession of beds attaining at some points a thickness of more than 1000 feet, which may have been thousands of years in forming.”*
One of the evidences of birds from the Cambridge green¬ sand, transmitted to the writer by their discoverer, Mr. Barret, is the lower half of the trifid metatarsal, showing the outer toe-
* Lyell, Manual of Elementary Geology, 8vo, 1855, p. 343.
AVES
291
joint much higher than the other two, and projecting backwards above the middle joint ; it indicates a bird about the size of a woodcock.
In the conglomerate and plastic clay at the base of the eocene tertiary system at Mendon, near Paris, the leg and thigh bones (tibia and femur) of a bird ( Gcistornis Parisiensis ) have been discovered : they indicate a genus now extinct. They belonged to a species as large as an ostrich, but more robust, and with affinities to wading and aquatic birds.*
In the eocene clay of Sheppy, fossil remains of birds have been found, indicating a small vulture (Lithornis vulturinus ) ; also a bird, probably of the king-fisher family (Haley or nis toliapicus), and a species of the sea-gull family. In the same formation at Higligate, remains of a species of the heron family have been found.
The fossil bones of birds from the gypsum quarries at Montmartre were referred or approximated by Cuvier to eleven distinct species. Good ornitholites have been obtained from the Hordwell fresh-water deposits.
The most ancient example of a passerine bird is the Pro- tornis Glarisiensis, founded on an almost entire skeleton dis¬ covered in the schistose rock of Glaris, referable to the older division of the eocene tertiary series. This skeleton is about the size of a lark, and in some respects similar to that bird.
Comparisons of the ornitholites of the eocene tertiaries show that the following ordinal modifications of the class of birds were at that period represented : the raptorial, or birds of prey, by species of the size of our ospreys, buzzards, and smaller falcons, and most probably also by an owl ; the insessorial, or tree-perching birds, by species seemingly allied to the nuthatch and the lark ; the scansorials or anisodactyles, by species as
* Hebert, “Comptes Rendus de 1’Acad. des Sciences,” 1855. Owen “On the Affinities of Gastornis Parisiensis,” Quarterly Journal of Geological Society, vol. xii., 1856, p. 204.
292
PALAEONTOLOGY
large as tlie cuckoo and king-fisher ; the rasorials, by a species of small quail ; the cursorials, by a species as large as, hut with thicker legs than, an ostrich ; the grallatorial, by a curlew of the size of the ibis, and by species allied to Scolopctx, T ring a, and Pelidnct, of the size of our woodcocks, lapwings, and sand- erlings ; and the natatorial, by species allied to the cormorant, hut one of them of larger size, though less than a pelican ; also by a species akin to the divers ( Merganser ).
The remains of birds become more abundant and varied as we approach the present tune ; especially in the miocene strata, so richly developed in France, although wanting in Britain. One of the most singularly-modified forms of beak is shown by the flamingo. The fossil skull of a species of this genus ( Phcenicopterus ) has been found in the miocene fresh-water deposits of the plateau of Gergovia, near Clermonte-Ferrand ; the entire metatarsal bone of a species of eagle ( Aquila ) or os¬ prey ( Pandion ) in the same deposits at Chaptusal, Allier ; and the humerus of a bird allied to and as large as the albatross, in the molasse coqtoilliere marine, at Armagne. Remains of a vulture, most probably a Cathartes, have been found in the miocene lacustrine deposits of Cantal. Indications of all the other orders of birds, save the great Cursores or Struthionidce, have also been discovered in miocene strata — those of wading birds being the most numerous.
Fossil eggs of birds occur in miocene deposits in Auvergne ; and impressions of feathers have been discovered in the pliocene calcareous marls at Montebolca. In pliocene brick-earth de¬ posits in Essex has been found a fossil metatarsal of a swan, as large as, and not distinguishable from, the existing wild swan ; in the pleistocene clay at Lawford a fossil humerus like that of a wild goose. But most of the ornitliolites of this recent tertiary period have been discovered in ossiferous caverns. They belong to birds closely resembling the falcon, wood-pigeon, lark, thrush, teal, and a small wader. The writer
AVES
293
has received information of skeletons of birds found deeply imbedded in stratified clay at Aberdeen afid Peterhead.
The most extraordinary additions to the present class have been obtained from the superficial deposits, turbaries, and caves in New Zealand *
This island is re¬ markable for the absence of abori¬ ginal species of land - mammals, and for the pre¬ sence of a small bird with very ru- climental wings, and the keel-less sternum and loose plumage of the Struthious order, but of a peculiar genus called Ap¬ teryx : the legs are very robust, and have three front toes and a very small back toe. Birds re¬ sembling the Apteryx in the shape of the sternum and bony structure of the pelvis and hind limbs, some retaining also the small back toe, others apparently without it, formerly existed in New Zealand
51 These remains are described in eight memoirs by the writer, published in the third and fourth volumes of the Transactions of the Zoological Society of London. The description of the first fragment of the bone, indicative of the Dinornis, is in vol. iii., p. 39, pi. 3.
Fig. 84.
A . Dinornis elephuntopus .
B. Leg-bones of Dinornis giganteus.
b, r. Impressions called Ornithichnites.
294
PALEONTOLOGY
under different specific forms ranging in height from 3 feet to 10 feet. They have been referred by the writer to the genera Dinornis and Palapteryx. The gigantic species are interesting, as exhibiting birds equal to the formation of tridac- tyle impressions as large as those of the Connecticut sandstones, called Ornithichnites ( Brontozoum ) gigcis (fig. 84, r, 5). In this cut is given a figure of the leg-bones of Dinornis giganteus (71), in which the tibia (i) measures upwards of a yard in length. In the entire skeleton (M) of another species, the metatarsus is as thick, but only half as long, as in the D. giganteus ; the frame¬ work of the leg is the most massive of any in the class of birds ; the toe-bones almost rival those of the elephant ; whence the name Dinornis depliantopus, given to this species. Several other species of these extinct tridactyle Avingless birds have been de¬ termined — e. g., Dinornis ingens, D. struthio'ides, D. rheidcs, D. dromioides, D. casuarinus, D. robustns, D. crassus , D. geranoides, D. curtus. With these remains have been found bones of a bird the size of a swan, but of an extinct genus (Aptornis) ; also those of a large coot ( Kotornis Mantelli ) which, founded origi¬ nally on fossil remains, was afterwards discovered living in the Middle Island of New Zealand. Two species of Apteryx, not distinguishable from the existing kinds, were contemporaries with the gigantic Dinornis, and the writer has received evi¬ dence that the D. depliantopus afforded food to the natives at probably no very remote period. Some of the smaller kinds of Dinornis may yet be found living on the Middle Island.
In Madagascar portions of metatarsal bones, indicating a three-toed bird ( Epiornis ) as large as, but generically distinct from, the Dinornis giganteus, have been discovered in alluvial banks of streams ; and with them entire eggs, measuring from 13 to 14 inches in long diameter. The contents of one of these eggs is computed to equal those of six ostrich eggs, or of one hundred and forty-eight hen’s eggs.
In the neighbouring island of Mauritius the dodo ( Didus
MAMMALIA
295
ineptus) lias been exterminated by man within the period of two centuries ; and in the islands of Bourbon and Rodriguez the “ solitaire” ( Pezophaps ) has also become extinct. Both these birds had wings too short for flight.
Class IV.— MAMMALIA.
( Warm-blooded , Air-breathing , Viviparous Vertebrates .)
Every calcified part of an animal, whether coral, shell, crust, tooth, or bone, can preserve its form and structure when buried in the earth during the changes there gradually operated in it, until every original particle may have been removed and replaced by some other mineral substance previously dissolved in the water percolating the bed containing the fossil. A bone, or other part so altered, is said to be “ petrified.” Not only are all its outward characters preserved, but even the minutest structure may be, and in most cases is, demonstrable in the fine sections under the microscope.
Fossil bones and teeth have been discovered in every intermediate stage of alteration, from their recent state to that of complete petrifaction. Recent bones consist of a soft — com¬ monly called animal or organic — basis, hardened by earthy salts, chiefly phosphate of lime* Fishes have the smallest proportion, birds the largest proportion, of the earthy matter in their bones. The soft part is chiefly a gelatinous substance.
Proportions of Hard and Soft Matter in the Bones of the
Vertebrate Animals.
FISHES.
|
Salmon. |
Carp. |
Cod. |
|
|
Soft . |
. 60-62 |
40-40 |
34-30 |
|
Hard . |
. 39-38 |
59-60 |
65-70 |
|
100-00 |
100-00 |
100-00 |
* That this combination of phosphorus and calcium has ever taken place in nature, save under the influences of a living organism, remains to he proved.
296
PALAEONTOLOGY
REPTILES.
|
Soft . Hard . |
frog. . 35-50 . G4-50 |
Snake. 31-04 69-96 |
Lizard. 46-67 53-33 |
|
100-00 |
100-00 |
100-00 |
|
|
Soft . Hard . |
MAMMALS. Porpoise. Ox. . 35-90 31-00 . 64-10 69-00 |
Lion. 27-70 72-30 |
Man. 31-03 68-97 |
|
100-00 100-00 |
100-00 |
100-00 |
|
|
Soft . Hard . |
BIRDS. Goose. . 32-91 . 67-09 |
Turkey. 30-49 69-51 |
Hawk. 26-72 73-28 |
|
100-00 |
100-00 |
100-00 |
The chemical nature of the hardening particles, and of the soft basis of bone, is exemplified in the subjoined table, includ¬ ing a species of each of the four classes of Yertebrata : — -
Chemical Composition of Bones.
|
Ingredients. |
Hawk. |
Man. |
Tortoise. |
Cod. |
|
Phosphate of lime, with ) trace of fluate of lime ... j Carbonate of lime . Phosphate of magnesia . Sulphate, carbonate, and f chlorate of soda . j" Giutin and chondrin . Oil . |
64-39 7-03 0-94 0-92 27-73 0-99 |
59-63 7-33 1-32 0-69 29-70 1-33 |
52-66 12-53 0-82 0-90 31-75 1-34 |
57-29 4-90 2-40 1-10 32-31 2-00 |
|
100.00 |
100-00 |
100-00 |
100-00 |
dhe most common change which hones first undergo is the loss of more or less of their original soft and soluble basis, this effect of long interment is readily tested by applying the specimen to the tongue, when the affinity of the pores of the earthy constituent, after having lost the gelatine for fluid, is so great, that the specimen adheres to the tongue like a piece of dry chalk. Bones and teeth in this state quickly absorb a
MAMMALIA
297
solution of gelatine,, and thus their original tenacity may be restored * Petrified fossils need no such treatment ; they
are usually harder and more durable than the original hone itself.
Ihe interpretation of such fossil remains requires a com¬ parison of them with the corresponding parts of animals now living, or of previously determined extinct species. In the case of the vertebrate animals, such comparison is limited to the osseous and dental systems. The interpretation of a vertebrate tossil, therefore, presupposes a knowledge of the various modi¬ fications of the skeleton and teeth of the existing vertebrate animals , and the more extensive and precise such knowledge may be, the more successful will be the efforts, and the more exact the conclusions, of the interpreter.
The determination of the remains of quadrupeds is beset, as Cuvier truly remarks, with more difficulties than that of other organic fossils. Shells are usually found entire, and with all the characters by which they may be compared with their analogues in the museums, or with figures in the illus¬ trated books, of naturalists. Fishes frequently present their skeleton or their scaly covering more or less entire, from which may be gathered the general form of their body, and frequently both the generic and specific characters which are derived from such internal or external hard parts. But the entire skeleton of a fossil quadruped is rarely found, and when it occurs, it gives little or no information as to the hair, the fur, or the colour of the species. Portions of the skeleton with the hones dislocated, or scattered pell-mell — detached bones and teeth, or their fragments merely — such are the conditions in which the petrified remains of the mammalian class most commonly present themselves in the strata in which they occur.
* The writer’s experience of this effect led him to suggest the application of a similar process to the long-buried ivory ornaments from the ruins of Nineveh in the British Museum ; it proved successful.
298
PALAEONTOLOGY
Prior to the time of Cuvier but little progress had been made in the interpretation of such fragmentary remains. The striking success which attended the application of the great comparative anatomist’s science to this previously neglected field of study, was referred by Cuvier to principles in the organization of animal bodies, which he termed the “ Correia- tion of Forms and Structures," and the “ Subordination of Organs” — principles which his clear-thinking biographer, M. Flourens* in common with most contemporary philosophers, has regarded as the most effective and successful instrument in the restoration of extinct animals. They will be exempli¬ fied in the course of the present section of tins work.
A terminal phalanx modified to fit a hoof may give, as Cuvier declared, the modifications of all the bones of the fore limb that relate to the absence of a rotation of the fore leg, and all the modifications of the jaw and skull that relate to the mastication of food by broad-crowned complex molars.
But there are certain associated structures for the coinci¬ dence of which the physiological law is unknown. “ I doubt,” writes Cuvier, “ whether I should have ever divined, if observa¬ tion had not taught it me, that the ruminant hoofed beasts should all have the cloven foot, and be the only beasts with horns on the frontal bone.”t We know as little why horns should be in one or two pairs on the frontal bone of those Ungulates only which have hoofs in one or two pairs ; whilst in the horned Ungulates with three hoofs, there should be either one horn, or two horns placed one behind the other in the middle line of the skull ; or why the Ungulates with one or three hoofs on the hind foot should have three trochanters on the femur, whilst those with two or four hoofs on the hind foot should have only two trochanters.
* Bloge Historique et 1’ Analyse Raison ti6e des Travaux de G. Cuvier, 12mo, Paris, 1841, p. 42.
f Ossemens Fossiles, 8vo, ed. 1834, tom. i., p. 184.
MARSUPIALIA
299
“ However,” continues Cuvier, “ since these relations are constant, they must have a sufficing cause ; hut as we are ignorant of it, we must supply the want of the theory by means of observation.* This, if adequately pursued, will serve to establish empirical laws almost as sure in their application as rational ones.” “ That there are secret reasons for all these relations, observation may convince us independently of general philosophy.” “ The constancy between such a form of such organ, and such another form of another organ, is not merely specific, but one of class, with a corresponding gradation in the development of the two organs.” t
“For example, the dentary system of non-ruminant Ungu¬ lates is generally more perfect than that of the Bisulcates ; inasmuch as the former have almost always both incisors and canines in the upper as well as the lower jaw ; the' structure of their feet is in general more complex, inasmuch as they have more digits, or hoofs less completely enveloping the phalanges, or more bones distinct in the metacarpus and metatarsus, or more numerous tarsal bones ; or a more distinct and better developed fibula ; or a concomitance of all these modifications. It is impossible to assign a reason for these relations ; but, in proof that it is not an affair of chance, we find that whenever a bisulcate animal shows in its dentition any tendency to approach the non-ruminant Ungulates, it also manifests a similar tendency in the conformation of its feet. Thus the camels, which have canines and two or four incisors in the upper jaw, have an additional bone in the tarsus, resulting from
* “Puisque ces rapports sont constants, il faut bien qu’ils aient une cause suffisante ; mais comme nous ne la connoissons pas, nous devons supplier au defaut de la th6orie par le rnoyen de l’observation.” (Tom. cit., p. 184.)
f “ En effet, quand on forme un tableau de ces rapports, on y remarque non- seulement. une Constance spticifique, si Ton peut s’exprimer ainsi, entre telle forme de tel organe, et telle autre forme d’un organe different ; mais Ton apei^oit aussi une Constance de classe et une gradation correspondante dans lcdeveloppe- ment de ces deux organes, qui montrent, presque aussi bien qu’un raisonne- ment efifectif, leur influence mutuelle.” (Tom. cit-., p. 185.)
300
PALEONTOLOGY
the scaphoid not being confluent with the cuboid ; and the small hoofs have correspondingly small phalanges. The musk- deer, which have long upper canines, have the fibula co-exten- sive with the tibia, whilst the other ruminants have a mere rudiment of fibula articulated to the lower end of the tibia.” " There is then a constant harmony between two organs to all appearance quite strangers to each other, and the gradations of their forms correspond uninterruptedly even in the cases where one can render no reason for such relations.” “ But in thus availing ourselves of the method of observation as a supple¬ mentary instrument when theory abandons us, we arrive at astonishing details. The smallest articular surface ( facette ) of a hone, the smallest process, presents a determinate character relating to the class, to the order, to the genus, and to the species to which they belong ; so that whoever possesses merely the well-preserved extremity of a hone, may, with applica¬ tion, aided by a little tact ( adresse ) in discerning analogies, and by sufficient comparison, determine all these things as surely as if he possessed the entire animal.” *
There have been, of course, instances, and will be, where for want of the “ efficacious comparison,” and the “ tact in dis¬ cerning likeness,” such results have not rewarded the endea¬ vours of the palaeontologist ; and these shortcomings, and the mistakes sometimes made, even by Cuvier himself, have been cast in the teeth of his disciples, as arguments against the principles by which they believed themselves guided in their endeavours to complete the glorious edifice of which their master laid the foundations.
The writer has, therefore, quoted from the well-known “Preliminary Discourse” to Cuvier’s great work on Fossil Remains, with a view to neutralize the efforts of statements reiterated in apparent ignorance of the clear and explicit man¬ ner in which Cuvier there defines the limits within which the
* Tom. cit., p. 187.
MARSUPIALIA
301
law of correlation of animal structures may be successfully applied, and indicates tlie instances in which— tlie physio¬ logical condition being unknown, and the coincident structures being understood empirically — careful observation and rigor¬ ous comparison must supply tlie place of the physiologically understood law.
Those who deny the existence of design in the construction of any part of an organized body, and who protest against the deduction of a purpose from the valves of the veins or the lens of the eye-ball, repudiate the reasoning which the palaeonto¬ logist carries out from the hoot to the grinder, or from the carnassial molar to the retractile claw, through the guidance of the principle of a pre-ordained mutual adaptation of such parts ; but such minds are not, nor have been, those who have contributed to the real advancement of physiology or palaeontology.
By reference to the “Table of Strata” (fig. l), it will be seen that the earliest evidence of a vertebrate animal is of the cold-blooded water-breathing class in the upper Silurian period. Next follows that of a cold-blooded but air-breath¬ ing vertebrate, under the batrachian grade, in the carbonifer¬ ous period. The warm-blooded air-breathing classes are first indicated, as birds, by footmarks in a sandstone of probably triassic but not older age ; and, as mammals, by fossil teeth from bone-beds of the upper triassic system in Wirtemberg, and of the same age near Frome, Somersetshire. Mam¬ malian remains have also been found in a coal-field in North Carolina, which may be earlier, but cannot be later, than the lias formation.
Genus Microlestes. — The mammalian teeth from German and English trias indicate a very small insectivorous quad¬ ruped, to which the above generic name was given by Professor Plieninger. The German specimens were discovered in 1847 in a bone breccia at Diegerloch, about two miles from Stutt-
302
PALAEONTOLOGY
gardt, the geological relations of which are well determined as between lias and Keuper sandstone. The teeth of Microlestes from Frome, submitted to the writer by the discoverer, Mr. Charles Moore, F.G.S., in 1858, are four in number, two being molars of the upper jaw, each with four fangs ; one a molar with a narrower crown and two fangs from the lower jaw ; and the fourth a small, pointed, front tooth. The crowns of the molars are short vertically in proportion to their breadth ; the distinct enamel contrasts with the cement-covered fangs ; the grinding surface shows a wide and shallow depression, sur¬ rounded by small, low, obtuse cusps, three of equal size being on one side, a larger cusp near one end, and smaller and less regular cusps on the side opposite the three. One lower molar shows a similar type, but with the three marginal cusps less equal in size : a second smaller, and from a more anterior part of the series has three low cusps on one side, and but one cusp on the other side of the crown, the grinding surface of which presents an elongate triangular form. This tooth had two fangs. The crown of the largest of the upper molars does not exceed one line in its longest diameter. Amongst existing Mammals, some of the small molars of the marsupial and insectivorous Myrmecobius of Australia offer the nearest resem¬ blance to these fossil teeth ; but a still closer one is presented by the small tubercular molars of the extinct oolitic Mammal called Plagiaulax (fig. 93, m, i and z).
Genus Dromatherium. — It would appear that the Mammal from the American triassic or liassic coal-bed ( Dromatherium sylvestre, Emmons) also found its nearest living analogue in Myrmecobius ; for each ramus of the lower jaw contained 10 small molars in a continuous series, 1 canine, and 3 conical incisors, the latter being divided by short intervals.
Genus Ampiiitiierium ( Thylacotherium , Yah)* — This genus
* For the full description and demonstration of the mammalian nature of this much-discussed fossil, see Owen, History of British Fossil Mammals, 8vo, p. 29.
MARSUPIAL I A
303
is founded upon a lew specimens ol lower jaw, one ramus of which (fig. 85) gave the entire dentition of its side,— viz., three small conical incisors (t), one rather larger canine (c), six pre- molais, unicuspid, with a small point at one or both sides of the base (p, 1-6), and six quinque-cuspid molars (m, i- 6) not departing very far from the type above described. The mo¬ lars, and most of the
Fig. 85.
Lower jaw and teeth of the Amphitherium Prevostii (twice nat. size.)
premolars, are implanted by two roots. The condyle of the jaw is convex, and is a little higher than the level of the teeth ; the coronoid process is broad and high ; the angle projects backward, with a feeble production inward. It is, again, to the marsupial Myrmecobius, amongst living forms, that the present genus is most nearly allied. The remains of Amphi¬ therium are from the lower oolitic slates of Stonesfield (fig. 87, stratum 8).
Genus Amphilestes* — This genus is founded on a ramus of the lower jaw, from the Stonesfield oolitic slate, showing true molars of a compressed form, with a large middle cusp and a smaller, but well marked, one at the fore and back part of its base ; the “ cingulum,” or basal ridge, peculiar to mammalian teeth, traverses the inner ridge of the crown, where it develops three small cusps, one at the base of the large outer or princi¬ pal cusp, and the other two forming the anterior and posterior ends of the crown. This form of tooth is unknown in existing Mammalia, but is as well, adapted for crushing the cases of coleopterous insects (elytra of which are found fossil in the same oolitic matrix) as are any of the multi-cuspid molars of small opossums, shrews, and bats. The Amphilestes Broderipii was somewhat larger than Amphitherium Prevostii.
* Owen, Hist. Brit. Foss. Main., p. 58, fig. 19 {Amphitherium Broderipii
304
PALAEONTOLOGY
Genus Phascolotherium. — Although the evidence of the very slight degree of inflection of the angular process of the lower jaw of AmphitheriuTn may favour its affinity to the placen¬ tal Insectivores, yet the range of variety to which that mandi¬ bular character is subject in the different genera of existing Marsupialia warns us against laying undue stress upon its feeble development in the extinct genus of the oolitic epoch, and incites us to look with redoubled interest at whatever other indications of a marsupial character may be present in the fossil remains of other genera and species of Mammalia that have been detected in the Stonesfield slate.
In the specimen of Phascolotherium (fig. 86) presented to the British Museum by William -T. Broderip, Esq., F.R.S., its
Fig 86.
Lower jaw and teeth of the Phascolotherium (nat. size in outline), Lower Oolite.
original describe!',* which is as perfect in regard to the dentition as the jaw of the Amphitherium above described, the marsupial characters are more strongly manifested in the general form of the jaw, and in the extent and position of the inflected angle, while the agreement with the genus Didelphys in the number of the premolar and molar teeth is complete. The forms of the crowns of those teeth differ from those in Didelphys, and correspond so closely with those in the Amphilestes Broderipii,
* Zoological Journal, vol. iii., p. 408, pi. xl., 1828.
MARSUPIALIA
305
as to show the closer affinity of the Pliascolothere with the latter oolitic Insectivora ; and, accordingly, whatever additional evidence of marsupiality is afforded by the Phascolotherium, may be regarded as strengthening the claims of both Amphi- lestes and Amphitherium to be admitted into the marsupial group. The general form and proportions of the coronoid process of the jaw of Phascolotherium resemble those in the zoophagous Marsupials ; and especially with that of the Thylacynus in regard to the depth and form of the entering notch between this process and the condyle.
The base of the inwardly-bent angle of the lower jaw pro¬ gressively increases in Didelpihys, Dasyurus, and Tliylacinus; and judging from the fractured surface of the corresponding part of the fossil, it 'most nearly resembles the jaw of Thyla- cinus. The condyle of the jaw is nearer the plane of the inferior margin of the ramus in the Tliylacine than in the Dasyures or opossums : and consequently, when the inflected angle is broken off, the curve of the line continued from the condyle along the lower margin of the jaw is least in the Tliylacine. In this particular, again, the Pliascolothere resem¬ bles that Australian Carnivore. In the position of the dental foramen, the Pliascolothere, like the Amphithere, differs from the zoophagous Marsupials and placental Carnivora and Insect¬ ivora, and resembles the Hypsiprymnus, a marsupial Herbivore, that orifice being near the vertical line dropped from the last molar tooth. In the direction of the line of the symphysis, the Pliascolothere resembles the Opossums more than the Dasyures or Thylacines. It is probable that the teeth at the fore part of the jaw showed the same correspondence. In the number of the molar series, the Phascolothere differs from Amphitherium, Amphilestes, and Myrmccoljius, and resembles the Thylacine and Opossum, but without having the premolars (p, i, 2, 3) distinguished, as in them, from the true molars (m, i, 2, 3, 4), by smaller and more simple crowns. As, however,
x
306
PALEONTOLOGY
these two kinds of teeth can only he determined by their order of development and succession, the Phascolothere may well have had three premolars and four true molars.
The difference between these teeth in the lower jaw of Didelphys is shown by the addition, in the true molars, of a pointed tubercle on the inner side of the middle cone. In Phascolotherium a mere basal ridge or cingulum extends along the inner side of the middle cone. Such a ridge is present in the last molar of Sarcophilus, but not in the other molars ; but in these there are two small hind cusps on the same transverse line, whilst that cusp appears to be single in Phascolotherium. The cingulum, moreover, in the second to the penultimate of the molar series of this fossil, extends so far as to form a small talon at the fore and back part of the crown ; thus making five points, which are very distinct in the third to the penultimate tooth inclusive ; and by this character the dentition of Phasco¬ lotherium differs materially from any existing Marsupial, and repeats the type of molar which, as yet, would seem to be peculiar to the Insectivora of the oolitic epoch. There is a feeble indication of this structure in the antepenultimate and penultimate molars of Tliylacinus, but the hinder division of the crown shows two small cusps on the same transverse line, besides the rudimental hindmost one ; and there is no cin¬ gulum. Upon the whole, it would seem that, though the affinity may not be close, Phascolotherium most resembles Tliylacinus amongst existing Mammals ; but Tliylacinus is now confined to Tasmania, and is there fast verging to extinction.
The resemblance shown by the lower jaw and its teeth of the Amphithere and Phascolothere to marsupial genera now confined to Australia and Tasmania, leads one to reflect on the interesting correspondence between other organic remains of the Oxfordshire oolite and other existing forms now confined to the Australian continent and surrounding sea. Here, for example, swims the Cestracion, or Port-Jackson shark, which
MARSUPIALIA
307
has given the key to the nature of the “ palates” from our oolites, now recognized as the teeth of congeneric larger forms of cartilaginous fishes.
Mr. Broderip, in his Memoir above quoted, observes, “that it may not be uninteresting to note that a recent species of Trigonia has very lately been discovered on the
coast of Australia, that land of marsupial animals. Our speci¬ men lies imbedded with a number of fossil shells of that genus.” Not only Trigonice but Terebra- tulce exist, and the latter abundantly, in the Australian seas, yielding food to the Cestracion, as their extinct analogues doubtless did to the allied Plagiostomes with crushing teeth, called A croclus, Psam- modus, etc. Arau-
Fig. 87.
{After Fitton.)
i. Rubbly limestone (cornbrash). z. Clay, with Terebratulites.
3. Limestone rock.
4. Blue clay.
5. Oolitic rock.
6. Stiff clay.
7. Oolitic rag, or limestone.
8. Sandy bed containing the Stonesfield slate.
car ice and cycadeous plants, like those found fossil in oolitic beds, flourish on the Australian continent, where marsupial quadrupeds now abound ; and thus appear to complete a picture of an ancient condition of the earth’s surface, which
308
PALEONTOLOGY
lias been superseded in our hemisphere by other strata and a higher type of mammalian organization. Fig. 87 repre¬ sents a section of the strata overlying the slates whence the fossil mammalian jaws, with associated Megalosaurs, Ptero- dactyles, and other oolitic organisms, have been obtained at Stonesfield in Oxfordshire. The vertical thickness of the strata through which the shaft is sunk to the gallery is 62 feet ; on the side opposite the right hand is marked the depth of the horizon¬ tal gallery, where the slate is dug which contains the fossils ; on the opposite side the strata are numbered in succession.
Genus Stereognathus. — The last evidence of a mamma¬ lian animal discovered in the Stonesfield slate is of peculiar interest, because it exhibits a type of grinding teeth quite dis¬ tinct from any of the previously acquired jaws from that lo¬ cality, and affords evidence of a small vegetable-feeding or omni¬ vorous quadruped. It consists of a portion of a lower jaw, im¬ bedded in the characteristic matrix (fig. 88), about 9 lines in extent, and containing three molar teeth (a, b, c). It is nearly straight ; the side exposed is convex vertically ; a slight bend downwards, and decrease of vertical diameter towards the end, indicates it to be part of a left ramus. This is unusually shal¬ low, broad or thick below, the side passing by a strong convex curve into the lower part ; a very narrow longitudinal ridge, continued after its subsidence by a few fine lines, forms a tract which divides the lateral from the under surface ; else¬ where the bone is smooth, without conspicuous vascular perforations. The depth or vertical diameter of the ramus is not more than two lines. Of the three teeth remaining in this portion of jaw, the middle one is the least mutilated. The
Stereognathus; portion of jaw, im¬ bedded in oolitic matrix (nat. size).
STEREOGNATHUS
309
crown of this tooth (fig. 89, B) is of a quadrate form, 3 milli¬ metres by 3 1 millimetres, of very little height, and supports six subequal cusps in three pairs, each pair being more closely comiected in the an- tero-posterior direction of the tooth than transversely.
The outer side of the crown (tig. 88, b), supported by a narrow fang which con¬ tracts as it sinks into the socket, shows two principal cusps or cones, and a small accessory basal cusp, hard and shining' enamel
Fig. 89.
The Stereognathus ; upper view of portion of jaw (nat. size), and magnified view of the middle tooth, B (Stonesfield
which covers these parts of Oolite).
the crown contrasts with the lighter cement that coats the root. The two outer lobes or cones are subcompressed, and placed obliquely on the crown, so that the hinder one (o', fig. 89) is a little overlapped externally by the front one o, the fore part of the base of the hinder one being prolonged inwards on the imier side of the base of the front cone. The two middle cones (h, i) are subcompressed laterally, with the fore part of their base a little broader than the back part. The two inner cones (p, p') have their inner surface convex, with their summits slightly inclined forwards. The fore part of the base of the hinder cone is prolonged obliquely towards the centre of the crown, beyond the contiguous end of the base of the front cone, so as to cause an arrangement like that of the two outer cones (o, o'), the obliquity of the posterior cone of both the outer and the inner pairs being such that they slightly converge as they extend forwards.
This type of tooth differs from that of all other known recent or extinct Mammals. The nearest approach to it is made by
310
PALAEONTOLOGY
the middle true molar of Pliolophus vulpiceps, a small extinct herbivorous Mammal from the London clay (fig. 96, m, 2).
Y That the fragment in question is the jaw of a Mammal is inferred from the implantation of the tooth by two or more roots. Most Mammals are known to have certain teeth so implanted. Such complex mode of implantation in bone has not been observed in any other class of animals. Why two or more roots of a tooth should be peculiar to viviparous quadrupeds, giving suck, is not precisely known. That a tooth, whether it be designed for grinding hard or cutting soft sub¬ stances, should do both the more effectually in the ratio of its firmer and more extended implantation, is intelligible. That a more perfect performance of a preliminary act of digestion should lie a necessary correlation, or be in harmony, with a more complete conversion of the food into chyle and, blood, — and that such more efficient type of the whole digestive ma¬ chinery should be correlated, and necessarily so, with the hot blood, quick-beating heart and quick-breathing lungs, with the higher instincts, and more vigorous and varied acts of a Mam¬ mal, as contrasted with a cold-blooded reptile or fish, — is also conceivable. To the extent to which such and the like reason¬ ing may be true, or in the direction of the secret cause of the constant relations of many-rooted teeth discovered by observa¬ tion, — to that extent will such relations ascend from the em¬ pirical to the rational category of laws. v The interest which the above-described fossil from the Stonesfield oolitic slate excites is not exclusively due to its antiquity, its uniqueness, or its peculiarity ; much is attached to its relations as a test in palaeontology of the actual value of a single tooth in the determination of other parts of the organ¬ ization of the animal. According to our opinion of these un¬ seen parts, we frame our expression of the nature and affinities, or of the place in the zoological system, of the extinct species. From the resemblance of the lower molars of Stereognathus to
STEREOGNATHUS
311
tliose of Pliolophus, which, though not close, is closer than to the teeth of any other known animal, it is probable that the Stereognathus was hoofed, and consequently herbivorous, or deriving the chief part of its subsistence from the vegetable kingdom. Cuvier has written, — “ La premiere chose k faire dans l'ctude d’un animal fossile est de reconnaitre la forme de ses dents molaires ; ou determine par la s’il est carnivore ou herbivore, et dans ce dernier cas, on peut s’assurer, jusqu’a un certain point de l’ordre d’lierbivores auquel il appartient.” * In the case in question the form of the molar teeth of one jaw is recognizable, hut the herbivority of the fossil is not thereby determined. AVe can only infer it to be more probable that the fossil was a Herbivore than an Insectivore or a mixed-feed¬ ing Carnivore.
Admitting the herbivority of the fossil, it is not certain that it was hoofed ; there is nothing in the form and structure of the tooth to prove that. Both form and structure are compatible with the bootless muticate type of herbivorous Mammal, as shown by the Manatee ; it is the small size of the Stereogna¬ thus which renders it less probable that it was a diminutive kind of Manatee, and more probable that it was a diminutive form of Ungulate. But seeing the manifold diversities of the multi-cuspid form of molar teeth in recent and extinct insec¬ tivorous unguiculate quadrupeds, it is not impossible but that the Stereognathus may have belonged to that order ; there is no known physiological law forbidding it.
The form of the cusps, and their regular symmetrical arrangement in the Stereognathus , as compared with the known modifications of multi-cuspid molars in certain small extinct forms of hoofed quadrupeds, constitute the grounds upon which an opinion is formed of its most probably belonging to the same section of Ungulata.
Then, is it not true, it may be asked, that by virtue oi
* Ossemens Fossiles, 4to, tom. iii., 1822, p. 1.
312
PALAEONTOLOGY
certain established laws of correlated structures, an extinct animal may be re-constructed from a single tooth or from a fragment of bone ? Is the Cuvierian basis, or what has been so regarded, of palaeontology unsound \ Not necessarily from aught that has been said or written on the subject of the Stereognathus. We do not know the comparative anatomy of the family of quadrupeds to which the Stereogna thus belonged. What we do know of its teeth suggests that that family may have had modifications of the skeleton so far different from those of any, the modifications of which are known, as to have constituted a type of, perhaps, a marsupial family ; but a type as well marked, and as distinct, as the type of skeleton which Cuvier inductively studied in the feline Carnivora (fig. 128), and in the ruminant Hcrbivora (fig. 129), and by which pre¬ liminary study he was enabled to enunciate that beautiful law of the “correlation of forms and structures” to which allusion has been already made, and which will be illustrated by exam¬ ples, and its mode of application pointed out, in another part of the present work.
, In certain instances of constant coincidences of structure, as demonstrated by comparative anatomy, the sufficient — i. e. recognizable, intelligible, or physiological — cause of them is not yet known. But, as Cuvier in reference to such instances truly remarks, “ Since these relations are constant, there certainly must be a sufficient cause for them.” * In certain other cases Cuvier believed that he could assign that “ sufficient cause,” and he selects, as such, the correlated structures in a feline Carnivore, and in a hoofed Herbivore. The physiological know¬ ledge displayed by him in his explanation of the condition of those correlations is most exact ; its application in the restora¬ tion of the Anoplotherium and P aloe other iuvi most exemplary.
In the ratio of the knowledge of the reason of the coinci¬ dences of animal structures — in other words, as those coinci- * Discoure sur les Revolutions de la Surface du Globe, 4to, 1826, p. 50.
STEREOGNATHUS
313
dences become “ correlations ” — is our faith in the soundness of the conclusions deduced from the application of such rational law of correlations ; and with the certainty of such application is associated a greater facility of its application. A knowledge of the physiological conditions governing the relations of the contents of the cavities of bones to the flight and other modes of locomotion in birds both enabled the writer to infer from one fragment of a skeleton that it belonged to a terrestrial bird deprived of the power of flight, and to predict that such a bird, but of less rapid course than the ostrich, would ultimately be found in New Zealand.*
This principle, however — those modes of thought — which Cuvier affirmed to have guided him in his interpretation of fossil remains, and which he believed to be a true due in such researches, were repudiated or contested by some of his contem¬ poraries.
Geoffroy St. Hilaire denied the existence of a design in the construction of any part of an organized body ; he protested against the deduction of a purpose from the contemplation of such structures as the valves of the veins or the converging lens of the eye.
Beyond the co-existence of such a form of flood-gate with such a course of the fluid, or of such a course of light with such a converging medium, Geoffroy affirmed that thought, at least his mode of thinking, could not sanely, or ought not to go.
The present is not the place for even the briefest summary of the arguments which have been adduced by teleologists and antiteleologists from Democritus and Plato down to Comte and Whewell. The writer would merely remark, that in the degree in which the reasoning faculty is developed on this planet and is exercised by our species, it appears to be a more healthy and normal condition of such faculty, — certainly one which has been productive of most accession to truths, as exemplified * Transactions of the Zoological Society, vol. iii., p. 32, pi. 3.
314
PALAEONTOLOGY
in tlie mental workings of an Aristotle, a Galen, a Harvey, and a Cuvier,— to admit the instinctive impression of a design or purpose in such structures as the valves of the vascular system and the dioptric mechanism of the eye. In regard to the few intellects, — they have ever been a small and unfruitful minority, — who do not receive that impression and will not admit the validity or existence of final causes in physiology, the writer has elsewhere expressed his belief that such intel¬ lects are not the higher and more normal examples, hut rather manifest some, perhaps congenital, defect of mind, allied or analogous to “ colour-blindness ” through defect of the optic nerve, or the inaudibleness of notes above a certain pitch through defect of the acoustic nerve.
The truth of a physiological knowledge of the condition of a correlated structure, and of the application of that know¬ ledge to palaeontology, is not affected by instances adduced from that much more extensive series of coincident structures of which the physiological condition is not yet known. Nor is the power of the application of the physiologically interpreted correlation the less certain because the merely empirically re¬ cognized coincidences have failed to restore, with the same certainty and to the same extent, an extinct form of animal.
Certain coincidences of form and structure in animal bodies are determined by observation. By the exercise of a higher faculty the reason, or a reason, of these coincidences is dis¬ covered, and they become correlations ; in other words, it is known not only that they do exist, hut how they are related to each other. In the case of coincidences of the latter land, or of “ correlations ” properly so called, the mind infers with greater certainty and confidence, in their application to a fossil, than in the case of coincidences which are held to he constant only because so many instances of them have been observed.
Because the application of the latter kind of coincidences is limited to the actual amount of observation at the period
SPALACOTHERIUM
315
of such, application, and because mistakes have been made through a miscalculation of the value of such amount, it has been argued that a rational law of the correlation of animal forms is inapplicable to the determination of a whole from a part ; * and it has not only been asserted that the results of such determination are unsound, but that the philosopher who believed himself guided by such law deceived himself and misconceived his own mental processes ! f But the true state of the case is, that the non-applicability of Cuvier’s law in certain cases is not due to its non-existence, but to the limited extent to which it is understood.
The consciousness of that limitation led the enunciator of the law to call the attention of palaeontologists expressly to the extent to which it could then be applied, as, for instance, to the determination of the class, but not the order ; or of the order, but not the family or genus, etc. ; and to caution them also as to the extent of the cases in which, the coincidences being only known empirically, he consequently enjoins the necessity of further observation, and of caution in their induc¬ tion. Cuvier expresses, however, his belief that such coin¬ cidences must have a sufficient cause, and that cause once discovered, they then become correlations and enter into the category of the higher law. Future comparative anatomists will have that great consummation in view, and its result, doubtlessly, will be the vindication of the full value of the law in the interpretation of fossil remains as defined by the illus¬ trious founder of palaeontology.
Genus Spalacotherium, Ow. — The next stratum overlying the older oolites in which mammalian remains have been detected, is a member of the newest oolitic series at Purbeck, Dorsetshire, called the “ marly ” or “ dirt-bed.” In a series of
* De Blainville, Osteographie, 4to, fasc. 1, 1839, p. 34. f Prof. Huxley, “ Lecture on Natural History,” etc., Royal Institution of Great Britain, Feb. 15, 1856.
316
PALAEONTOLOGY
fossils discovered there by Mr. W. E. Brodie, and transmitted for determination in 1854 to the writer, amongst the remains of fishes and small Saurians, constituting the majority of the specimens, were detected three unequivocal evidences of a mammalian species, which were described under the name of
Spalacotherium* tricuspidens. The specimen here selected (fig. 90) to exemplify the above extinct insectivorous
Spalacotherium tricuspidens (twice nat. Mammal, is a right raillUS of size), Purbeck beds. the lower jaw. The posterior
half contains four teeth, and extends backward beyond the dental series ; but instead of showing the compound structure which that part of the jaw exhibits in the lizard tribe, it con¬ tinues undivided ; the convex surface showing a smooth depression for the insertion of the temporal muscle ; the lower boundary answering to that going to the condyle and angle of the jaw, and the upper one to that going to the coronoid process in the ramus of the jaw of the mole and shrew. The crowns of the teeth are long, narrow, and tricuspid, the inner part of the crown being produced into a point both before and behind the longer cusp which forms the chief outer division of the crown. Each of these teeth is implanted by a fang divided externally into two roots, in a distinct socket in the substance of the jaw. The multicuspid crown, the divided root of the tooth, its complex implantation, and the undivided or simple structure of the ramus of the jaw, all concurred, therefore, to prove the mammalian nature of this fossil.
ihe other specimens showed that the Spalacotherium had ten molar teeth in each ramus of the lower jaw, preceded by a small canine and incisors. The anterior molars arc compressed, increase in height and thickness to the sixth, and from the seventh decrease in size to the hindmost, which seems to be
* From (T7raAai, a mole ; 9riplov, a beast.
Fig. 90.
TRICONODON
317
the last of the series. The sharp multicuspid character of so much of the dental series as is here preserved, repeats the general condition of the molar teeth of the small insectivorous Mammalia in a striking degree : one sees the same perfect adaptation for piercing and crushing the tough chitinous cases and elytra of insects. The particular modification of the pointed cusps, as to number, proportion, and relative position, resembles in some degree that of the Cape mole ( Ghrysochlora aurea), but both in these respects and in the number of molars, the dentition accords more closely with that of the extinct Ampkitherium. The chief interest in the discovery of the Spalacotherium is derived from its demonstration of the exis¬ tence of Mammalia about midway between the older oolitic and the oldest tertiary periods.
Both the Oxford oolitic slate and the Purbeck marly shell- beds give evidence of insect life ; in the latter formation abun¬ dantly. The association of these delicate Invertebrata with remains of plants allied to Zamia and Gycas, is indicative of the same close interdependency between the insect class and the vegetable kingdom, of which our power of surveying the phenomena of life on the present surface of the earth enables us to recognize so many beautiful examples. Amongst the numerous enemies of the insect class ordained to maintain its due numerical relations, and organized to pursue and secure its countless and diversified members in the air, in the waters, on the earth and beneath its surface, bats, lizards, shrews, and moles now carry on their petty warfare simultaneously, and in warmer latitudes work together, or in the same localities, in their allotted task. No surprise need therefore be felt at the discovery that Mammals and Lizards co-operated simultan¬ eously and in the same locality at the same task of restraining the undue increase of insect life during the period of the de¬ position of the Lower Purbeck beds.
Genus Triconodon, Ow.
318
PALAEONTOLOGY
Sp. Triconodon mordax. — This name is proposed for a small zoophagous Mammal, whose generic distinction is shown by the shape of the crowns of the molar teeth of the lower jaw, which consist of three nearly equal cones on the same longi¬ tudinal row, the middle one being very little larger than the front and hind cone ; and these cones are not complicated by
any cingulum or accessory basal cusp. The convex condyle is below the level of the alveoli, and there is no angular process projecting beneath it. The co- Jaw of Triconodon mordax ronoid process is broad and high, with (nat. size), Purbeck. its hinder point not extended so far back as the condyle ; the depression marking the insertion of the temporal muscle extends nearly to the lower border of the jaw. There are the obscure remains of three broken incisors, and the point of apparently a canine ; next come the two stumps, or broken roots of a small premolar ; then the crown of a second double rooted premolar, which show a principal cone and a small anterior cusp ; the next tooth is wanting ; then there is a larger premolar, with the two fangs raised some way out of their socket : the crown of this tooth shows a principal cone, with a small anterior and large poste¬ rior talon ; it rises, apparently from partial displacement, higher than the succeeding molars ; these are three in number, and present the characteristic three-coned structure already described ; each cone is smooth, and convex externally. The three cones seem to answer to the three middle or principal cones of the molars of Amphilestes and Phascolotlierium, but the front and hind cones are raised to near equality with the middle cone in Triconodon.
The lower jaw of this species, in the relation of the condyle to the lower border, resembles that of Phascolotlierium more than that of Amphitherium, but it differs from both ; there is not the same gradual curve from the condyle to the symphysis
PLAGIAULAX
319
as in PTiascolotherium j and tlie condyle, besides being on a lower level, is divided by a less deep notch from the coronoid process. This process is larger in proportion to the entire jaw ; approaches more nearly to the quadrate or rhomboid form, the upper border being less curved ; it affords a more extensive surface of attachment to the principal biting muscles than in most predatory extinct or recent quadrupeds. This character, with the depth and strength of the jaw, suggested the specific name. F rom the shape of the exposed part of the ramus, we may conclude that the part answering to the angle is bent in¬ wards, and that Triconodon was a genus of the marsupial order. The specimen was discovered by Mr. Beccles in the same “ dirt- bed” at Purbeck as that in which Spcclacotherium was found.
Genus Plagiaulax, * Fr. — The most remarkable of Mr. Beccles’ discoveries in the above formation are the mammalian jaws indicative of the genus above named, of which two species have been determined by Dr. Falconer.
Sp. Plagiaulax Becclesii, Fr. — Two specimens exemplified the shape and pro¬ portions of the entire jaw of this species (fig. 92). The fore¬ most tooth (i) is a very large one, shaped like a canine, but implanted by a
, , , . , Plagiaulax Becclesii (twice nat. size), Purbeck.
thick root m the
fore part of the jaw, like the large lower incisor of a shrew or wombat. The three anterior teeth in place have compressed trenchant crowns, and rapidly augment in size from the first (2) to the third (4). They are followed by sockets of two much smaller teeth, shown in other specimens to have sub-
* An abbreviation for Plagiaulacodon, from nAaytos, oblique, and av\ a£, groove; having reference to the diagonal grooving of the premolar teeth.
320
PALEONTOLOGY
tuberculate crowns resembling those ot Microlestes. The large front tooth of Plagiaulax is formed to pierce, retain, and kill ; the succeeding teeth, like the camassials of Carnivora, are, like the blades of shears, adapted to cut and divide soft substances, such as flesh. As in Carnivora, also, these sectorial teeth are succeeded by a few small tubercular ones. The jaw conforms to this character of the dentition. It is short in proportion to its depth, and consequently robust, sending up a broad and high coronoid process (b), for the adequate grasp of a large temporal muscle ; and the condyle (c) is placed below the level of the grinding teeth — a character unknown in any herbivorous or mixed-feeding Mammal ; whilst the lever of the coronoid process is made the stronger by the condyle being carried farther back from it than in any known carnivorous or herbivorous animal. The angle of the jaw makes no projec¬ tion below the condyle, but is slightly bent inward, according to the marsupial type.
Sp. Plagiaulax minor, Fr. — In this species the first premolar
(fig. 93, p, i) is preserved ; the rest (p, 2, 3, and 4) show nearly the same shape and propor¬ tions as in P. Becclesii. The first molar (m, 1) has a broad depression on the grinding Plagiaulax minor (four times nat. size), surface, surrounded by tuber-
Purbeck (after Lyell).
cles, of which three are on the
outer border ; the marginal tubercles of the second smaller tooth are smaller and more numerous.
In the general shape and proportions of the large premolar (p, 4) and succeeding molars, Plagiaulax most resembles Thylacoleo (fig. 141, p, m, 1 and 2), — a much larger extinct predaceous Marsupial from tertiary beds in Australia. But the sectorial teeth in Plagiaulax are more deeply grooved ; whence its name. The single compressed premolar of the
PLAGIAULAX
321
kangaroo-rat is also grooved ; but it is differently shaped, and is succeeded by four square-crowned double-ridged grinders adapted for vegetable food ; and the position of the condyle, the slenderness of the coronoid, and other characters of the lower jaw, are in conformity to that regimen. In Thylacoleo the lower canine or canine-shaped incisor projected from the fore part of the jaw close to the symphysis, and the correspond¬ ing tooth in Plagiaulax more closely resembles it in shape and direction than it does the procumbent incisor of Hypsiprymnus. From this genus Plagiaulax differs by the obliquity of the grooves on its premolars ; by having only two true molars in each ramus of the jaw, instead of four ; by the salient angle which the surfaces of the molar and premolar teeth form, instead of presenting a uniform level line ; by the broader, higher, and moie vertical coronoid j and by the very low position of the articular condyle.
The physiological deductions from the above-described characteristics of the lower jaw and teeth of Plagiaulax are, that it was a carnivorous Marsupial. It, probably found its prey in the contemporary small insectivorous Mammals and Lizards, supposing no herbivorous form, like Stereognathus, to have co-existed during the upper oolitic period.
In the Woodwardian Museum at Cambridge is a specimen of anchylosed cervical vertebrce of a cetaceous animal as large as a grampus, but presenting specific distinctions from all known recent and fossil species. It is stated to have been found in the brown clay or “till” near Ely ; but in its petri¬ fied condition, colour, and specific gravity, it is so different from the true bones of the “till,” and so closely like the fossils of the Kimmeridge clay, as to make it extremely probable that it has been washed out of that formation.
ISTo evidence of the mammalian class has yet been met with in the chalk beds.
Y
322
PALAEONTOLOGY
Tlie examples of tlie Mammalia first met with in tertiary strata are the Coryphodon and P cdceocyon, respecti\ ely 1 epi e senting the ungulate (herbivorous) and unguiculate (carnivor¬ ous) modifications of the class ; their remains have been found in the plastic clay and equivalent lignites in England and France.
Genus Coryphodon, Ow. — Rarely has the writer felt more misgiving in regard to a conclusion based, in palaeontology, on a single tooth or bone, than that to which he arrived after a study of the unique fragment of jaw with one tooth dredged up off the Essex coast, and on which he founded the genus Coryphodon*
The marked contraction of the part of the jaw near one end of the tooth seemed, at first view, clearly to show it to be the narrower fore part of the ramus j in that case the tooth would have been a premolar, and of comparatively little value in the determination of a genus or species. But a closer in¬ spection showed the line of abrasion of the summits of the two transverse ridges of the tooth to be on one side, and the gene¬ ral law of the relative apposition and reciprocal action of the upper and lower grinders in tapiroid Pachyderms determined that those oblique linear abrasions must be on the hinder side of the ridges. The smaller characters carried conviction against the showing of the larger and more catching ones. So, in determining the position of the nautilus in its pearly abode, when the animal without its shell was first brought to Eng¬ land in 1831, the reasons afforded by some small and incon¬ spicuous parts in like manner outweighed the first impressions from more obvious appearances, as well as the bias from the general analogies of testaceous Univalves. Some contemporary naturalists asserted, and for a time it was believed, that the nautilus had been put upside down in its shell, j- just as some
* History of British Fossil Mammals, 8vo, p. 299, figs. 103, 104.
f In plate i. of the writer’s Memoir of the Nautilus, 4to, 1832.
CORYPHODON
323
contemporary anatomists surmised that the writer had mis¬ taken the tore for the hack part of the jaw of his Coryphodon, which, in that case, might only he the known Lophiodon. In both instances the conclusions founded on the less obvious characters have proved to he correct. And the writer would remark that, in the course of his experience, he has often found that the prominent appearances which first catch the eye, and indicate a conformable conclusion, are deceptive ; and that the less obtrusive phenomena which require searching out, more frequently, when their full significance is reasoned up to, guide to the right comprehension of the whole. It is as if truth were whispered rather than outspoken by Nature.
Truth, it is sometimes said, lies at the bottom of a well. The first additional glimpse that the writer obtained of the veritable nature of one of our most ancient tertiary Mammals was derived from the inspection of a fossil tooth brought up from a depth of 160 feet, out of the “plastic clay,” during the operations of sinking a well in the neighbourhood of Camber¬ well, near London. It was a canine tooth,* belonging, from its size (near 3 inches in length), to a large quadruped, and, from the thickness and shortness of its conical crown, not to a carnivorous but to a hoofed Mammal, most resembling in shape, though not identical with, that of the crown of the canine tooth of some large extinct tapiroid Mammals, which Cuvier had referred to his genus Lophiodon, but which lias proved to belong to Coryphodon.
The last lower molar of Lophiodon has three lobes ; the molar determined to be the ultimate one, in the fragment of lower jaw above referred to, resembles that of the tapir in the absence of a third or posterior lobe, but the posterior ridge or part of the cingulum is less developed than in the tapir. It presents two divisions in the form of transverse ridges or eminences, the front ridge being the largest, and with its edge * Hist. Brit. Foss. Mamm, p. 306, fig. 105.
324
PALEONTOLOGY
most entire. From tlie outer end ot each division a ridge is continued obliquely forward, inward, and downward . the ante¬ rior one extends to the antero-internal angle of the base of the crown ; the posterior one terminates at the middle of the inter¬ space between the two chief divisions of the crown. The trenchant summit of the anterior ridge is slightly concave toward the fore part of the tooth, as in that of Lophiodon ; hut its outer and inner ends rise higher, and appear as more dis¬ tinct cones or points ; whence the generic name of Goryphodon. The posterior division is lower than the anterior one, and is bicuspid ; the trenchant margin connecting the outer and inner points does not extend across the crown parallel with the anterior ridge, as in Tapirus and Lophiodon, hut bends hack so as to form an angle, the apex of which rises into a third point.
Some lopliiodontoid fossils from the lignites of Soissons and Laon, and from the plastic clay of Meudon in France, including the upper molar tooth figured by Cuvier in the chapter of the Ossemens Fossiles entitled “ Animaux voisins de Tapirs,” pi. vii., fig. 6, belong to the genus Gorypliodon. Cuvier compares this tooth with one from Bastberg, which he figures in pi. vi., fig. 4, and which is certainly the last upper molar of a true Lophiodon, and points out truly that the Soissons tooth differs in the ex¬ ternal border passing into the posterior one, so that, instead of being quadrangular, its crown is triangular ; but he explains this difference on the hypothesis that the Bastberg tooth was a penultimate molar. The reduction of the second or posterior ridge to a semi-circular one, developed at its middle and hind¬ most part into a prominent cone, so far agrees with the modi¬ fication of the same part of the last molar of the lower jaw of the Gorypliodon as to render it very probable that the last upper molar from Soissons, figured by Cuvier in pi. vii., fig. 6, above quoted, also belongs to the genus Gorypliodon. Cuvier states that the entire skeleton was found, indicative of an
PLIOLOPHUS
325
animal as long and almost as large as a bull ; but that the workmen employed in the sandpit ( sabloniere ) preserved only that one tooth. Both the lower molar from Harwich, and the upper one from Soissons, indicate an animal of at least double the size of the American tapir.
Professor Hebert * has recently described a very instructive series of teeth and bones from the oldest eocene deposits in France, which he refers to the genus Coryphodon : the last molar is identical in form with the tooth from the plastic clay of Essex, on which the genus was originally founded.
Genus Pliolophus, Ow. — The most complete and instruc¬ tive example of a Mammal from the next overlying division of the eocene tertiaries, viz., the “London clay,” is that which the writer has described t under the name of Pliolophus vidpi- ceps. It is a hoofed Herbivore, but presents a dentition not exhibited by any later or existing species of Mammal.
The length of the skull (fig. 91) is 4 inches, its extreme
Fig. 94.
Skull of Pliolophus vulpiceps (half nat. size), London clay.
breadth 2 inches 2 lines, the height of the cranium opposite the first premolar tooth 9 lines. Its shape and characteristics
* Comptes Eendus de l’Acad. des Sciences, Paris, 26th January 1857 ( Cory¬ phodon Oweni, Hebert).
-j- Quarterly Journal of the Geological Society, vol. xiv., p. 54.
326
PALAEONTOLOGY
determine the hoofed nature of this species, and its affinities to the Perissodactyla, or the order of Ungulata with toes in odd number. The extent and well-defined boundary of the tem¬ poral fossae by the occipital (3), parietal (7), and post-frontal ridges, and their free communication with the orbits, give almost a carnivorous character to this part of the cranium of Pliolophus ; hut as in the hog, Hyrax, and Palaeothere, the greatest cerebral expansion is at the middle and toward the fore part of the fossae, with a contraction toward the occiput ; the brain-case not continuing to enlarge backward to beyond the origin of the zygomata, as in the fox. The zygomatic arches have a less outward span than in the Carnivora, In this part of the cranial structure Pliolophus resembles Palceo¬ therium more than it does any existing Mammal ; but the post-frontal processes are longer and more inclined backward. The incompleteness of the orbit occurs in both Anoplotherium and Palceotherium, as in Rhinoceros, Tapirus, and the hog tribe ; but in the extent of the deficient rim, Pliolophus is inter¬ mediate between Palceotherium and Tapirus. The orbit is not so low placed as in Palceotherium, Tapirus, and Rhinoceros, nor so high as in Hyrax or Sus. The straight upper contour of the skull (7 to 15) is like that in the horse tribe and Hyrax, and differs from the convex contour of the same part in the Anoplothere and Palaeothere. The size of the antorbital fora¬ men (a) indicates no unusual development of the muzzle or upper lip. In the conformation of the nasal aperture by four bones (two nasals, 15, and two premaxillaries, 22), Pliolophus resembles the horse, Hyrax, hog tribe, and Anoplothere, and differs from the rhinoceros, tapir, and Palaeothere, which have the maxillaries, as well as the nasals and premaxillaries, enter¬ ing into the formation of the external bony nostril.
The ungulate and herbivorous character of Pliolophus is most distinctly marked by the modifications of the lower jaw, especially by the relative dimensions of the parts of the ascend-
PLIOLOPHUS
327
ing ramus which give the extent of attachment of the biting (temporal) and grinding (masseteric and pterygoid) muscles respectively. In the shape of the mandible Pliolophus most resembles Tapir us among existing Mammals, and the Palceo- therium among the extinct ones in which that shape is known. As in almost every species of eocene quadruped yet discovered, the Pliolophus presents the type-dentition of the placental dipliyodont series, viz. —
. 3—3 1—1 4-4
* 3-3’ C l=i> P
3 — 3 , . *
4=4> “ 5=3 =
The incisors are preserved in the lower jaw with marks of attrition on their crowns demonstrating corresponding teeth of the same number (six), and of similar size, in the upper jaw, from which the alveolar part of the premaxillaries had been broken away.
The canines are small in both jaws : they are separated by a vacant space from the outer incisors, and by a longer inter-
Fig. 95. Kg- 96.
True molars, upper jaw (twice nat. True molars, lower jaw (twice
size), Pliolophus. nat. size), Pliolophus.
val from the first premolars. These form a continuous series with the remaining teeth in the upper jaw, but are separated
* See Ency. Brit., art. Odontology, vol. xvi., p. 478, for the “ Homologies of the Teeth,” and explanation of their symbols.
328
PALEONTOLOGY
by a space of about half their breadth from the second pre¬ molar in the lower jaw. The succeeding teeth (p i, 2, 3, 4) increase in size to the penultimate molar in the upper, and to the last molar in the lower jaw (p 4, in figs. 95 and 9G), which tooth has a third lobe.
In the last premolar upper jaw (fig. 95, p 4) the cingulum is uninterrupted along the outer side from its anterior well- developed talon (c) to the back part. The two outer cones resemble those of the true molars; but there is only one inner cone, and the crown ofp 4 differs accordingly from that of to 1, in being triangular rather than square. A ridge is con¬ tinued from the interspace between the anterior talon (c), and the outer anterior lobe obliquely inward and backward to the inner lobe, swelling into a small tubercle at the middle of its course.
The first molar (to i ) presents four low thick cones, two internal and two external : each external cone is connected with its opposite internal one by a low ridge, swelling into a tubercle at the middle of its oblique course. The cingulum (cc) seems to be continued uninterruptedly round the crown ot this tooth, thickest at the fore and back part, and at the interspace of the inner lobes ; and developing the small acces¬ sory antero-external tubercle. The second molar (to 2) is similar to, but rather larger than, the first ; the tubercle on the oblique ridge connecting the two front lobes is less developed. The cingulum is obliterated on the inner side of the posterior lobe.
The last molar is rather narrower behind than m 2 ; the tubercle on the anterior of the oblique connecting ridges is smaller : that on the posterior ridge is almost obsolete.
In the last lower premolar (fig. 9(1, p 4) the division and development of the anterior lobe gives rise to a pair of cones, fine external (a), the other internal ( b ), connected anteriorly hy a basal ridge, in front of which is the fore part of the
LOPHIODON
329
Fig. 97.
True molar, lower jaw (magn.), Ste- reognathus ooli-
cingulum. The low posterior lobe (c) shows the rudiment of a second internal cone (d).
The first molar (fig. 9G, m i ) has a pair of front lobes and a pair of hind lobes, with an oblique ridge continued from postero-internal lobe to the interspace between the front pair.
The second molar (m 2 ) shows an increase of size ; but its chief and most interesting modification is the development of a tubercle (e) between the two anterior lobes, making three cones on the same transverse line, and thus repeating the character of the molar tooth of Stereogncithus (fig. 97, e). The oblique ridge from the outer and hinder lobe (c) abuts against the inter¬ mediate tubercle (e). The nearest approach to the above dentition is made by the extinct tlcus- Hyracotherium ; also a fossil from the London clay.
The third trochanter on the femur of Pliolophus, and the association of three metatarsals in one portion of the matrix, as if belonging to the same hind foot, confirm the essentially perissodactyle affinities of that genus as shown by the skull and teeth. Pliolophus and Hyracotherium form a well-marked section in the lophiodont family, which seems to have pre¬ ceded the paheotherian family in the order of appearance, and to have retained more of the general ungulate type than that family. This is shown by the graduation of the tapiroid modification of the molar teeth into one more nearly resem¬ bling that of the Anthracotheria and Chceropotami, by the absence of the postero-internal cone on the ultimate premolar, by which all the premolars are, as in artiodactyles, less com¬ plex than the true molars, by the form and position of the nasal bones and by the structure of the external nostril.
Genus Lophiodon, Cuv. — In the year 1800 Cuvier* first announced the discovery of the fossil remains of a quadruped * Bulletin ties Sciences, PariR, Nivose, an. viii., No. 34.
330
PALEONTOLOGY
allied to and of the size of tlie tapir, in the lacustrine deposits of the Montagne Yoir, near Issel, department of Aude in Languedoc. The outer incisor of the lower jaw was shortened to give room to the longer corresponding incisor above, as in the tapir ; the canines offered the same proportional develop¬ ment; but the three first molars (premolars) of the lower jaw presented a more simple structure, having the crown com¬ pressed, and forming two cones, the front one being the largest ; — in short, a structure, the type of which is presented only by the first of the three premolars (^n) in the genus Tapirus*
Years elapsed ere Cuvier obtained clear evidence of the structure of the upper molars of this new fossil Mammal. Such detached teeth as had been obtained from the fresh¬ water formations near Issel were referred, owing to the way in which they departed from the type of the upper molar teeth of the Tapir, to the genus Rhinoceros. This fact is indicative of the annectant affinities of the Lopliiodon in the perissodactyle series, f Besides the character of form, the upper molar series of Lophiodon differs, like the lower one, from that in Tapirus, in the greater simplicity of the last two premolars ; these teeth have a single cone on the inner side in Lophiodon ; they have there two cones in Tapirus, forming the inner terminations of two transverse ridges, as in the true molars. These teeth in the Lophiodon differ from those in the Tapirus in the greater fore-and-aft expanse of the outer terminations of the transverse ridges, and the less depth of the cleft between them : a more complete coalescence of those parts causes a more entire outer wall of the crown, and com¬ pletes the transition to the Rhinoceros type, towards which the Palseotherium offers the next step.
Genus Paleotiierium, Cuv.— This extinct genus of quad¬ ruped was restored (fig. 98) by Cuvier through a series of admirably instructive steps, ultimately verified by a complete * E|1CY- Brit,, art. Odontology, p. 471, fig. 130, p z. f Ibid., p. 470.
PALiEOTHERIUM
331
series of fossils, obtained chiefly from the upper eocene gypse¬ ous formation at Montmartre and other parts of France. The
Restoration of the Palceotherium (Eocene Gyps).
molar teeth of Pctlceotheriuvi (fig. 99) approach nearer to those of the rhinoceros ; but in the number, kind, and general ar¬ rangement the entire dentition resembles that of Pliolophus. The skull affords indications that the Palseothere possessed a short proboscis. It had three toes on each foot, each termi¬ nated by a hoof ; the middle one being the largest. The femur had a third trochanter, and the dorso-lumbar vertebrae were 21 in number. Several species of Palceotherium have been determined, ranging from the size of a sheep (P. curtum ) to that of a horse (P. magnum).
Fig. 99 gives the grinding surface of an upper molar ot this species from the upper eocene of the Bembridge beds,
Isle of Wight. The crown is divided into an anterior (b, d)
Fig. 99.
Upper molar, Palceotherium magnum (Eocene).
and posterior (a, c) part by an
332
PALAEONTOLOGY
oblique fissure (e), continued from near the middle of the inner surface of the crown obliquely across two-thirds of the tooth. Each division is subdivided partially into an outer (ab) and an inner (cd) lobes ; the anterior division, by the terminal expansion (i) of the fissure ( e ), the posterior one by the fissure ( g ). The lobes (c and d) are bordered near their base by a ridge. This is the type of grinding surface, on which are superinduced the modifications of that surface in the upper molars of the rhinoceros and horse. The dental formula of
Palceotheidum is i
- 3> c 1-
V 4—45
m
The canines
exceed in length the other teeth, and there are consequently vacancies in the dental series for the lodgment of the crowns of the canines when the mouth is shut.
Genus Anoplotherium, Cuv. — With the same dental for¬ mula as in Palceotherium, the present genus, like Dicliodon (fig. 102) has no interval in the series of teeth ; neither the canine nor any other tooth rising above the general level. The grind¬ ing surface of the molar teeth somewhat resembles and prefigures the ruminant type ; in the upper jaw the crown (fig. 100) is divided into a front (/c) and a back (fd) lobe by a valley (e) extending two thirds across. A second valley (gi) crosses its termination at right angles, forming a curved depression in each
rium commune (Eocene division, which it thus subdivides into Gyps).
two lobes, concave towards the outer side of the tooth. There is a large tubercle (mj at the wide entry of the valley (e). The Anoplotliere (fig. 101) was of a lighter and more elegant form than the Palseothere : its limbs terminated each in two digits, with the metapodial bones distinct, and the last phalanx hoofed. Some transitory cha¬ racters of the embryo ruminant were retained throughout life by the Anoplothere. The species restored in fig. 1 01 was about
Upper
Fig. 100.
molar, Anoplotlie-
DICHODON
333
the size of a fallow-deer : it had a long and strong tail, and was probably of aquatic habits. Smaller and more delicate species of Anoplotlierioids from upper eocene strata have been referred to distinct genera by later palaeontologists. The re¬
searches of Baron Cuvier, which resulted in the restoration of the Palceotherium and Anoplotlierium, are the most instructive which the palaeontologist can study. They form the third volume of the 4to edition of the Ossemens Fossilcs, 1822-5.
Genus Dichodon, Ow. — The upper eocene beds of Hamp¬ shire have yielded evidence of an extinct form of even-toed (artiodactyle) hoofed quadruped, most interesting as a transi¬ tional form between the Anoplotlierioids and the true Rumi¬ nants. Like the Anoplotlierium the dental series is continu¬ ous, without break — a character which is only manifested by mankind among existing Mammals — the crowns of the teeth, in Dichodon, being all of nearly equal height, as they are in man. On each side of both upper and loiver jaws there are ill the Dichodon (fig. 102) three incisors (i i, 2, 3), one canine (c), four premolars (p 1, 2, 3, 4 ), and three true molars (mi, 2, 3 ) —in all forty-four teeth, constituting the typical diphyo- dont* dentition which so many mammalian genera, on their first appearance in the eocene strata, exhibit. It is formulized
as follows :—i g, c g, p g, m g - 44. From the first incisor
* See Ency. Brit., art. Odontology, p. 439.
334
PALAEONTOLOGY
fc.o S
S 2
to the third premolar the teeth have a more or less trench¬ ant crown. The hack of the third premolar (p 3), and all the fourth premolar (p. 4), show the crushing form of
crown ; the pat¬ tern of which in the true molars, after the wearing -£ down of the first
'g, sharp cusps, pro-
“ duces the double
1 crescentic lines of
O
enamel which are now peculiar to ° the Ruminants
■$ amongst hoofed
§ quadrupeds. The
first ( p 1), second ( p 2), and third (p 3) premolars, have their crown much extended from before back¬ wards, with three progressively more developed and pointed compress¬ ed cusps on the same line : to which is added, in the upper jaw, an inner ridge, de¬ veloped in the third premolar (P 3) into an inner posterior cusp. The fourth premolar (p 4j
DICHODON
335
has a thicker and shorter crown with two pairs of cusps. The upper true molars (m i, 2, 3 ) have the two pairs of cusps sharp and pointed, with a series of five low accessory points developed from the outer part of the cingulum. . The lower molars (m 1, 2, 3) have as complex crowns as the upper ones, but with the accessory basal points (a, h, c, e) developed from the inner, instead of the outer side of the crown, and with the convex sides of the chief cusps turned in the opposite direc¬ tion to those above. At the upper part of fig. 102 the outer side of the true molars, of a the last premolar, of the canine, and of the incisors, is shown, together with the grinding surface of the three anterior premolars in the xjPPerg molar of upper jaw. Below these the inner surface Dichodon. of the entire series of the lower teeth is shown, together with the grinding surface of the three true molars, the last of which (m 3) here supports a third pair of lobes (e.) As compared with the anoplotlierian molar (fig. 100), the outer lobes (ct, V) of that of the Dichodon (fig. 103) are thicker and sharper ; the inner ones (c, d ) — especially the latter — are developed to an equality with the outer ones, and more distinctly separated from them. Tim valley (m) extends across the whole breadth of the tooth, and is crossed at right angles by the fore-and-aft doubly-curved valley (g and i). The extinct species showing the above characters, and on which the genus was founded* was nearly the size of a fallow- deer : it is called Dichodon cuspidatus, in reference to the num¬ ber of sharp points on the unworn molars. The dentition indicates that its food may have been of a peculiar character, perhaps not exclusively of a vegetable nature.
In the same upper eocene formation of Hampshire have been found instructive examples of some smaller members of the extinct anoplotlierioid family.
* Quarterly Journal of the Geological Society, tom. iv., 1847, p. 36, pi. 4.
336
PALAEONTOLOGY
Genus Dichobune.— The genus Dichobune (from htyjz, bipar¬ tite ; (3 ow'05, collis ) was proposed by Cuvier, in the second edition of his Ossemens Fossiles, 4to, tom. iii., 1 822, p. 64, for the A noplotherium minus of the original Memoir in the Annales du Museum, tom. iii., 1803, and for the A. leporinum of the 4to edition, 1822, tom. i., pi. 2, fig. 3 ; and tom. iii., pp. 70 and 251. It is closely allied to the anoplotlierioid genus Xipho- don ; the dental formula is the same, only there is a slight interval between the canine and the first premolar in both jaws ; the first three premolars are subcompressed, subtren- chant, but less elongated from behind forwards than in Xipho- don. Besides the two normally-developed and functional digits on each foot, there may be one, sometimes two, small supplemental digits.
The best illustration of the structure of the upper true molars is afforded by the figure of one of these teeth in the Proceedings of the Geological Society, May 20, 1846, published in the Quarterly Journal, vol. ii., p. 420. “ The anoplotherian
character of the tooth is shown by the large size of the lobe (p> x> fig- 1), and the subgeneric peculiarity by the continua¬ tion of its dentinal base with that of the inner and anterior lobe (id), at the early stage of attrition presented by the crown of the tooth in question. In the large and typical Anoplo- theria, the lobe (p) preserves its insular form and uninterrupted contour of enamel until the crown is much more worn down than in the present tooth (fig. 1 ). In this respect, as in the modifications of the lower molar teeth, the genus Dichobune shows its closer affinity to the true Buminants ; but the little fold of enamel dividing the lobe id from p distinguishes the upper molar tooth in question from that of any Ruminant.” (P. 421.)
A new and interesting species of this genus, called Dicho¬ bune ovina, has been founded upon an almost entire lower jaw with the permanent dental series, wanting only the four middle
XIPIiODON
337
incisors, which now forms part of tlie palaeontological collec¬ tion m the British Museum. The dental formula, as shown by the mandibular teeth, and by the evidence on their crowns of the presence of the teeth of the upper jaw, is the typical one in diphyodont Mammalia, viz ,—i |=f, c 1=1, p =
The canine, with a crown like that of the first premolar, and not longer, is separated from it by an interval of half the breadth of the crown, and by a narrower interval from the outer incisor. The first premolar is divided by an interval of scarce a line’s breadth from the second. The rest of the molar series are in contact. The total length of the lower jaw is 5 inches 11 lines (0ra-148) ; that of the molar series is 2 inches 11 lines (0 0/5) ; that of the three true molars is 1 inch 4i lines (0m 035). The near equality in height of the crowns of all the teeth, and their general character, show that the animal belonged to the anoplotherioid family. The dentition of the present species differs from that of Dichodon in the absence of the accessory cusps on the inner side of the base of the true molars ; and both from Dichodon cuspidatus and Xiphodon gracilis in the minor antero-posterior extent of the premolars ; it corresponds with Dichobune (as represented by the D. leporina, Cuvier) in the proportions of the premolars and in the separation of the canine from the adjoining teeth : to this genus, therefore, the fossil is referable, provisionally, in the absence of knowledge of the molars of the upper jaw, which are the most characteristic : and the writer has proposed to call the species, from the size of the animal repre¬ sented by the fossil, Dichobune ovina. It is from Hampshire eocene.
Genus Xiphodon. — The genus Xiphodon was indicated, and its name proposed, by Cuvier, for a small and delicate, long and slender-limbed, anoplotherian animal, which, in his first Memoir ( Annales du Museum, tom. iii., p. 55, 1803), he had called Anoplotherium medium; but he altered the name, in
z
338
PALAEONTOLOGY
the second 4to edition of the Ossemens Fossiles (tom. iii., pp. 69 and 251, 1822), to that of Anoplotherium gracile.
The distinction indicated by Cuvier is now accepted by palaeontologists as a generic one, and a second species (. Xipho - don Geylensis ) has been added by M. G-ervais ( Paleontographie Frangaise, 4to, 1845, p. 90) to the type-species, Xiphodon gracilis, of which he figures an instructive portion of the den¬ tal series of both jaws, obtained from the lignites of Debruge near Apt. The dental formula of Xiphodon is the typical
. 3—3 l_l 4—4 „„ 3—3 a -
one, viz. % 3-3, <q— 15 p^, m3=3 = 44.
The teeth are arranged in a continuous series in both jaws. The canines and first three premolars have the crowns more extended antero-posteriorly, lower, thinner, transversely, and more trenchant, than in the type Anoplotheria (whence the name Xiphodon, or sword-tooth). The feet are didactyle, with metacarpals and metatarsals distinct. The tail is short. The lower true molars have two pairs of crescentic lobes with the convexity turned outwards. It was nearly allied to Dicliodon.
Genus Mickotherium. — Entire crania of Microthcrium, from the lacustrine calcareous marls of the Puy-de-D6me, are in the British Museum, and these show that the hinder division of the upper true molars was complicated by the additional (third) cusp.
With regard to Microthcrium, the unusually perfect fossil skulls of that small Herbivore, which did not exceed in size the delicate chevrotains of Java and other Indo- Archipelagic islands — e.g. Tragulus kanchil — are of importance in regard to the question of their alleged affinity to the Ruminantia, on account of the demonstration they give of the persistent and functional upper incisor teeth. The little eocene even-toed Herbivores, like the larger Anoplotherioids, thus departed from the characters of the true Ruminants of the present day, in the same degree in which they adhered to the more general type of the artiodactyles. Had M. de Blainville, who believed
HY^ENODON
339
them to be Ruminants, possessed no other evidence of the Microtherium than of the Dichobune murina and Dichobune dbliqua, Cuv., he would have had the same grounds for refer¬ ring the Microtheria, as the Dichobunes, to the genus Tragulus or M oschus (les Chevrotains) ; but the entire dentition of the upper jaw of the species Anoplotherium murinum and A. obliquum, referred by Cuvier to his genus Dichobune, must be known before the existence of Ruminants in the upper eocene gypsum of Paris can be inferred.
PTo doubt the affinity of these small Anoplotherioids to the Chevrotains was very close. Let the formative force be trans¬ ferred from the small upper incisors to the contiguous canines, and the transition would be effected. We know that the ruminant stomach of the species of Tragulus is simplified by the suppression of the psalterium or third bag. The stomach of the small Anoplotherioids, whilst preserving a certain degree of complexity, might have been somewhat more simplified. The certain information which the gradations of dentition dis¬ played by the above-cited extinct species impart, testifies to the artificial character of the order Ruminantia of the modern systems, and to the natural character of that wider group of even-toed hoofed animals for which has been proposed the term Artiodactyla*
Genus Hy^nodon, Laiz. — With the delicate and beautiful Herbivora of the upper eocene and lower miocene periods, there coexisted carnivorous quadrupeds, which, to judge by the character of their flesh-cutting teeth (carnassials), were more fell and deadly in their destructive task than modern wolves or tigers. Of these old extinct Carnivora a species of the remarkable genus Hycenoclon, of about the size of a leopard, has left its remains in the upper eocene of Hordwell, Hampshire. Pig. 104 shows the dentition of the under jaw of another species of the same genus from miocene beds at
* Quarterly Journal of the Geological Society, to!, iv., 1847.
340
PALAEONTOLOGY
Debruge and Alais, France. The carnassial teeth (in, i, 2, 3), instead of being one in number in each ramus of the jaw, as in modern Felines, were three in number, equally adapted by their trenchant shape, to work like scissor-blades on the teeth
of the upper jaw, in the act of cut¬ ting flesh. After the small inci¬ sors came a pair of large piercing and prehensile Dentition, lower jaw, °f Hycenoclon. canines (c), fol¬
lowed by four compressed pointed and trenchant premolars (p, i, 2, 3, 4) in each side of the jaw ; the whole of this carni- vorous dentition conforming to the diphyodont type : —
.3-3
4-
4-4
44.
3-3
Genus Amphicyon. — With the foregoing predecessor of the digitigrade Carnivora was associated a forerunner of the
plantigrade fa¬ mily, viz., a large extinct species having the mo- lars tuberculated, after the pattern of those of the bears ; but re- Dig. 105. tabling, like Hy-
Dentition, upper jaw, of Amphicyon. cenodon, the per¬
fect type of diphyodont dentition. Fig. 105 shows the teeth of one side of the upper jaw of the Amphicyon giganteus. The first and second molars (in, 1 and 2 ) have each two tubercles on the outer side and one on the inner side ; the last tubercular molar (in, 3 ) is of very small size. Fossil remains of Amphi-
DIDELPHIS
341
cym have been found principally in the miocene deposits at Sansans, south of France. Those of a smaller species from the miocene at Eppelsheim, have been referred to the wolverine genus, as Gulo diaphorus , Ivaup.
The proofs of the abundant mammalian inhabitants of the eocene continent were first obtained by Cuvier from the fos¬ silized remains in the deposits that fill the enormous Parisian excavation of the chalk. But the forms which that great anato¬ mist restored were all new and strange, specifically, and for the most part generically, distinct from all known existing quad¬ rupeds. By these restorations the naturalist was first made acquainted with the aquatic cloven-hoofed Anoplothere, and with its light and graceful congeners, the Dichobunes and Xiphodon, with the great Pakeotheres, which may be likened to hornless rhinoceroses, with the more tapiroid Lophiodon, with the large peccari-like Choeropotamus, and with about a score of other genera and species of placental Mammalia.
Almost the sole exception to the generic distinction of these eocene forms from modern ones was yielded by the opossum of Montmartre ( Didelphis Gypsorum, fig. 106) ; and what made this discovery the more remarkable was the fact that all the known existing species of that marsupial genus are now confined to America, and the greater part to the southern division of that continent. An opossum appears to have been associated with the Hyracotheriiun in the eocene sand of Suffolk ; where likewise, a porcine beast with tusks like ordinary canines, and some remains of a monkey (Eopithecus), have been found. With respect to the Didelphis Gypsorum, its generic relations were deduced from characters of the lower jaw and teeth ; but these were associated with other parts of the skeleton in the same block of stone. When Cuvier expressed his convictions from the teeth and other parts first exposed and examined, his scientific associates were incredulous. He invited them, there-
342
PALEONTOLOGY
fore, to witness a crucial test. The outline of the back part
of the pelvis was exposed, the fore part buried in the matrix. By his delicate use of the graving-tool, Cuvier brought to light the fore¬ part of the pelvis with the two marsupial bones (fig. 10G, a, a) in their natural position. He thus demon¬ strated that there had been buried in the soft fresh¬ water deposits, hardened in after ages into the building- stone of Paris, an animal whose genus at the present day is peculiar to America. It is not uninteresting to remark that the Peccari, the nearest existing ally to the old Chceropotamus, is, like the opossum, now peculiar to America ; and that two species of tapir, the nearest living allies to the Lophiodon and Paleeothere, exist in South America.
The marine deposits of the miocene epoch show the remains
of extinct genera of dolphins ( Ziphius and Dioplodon ) and of whales ( Balcenodon ). Petrified cetaceous teeth and ear-bones, called “ cetotolites ” (fig. 107)
Cetotolite or fossil ear-bone of Balceno- have been washed out of pre- don gibbosus (Red Crag, Suffolk), vious strata into the red crag
of Suffolk. These fossils belong to species distinct from any known existing Cetacea, and which, probably, like some con¬ temporary quadrupeds, retained fully-developed characters which are embryonic and transitory in existing cognate
Fig. 106.
Pelvis and marsupial bones of Didelplds Gypsorum (Eocene, Paris).
BALA2N0D0N
343
Mammals. The teeth of these Cetacea were determined in 1840, the ear-hones in 1843. The vast numbers of these fossils, and the proportion of phosphate of lime in them, led Professor Henslow* to call the attention of agricultural chemists to the red crag as a deposit of valuable manure. Since that period it has yielded a large supply, worth many thousand pounds annually, of the superphosphates. The red crag is found in patches from Walton-on-Naze, Essex, to Aldbro’, Suffolk, extending from the shore to 5 or 15 miles and more inland. It averages in thickness 10 feet, but is in some places 40 feet. Broken-up septarian nodules form a rude flooring to the crag, left by the washing off of the London clay, and called “rough stone.” The phos- phatic fossils, or “ cops” as they are now locally termed, occur in greatest abundance immediately above the “rough-stone.” Thousands of cubic acres of earlier strata must have been broken lip to furnish the cetacean nodules of the “ red crag.” This is a striking instance of the profitable results of a seem¬ ingly most unpromising discovery in pure science, — the deter¬ mination of what in 1840 was regarded as a rare, unique, and most problematical British fossil-f
Our knowledge of the progression of mammalian life dur¬ ing the miocene period is derived chiefly from continental fossils. These teach us that one or two of the generic forms most frequent in the older tertiary strata still lingered on the earth, but that the rest of the eocene Mammalia had been superseded by new forms, some of which present characters intermediate between those of eocene and those of pliocene genera. The Dinotlierium and narrow-toothed Mastodon, for example, diminish the interval between the Lophiodon and the elephant ; the Anthracotherium and Hippohyus, that between Chceropotamus and Hippopotamus; the Acerotheriwm was a
* Proceedings, and Quart. Jour. Geol. Soc.,
-J- History of British. Fossil Mammals, 8vo, p. 53 b.
344
PALAEONTOLOGY
link connecting Palceotherium with Rhinoceros ; the Hippo- therium linked on Paloplotherium with Equus.
One of the most extraordinary of the extinct forms of the cetaceous order has been restored from fossil remains dis¬ covered in formations of the miocene age in Europe and North America. The teeth of this carnivorous whale, for which the generic name Zeugloclon seems now to he generally accepted, were first described and figured by the mediaeval palaeontolo¬ gist Scilla, in his treatise entitled De Corporibus Marinis (4 to, 1747, tab. xii., fig. 1), and have since given rise to various interpretations. The originals were obtained from the miocene strata at Malta, and are now preserved in the Woodwardian museum at Cambridge.
The remains of a gigantic species of the same genus, dis¬ covered by Dr. Harlan in miocene formations of Arkansas, Mississippi, were described and figured by him as those of a reptile, under the name of Basilosaurus * Teeth of a smaller
species, discovered byM. Grateloup, in miocene beds of the Gironde and Herault, were ascribed by him also to a reptile, under the name of Squa- lodon.-\ In 1839 Dr. Har¬ lan brought over his spe¬ cimens of Basilosaurus — to London, and submit-
Deciduous and permanent teeth of the Zeug - ted them t° the Writer’s lodon. inspection, by whom
they were determined to be mammalian and cetaceous. The entire skeleton has since been obtained from miocene deposits iu Alabama, revealing a length of body of about 70 feet. The
* Medical and Physical Researches, p. 333, t Act. Soc. Linn, de Bordeaux, 1840, p. 201.
ZEUGLODON
345
skull is very long and narrow ; the nostril single, with an upward aspect, above and near the orbits. The jaws are armed with teeth of two lands, set wide apart ; the anterior teeth have subcompressed, conical, slightly-recurved, sharp-pointed crowns, and are implanted by a single root ; the posterior teeth are larger, with more compressed and longitudinally extended crowns (fig. 108), conical, but with a more obtuse point, and with both front and hind borders strongly notched or serrated. The crown is contracted from side to side in the middle of its base, so as to give its transverse section an hour-glass form (fig. 109), and the opposite wide longitudinal grooves which produce this form become deeper as the crown approaches the socket, where they meet and divide the root
into two fangs.
The name Zcu- ^''ansverse secti°n of a tooth of the Zeuglodon. Nat. size.
cjlodon (yoke-tooth) refers to this structure. The mode of suc¬ cession of the teeth in this genus conforms to the general mammalian type more than does that of any of the existing carnivorous Cetaceans. In the figure given by Dr. Carus* of a portion of the jaw of Zeuglodon ceto'ides, a deciduous molar (fig. 108, a) is about to be displaced and succeeded, vertically, by a second larger molar. This mode of succession is not known in the Platanista or Inia, which among existing true Cetacea present teeth most like those of Zeuglodon ; but it is a mode of succession and displacement affecting certain teeth in the herbivorous Cetacea, or Sirenia ; and we thus seem to have in the Zeuglodon another of those numerous instances of a more generalized character of organization in older tertiary Mam-
* Nova Acta Ores. Leop. Carol., vol. xxii., tab. xxxix. B, fig. 2, p. 340.
346
PALAEONTOLOGY
malia. Iu systematic characters, Zeuglodon typifies a distinct family or group, intermediate between Cetacea proper and Sirenia.
Of the latter family or order, however, represented at the present day by the Dugongs, Manatees, and Stellerians or Arctic Manatees (if the species still survives), there were abundant and more widely distributed representatives during the miocene period, having, upon the whole, the nearest affinity with the existing African Manatee ( Manatus Senega- lensis ), but with associated characters of the Dugong (. Halicore ). There were, e. g., two incisive tusks in the upper jaw, and four or five small incisors along the deflected part of each ramus of the lower jaw. The upper molars, with three roots, were thickly enamelled, like those of the Manatee, but with a pat¬ tern of grinding surface which led Cuvier to attribute detached specimens to a small species of Hippopotamus. The lower molars had two roots. All the bones have the dense or solid structure of those of the Sirenia. On the remains of this remarkable amphibious Mammal, discovered by Kaup in 1838, in the miocene beds at Eppelslieim, he founded the genus Hali- therium. Other remains have been discovered in Piedmont, Aste, and many parts of France, from the “ calcaire grossier” of the Gironde, containing Lopliiodont fossils, up to the plio¬ cene near Montpellier ; at which period the Halitherium seems to have become extinct.
Genus Macrotherium, Lartet. — The edentate order, which is so abundantly and variously represented in South America, which has its Orycteropes and Pangolins in Africa, and its Manises in tropical Asia, has no living representative in Europe. Perhaps the most unexpected form of Mammal to be revealed by fossil remains from European tertiary deposits, after a Marsupial, was a member of the edentate order. Cuvier, by whom the evidence of this extinct animal was first made known, prefaces his description of the single mutilated
MACROTHERIUM
347
phalangeal bone, on which that evidence was founded, by the remark, that “nothing proves better the importance of the laws of comparative osteology than all the consequences which one may legitimately draw from a single fragment.” One will- ingly admits the proof so afforded of the former existence of animals now unknown ; but one may demur to the conclusion that their extinction was due to some sudden catastrophe.
The single mutilated ungual phalanx on which Cuvier based his conclusions in regard to the species in question was discovered, associated with remains of Rhinoceros, Mastodon, Dinotlierium, and Tapir, in a formation near Eppelsheim, Hesse-Darmstadt, which is now determined to belong to the miocene division of the tertiary series. This phalanx shows two distinctive characters of the edentate order : — 1st, Its posterior surface for articulation with the antepenultimate phalanx is a double pulley, hollowed out on each side, with a salient crest between, constituting the firm kind of ginglymoid joint peculiar to certain Edentata; 2 d, The concave arch formed by that pulley curves furthest backward at its upper part, which would prevent the claw being retracted upward, as in the cat tribe, and constrain the flexion downward — “ ainsi c’est necessairement un ongueal d’edente.”* To the foregoing characters are joined two others which Cuvier believed to determine “ as necessarily” the genus. The spe¬ cies of Myrmecophaga have on the upper part of the pointed end of the claw-phalanx a groove, indicative of a disposition to bifurcate ; in the species of Manis the bifurcation is complete, the cleft extending as far as the middle of the claw-bone : so likewise in this fossil. The Pangolins {Manis) have not those bony sheaths which, in the sloths, some ant-eaters and arma¬ dillos, rise from the base and cover the root of the claw ; there Avas a like absence of any claw-sheath in the fossil. Thus the fossil claw-bone has no homologue in existing nature save those
* Ossemcns Fossiles, 4to, t. v., pt. i., p. 1 9 3 .
348
PALAEONTOLOGY
of the Manis ; and, “ according to all the laws of co-existence, it is impossible to doubt that the most marked relations of the animal that bore it should have been with that genus of quadrupeds.”* But what must have been its size \ The phalanx was not one of the largest on the foot — for it had not those slight raised borders which one sees in the large claw-bones of the Pangolins. This question, which Cuvier answered by the proportions of the short-tailed Manis, at 24 French feet, has had a more reasonable reply given to it by certain other bones of the skeleton subsequently discovered in the miocene tertiaries of France. These discoveries have like¬ wise rectified and moderated the absolute application of the correlative law to the necessary determination of the genus as well as of the order. The relations of the double-jointed and cleft phalanx to the Edentata is beautifully confirmed ; but the additional fossils, and especially some evidences of teeth, have shown that it belonged to a peculiar and now extinct genus intermediate between the Manis and the Oryderojms. And these relations are deeply interesting, on account of the geographical position of both those edentate genera, on tracts of land, viz., which are now most contiguous to the continent containing the remains of the extinct osculant genus.
The locality in France is near the village of Sansan, near Auch, department of Gers, Ifaute-Pyrenees. The formation is a lacustrine deposit of the miocene period.
Portions of two molar teeth have been found, 1 inch 8 lines in greatest transverse diameter ; the tooth preserving the same size and shape through the whole length of the portion — viz., 11,- inch. They resemble in shape those of the Orycterope, but are less regular and have not the same tubu¬ lar tissue. Their microscopic texture appears not to have been analyzed ; it would be important to determine whether it resembled that of the teeth of the sloths or armadillos. The * Ossemens Fossiles, 4to, t. v., pt. i., p. 194.
MACKOTHERIUM
349
lmmerus differs from that of the ant-eaters and armadillos by its greater length in proportion to its breadth, and by the peculiar flattening from before backwards of its lower half, and especially at the condyles, above which it is expanded transversely by both external and internal supra-condyloid ridges. It is not perforated above the inner condyle, as the same bone is in both the Mctnis and Orycteropus. In the degree to which it departs from the type of the ant-eaters it approaches that of the Megatherioids and sloths — viz., in its relative length, flattening at the distal end, and the imperfo¬ rate character of that end. The radius also presents a sloth¬ like character in its greater proportionate length, which exceeds that of the humerus ; and in the compression of its lower slightly-expanded end. In both the Pangolin and Orycterope, the radius is shorter than the humerus. The ulna differs likewise from both that of the Pangolin and Orycterope, and still more from that in the Armadillos by the much smaller development of the olecranon, whereby, again, it more resembles that of the sloths. The femur is relatively longer and more slender than that of the terrestrial and fos- sorial Edentata ; it has not the third trochanter which charac¬ terizes it in the Orycterope, nor so marked a development of the great and small trochanters as in the Pangolin. In the flattened form of the shaft of the femur, and the position of the rotular surface near one side of the distal end, it resembles the femur of the Megatherium and Mylodon. It is shorter than the humerus ; whereas, in both the Pangolin and Oryc¬ terope the femur is longer : in this respect the femur of the Macrothere resembles that of the sloths. The great width of the popliteal space dividing the condyles is an edentate and more especially a megatherioid character. The internal con¬ dyle is much broader than the external one, as it likewise is in the Megatherioids ; it is certainly with the femur of the latter family of the Edentata, rather than with that of the
350
PALAEONTOLOGY
Proboscidians or Pachyderms, that one should compare the femur of the Macrothere : it is not so long or so slender relatively as in the sloths. The tibia is much shorter than the femur, and in the expansion of its proximal end and its rela¬ tive length to the femur it resembles that of the Megatheroids more than that in the Pangolin or Orycterope ; it was not anchylosed to the tibia as in the Armadillos, Glyptodons, and Megatherium, but remained a distinct bone, as in the Mylodon and sloths.
Genus Pliopithecus, Gerv. — In the same miocene deposits of the south of France as those which contained the Macro- therium, fossil remains of two kinds of Quadrumana, resembling a small and large species of Hylobatcs, have been discovered. The smaller of these extinct apes, called Pliopithecus ccntiquus by Gervais, is based upon the lower jaw and dentition. The teeth occupy an extent of I-5- inch ; the turn incisors are narrower, the canine less, and the last molar is larger than in the siamang (. H . syndactylct ). As in this species the first premolar is uni-cuspid, and the hind talon of the second is more produced than in the chimpanzee and gorilla, and to the degree in which the fore-and-aft diameter of the tooth exceeds the transverse one, it departs farther from the human type ; in the degree of the development of the talon or third lobe of the last lower molar, the Pliopithecus resembles the tailed monkeys (S 'emnopitliecus and Innus ).
Genus Dryopjtiiecus, Part. — In the larger miocene ape (Dryopitliecus Fontani, Lart.) the canine is relatively larger than in the Hylobatcs, and the incisors, to judge by their alveoli, are relatively narrower than in the chimpanzee and human subject. The first premolar has the outer cusp pointed, and raised to double the height of that of the second premolar, and its inner lobe is more rudimental than in the chimpanzee,*
* Compare Comptes Rendus de l’Acad. des Sciences, tom. xiiii. (July 28, 1856, plate, fig. 7), with Trans. Zool. Soc., vol. iv\, plate 32, fig. 3, p. 3.
MESOPITHECUS
35]
and departs proportionally from tlie human type. The poste¬ rior lobe or talon of the second premolar is more developed, and the fore-and-aft extent of the tooth greater, than in the chimpanzee, thereby more resembling the second premolar of the siamang, and less resembling that of the human subject. The last (third) molar is undeveloped in the fossil jaw of the Dryopithecus, and its amount of departure from the human type, and approach to that of Innus, cannot be determined. The canine is more vertical in position than in Troglodytes or Pithecus, but this character is offered by some of the small South American apes, and cannot be cited as a mark of real affinity. From the portion of humerus associated with the jaw of Dryopithecus, the arm would seem to have been pro¬ portionally longer and more slender than in the chimpanzee and gorilla, with a cylindrical shaft, more like that in the long-armed apes ( Hylobates ), and less like the arm of the human subject.
The characters of the nasal bones, orbits, mastoid processes, relative length of upper limb to trunk, relative length of arm to fore arm, relative length and size of thumb, relative length of lower limb ; and, above all, the size of the hallux and shape of the astragalus and calcaneum, must be known before any opinion can be trusted as to the proximity of Dryopithecus to the human subject.
Genus Mesopithecus, Wagn. — In tertiary formations of Greece, at the base of Pentelicon, remains of a Quadrumane have been found, which Professor Wagner* regards as transi¬ tional between Hylobates and Scmnopithecus : the third lobe of the last molar is, however, as well developed as in the latter genus.
In the pliocene deposits of Montpellier remains of a monkey occur, referred by Ohristol to a Cercopithecus ; and in pliocene brick-earth in Essex the writer has determined part of the fossil jaw and teeth of a Macacus.
* Abhanglungen der k. bayer Akademie, bd. ii., 1854, Muncken.
352
PALAEONTOLOGY
Genus Dinotiierium, Cuv. and Kp. — This name was given by Kaup, after the discovery of the singular shape and arma¬ ture of the lower jaw, to the huge bilophodont Mammal, first made known by Cuvier under the name of “ Tapir gigantesque.” The length of the skull, from /to cl, in fig. 1 10, is 3 feet 8 inches.
Fig. 110.
Skull of Dinotiierium giganteum (Miocene, Eppelsheim).
The teeth in this skull, in addition to the two large deflected tusks of the lower jaw, are five in number on each side of both jaws. A study of the changes of dentition in fossils of young Dinotheria show that the first two teeth answer to the third and fourth premolars, as signified by the symbols p, 3 and 4 ; and that the rest are true molars (m, i, z, 3). Of these, the first tootl 1 (p, 3), is rather trenchant than triturant ; the third tooth ( 1 ) has three transverse ridges. The other grinders have two transverse ridges. This “ bilophodont ”
MASTODON
353
or two-ridged type is shown by the molars of the Tapir, (fig. Ill), Lophiodon, Megatherium, Diprotodon, Nototherium, Kangaroo, and Manatee. In the general shape of the skull and aspect of the nostrils Dino- therium most resembles Mana- tus. Bones of limbs have not Molar series, lower jaw, Tapir, yet been found so associated with teeth as to determine the ordinal affinities of Uinotherium. Yet cranial and dental evidences of the genus have been discovered in miocene deposits of Germany, France, Switzerland, and Perim Island, Gulf of Cambay.
Genus Mastodon, Cuv. — The earliest appearance of this genus of proboscidian or elephantoid Mammal is in tertiary strata of miocene age, and by a species in which the fore part of the lower jaw was produced into a pair of deep sockets containing tusks ; but these are only slightly deflected from the line of the grinding teeth (fig. 112, C ). This species of Mastodon, discovered in the miocene of Eppelsheim, was called longirostris by Kaup ; but he afterwards recognized it as the same with a species which had been previously called Masto¬ don arvernensis (Croizet and Jobert).* Both belong to that section of Mastodon in which the first and second true molars have each four transverse ridges, t and for which Dr. Falconer proposes the name Tetralophodon. In the newer tertiary deposits of North America remains of a Mastodon (M. Ohio- ticus ) have been discovered, in which the transverse ridges of the grinders are in shape more like those of the Dinothere than in any other Mastodon ; the first and second, moreover, are bilophodont, the third trilophodont ; but this is followed by two three-ridged molars and a last larger molar with four
* Beitrage zur Naeheren Kenntniss der Urweltliclien Saengethiere, 4to, t857, p. 19. The name angustidens was first applied by Cuvier to teeth of this type or species.
f First demonstrated by Kaup, Ossemens Fossiles de Darmstadt, 41 o, 183b.
2 A
354?
PALAEONTOLOGY
or five ridges* For the Mastodons with penultimate and antepenultimate grinders with three ridges, Dr. Falconer pro¬
poses the name Trilophodon. In the Mastodon Ohioticus the lower jaw has two tusks in the young of both sexes; these * Owen’s “ Odontography,” 4to, 1845, p. 617, pi. 144.
MASTODON
355
are soon shed in the female, hut one of them is retained by the male (fig. 112, B). The upper tusks are long and retained in both sexes (fig. 112, A).*
-A_n almost entire skeleton of a Mastodon (J\f. tunccncis ) has been discovered in the pliocene deposits of Aste, Pied¬ mont, and has been described and figured by Professor Sis- monda,f from whose beautiful Memoir fig. 112 is taken. The total length from the tail to the end of the tusks is 17 feet. The teeth have the same narrow shape and multi-mammillate structure as in M. arvernensis, but in the numerical character of transverse divisions of the crown this species agrees with M. Ohioticus.
The Mastodons were elephants with the grinding teeth less complex in structure, and adapted for bruising coarser vegetable substances. The grinding surface of the molars (fig. 113), instead of being cleft into numerous thin plates, was divided into wedge-shaped transverse ridges, and the summits of these were subdivided into smaller cones, more or less resembling the teats of a cow, whence the generic name.J A more important modification appeared to distin¬ guish the extinct genus, in respect of the structure of the molar teeth ; the dentine, or princi¬ pal substance of the crown of the tooth (fig. 1 1 3, d) is cover¬ ed by a thick coat Fig. 113.
of dense and brittle uPPer molar of Mastodon,
enamel (e) ; a thin coat of cement is continued from the
* Owen’s “Odontography,” p. 618. f Osteografia di un Mastodonte augnstidente, 4lo, 1851. 1
| /acuttos, a nipple; oSovs, a tooth.
356
PALAEONTOLOGY
fangs upon the crown of the tooth, but this substance does not fill up the interspaces of the divisions ol the crown, as in the elephant’s grinder (fig. 118, c). Such at least is the character of the molar teeth of the two species of Mastodon, which Cuvier has termed Mastodon giganteus and Mastodon angustidens (fig. 113). Fossil remains of proboscidians have subsequently been found principally in the tertiary deposits of tropical Asia, in which the number and depth of the clefts of the crown of the molar teeth, and the thickness of the intervening cement, are so much increased as to establish transitional characters between the lamello-tuberculate teeth of the elephants and the mam inflated molars of the typical Mastodons, showing that the characters deducible from the molar teeth are rather the distinguishing marks of species than of genera in the pre¬ sent family of mammalian quadrupeds.
The dentition of this family may be expressed by the formula —
d i
l.i .
1.1 o.o 7 3.3 1.1
1.1 ’ C do ’ 1 m 3.3 ’ P 1.1
m
3.3
o
4 ;
that is to say, in the Proboscidians in which the dentition most nearly approached to the typical one, thirty-four teeth were developed, as follows : — in the upper jaw, two deciduous
incisors, followed by two per¬ manent incisors developed as tusks ; six deciduous molars (three on each side, d 2,3,4, fig- 114); two premolars (one on each side, p 3, fig. 1 1 4), and six true molars (three on each side, m 1, 2, 3, figs. 1 14 and 1 1 5) ; — in the lower jaw, two incisors as tusks (uncertain whether preceded by deciduous tusks), deciduous molars, premolars, and molars, as in the upper jaw.
The elepliantoid animal ( Mastodon longirostris, Kaup ; Mas¬ todon angustidens, in part, Cuvier) which exhibited the above
Deciduous dentition, young Mastodon longirostris.
MASTODON
357
instructive dentition of the proboscidian family, once roamed over the part of the earth now forming England, France, Italy, and Germany. The first steps in our knowledge of its dentition were made by Cuvier, who called it the narrow-toothed Masto¬ don “ Mastodon a dents etroites,” or Mastodon angustidens. This name was suggested by the less breadth of the grinding surface of the teeth as compared with those of a previously described species of Mastodon from North America, called the Mast.
Dentition of' old Mastodon longirostris
giganteus or M. Oliioticus. Cuvier describes and figures a last molar, upper jaw, from Trevoux, consisting, as in the specimen from Norfolk Crag (fig. 113), and as in that from Eppelsheim (fig. 1 1 5, m 3), of five transverse ridges, with a front and back talon or subsidiary ridge. The latter is the largest, and sub¬ divided into teat-shaped tubercles, so as almost to merit the name of a sixth division of the tooth. The principal ridges are divided into two chief or primary tubercles, with secondary tubercles in the interspace ; the chief tubercles are more or
358
PALAEONTOLOGY
less deeply grooved lengthwise, or cleft at top, so that masti¬ cation wore them down to small circles of dentine surrounded by a thick border of enamel, and further attrition reduced these to a trilobed or trefoil form.
The last lower molar of the Mast, angustidens from La Rochetta di Tanaro,* exhibits the same five principal trans¬ verse ridges and the hinder one, as in the corresponding tooth in the Eppelsheim Mastodon (fig. 115, vi 3), and being the first of the series of narrow mastodontoid teeth to which Cuvier applied the name angustidens, it may be regarded as the type of that species. The characteristic premolar of the Mast, angustidens, with a quadrate crown of two ridges, each cleft into two tubercles (fig. 114, p 3), is figured by Cuvier, in Op. cit. pi. i., fig. 3, and again, in situ, with the last deciduous molar (cl 4) in a portion of the upper jaw of the Mastodon angustidens from Dax (ib. pi. iii., fig. 2). The nature of this quadritubercrdate tooth as a premolar, i.e., as a tooth which displaced and succeeded an earlier or deciduous tooth in the vertical direction, was recognized by Cuvier. “ Je crois encore qu’on peut en conclure que la dent anterieure etait susceptible de remplacement de liaut ou bas, comme dans l’liippopotame : ma raison est, que cette petite dent de Dax 11’est pas encore usee et qu’il faut qu’elle soit venue apres la grande qui best ”f Dr. Kaup has described and figured the same premolar in the upper jaw of a younger individual of the Mastodon angustidens (his longirostris ), in which it is still concealed in its formative cavity above the tliree-lobed deciduous tooth which it has replaced in Cuvier’s specimen. The tooth next behind, which is the homologue of the last milk-molar (d 4. fig. 114) of the typical series, consists, in both the Dax and Eppelsheim speci¬ mens, of three principal ridges and a posterior bituberculate talon ; this accessory portion being more developed in the
* Cuvier, Op. cit. Divers Mastodontes, pi. iv., fig. 1, top view, fig. 2, side view, f Ossemens Fossiles, 4to, 1821, tom. i., p. 256.
MASTODON
359
Eppelslieim specimen. Whether such difference he valid for a specific distinction may he doubted ; hut that Cuvier assigned the name angustidens to a Mastodon with narrower molars than the M. giganteus, which had a quadri-tuberculate premolar, a penultimate molar of four principal divisions and a talon, and a last molar with five principal divisions and a talon, is certain. To that Mastodon, therefore, which has the same shaped and sized ultimate and penultimate true molars and premolar, the same name is here assigned.
The antepenultimate molar (fig. 114, m i) consists of four ridges and a talon.
Three molars are developed anterior to this tooth ; the first (fig. 1 1 4, d z) is the smallest, with a subquadrate crown of two transverse ridges. The second molar (ib., d 3), of twice the size of the first, has three ridges. The third molar (ib., d 4), with an increase of one-third the bulk of the former, has three ridges and a bituberculate talon, which in some specimens might almost be reckoned as a fourth ridge. The two-ridged premolar (ib., p 3) above described, takes the place of the second of the above molars, after the first and second are shed. The above definition of the molar series applies to both upper and lower jaws, the cut (fig. 114), and the symbolic letters and numbers, preclude the necessity of verbal description.
From the analogy of the existing elephants, it may be in¬ ferred that the long tusks (fig. 115, i) supported by the pre- maxillaries, were preceded by a pair ot small deciduous incisors. There is not such ground for concluding theii existence in the mandible ; but this jaw, in the male Mastodon longirostris (fig. 115), supported two incisive tusks, shorter and straighter than those above.
In the proboscidian quadrupeds the molar teeth, progres¬ sively increasing in size, and most of them in complexity, follow each other from before backwards, at longer intervals than in other quadrupeds, and are never simultaneously in
360
PALAEONTOLOGY
place. Not more than three are in use at any period on one side of either jaw ; all the molars, save the penultimate (fig. 115, m 2) are shed by the time the crown of the last molar has cut the gum, and the dentition is finally reduced to m 3 on each side of both jaws, with commonly the loss of the inferior tusks, as in the old Mastodon turicencis, from the tertiary deposits of the Po, described and figured by Sis- monda.*
The genus was represented by species ranging, in time, from the miocene to the upper pliocene deposits, and in space, cosmopolitan with tropical and temperate latitudes. The transition from the mastodontal to the elephantine type of dentition is very gradual.
Genus Elephas, L. — The latest form of true elephant which obtained its sustenance in temperate latitudes is that which Blumenbach called primigenius, the “ Mammoth ” of the Siberian collectors of its tusks (fig. 119). Its remains occur chiefly, if not exclusively, in pleistocene deposits, and have
even been found in tur¬ bary near Holyhead. Its grinders (fig. 116) are broader, and have narrower and more numerous and close-set transverse plates and ridges, than in other Upper grinder of the Mammoth [Elephas primi- elephants. Ill the ex- yemus). isting Indian species,
(%• 117), the molars are relatively narrower, the plates (d d) are less numerous, and their enamelled border (e e ) is festooned. I11 the African elephant (fig. 118) the plates are still fewer, are relatively larger, and so expanded at the middle as to present a lozenge shape. The Elephas prisms, Gdf.,of European * Osteografia di un Mastodoute Angustidente, 4to, Turin, 1851.
ELEPHAS
361
pliocene beds, has molars most like those of the present African species. The tusks of the elephant, like those of the Mastodon,
Fig. 117.
Upper molar, Asiatic Elephant.
consist of true ivory, which shows, in transverse fractures or sections, strike proceeding in the arc of a circle from the
d f c
Fig. 118.
Upper molar, African Elephant.
centre to the circumference in opposite directions, and forming, by their decussations, curvilinear lozenges. This character is a valuable one in the determination of fragments of fossil tusks.
The tusks of the extinct Elephas primigenius, or mam¬ moth, have a bolder and mire extensive curvature than those of the Elephas indicus ; some have been found which describe a circle, but the curve being oblique, they thus clear the head, and point outward, downward, and backward. The numerous fossil tusks of the Mammoth which have been dis¬ covered and recorded, may be ranged under two averages ol size — the larger ones at nine feet and a half, the smaller at
362
PALAEONTOLOGY
five feet and a half in length. The writer has elsewhere assigned reasons for the probability of the latter belonging to the female Mammoth, which must accordingly have differed from the existing elephant of India, and have more resembled that of Africa, in the development of her tusks, yet mani¬ festing an intermediate character by their smaller size. Of the tusks which are referable to the male Mammoth, one from the newer tertiary deposits in Essex measured nine feet ten inches along the outer curve, and two feet five inches in cir¬ cumference at its thickest part ; another from Esclischoltz Bay was nine feet two inches in length, and two feet one and a half inches in circumference, and weighed one hundred and sixty pounds. A specimen, dredged up off Dungeness, measured eleven feet in length. In several of the instances of Mammoth’s tusks from British strata, the ivory has been so little altered as to be fit for the purposes of manufacture ; and the tusks of the Mammoth, which are still better pre¬ served in the frozen drift of Siberia, have long been collected in great numbers as articles of commerce.
In a specimen of the extinct Indian elephant (Elephas ganesa, Fr. and C.) preserved in the British Museum, the tusks are ten feet six inches in length, and in consequence of their small amount of curvature, they project eight feet five inches in front of the head. Their apparent disproportion to the size of the skull is truly extraordinary, and exemplifies the maxi¬ mization of dental development.
The mammoth is more completely known than most other extinct animals by reason of the discovery of an entire speci¬ men preserved in the frozen soil of a cliff at the mouth of the river Lena in Siberia. The skin was clothed with a reddish wool, and with long black hairs. It is now preserved at St. Petersburg, together with the skeleton (fig. 119). This mea¬ sures, from the fore part of the skull to the end of the muti¬ lated tail, 16 feet 4 inches ; the height, to the top of the dorsal
ELEPHAS
363
spines, is 9 feet 4 inches ; the length of the tusks, along the curve, is 9 feet 6 inches. Parts of the skin of the head, the eye-hall, and of the strong ligament of the nape which helped
to sustain the heavy head and teeth, together with the hoofs, remain attached to the skeleton. These huge elephants, adapted by their clothing to endure a cold climate, subsisted on the branches and foliage of the northern pines, birches,
PALAEONTOLOGY
364
willows, etc. ; and during the short summer they probably migrated northward, like their contemporary the musk-buffalo which still lingers on, to the 70th degree of 1ST. latitude, re¬ treating during the winter to more temperate quarters. The mammoth was preceded in Europe by other species of ele¬ phant — -e.ej., Elephas priscus, G-oldfuss, and Elephas meridioncdis, Nesti, which, during the pliocene period, seem not to have gone northward beyond temperate latitudes.
Genus Hippopotamus, L.— The discovery, in lacustrine and flnviatile deposits of Europe, of the remains of an amphibious o-enus of Mammal now restricted to African riveis, gw es scope
iD
for speculating on the nature of the land which, uniting Eng¬ land with the Continent, was excavated by lakes and inter¬ sected by rivers, with a somewhat warmer temperature than at present, to judge by a few S. European shells which occui in the fresh-water formations — e. <j., at (drays, Essex, where remains of the large extinct Hippopotamus major have been found. The specimen of the lower jaw (fig. 121) was dis¬ covered in similar deposits on the Norfolk coasts. Other localities are specified in the writer’s “ History of British 1 ossil Mammals.”
The first premolar has a simple subcompressed conical crown, and a single root ; it rises early, and at some distance in advance of the second premolar, and is soon shed ; the other premolars form a continuous series with the true molars in the existing species, but in the Hippopotamus major the second premolar is in advance of the third by an interval equal to its own breadth. This and the fourth premolar re¬ tain the simple conical form, but with increased size, and are impressed by one or two longitudinal grooves on the outer surface, which, when the crown is much worn, give a lobate character to the grinding surface. The true molars are pri¬ marily divided into two lobes or cones by a wide transverse valley, and each lobe is subdivided by a narrow antero-pos-
RHINOCEROS
365
terior cleft into two lialf cones, witli their flat sides next each other ; the convex side of each half cone is indented by two angular vertical notches, bounding a strong intermediate pro¬ minence. When their summits begin to be abraded, each lobe, or pair of demicones, presents a double trefoil of enamel on the grinding surface, as shown in fig. 120 ; when attrition has proceeded to the base of the half cones, then the grinding surfaces of each lobe presents a quadrilobate figure. The crown of the last molar tooth Molar tooth, Hippopotamus,
of the lower jaw is lengthened out by a fifth cone, developed behind the two normal pairs of half cones, and smaller in all its dimensions.
The hippopotamus is first met with in pliocene strata. The remains of H. major have hitherto been found only in Europe ; they are common along the Mediterranean shore, and do not occur north of the temperate zone. In Asia this
Fig. 121.
Lower jaw of Hippopotamus major (fresh- water Pliocene, Cromer, Norfolk).
form of Pachyderm was represented, perhaps at an earlier period, by the genus Hexaprotodon — essentially a hippopo¬ tamus, with six incisor teeth, instead of four, in each jaw.
3GG
PALAEONTOLOGY
Genus Rhinoceros, L. — The rhinoceros, like the elephant, was represented in pliocene and pleistocene times, in tempe¬ rate and northern latitudes of Asia and Europe, by extinct species. One ( Rhinoceros leptorhinus ) associated with the Hippopotamus major in fresh-water pliocene deposits ; another (. R . tichorrhinus) with the mammoth in pleistocene beds and drift. The discovery of the carcase of the ticliorrine rhino¬ ceros in frozen soil, recorded by Pallas in his “ Voyages dans l’Asie Septentrion al e,”* showed the same adaptation of this, at present tropical, form of quadruped to a cold climate, by a twofold covering of wool and hair, as was subsequently de¬ monstrated to be the case with the mam¬ moth. Both the above-named fossil rhinoceroses were two-horned ; but they were preceded, in the pliocene and miocene periods, by species devoid of horns, yet a rhino¬ ceros in all other essentials (Acero- therium, Ivaup).
The modifica¬ tions which the upper molars of the rhinoceros present as compared with those of its antetype, the Palaeotherium, will be readily understood by comparing fig. 99 with fig. 122, and are as follows : — The concavities (//) on the outer side of the crown, in fig. 99, are almost levelled, and from one of them a * 4to, 1793, pp. 130-132.
k
Fig. 122.
Upper molar, Rhinoceros. Nat. size.
SUIDiE
367
sliglit convexity projects, in some species of Rhinoceros, giving a gently undulated surface to that side of the tooth. The valley (e) is more expanded at its termination (i), in the Rhinoceros ; and, in some species, it bifurcates and deepens, so that one branch may form an insulated circle of enamel when the crown is worn. The posterior valley ( g ) is usually deeper and more extended. The ordinary lobes [a, b, c, d) are very similar, and produce, by the confluence of a with c, and of b with d, the two oblique tracts of dentine which are more decidedly esta¬ blished as transverse ridges in the Lophiodont or Tapiroid group. A basal ridge (r) girts more or less completely the inner and the fore and hind parts of the base of the crown. Not fewer than twenty species of extinct rhinoceroses are entered in Palaeontological catalogues.
The extinct Cheer opotamus, Anthracotherium, H yopotamus, and Hiipoliyus, had the typical dental formula, and this is preserved in the existing representative of the same section of non-ruminant Artiodactyles, the hog. The first true molar when the permanent dentition is completed, exhibits the effects of its early development in a more marked degree than in most other Mammalia, and in the Wild Boar has its tubercles worn down and a smooth field of dentine exposed by the time the last molar has come into place ; it originally bears four primary cones, with smaller sub-divisions formed by the wrinkled enamel, and an interior and posterior ridge. The four cones produced by the crucial impression, of which the transverse part is the deepest, are repeated on the second true molar with more complex shallow divisions, and a larger tuber- culate posterior ridge. The greater extent of the last molar is chiefly produced by the development of the back ridge into a cluster of tubercles ; the four primary cones being distin¬ guishable on the anterior main body of the tooth. The crowns of the lower molars are very similar to those above, but are
PAL/EONTOLOGY
368
ratlier narrower, and the outer and inner basal tubercles are
much smaller, or are wanting ; the grinding surface of the last is shown in fig. 123.
Extinct species of hog have been found in miocene beds at
Fig. 123. Eppelsheim (Sws palceochcerus,
Last lower molar, Hog. Nat. size. Rp ^ and at Simorre (& SWlor-
rcnsis , Lt.) ; in pliocene beds (S. arvernensis, Crt.), and in pleis¬ tocene and later deposits, where the species (S. scrofa fossilis ) is indistinguishable from the present wild boar.
Order Ruminantia.
Of other forms of beasts subsisting on the vegetable pro¬ ductions of the earth, and more akin to actual European Her- bivora, there co-existed, in Europe, with the now exotic genera Eiephas, Rhinoceros , Hippopotamus, etc., a vast as¬ semblage of species, nearly all of which have passed away. The quadrupeds called “ Ruminants,” from the characteristic second mastication of the partly-digested food by the act called “ rumination” or “ chewing the cud,” constitute at the present period a circumscribed group of Mammalia, which Cuvier believed to be “the most natural and best-defined order of the class.”* He characterized it as having incisive teeth only in the lower jaw (fig. 128, c), which were replaced in the upper jaw by a callous gum. Between the incisors and molars is a diastema, in which, in certain genera only, may be found one or two canines. The molars (fig. 128), h, almost always six on eacli side of both jaws, have their crown marked by two double crescents, with the convexity turned inwards in the upper set, outwards in the lower. The four legs are termi¬ nated by two toes and two hoofs, flattened at the contiguous
* Ri'gne Animal, tom. i., p. 254.
RUMINANTIA
369
sides, so as to look like a single hoof cloven ; whence the name “ cloven-footed,” also given to these animals. The perfect cir¬ cumscription and definition of this order, so desirable by the systematic zoologist, is indeed invaded, in the actual Ruvii- nantia, by certain peculiarities of the camel tribe.
In entering upon the evidences of the first appearance in this planet of the order of animals, which now are the most valuable to man, it may be well to call to mind the characters of the Anoplotherium. The upper true molars have two double crescents, convex inwards, one of the inner ones being- encroached on by a large tubercle, the reduced homologue of which may be seen in the internal inner space of the crescents in the ox and some other Euminants. The lower true molars also, at one stage of attrition, form crescentic islands of enamel, with the convexity turned outwards, as in Euminants, the last molar having the accessory crescent behind. The functional hoofs were two in number on each foot, but must have resem¬ bled those of the camel tribe in shape ; the scaphoid and cuboid of the tarsus were distinct also, as in the Cctmelidce; and the metacarpal and metatarsal bones were divided, as in the water musk-deer (. Moschus ciquaticus ), and in the embryos of all Euminants. The dentition of the extinct Dichodon (figs. 102, 103) made a still nearer approach to that of the Eumi¬ nants. The chief distinction of this and other extinct Herbi¬ vores with double crescentic molars is the completion of the upper series of teeth by well-developed incisors. But the pre- maxillaries in the new-born camel contain each three incisors, one of which becomes fully developed. The Camelidce are horn¬ less, like the Anoplotherioids and Dichodonts ; and with one exception — the giraffe — all Euminants are born without horns.
Thus the Anoplotherium, in several important characters, resembled the embryo Euminant, but retained throughout life those marks of adhesion to a more generalized mammalian type. The more modified or specialized form of hoofed animal,
2 B
370
PALAEONTOLOGY
with cloven feet and ruminating stomach, appears at a later period in the tertiary series.
The modification of the upper molars of the existing Rumi¬ nant quadrupeds consists in the lower and less pointed lohes of
the crown, the unworn summits of which are at first rather trenchant, like curved blades, than piercing. They are soon abraded by mastica¬ tion, and present the crescentic lobes of dentine (ct, b, c, ct) shown in fig. 124 The transverse double-crescentic valley (g, i) contains a thicker layer Upper molar of Megaceros. 0f cement, and forms two detached crescents in worn teeth. The premolars resemble in structuie one half of the true molars.
Family I.— Bovim®.
Fossil molars of the ruminant type and bovine character have hitherto been found, with unequivocal evidence, to the writer’s knowledge, only in beds or breccias of pliocene and pleistocene age. At those periods in Britain there existed a very large species of bison {Bison prise us), and a larger species of ox {Bos antiqiius ), from pliocene fresh-water beds ; whilst a somewhat smaller but still stupendous wild ox {B. primige- nius ) has left its remains in pleistocene marls of England and Scotland. With this was associated an aboriginal British ox of much smaller stature and with short horns {B. longifrons), which continued to exist until the historical period, and was probably the source of the domesticated cattle of the Celtic races before the Roman invasion. A buffalo, not distinguish¬ able from the musk kind {Bubalus moschatus ), now confined to the northern latitudes of North America, roamed over similar latitudes of Europe and Asia in company with the hair-clad elephants and rhinoceroses.
CERVILlE
37 i
Family II. — Cervidmi.
Cuvier* first made known the fact of teeth with the charac¬ ter of ruminant molars, and of portions of antlers, being asso¬ ciated with remains of Lophiodon and Mastodon in the fresh¬ water nuocene beds of Montabusard, department of the Loiret. These early ruminant fossils agreed in size with the roebuck ; but there were characters showing that they differed almost generically from all known deer. In 1831 Professor Kaup received from the miocene strata near Eppelsheim, Darmstadt, the entire cranium of a small Kuminant, the teeth of which were identical with those described and figured by Cuvier ; but the series being complete, showed that the animal had long procumbent canines, as in the Moschus vioschiferus ; in some secondary characters of the teeth, however, as in the proportions of the premolars, and especially the presence of the first of that series, at least in the lower jaw, it was generi¬ cally distinct from Moschus or Tragulus. Moreover, the animal had possessed, like the males of the small deer of India called “ Muntjac” antlers as well as long canine teeth. Both in the miocene beds of Ingre and Eppelsheim, antlers have been found which were supported on long pedicles, as in the muntjac, and simply bifurcate near their end. It is probable that these horns, which have been referred to the nominal species Cervics anocerus, may belong to the Dorcatherium of Kaup.
Other species of Gcrvidce were, however, associated with that remarkable form in the miocene period. Dr. Kaup ascribes some more or less mutilated antlers, which had been shed, to a species he calls G. dicranocerus. The beam rises from one to two inches without sending off any branch or brow- antler ; it then sends off a branch so large and so oblique that the beam seems here to bifurcate ; the anterior prong is, how¬ ever, the smallest and shortest. The writer has received similar shed and mutilated antlers from the red crag of Sussex, which
* Ossemens Fossiles, 4to, tom. iv., p. 104, pi. viii., figs. 5 and 6.
372
PALAEONTOLOGY
seems to contain a melange of broken-up beds of eocene, mio- cene, and pliocene age*
The cervine Ruminants have been divided into groups according to the forms of the antlers. Of the group with
Fig. 125.
Megaceros Hibernicus (Pleistocene marl).
antlers expanded and flattened at top, of which the fallow-deer ( Darna) is the type, no fossil examples have been found in Britain. Cuvier has described and figured antlers of great size from the pliocene deposits of the valley of the Somme, near * Quarterly Jour, of the Geol. Soc., vol. xii., 1856, p. 217, figs. 14-16.
CERVIDjE
373
Abbeville, which, from the relative position and direction of the brow-snag and mid-snag, and from the terminal palm, he regards as a large extinct species of fallow-deer ; the name Gervus Somonensis has since been attached to this species. But there once existed a group ( Mcgaceros , fig. 125) charac¬ terized by a form of antler at present unknown amongst exist¬ ing species of deer. With a beam (6) expanding and flattening towards the summit, and a brow-snag (p), as in the Dama tribe, this antler shows a back-snag ( bz ). Moreover, in antlers, showing an expanse of ten feet in a straight line from tip to tip, and which, from their size and form, seem to have been deve¬ loped by the deer at its prime, the brow-snag expands and sometimes bifurcates— a variety never seen in the fallow-deer, but which becomes exaggerated in the rein-deer group. The representative of the subgenus Mcgaceros is an extinct species (If. Hibernicus, fig. 125), remarkable for its great size, and especially for the great relative magnitude and noble form of its antlers : it is the species commonly but erroneously called the “Irish elk;” for it is a true deer, intermediate between the fallow and rein-deer ; and though most abundant in, it is not peculiar to, Ireland. In that country it occurs in the shell-marl underlying the extensive turbaries. In England its remains have been found ha lacustrine beds, brick-earth, red crag, and ossiferous caves*
The rein-deer (Cervus Tarandus) has peculiar antlers (fig. 126), and proportionably the largest of any of existing species. The beam is somewhat flattened throughout, but expands only and suddenly at its extremity, a similar expansion charac¬ terizing the brow-snag (hr) and mid-snag (bz), two, three, or more points being developed from all these expansions in fully- developed antlers. The brow-snag is remarkable for its length. There is also frequently a short back-snag. It is plain, therefore, from the presence of this snag, from the great rela-
* Owen, History of British Fossil Mammals, p. 444.
374
PALAEONTOLOGY
tive size of the antlers, from the complex brow-snag, and the terminal expansion of the beam, that we have in the rein-deer the nearest of kin to the extinct Megaceros.
The existing species ( Tarandus ) is restricted to northern latitudes, ranging to extreme ones in Europe, and in America from the Arctic Circle southward to the latitude of Newfound¬ land, where the large variety called “ Carabou” still exists. Rein-deer of similar size, ranged over continental Europe, appear to have been seen by Caesar in Germany, and have left good
Fig. 126.
Skull and antlers of Cervus Tarandus.
evidence of their existence in many parts of England. The specimen figured (fig. 126) was found in pleistocene “till” at Bilney Moor, East Dereham.
A large deer, with subcompressed ramified antlers, slightly expanding at the base of the terminal divisions, but differing
CERVIDAS
375
from the rein-deer in the absence of the brow-snag, has left its remains in the pleistocene sands of Liege, near Pfzenas, France. It is the Gervus martialis of Gervais ; and seems to have been an intermediate form between the rein-deer ( Tar an - dus ) and the elk {A Ices). There is no existing representative of this interesting annectant form of deer.
In formations of corresponding age in France, called “ allu¬ vions volcaniques” by Gervais* fossil antlers of two other extinct species of deer have been discovered, in which, as in A Ices, the brow-antler is absent, but in which the beam does not expand into a palm.
In North America remains of a large deer ( Gervus ameri- canus fossilis, Harlan), much resembling the Wapiti {Gervus canadensis ) have been found in pleistocene deposits on the banks of the Ohio. In South America Dr. Lund discovered fossil antlers of two species in bone-caves in Brazil : they were associated with remains of an ante¬ lope {Antilope maqitinensis,
Lund) of which genus no living representative is now known in South America.
Of deer with antlers of the type of the existing red- deer {G. elaphus), a species is indicated in pleistocene beds and bone caves which rivalled the Megaceros in bulk {Strongyloceros spclceus ) ; and with this are found, in similar places of deposit, remains of a red-deer with antlers
Fig. 127.
Antler of Red-deer, from alluvium, Ireland.
* Zoologie et Pal6ontologie Frai^aiee, 4to, p. 82.
376
PALEONTOLOGY
equalling or surpassing the finest that have been observed within the historical period.
Fig. 127 represents one of a pair of antlers from the bed of the Boyne at Drogheda, now in the museum of Sir Philip Egerton, Bart., which measures 30 inches in length, and sends off not fewer than fifteen branches or “ snags.” a is the “ brow-snag,” which rises immediately above the “ burr ;” b the second, e the third, and d the “ crown” or terminal cluster of snags, which gave to the deer developing them at the period of his full perfection the title of “ crowned hart.”
The little roebuck, like the red-deer, appears from its fossil remains to have continued to exist from the prehistorical pleistocene times to the present period.
Order Carnivora.
The quadrupeds which subsist by preying upon others co-existed under corresponding varieties of form, and in ade¬ quate numbers, with the numerous and various Herbivora of the newer tertiary periods. A brief description has already been made of some of the singular forms, the genera of which are extinct, that lived in eocene and miocene times.
Genus Galecynus, Ow.— In 1829 the fossil skeleton of a Carnivore, of the size of a fox, was discovered by Sir Roderick I. Murchison in the pliocene schist of (Eningen. On a close comparison of this specimen, the writer finds that the first premolar is smaller, and the third and fourth larger than in the fox, and all the teeth are more close-set and occupy a smaller space than in the genus Canis ; the bones of the feet are more robust ; and these, with other characters, indicate an extinct genus intermediate between Canis and Viverra .* The unique specimen is now in the British Museum.
Genus Felis, L. — As it is by this form of perfect Carnivore that Cuvier chiefly illustrated his principle of the correlation
* See Quarterly Journal of the Geological Society, vol. iii., 1847, p. 55.
CARNIVORA
677
of animal structures, it will be exemplified more particularly in this place, and by the aid of tbe subjoined cut (fig. 128). The founder of palaeontology thus enunciates the law which he believed to guide effectively his labours of reconstructing extinct species : —
“ Every organized being forms a whole, a single circum¬ scribed system, the parts of which mutually correspond and concur to the same definitive action by a reciprocal re-action. None of these parts can change without the others also changing, and consequently each part, taken separately, indi¬ cates and gives all the others.”*
Cuvier did not predicate that law by an a priori method, by any of those supposed short cuts to knowledge, the fallacy of which Bacon so well exposes ; he arrived at the law induc¬ tively, and after many dissections had revealed to him the facts — of the jaw of the Carnivore being strong by virtue of certain proportions ; of its having a peculiarly shaped and articulated condyle, with a plate of bone of breadth and height adequate for the implantation of muscles, with power to inflict a deadly bite — a process grasped by muscles of such magni¬ tude as necessitated a certain extent of surface for their origin from the cranium, with concomitant strength and cur¬ vature of the zygomatic arch ; the facts of the modified occi¬ put and dorsal spines in relation to vigorous uplifting and retraction of the head when the prey had been griped ; the size and shape of the piercing, lacerating, and trenchant teeth ; the mechanism of the retractile claws, and of the joints of the limb that wielded them ; — it was not until after Cuvier had recognized these facts, and studied them and their correlations in a certain number of typical Carnivora, that he felt justified in asserting that “ the form of the tooth gives that of the con¬ dyle, of the blade-bone (s), and of the claws, just as the equa¬ tion of a curve evolves all its properties ; and exactly as, in
* Ossemens Fossiles, 4to, tom. i. (1812), p. 58.
378
PALAEONTOLOGY
taking each property by itself as the base of a particular equation, one discovers both the ordinary equation and all its properties, so the claw, the blade-bone, the condyle, the femur, and all the other bones individually, give the teeth, or are
given thereby reciprocally ; and in commencing by any of these, whoever possesses rationally the laws of the organic economy will be able to reconstruct the entire ani¬ mal.” The principle is so evident, that the non-anatomi- cal reader will have little diffi¬ culty in satisfactorily compre¬ hending it by the aid of the subjoined diagram.
In the jaws of the lion (fig. 128, h, 111), there are large pointed teeth (laniaries or ca¬ nines, c) which pierce, lacerate, and retain its prey. There are also compressed trenchant teeth ( h ), which play upon each other like scissor-blades in the movement of the lower upon the upper jaw. The lower jaw (m) is short and strong ; it articulates to the skull by a transversely extend-
Palseontological characters of a Feline ed convexity 01’ COlldyle (d), armvoie. received into a corresponding
concavity (e), forming a close-fitting joint, which gives a firm
attachment to the jaw, but almost restricts its movements to one plane, as in opening and closing the mouth. The plate
CARNIVORA
379
of bone, called coronoid process (r), which gives the surface of attachment to the chief biting muscle (crotaphyte or temporal) is broad and high ; the surface on the side of the skull (tem¬ poral fossa, t) from which that muscle arises is correspond¬ ingly large and deep, and is augmented by the extension of ridges of bone from its upper and hinder periphery.
The bar or bridge of bone (zygomatic arch) which spans across the muscle, bends strongly outwards to augment the space for its passage ; and as it gives origin to another power¬ ful biting muscle (masseter), the arch is also bent upwards to form the stronger point of resistance during the gripe of that muscle. From almost all the periphery of the back surface of the skull there is a strong pitted ridge, affording extensive attachment to powerful muscles which raise the head, together with the animal’s body which the lion may have seized with his jaws ; this beast of prey being able to drag along the car¬ case of a buffalo, and with ease to raise and bear off the body of a man. If we next examine the framework of the fore limb, which is associated with the above-defined structure of the skull, we find that the fore paw consists of five digits (1-5) ; the innermost and shortest ( 1 ) answering to our thumb, and having two bones ; the other four digits having each three bones or “phalanges.” All those digits enjoy a certain free¬ dom of motion and power of reciprocal approximation for grasping ; but their chief feature is the modification of the terminal phalanx, which is enlarged, compressed, subtriangular, and more or less bent ; with a plate of bone, as it were, re¬ flected forwards from the base, from which the pointed termi¬ nation of the phalanx projects like a peg from a sheath. A powerful, compressed, incurved, sharp-pointed, hard, horny claw is fixed upon that peg, its base being firmly wedged into the interspace between the peg and the sheath. The toe-joint so armed is retractile. This complex, prehensile, and destruc¬ tive paw is articulated to the two bones ol the fore leg (ra-
380
PALAEONTOLOGY
clius, n, and ulna, u) ; they are both strong, are both distinct, are firmly articulated to the arm-bone (A) by a joint, which, although well knit, allows great extent and freedom of motion in bending and extension ; and, besides this, the two bones are reciprocally joined so as to rotate on each other, or rather the radius upon the ulna, carrying with it, by the greater expansion of its lower end, the whole paw, which can thus be turned “ prone” or “ supine f whereby its application as an instrument for seizing and tearing is greatly advantaged. The humerus or arm-bone (A) is remarkable for the extension of strong ridges from the outer and inner sides, just above the elbow-joint. These ridges indicate the size and force of the supinator, pronator, flexor, and extensor muscles of the paw. To defend the main artery of the fore leg from compression during the action of these muscles, a bridge of bone («) spans across it as it passes near their origin. The upper end of the arm-bone is equally well marked by powerful ridges for mus¬ cular implantation, especially for the deltoid ; but these ridges do not project beyond the round “ head” of the bone, so as to impede its movements in the socket.
The blade-bone (scapula s ) is of great breadth, with well- developed processes (spine, acromion, and coracoid) for mus¬ cular attachments ; the size and shape of this bone relate closely to the volume of the muscles which operate upon the arm-bone and fore limb. A small clavicular bone (6) is inter¬ posed between a muscle of the head and one of the arm, giving additional force and determination of action recipro¬ cally to both muscles.
Such are some of the modifications of the teeth and frame¬ work of a beast of prey, which concur, and were deemed by Cuvier to be correlated, in the organization of such animals.
Let us compare them with those of the corresponding parts in an ox (fig. 129). The teeth answering to the great laniaries in the lion are absent ; at most, one recognizes the
HERBIVORA
381
liomologues of the lower canines, reduced in size and altered in shape, so as to form the outer teeth (c) of a bent row of incisors terminating the lower jaw. The hack teeth (h)
instead of being trenchant, have broad and flat crowns,
roughened with hard ridges, opposing each other with a grinding action, like mill¬ stones. The lower jaw is long and slender ; it articulates to the skull by a flat condyle («'), admitting of rotatory move¬ ments upon a flattened arti¬ cular surface on the skull, and limiting the extent of opening and shutting the mouth. The coronoid process (r) is very slender, and the fossa which marks the size of the temporal muscle (t) is correspondingly small. The zygomatic arch (o) is short and feeble, and its span is narrow ; it is almost straight, or with a slight bend downwards. The parts of the skull (pterygoid plates) which afford attachment to the rotat¬ ing muscles of the jaw, and the (angular) part (/) of the jaw into which they are in¬
Palasontological characters of a Ruruinant {Bos).
serted, are of great extent.
The ox masticates grass with great efficiency ; it inflicts no injury to other animals with its teeth. The horns are its weapons, and they are chiefly defensive.
382
PALAEONTOLOGY
The fore foot of the ox is reduced to two principal toes, with two rudimentary ones dangling behind. Each of these has its extremity enveloped by a thick horny case, or hoof ; this modification is accompanied by a junction or coalescence of the radius (n) and ulna (%), preventing reciprocal rotation or movement of those bones on each other ; by a joint restricting the movement of the fore arm (antibrachium) upon the arm (brachium or humerus, h) to one plane ; by a long and narrow blade-bone (s'), with a stunted coracoid and no clavicle ; in short, by modifications adapting the limb to perform the movements required for locomotion, and almost restricting it to such. This type of fore limb is always associated with broad grinding teeth, and with the modifications of jaw and skull above defined. The due amount of observation assured Cuvier that these several modifications, like the contrasted ones in the Carnivora, were correlated, and he enumerates the physio¬ logical grounds of that correlation.
These grounds may be traced to a certain degree in the secondary modifications of the carnivorous order. If the retractibility of the claw be suppressed, the carnassiality of the teeth is reciprocally modified. If the unguiculate foot is reduced from the digitigrade to the plantigrade type, the dentition is still more altered, and made more subservient to a mixed diet.
By the application of the correlative principle to the fossil mammalian remains of pliocene and later deposits, the Her- bivora have been distinguished from the Carnivora ; and out of the latter have been reconstructed extinct species of the feline, viverrine, ursine, and other families of the order. In England and continental Europe a peculiarly destructive feline quadruped existed, with the upper canines much elon¬ gated, trenchant, sharp-pointed, sabre-shaped, whence the name Machairodus proposed for this feline sub-genus. It was represented by species as large as a lion (M. cultridens and
CARNIVORA
383
31. latidens ) ; and by others of the size of a leopard (31. pal- midens and 31. megcmtereon ). This form is first found in the miocene of Auvergne and of Eppelslieim ; next in the plio¬ cene of the Val d’Arno ; and finally in cave breccia in Devonshire.
The penultimate tooth in the upper jaw and the last tooth in the lower jaw were denominated by Cuvier “dents carnassieres.” The carnassial or sectorial is a very charac¬ teristic tooth in the carnivo¬ rous order, but undergoes many
preserves
Fig. 130.
modifications, and its typical form, as repre- Working surface of the upper sectorial sented in figures 130 and 131, tooth’ Hysena' Nat- size- only in the most strictly flesh-feeding species. In it may be distinguished the part called the “blade” (fig. 130, b, b), and the part called the “ tubercule” (fig. 130, t ). The lower sec¬ torial in the genus Felis consists exclu¬ sively of the blade (fig. 131), which is pretty equally divided into two lobes.
The blade of the upper sectorial always plays upon the outside, and a little in advance of the lower sectorial.
The upper sectorial succeeds and displaces a deciduous tubercular molar in all Carnivora, and is, therefore, essen¬ tially a premolar tooth ; the lower sec¬ torial comes up behind the deciduous
series and has no immediate predeces- g^e view of lower sectorial sor ; it is, therefore, a true molar, and tooth> Lion- Nat- Blze- the first of that class. The sectorial teeth present gradational varieties of form in the carnivorous series, from 3dctchairodus, in which the crown consists exclusively of the “blade” in both jaws, to Ursus (fig. 132, m i), in which it is totally tubercular ;
384
PALAEONTOLOGY
the development of the tubercle bearing an inverse relation to the carnivorous propensities of the species.
Fig. 132.
Dentition of the Bear ( Ursus ).
The finest examples of the large pleistocene lion (Felis spelcea ) have been discovered in bone-caves — e.g., in those of Barnwell, Somersetshire, and of Belgium. The production of the apex of the nasal process of the maxillary, as far back as that of the nasal bone, proves this species to have been a lion, not a tiger. It roamed over pliocene and pleistocene Europe, and has left its remains in many stratified deposits of the former period in Britain.
Under similar circumstances have been found, more abundantly in Germany, the remains of the gigantic bear ( Ursus spelceus), and more abundantly in England those of the great hyaena {Hyaena spelcea \ probably a spotted one, like the fierce “ Crocuta” of the Cape. Wolves, foxes, badgers, otters, wolverines, and martin-cats, foumarts and weasels, have left their remains in the newer tertiary deposits and bone caves. Bats, moles, and shrews, were then, as now, the forms that preyed upon the insect world in Europe. The majority of these Carnivora, like the hares, rabbits, voles, and other Kodents, are not distinguishable from the species which still exist. These smaller unguiculate Mammals, like the smaller pleistocene Ruminants, seem to have survived those
RODENTIA
385
changes during which the larger species perished. It is pro¬ bable that the horse and ass are descendants of species of pleistocene antiquity. At the pliocene period there existed a species similar in size to a zebra. There is no certain character by which the present wild boar can he distinguished specifically from the Sus, which was contemporary with the mammoth.
Order Eodentia.
This order includes an extensive series of small Mam¬ mals in which a single pair of large, curved, ever-growing incisors in each jaw is associated with many other peculia¬ rities of structure. These incisors (fig. 1 83, i), sepa¬ rated by a wide interval from a short series of molars, characterize the whole order of Eodents ; the single exceptional family, Leporidce, includ¬ ing hares, rabbits, and Fig. 133.
Picas or tailless hares of Sku11 and teeth of a Porcupine. Siberia, retaining a second minute incisor behind each of the larger ones in the upper jaw.
The small size of the great majority of the species of this order leads to the neglect or the oversight of their fossil remains by the labourers in quarries and other deposits of stone, to whom the palaeontologist is usually indebted for his first acqriaintance with characteristic fossils of such formations. No evidence has yet been obtained of any unequivocal remains of a rodent animal in strata more ancient than the eocene tertiary deposits. Cuvier detected remains of Eodents allied to the dormouse (M yoxus) and squirrel ( Sciurus ) in the eocene building-stone of the Mont¬ martre quarries near Paris. The lacustrine marls of the middle
2 c
386
PALAEONTOLOGY
(miocene) tertiary period have yielded evidences of not fewer than eleven genera of Bodentia distinct from any now known to exist. The deposits at Eppelsheim, near Darm¬ stadt, of the same miocene age, have given evidence of Rodents akin to the marmot and the heaver. The more recent tertiary formations and the hone-caves in England have furnished fossil remains not distinguishable from the existing heaver, hare, and rahhit, water-vole and field-vole, as well as remains of a Pica, or tailless hare, belonging to the genus Lagomys, now confined as an existing species to Asia ; and of a very large Rodent, akin to the heaver, called Trogon- therium. Similar fossil remains have been abundantly found in the pliocene and pleistocene formations of continental Europe, including representatives of the genus Hystrix, or fossil porcupines (II. refossa, Ger.), from the pliocene of Issoire (fig. 133). The coeval deposits of America have yielded fossil remains of extinct species belonging to genera — e. g., Lago- stomus, Ecliimys, Ctcnomys, Cwlogenys, and other Cavies — now restricted to South America. In North America, fossil remains of a Rodent of comparatively gigantic size have recently been discovered. Some parts of the skeleton, and more especially the dentition of the rodent order, are highly characteristic — the form of the articular surface for the lower jaw, which is a longitudinal groove, the molars, especially of the phytiphagous kinds, crossed by enamel plates more or less transverse — these, with the long, curved, chisel-shaped incisors, two in each jaw, suffice to determine the ordinal relations of the fossil. The incisors alone would not be always so safe a guide, for the rodent modification of these teeth is repeated in the marsupial wombat and the lemurine aye-aye.
With regard to the Rodentia, the great beaver ( Trogon - thorium ) seems to have become extinct in England and the Europseo- Asiatic continent before the historical period ; whilst the smaller pliocene beaver continued to exist with \is, like
EUROPE O-ASIATIC MAMMALS
387
the wolf, until hunted down by man. It still survives in a few of the great continental rivers. Of the little Lagomys of our ossiferous caves no living example remains in either England or Europe. The species, indeed, may he extinct : its genus is now limited to Central and Southern Asia.
GEOGRAPHICAL DISTRIBUTION OF PLEISTOCENE MAMMALS.
A most interesting generalization has been educed from the mass of facts relating to the fossil Mammals of the later tertiaries — viz., the close correspondence between the fauna of those and of the present periods in the Europseo- Asiatic expanse of dry land. For here species continue to exist of nearly all those genera which are represented by pliocene and post-pliocene mammalian fossils of the same natural continent, and of the immediately adjacent island of Great Britain.
The hear has its haunts in both Europe and Asia ; the heaver of the Blione and Danube represents the great Trogontherium ; the Lagomys and the tiger exist on both sides of the Himalayan mountain chain ; the liyiena ranges through Syria and Hindostan ; the Bactrian camel typifies the huge Merycotheriuni of the Siberian drift ; the elephant and rhinoceros are still represented in Asia, though now con¬ fined to the south of the Himalayas. The true macacques are peculiar to Asia, and though most abundant in the southern parts of the continent and the Indian Archi¬ pelago, also exist hi Japan ; a closely-allied sub-genus ( Innus ) is naturalized on the rock of Gibraltar at the pre¬ sent day. A fossil species of Macacus was associated with the elephant and rhinoceros in England during the period of the deposition of the newer pliocene fresh water beds. The more extraordinary extinct forms of Mammalia, called EIcis- motlierium and Sivathcrium, have their nearest existing pachy- dermal and ruminant analogues in the same continent to
388
PALEONTOLOGY
which those fossils are peculiar. Cuvier places the Elasmo- there between the horse and rhinoceros. The existing four¬ horned antelopes, like their gigantic extinct analogues, the Sivathere and Bramathere, are peculiar to India. It may he regarded as part of the same general concordance of geogra¬ phical distribution, that the genus Hippopotamus, extinct in England, in Europe, and in Asia, should continue to be repre¬ sented in Africa, and in none of the remoter continents of the earth — Africa also having its hyaena, its elephant, its rhino¬ ceros, and its great feline Carnivores. The discovery ol extinct species of Camelopardalis in both Europe and Asia, of which genus the sole existing representative is now, like the hippopotamus, confined to Africa, adds to the propriety of regarding the three continuous continental divisions of the Old World as forming, in respect to the geographical distribu¬ tion of pliocene, post-pliocene, and recent mammalian genera, one great natural province. The only large edentate animal ( Pangolin gigantesque, Cuvier ; Macrotherium, Lartet) hitherto found in the tertiary deposits of Europe, manifests its nearest affinities to the genus Manis, which is exclusively Asiatic and African.
Extending the comparison between the existing and the latest of the extinct series of Mammalia to the continent of South America, it may be first remarked that, with the exception of some carnivorous and cervine species, no repre¬ sentatives of the above-cited mammalian genera of the Old World of the geographer have yet been found in South America. Buffon* long since enunciated a similar generali¬ zation with regard to the existing species and genera of Mammalia ; it is almost equally true in respect of the fossil. Not a relic of an elephant, a rhinoceros, a hippopotamus, a bison, a by aria, or a lagomys, has yet been detected in the caves or the more recent tertiary deposits of Sonth America.
* Histoire Natuvelle, tom. ix., p. 13, 4to, 1758.
SOUTH- AMERICAN M AM M ALS
389
On tlie contrary, most of the fossil Mammalia from those formations are as distinct from the Europseo-Asiatic forms as they are closely allied to the peculiarly South American existing genera of Mammalia.
The genera Equus, Tapir us, and the still more ubiquitous Mastodon, form the chief, if not sole exceptions. The repre¬ sentation of Equus during the pliocene period by distinct species in Asia (A. primigenius ) and in South America (A. curvidens ), is analogous to the geographical distribution of the species of Tapir us at the present day.
South America alone is now inhabited by species of sloth, of armadillo, of cavy, aguti, ctenomys, and platyrrhine monkey ; but no fossil remains of a quadruped referable to any of these genera have yet been discovered in Europe, Asia, or Africa. The types of Bradypus and Dasypus were, how¬ ever, richly represented by diversified and gigantic specific
Extinct Terrestrial Sloth, Mylodon robustus (Pleistocene, S. America).
forms in South America during the geological periods imme¬ diately preceding the present. The skeleton of one of these forms of the sloth tribe is represented in fig. 134 ; it measures
390
PALAEONTOLOGY
from the fore part of the skull to the end of the tail, 1 1 feet. 1 1 was discovered buried 1 2 feet deep in the fluviatile depo¬ sits seven leagues north of the city of Buenos Ayres in the year 1841. It forms the subject of a work entitled, Descrip¬ tion of the Skeleton of an Extinct Gigantic Sloth ( Mylodon robustus ),* in which are set forth in detail the grounds for regarding it as a member of the same natural family as the present small arboreal sloth, and as being modified to obtain its leafy food by uprooting and prostrating trees.
A still larger species of terrestrial sloth {. Megatherium ) co¬ existed with the Mylodon in South America, Its skeleton, now complete in the British Museum, measures 18 feet ; its dentition
Fig. 135.
Section of upper molar teeth, Megatherium (one-third nat. size), Pleistocene,
South America.
agrees as to number and kind of teeth with that of the sloths ( Bradypus ). But the molars (fig. 135) are longer, more deeply implanted, of more complex structure, and with grinding
* 4to, 1842, Van Voorst.
MEGATHERIUM
391
surfaces of the bilophodont type. The elephants, which sub¬ sist on similar food to that of the Megatherium, had their grinding machinery maintained by a numerous succession of teeth : the same end was attained in the Megatherium, by a constant growth and renovation of the same teeth. The for¬ mative pulps were lodged in the deep basal cavities, exposed in the section figured (fig. 135). The molar teeth were five in number on each side of the upper jaw, and four in number on each side of the lower jaw (fig. 136).
In this bone the fore part is much pro¬ longed, and grooved above, to support a long, cylindrical, powerfully muscular tongue, by which the Megatherium, like the giraffe, stripped off the small branches of the trees its colossal strength enabled it to prostrate. The dentition of Mylodon differed only from that of Megatherium, in the shape of the teeth.
The same may be said of the allied genera Megalonyx and Scelidotherium.
They were contemporary and geographi¬ cally associated genera of the same, now quite extinct, family of great terrestrial sloths.
In like manner, the small loricated and banded quadrupeds of South America called armadillos were repre¬ sented in pleistocene times in that continent by as well-defended species, rivalling the Megathe- rioids in bulk. The specimen of the almost entire skeleton and bony armour (fig. 137) is one of the smaller species of these
areat extinct non-banded armadillos \ yet it measures from the ©
snout to the end of the tail, following the curve of the back, 9 feet ; the tesselated trunk-armour being 5 feet in length and 7
Fig. 136.
Lower jaw and teeth of Megatherium (Pleistocene, South America).
392
PALAEONTOLOGY
feet across, following the curve at the middle of the hack. These large extinct species differ from the modern armadillos, in having no hands or joints in their coat of mail, for the purpose of contracting or bending the body into the form of a ball. They also differ in the fluted form of the teeth (fig. 1 38) ; whence the generic name ( Glyptodon ) assigned to them. The species are distinguished, like their present puny representa¬ tives ( Dasypus ), by peculiar patterns of the outer surface of the constituent ossicles of the tesselated mail. In the species figured (6r. clavipes ), a large raised central circular plate is surrounded by smaller portions. The species named G. reticulatus, G. tuber-
Fig. 137.
Extinct gigantic Armadillo ( Glyptodon clavipes).
culatus, G. ornatus, etc., have their names from other modi¬ fications of the sculptured surface of their armour. Above the principal figure in cut 1 37 are shown the front and back margins of the body-armour ; below it, opposite the left hand, are upper and under views of the cranium, which was defended by a tesselated bony casque. The tail also had its indepen¬ dent osseous sheath, supported by the vertebrae within, as shown in the figure opposite the right hand.
GLYPTODON
393
Toxodon * Macrctuchemia ,t and Protopithecus,\ are addi¬ tional evidences of extinct South American Mammals, matched only by species now peculiar to that continent.
Australia in like manner yields evidence of an analogous correspondence between its last extinct and its present aboriginal mammalian fauna, which is the more interesting on account of the very peculiar organization of most of the native quadrupeds of that division of the globe. That the Marsupial ia form one great natural group, is now gene¬ rally admitted by zoologists ; the represen¬ tatives in that group of many of the orders of the more extensive placental sub-class of the Mammalia of the larger continents have also been recognized in the existing genera and species : the dasyures, for ex¬ ample, play the parts of the Carnivora, the bandicoots (Peramdes) of the Insectivora, the phalangers of the Quadrumana, the wombat of the Rodentia, and the kangaroos, in a remoter degree, that of the Ruminantia.
The first collection of mammalian fossils from the ossiferous caves of Australia § brought to light the former existence on that continent of larger species of the same peculiar marsupial genera : some, as the Thylacine, and the dasyurine sub-genus represented by the I). ursinus, are now extinct on the Australian continent, Put one species of each still exists on the adjacent island of Tasmania ; the rest were extinct wombats, phalangers, poto-
* Owen, “Fossil Mammalia of the Voyage of the Beagle,” 4to, 1839.
i | Lund. Annales des Sciences Nat., 2d series, tom. xiii., p. 313.
£ Mitchell’s (Sir Thos.) Three Expeditions into the Interior of Australia, 8vo, 1838, vol. ii., p. 359.
Fig. 138.
Teeth of great extinct Armadillo ( Glyptoclon clavipes ), Pleistocene, South America.
394
PALAEONTOLOGY
roos, and kangaroos — some of the latter („ Macropus Atlas, M. Titan ) being of great stature. A single tooth, in the same collection of fossils, gave the first indication of the former existence of a type of the marsupial group, which represented the Pachyderms of the larger continents, and which seems now to have disappeared from the face of the Australian earth. Of the great quadruped, so indicated under the name Diprotodon in 1838, successive subsequent acquisitions have established the true marsupial character and the near affini¬ ties of the genus to the kangaroo {Macropus), but with an osculant relationship with the herbivorous wombat. The
Fig. 139.
Skull, gigantic Pachydermoid Kangaroo ( Diprotodon Australis ) Pleistocene
Australia.
entire skull of the Diprotodon Australis (fig. 139) has lately been acquired by the British Museum, showing in situ the tooth (i) on which the genus was founded. This skull measures 3 feet in length ] that of a man is inserted in the cut to exemplify the huge dimensions of the primeval kangaroo. Like the contemporary gigantic sloth in South America, the Diprotodon of Australia, while retaining the dental formula of its living liomologue, shows great and
AUSTRALIAN MAMMALS
395
remarkable modifications of its limbs. The hind pair were much shortened and strengthened, compared with those of the kangaroo ; the fore pair were lengthened as well as strength¬ ened ; yet, as in the case of the Megatherium, the ulna and radius were maintained free, and so articulated as to give the fore paw the rotatory actions. These in Diprotodon, would be needed, as in the herbivorous kangaroo, by the economy of the marsupial pouch. The dental formula of Diprotodon was i c -%,p 28,* and, as in Macropus major,
the first of the grinding series (p) was soon shed; but the other four two-ridged teeth were longer retained, and the front upper incisor (i, i) was very large and scalpriform, as in the wombat. The zygomatic arch sent down a process for augmenting the origin of the masseter muscle, as in the kangaroo. The foregoing skull, with parts of the skeleton, of the Diprotodon Australis, were discovered in a lacustrine deposit, probably pleistocene, intersected by creeks, in the plains of Darling Downs, Australia.
The same formation has yielded evidence of a somewhat
smaller extinct herbivorous genus (A oto- therium), combining, with essential affi¬ nities to Mcicropus, some of the characters of the Koala (Phascolarctus). t The writer has recently communicated de¬ scriptions and figures of the entire skull of the NototTierium Mitchelli to the Geo¬ logical Society of London.^ The genus Phccscolomys was at the same period represented by a wombat (P. gig as) of the magnitude of a tapir, one of tire grinding teeth of which is represented, of the natural size, in fig. 110.
* gee that of Macropus, explained in Ency. Brit., article Odontology, p. 449.
f “Report on the extinct Mammals of Australia,” Trans, of Brit. Assoc.,
1844.
| Quarterly Journal of the Geol. Soc., pt. iv., 1858.
Grinding surface of molar of Pliascolomys gigas (nat. size), Pleistocene, Australia.
39G
PALAEONTOLOGY
The pleistocene marsupial Carnivora presented the usual relations of size and power to the Herbivora, whose undue in¬ crease they had to check. Tig. Til represents an almost entire skull, with part of the lower jaw of an animal ( Thylacoleo )
Fig. 141.
Skull of a large extinct Marsupial Carnivore [Thylacoleo carnifex), Pleistocene, Australia.
rivalling the lion in size, the marsupiality of which is demon¬ strated by the position of the lacrymal foramen (/) in front of the orbit ; by the palatal vacuity (0), by the loose tympanic bone, the development of the tympanic bulla in the alisphenoid, by the very small relative size of the brain, and other characters detailed in the “Philosophical Transactions”* for 1859. The carnassial tooth (j>) is 2 inches 3 lines in longitudinal extent, or
* “On the Fossil Mammals of Australia. Part I. Description of the Thylacoleo carnifex." By Prof. Owen, etc.
THYLACOLEO
397
nearly double the size of that in the lion. The upper tuber¬ cular tooth (m, i) resembles in its smallness and position that in the placental Felines. But in the lower jaw the carnassial Op) is succeeded by two very small tubercular teeth (m, i and 2), as in Plagictulax (fig. 93, p. 320) ; and there is a socket close to the symphysis of the lower jaw of Thylacoleo which indicates that the canine may have terminated the dental series there, and have afforded an additional feature of resemblance to the Plagictulax.
The foregoing are some of the more interesting illustrations of the law, that “ with extinct as with existmg Mammalia, par¬ ticular forms were assigned to particular provinces, and that the same forms were restricted to the same provinces at a former geological period as they are at the present day.”* That period, however, was the more recent tertiary one.
In carrying back the retrospective comparison of existing and extinct Mammals with those of the eocene and oolitic strata, in relation to their local distribution, we obtain indica¬ tions of extensive changes in the relative position of sea and land during these epochs, in the degree of incongruity between the generic forms of the Mammalia which then existed in Europe and any that actually exist on the great natural conti¬ nent of which Europe now forms part. It would seem, indeed, that the further we penetrate into time for the recovery of extinct Mammalia, the further we must go into space to find their existing analogues. To match the eocene Palseotheres and Lopliiodons, we must bring Tapirs from Sumatra or South America, and we have to travel to the antipodes for Myrmeco- bians, the nearest living analogues to the Amphitheres of our oolitic strata.
On the problem of the extinction of species, little, demon¬ stratively, can be said; and on the more mysterious subject
* Report on the Extinct Mammals of Australia, 1844.
398
PALAEONTOLOGY
of their coming into being, no light has yet been thrown by experiment or observation. As a cause of extinction in times anterior to man, it is most reasonable to assign the chief weight to those gradual changes in the conditions affect¬ ing a due supply of sustenance to animals in a state of nature which must have accompanied the slow alternations of land and sea brought about in the aeons of geological time. Yet this reasoning is applicable only to land-animals ; for it is scarcely conceivable that such operations can have affected sea-fishes. There are characters in land-animals rendering them more obnoxious to extirpating influences, which may explain why so many of the larger species of par¬ ticular groups have become extinct, whilst smaller species of equal antiquity have survived. In proportion to its bulk is the difficulty of the contest which, as a living organism, the individual of such species has to maintain, against the sur¬ rounding agencies that are ever tending to dissolve the vital bond, and subjugate the living matter to the ordinary chemical and physical forces. Any changes, therefore, in such external agencies as a species may have been originally adapted to exist in, will militate against that existence in a degree proportionate to the bulk of the species. If a dry season be gradually pro¬ longed, the large Mammal will suffer from the drought sooner than the small one ; if such alteration of climate affect the quantity of vegetable food, the bulky Herbivore will first feel the effects of stinted nourishment ; if new enemies be intro¬ duced, the large and conspicuous animal will fall a prey, while the smaller kinds conceal themselves and escape. Small quadrupeds are more prolific than large ones. Those of the bulk of the Mastodons, Megatheria, Glyptodons, and Diproto- dons are uniparous. The actual presence, therefore, of small species of animals in countries where larger species of the same natural families formerly existed, is not the consequence of degeneration — of any gradual diminution of the size of such
EXTINCTION OF SPECIES
399
species — but is the result of circumstances which may be il¬ lustrated by the fable of the “oak and the reed;” the smaller and feebler animals have bent and accommodated themselves to changes to which the larger species have succumbed.
That species, or forms so recognized by their distinctive characters and the power of propagating them, have ceased to exist, and have successively passed away, is a fact no longer questioned. That they have been exterminated by exceptional cataclysmal changes of the earth’s surface has not been proved. That their limitation in time, in some instances or in some measure, may be due to constitutional changes accumulating by slow degrees in the long course of generations, is possible. But all hitherto observed causes of extirpation point either to continuous slowly operating geological changes, or to no greater sudden cause than the, so to speak, spectral appear¬ ance of mankind on a limited tract of land not before inhabited. It is most probable, therefore, that the extinction of species, prior to man’s presence or existence, has been due to ordinary causes — ordinary in the sense of agreement with the laws of organization and of the never-ending mutation of the geo¬ graphical and climatal conditions on the earth’s surface. The species, and individuals of species, least adapted to bear such influences, and incapable of modifying their organization in agreement therewith, have perished. Extinction, therefore, on this hypothesis, implies the want of self-adjusting power in the individuals of the species subject thereto.
But admitting extinction as a natural law, which has operated from the beginning of life under specific forms of plants and animals, it might be expected that some evidence of it should occur in our own time, or within the historical period. Reference has been made to several instances of the extirpation of species, certainly, probably, or possibly, due to the direct agency of man. The hook-billed parrot ( Nestor productus) of Philip’s Island, west of New Zealand, is, perhaps,
400
PALAEONTOLOGY
the latest instance of this kind. But this cause avails not in the question of the extinction of species at periods prior to any evidence of human existence ,' it does not help us in the explanation of the majority of extinctions, as of the races of aquatic Invertebrata and Vertebrata which have successively passed away.
The Great Auk (Aka impennis, L.) seems to be rapidly verging to extinction. It has not been specially hunted down, like the dodo and dinornis, but by degrees has become more scarce. Some of the geological changes affecting circum¬ stances favourable to the well-being of the A lea impennis , have been matters of observation. The last great auks, known with anything like certainty to have been seen living, were two which were taken in 1844 during a visit made to the high rock, called “ Eldey,” or “ Meelsoekten,” lying off Cape Beyki- anes, the S. W. point of Iceland. This is one of three principal rocky islets formerly existing in that direction, of which the one specially named from this rare bird “ Geirfugla Sker ” sank to the level of the surface of the sea during a volcanic disturb¬ ance in or about the year 1830. Such disappearance of the fit and favourable breeding-places of the A Icct impennis must form an important element in its decline towards extinction. The numbers of the bones of Alca impennis on the shores of Iceland, Greenland, and Denmark, attest the abundance of the bird in former times.
Within the last century, academicians of Petersburg and good naturalists described and gave figures of the bony and the perishable parts, including the alimentary canal, of a large and peculiar fucivorous Sirenian — an amphibious animal like the Manatee, which Cuvier classified with his herbivorous Cetacea, and called Rytina Stclleri, after its discoverer. This animal inhabited the Siberian shores and the mouths of the great, rivers there disemboguing. It is now believed to be extinct, and this extinction appears not to have been due to any special
HUMAN REMAINS
401
quest and persecution by man. We may discern in this fact the operation of changes in physical geography, which have at length so affected the conditions of existence of the Siberian manatee as to have caused its extinction. Such changes had operated, at an earlier period, to the extinction of the elephant and rhinoceros of the same region and latitudes : a future generation of zoologists may have to record the final disappear¬ ance of the Arctic buffalo (Qvibos moschatus}. Remains of Ovibos and Rytina show that they were contemporaries of Elephas primigenius and Rhinoceros tichorrhinus.
But recent discoveries indicate that, in the case of the last two extinct quadrupeds, a rude primitive human race may have finished the work of extermination, begun by ante¬ cedent and more general causes.
Flint weapons called “ celts,” unquestionably fashioned by human hands, have been discovered in stratified gravel, containing remains of the mammoth, in the valley of the Somme near Abbeville and Amiens, at different periods, from the year 1847 (Boucher de Perthes, “Antiquites cel- tiques et antediluviennes,” Paris, 1847) to the present time.
These evidences of the human species have been extracted from the deposit in question, by Mr. Prestwich (“ ] 7 feet from the surface in undisturbed ground,” “ Proceedings of the Royal Society,” May 26, 1859) ; by Mr. Flower, (“ 20 feet from the surface, in a compact mass of gravel,” “ Times,” November 18, 1859) ; by M. Gaudry (“ LTnstitut,” October 5, 1859) ; and by M. Geo. Poucliet, — all with their own hands in the course of the year 1859. Besides the Elephas primigenms, remains of Rhinoceros tichorhinus, Cervus somonensis, Ursus spelmis, and of a large extinct Bovine animal, have been found in the same bed of gravel.
Mr. Prestwich, F.G.S., after a careful study of the geolo- logical relations of this bed, refers it to the post-pliocene
2 D
402
PALEONTOLOGY
age ; and to a period “ anterior to the surface assuming its present outline, so far as some of its minor features are con¬ cerned.”
Similar flint weapons had been discovered by Mr. John Frere, F.E.S. (“ Archeologia,” vol. xiih, “ An account of flint weapons discovered at Hoxne in Suffolk,’ 1800) in a bed of flint gravel, 16 feet below the surface, of the same geological age as that in the valley of the Somme.
Flint weapons have been discovered mixed indiscrimi¬ nately with the bones of the extinct cave-bear and rhino¬ ceros. One in particular was met wfith beneath a fine antler of a rein-deer, and a bone of the cave-bear, imbedded in the superficial stalagmite in the bone-cave at Brixham, Devon¬ shire, during the careful exploration of that cave conducted by a committee of the Geological Society of London in 1858 and 1859.
Dr. Falconer, F.G.S., has communicated (“ Proceedings of the Geological Society,” June 22, 1859) the results of his examination of ossiferous caves in Palermo ; and in respect to the “ Maccagnone cave,” he draws the following infer¬ ences : — That, “ it was filled up to the roof within the human period, so that a thick layer of bone splinters, teeth, land- shells, coprolites of hyaena, and human objects, was aggluti¬ nated to the roof by the infiltration of water holding lime in solution ; that subsequently and within the human period, such a great amount of change took place in the physical configuration of the district as to have caused the cave to be washed out, and emptied of its contents, excepting the floor- breccia and the patches of material cemented to the roof, and since coated with additional stalagmite.” (P. 136.)
Sir Charles Lyell believes “ the antiquity of the Abbeville and Amiens flint instruments to be great indeed, if compared to the times of history or tradition. . . .” “ It must have re¬
quired a long period for the wearing down of the chalk which
ORIGIN OF SPECIES
403
supplied the broken flints for the formation of so much gravel at various heights, sometimes 100 feet above the present level of the Somme, for the deposition of fine sediment including entire shells both terrestrial and aquatic, and also for the denudation which the entire mass of stratified drift has under¬ gone, portions having been swrept away, so that what remains of it often terminates abruptly in old river cliffs, besides being covered by a newer unstratified drift. To explain these changes, I should infer considerable oscillations in the level of the land in that part of France ; slow movements of up¬ heaval and subsidence, deranging but not wholly displacing the course of ancient rivers. Lastly, the disappearance of the elephant, rhinoceros, and other genera of quadrupeds, now foreign to Europe, implies in like manner a vast lapse of ages, separating the era in which the fossil implements were framed, and that of the invasion of Gaul by the Romans.”*
As to the successive appearance of new species in the course of geological time, it is first requisite to avoid the common mistake of confounding the propositions, of species being the result of a continuously operating second¬ ary cause, and of the mode of operation of such creative cause. Biologists may entertain the first without accepting any cur¬ rent hypothesis as to the second.
That the species of the mineralogist and the botanist should be owing to influences so different as is implied by the opera¬ tion of a second cause, and the direct interference of a first cause, is not probable. The nature of the forces operating in the production of a lichen may not be so clearly understood as those which arranged the atoms of the crystal on which the lichen spreads. Poucliet has contributed the most valuable evidence as to the fact and mode of the production by external
* Address, on opening the Section of Geology, at the Meeting of the British Association at Aberdeen, September 15, 1859.
404-
PALEONTOLOGY
influences of species of Protozoa.* With regard to the species of higher organisms, distinguishable as plants and animals, their origin is as yet only matter of speculation.
Buffont regarded varieties as particular alterations ot species, which illustrated the mutability of species themselves. The so-called varieties of a species, species of a genus, genera of an order, etc., were with him but so many evidences of the progressive degrees of change, which had been superinduced by time and successive generations, and chiefly by degrada¬ tion from a primordial type. Applying this principle to the species of which he had given the history in his great work, he believed himself able to reduce them to a very small number of primitive stocks, of which he enumerates “ fifteen.”
Lamarck,| adverting to observed ranges of variation in certain species, affirmed that such variations would proceed and keep pace with the continued operation of the causes pro¬ ducing them ; that such changes of form and structure would induce corresponding changes in actions, and that a change of actions, when habitual, became another cause of altered struc¬ ture ; that the more frequent employment of certain parts or organs leads to a proportional increase of development of such parts ; and that as the increased exercise of one part is usually accompanied by a corresponding disuse of another part, this very disuse, by inducing a proportional degree of atrophy, becomes another element in the progressive mutation of organic forms.
A third theorist § calls to mind the instances of sudden departure from the specific type, manifested by a malformed or monstrous offspring, and quotes the instances in which such malformations have lived and propagated the deviating structure. He notes also the extreme degrees of change and * Heterogenie, 8vo, 1859.
t Histoire Naturelle, Deg6neration des Animaux, tom. iv., p. 311. t Philosophic Zoologique, 8vo, 1809, tom. i., chs. 3 and 7.
§ “ Yestiges of tlie Natural History of Creation.”
ORIGIN OF SPECIES
405
of complexity of structure undergone by the germ and embryo of a highly organized animal in its progress to maturity. He speculates on the influence of premature birth, or on a some¬ what prolonged fetation, in establishing the beginning of a specific form different from that of the parent.
Mr. Wallace,* assuming that varieties may arise in a wild species, shows how such deviations from type may tend to adapt a variety to some changes in surrounding conditions, under which it is better calculated to exist, than the type- form from which it deviated.
Ho doubt the type-form of any species is that which is best adapted to the conditions under which such species at the time exists ; and as long as those conditions remain unchanged, so long will the type remain ; all varieties departing therefrom being in the same ratio less adapted to the environing conditions of existence. But, if those con¬ ditions change, then the variety of the species at an antece¬ dent date and state of things will become the type-form of the species at a later date, and in an altered state of things.
Mr. Charles Darwin had, previously to Mr. Wallace, pondered over and worked at this principle, which he illustrates by ingenious suppositions, of which I select the following : — “ To give an imaginary example from changes in progress on an island : — let the organization of a canine animal which preyed chiefly on rabbits, but sometimes on hares, become slightly plastic ; let these same changes cause the number of rabbits very slowly to decrease, and the number of hares to increase ; the effect of this would be that the fox or dog would be driven to try to catch more haies , his organization, however, being slightly plastic, those indi¬ viduals with the lightest forms, longest limbs, and best eye¬ sight, let the difference be ever so small, would be slightly favoured, and would tend to live longer, and to survive during
Proceedings of the Linnaean Society, August 1858, p. 57.
406
PALAEONTOLOGY
that time of the year when food was scarcest ; they would also rear more young, which would tend to inherit these slight peculiarities. The less fleet ones would he rigidly destroyed. I can see no more reason to doubt that these causes in a thousand generations would produce a marked effect, and adapt the form of the fox or dog to the catching of hares instead of rabbits, than that greyhounds can be improved by selection and careful breeding*
Observation of animals in a state of nature, however, is still required to show their degree of plasticity, or the extent to which varieties do arise ; whereby grounds may be had for judging of the probability of the elastic ligaments and joint- structures of a feline foot, for example, being superinduced upon the more simple structure of the toe with the non- retractile claw, according to the principle of a succession of varieties in time.
Farther discoveries of fossil remains are also needed to make known the antetypes, in which varieties, analogous to the observed ones in existing species, might have occurred, seriatim, so as to give rise ultimately to such extreme forms as the Giraffe.
This application of palaeontology has always been felt by myself to be so important that I have never omitted a proper opportunity for impressing the results of observations showing the “more generalized structures” of extinct, as compared with the “more specialized forms” of recent animals.
But observation of the effects of any of the above hypo¬ thetical transmuting influences in changing any known species into another has not yet been recorded. And past expe¬ rience of the chance aims of human fancy, unchecked and unguided by observed facts, shows how widely they have ever glanced away from the gold centre of truth.
* Proceedings of the Linnsean Society, August 1858, p. 49. The principle is more fully illustrated in the work “On the Origin of Species,” 8vo, 1859.
SUCCESSION OF MAMMALIA
407
The principles, based on rigorous and extensive observa¬ tion of facts, which have thus been inductively established, and have tended to impress upon the minds of the closest reasoners in Biology a conviction of a continuously operative secondary creational law, are the following : — the law of irre¬ lative or vegetative repetition : the law of unity of plan or rela¬ tions to an archetype : the phenomena of parthenogenesis : the progressive departure from general type as exemplified in the series of species from their first introduction to the present time.
Table of Geological Distribution of Mammals.
|
Irfars n- -pLSlCOL. |
Rodent- ut. |
Zh.secli-1 vor a |
Ch.eu.Top- tird r |
letacea |
iirenia. |
oxo ion|-Pro Los- tta. -ciaea. |
Peri ss- dactylu. |
drtic- daciyla. |
Carta- vora - |
Duaolnx- man.a. m |
5 (.'man a 17 |
Modem. |
|||
|
A/o<£ern Pliocene |
-r |
f |
t |
-t- |
1 |
f |
:P |
% |
=|= |
4 |
f |
4 |
Pliocene Miocene |
||
|
Vhtocfine. .Eocene |
1 |
-4- |
IL |
w |
? |
Eocene |
|||||||||
|
f'4 |
Ji - |
||||||||||||||
|
Crefca- .ceoas |
Greta. - .ceoas WeaUcn |
||||||||||||||
|
"We ctlden |
9 |
« |
Tu-rb eck. |
||||||||||||
|
Oolite- Lias Trias Ter va an |
i TAascoloti rJicrfleste- |
kere |
? |
— |
tz |
? |
1 - |
Oolite L LCI.Z Trla.0 jermiaiv |
Fig. 142.
The Table (fig. 142) expresses the sum of the observa¬ tions at the present date, on the succession, appearance, and geological relations of the several orders of the Mammalian
class.
The earliest evidences are of small species, which, when¬ ever they have presented grounds for ordinal determination, have proved to belong to the low organized Marsupialia. The doubt, when it has existed, lies between this and the Insecti¬ vorous order, also low in the class according to cerebral characters.* One example only, from Stonesfield oolite, the Stereognathus, may prove to be a minute Ungulate, as is indi¬ cated by the note of interrogation under Penssodactyla. ihe
* Owen, “ On the Classification and Geographical Distribution of the Mammalia,” 8vo, 1 859.
408
PALAEONTOLOGY
similar mark, under Cetacea, refers to the fossil, probably washed out of an Upper Oolitic bed, referred to at p. 321. The Marsupialia recur, under distinct generic forms, in the eocene strata, and, according to actual knowledge, present their fullest development in pliocene and modern times, more especially in Australia. The orders Bruta, Perissodactyla, and Carnivora, have become reduced in numbers ; the Proboscidia still more so ; the representatives of the singular group Toxodontia have wholly disappeared.
The sum of the evidence which has been obtained seems to prove that the successive extinction of Microlestes, Amphi- theria, Spalacotheria, Triconodons, and other mesozoic forms of mammals, has been followed by the introduction of much more numerous, varied, and higher-organized forms of the class, during the tertiary periods.
It may be, however, objected that negative evidence cannot satisfactorily establish the proposition that the mammalian class is of late introduction, nor prevent the conjecture that it may have been as richly represented in primary and more ancient secondary as in tertiary times, could we but get remains of the terrestrial fauna of the continents. To this objection it may be replied: in the palaeozoic strata, which, from their extent and depth, indicate, in the earth’s existence as a seat of organic life, a period as prolonged as that which has followed their deposition, no trace of mammals has been observed. Were mammals peculiar to dry land, such nega¬ tive evidence would weigh less in producing conviction of their non-existence during the Silurian and Devonian aeons, because the explored parts of such strata have been deposited fiom an ocean, and the chance of finding a terrestrial and air- breathing creature’s remains in oceanic deposits is very remote. But in the present state of the warm-blooded, air-breathing, viviparous class, no genera and species are represented by such numerous and widely dispersed individuals, as those of
SUCCESSION OF CLASSES
409
the order Cetacea, which, under the guise of fishes, dwell, and can only live, in the ocean.
In all Cetacea the skeleton is well ossified, and the vertebrae are very numerous : the smallest Cetacean would he deemed large amongst land-mammals ; the largest surpass in hulk any creatures of which we have yet gained cognizance : the hugest ichthyosaur, iguanodon, megalosaur, mammoth, or megathere, is a dwarf in comparison with the modern whale of a hundred feet in length.
During the period in which we have proof that Cetacea have existed, the evidence in the shape of hones and teeth, which latter enduring characteristics in most of the species are peculiar for their great number in the same individual, must have been abundantly deposited at the bottom of the sea ; and as cachalots, grampuses, dolphins, and porpoises are seen gambolling in shoals in deep oceans, far from land, their remains will form the most characteristic evidences of verte¬ brate life in the strata now in course of formation at the bottom of such oceans. Accordingly, it consists with the known characteristics of the cetacean class to find the marine deposits Avhich fell from seas tenanted, as now, with vertebrates of that high grade, containing the fossil evidences of the order in vast abundance.
The red crag of Suffolk and Essex contains petrified frag¬ ments of the skeletons and teeth of various Cetacea, in such quantities as to constitute a great part of that source of phos¬ phate of lime for which the red crag is worked for the manu¬ facture of artificial manure. The scanty and dubious evidence of Cetacea in secondary beds seems to indicate a similar period for their beginning as for the soft-scaled cycloid and ctenoid fishes which have superseded the ganoid orders of mesozoic times.
We cannot doubt but that had the genera Ichthyosaurus, Pliosaurus, or Plesiosaurus, been represented by species m the
410
PALEONTOLOGY
same ocean that was tempested by the Balaenodons and Dio- plodons of the miocene age, the bones and teeth of those marine reptiles would have testified to their existence as abun¬ dantly as they do at a previous epoch in the earth’s history. But no fossil relic of an enaliosaur has been found in tertiary strata, and no living enaliosaur has been detected in the present seas: and they are consequently held by competent naturalists to be extinct.
In like manner does such negative evidence testify to the non-existence of marine mammals in the liassic and oolitic times. In the marine deposits of those secondary or mesozoic epochs, the evidence of vertebrates governing the ocean, and preying on inferior marine vertebrates, is as abundant as that of air-breathing vertebrates in the tertiary strata ; but in the one the fossils are exclusively of the cold-blooded reptilian class, in the other, of the warm-blooded mammalian class. The Encdiosauria, Cetiosauria, and Crocodilia, played the same part and fulfilled similar offices in the seas from which the lias and oolites were precipitated, as the Delpliinidce and Balcenidce did in the tertiary seas, and still do in the present ocean. The unbiassed conclusion from both negative and positive evidence in this matter is, that the Cetacea succeeded and superseded the Enaliosauria. To the mind that will not accept such conclusion, the stratified oolitic rocks must cease to be trustworthy records of the condition of life on the earth at that period.
So far, however, as any general conclusion can be deduced from the large sum of evidence above referred to, and con¬ trasted, it is against the doctrine of the Uniformitarian. Organic remains, traced from their earliest known graves, are succeeded, one series by another, to the present period, and never re-appear when once lost sight of in the ascending search. As well might we expect a living Ichthyosaur in the Pacific, as a fossil whale in the Lias: the rule governs as
SUCCESSION OF CLASSES
Ill
strongly in the retrospect as the prospect. And not only as respects the Vertebrata, hut the sum of the animal species at each successive geological period has been distinct and pecu¬ liar to such period.
Not that the extinction of such forms or species was sudden or simultaneous : the evidences so interpreted have been but local. Over the wider field of life at any given epoch, the change has been gradual ; and, as it would seem, obedient to some general, continuously operative, but as yet, ill-compre¬ hended, law. In regard to animal life, and its assigned work on this planet, there has, however, plainly been “ an ascent and progress in the main.”
Although the mammalia, in regard to the plenary develop¬ ment of the characteristic orders, belong to the Tertiary division of geological time, just as “ Echini are most common in the superior strata; Ammonites in those beneath, and Producti with numerous Encrini in the lowest’* of the secondary strata, yet the beginnings of the class manifest themselves in the formations of the earlier preceding division of geological time.
We are not entitled to infer from the Lucina of the per- mian, and the Opis of the trias, that the Lamellibranchiate Mollusks existed in the same rich variety of development at those periods as during the tertiary and present times ; and no prepossession can close the eyes to the fact that the Lamelli¬ branchiate have superseded the Palliobranchiate bivalves.
On negative evidence, Orthisina, Theca , Produda, or Spirifer are believed not to exist in the present seas: on negative evi¬ dence the existing genera of siphonated bivalves and univalves are deemed to have been very rare in permian, tiiassic, 01 oolitic times. To suspect that they may have then abundantly existed, but have hitherto escaped observation, because certain Lamellibranchs with an open mantle, and some holostomatous
* A generalization of William Smith s.
412
PALAEONTOLOGY
and asiphonate Gastropods, liave left their remains in secondary strata, is not more reasonable, as it seems to me, than to con¬ clude that the proportion of mammalian life may have been as great in secondary as in tertiary strata, because a few small forms of the lowest orders have made their appearance in triassic and oolitic beds.
Turning from a retrospect into past time for the prospect of time to come, I may crave indulgence for a few words, of more sound, perhaps, than significance, relative to the amount of prophetic insight imparted by Palaeontology. But the re¬ flective mind cannot evade or resist the tendency to speculate on the future course and ultimate fate of vital phenomena in this planet. There seems to have been a time when life was not ; there may, therefore, be a period when it will cease to be.
Our most soaring speculations still show a kinship to our nature : we see the element of finality in so much that we have cognizance of, that it must needs mingle with our thoughts, and bias our conclusions on many things.
The end of the world has been presented to man’s mind under divers aspects : as a general conflagration ; as the same, preceded by a millennial exaltation of the world to a paradisiacal state, — the abode of a higher race of intelligences.
If the guide-post of Palaeontology may seem to point to a course ascending to the condition of the latter speculation, it points but a very short way, and in leaving it we find ourselves in a wilderness of conjecture, where to try to advance is to find ourselves “ in wandering mazes lost.”
With much more satisfaction do I return to the legitimate deductions from the phenomena which have been under review.
In the survey which has been taken of the various forms of life that have passed away — of their characters, succession, geo¬ logical position, and geographical distribution — if I have sue-
CONCLUSION
413
ceeded in demonstrating the adaptation of any structure to the exigencies, habits, and well-being of the species, I have fulfilled one object which 1 had in view, viz., to set forth the beneficence and intelligence of the Creative Power.
If, in all the striking changes of form and proportion which have passed under review, we could discern only the results of minor modifications of a few essential elements, we must be the more strikingly impressed with the unity of that Cause, and with the wisdom and power, which could produce so much variety, and at the same time such perfect adaptations and en¬ dowments, out of means so simple. For, in what have those contrasted limbs, hoofs, paws, fins, and wings, so variously formed to obey the behests of volition in denizens of different elements, differed from the mechanical instruments which we ourselves plan with foresight and calculation for analogous uses, save in their greater complexity, in their perfection, and in the unity and simplicity of the elements which are modified to constitute these several locomotive organs (
Everywhere in organic nature we see the means not only subservient to an end, but that end accomplished by the simplest means. Hence we are compelled to regard the Great Cause of all, not like certain philosophic ancients, as a uniform and quiescent mind, as an all-pervading anima mundi, but as an active and anticipating intelligence.
By applying the laws of comparative anatomy to the relics of extinct races of animals contained in and characterizing the different strata of the earth’s crust, and corresponding with as many epochs in the earth’s history, we make an important step in advance of all preceding philosophies, and are able to demonstrate that the same pervading, active, and beneficent intelligence which manifests His power in our times, has also manifested His power in times long anterior to the records of our existence.
But we likewise, by these investigations, gain a still more
414
PALAEONTOLOGY
important truth, viz., that the phenomena of the world do not succeed each other with the mechanical sameness attributed to them in the cycles of the epicurean philosophy ; for we are able to demonstrate that the different epochs of the earth were attended with corresponding changes of organic structure ; and that, in all these instances of change, the organs, still illustra¬ ting the unchanging fundamental types, were, as far as we could comprehend their use, exactly those best suited to the functions of the being. Hence we not only show intelligence evoking means adapted to the end ; but, at successive times and periods, producing a change of mechanism adapted to a change in external conditions. Thus the highest generalizations in the science of organic bodies, like the Newtonian laws of universal matter, lead to the unequivocal conviction of a great First Cause, which is certainly not mechanical.
INDEX
AcALF.rH.-K, 17. Acanthias, 100. Acantliocladia, 28. Acauthodes, 131. Acanthodii, 130. Acanthopteri, 146. Acanthospongia, 6. Acanthoteuthis, 91. Acervularia, 23. Acervulina, 11. Acheta, 47.
Acrodus, 109. Acrolepis, 138. Acteonella, 80. Acteonina, 74, 80. Acrocidaris, 36. Acrosalenia, 36. Actinoceras, 85. Actinocrinus, 31. Actinocyclus, 13, 14. Actinoida, 21. Actinophrys, 9. iEolodon, 271. iEtobates, 115. Agathistega, 11. Agnostus, 42.
Alaria, 73.
Alca, 400.
Alecto, 28.
Alligator, 273. Alveolina, 12. Amblypterus, 137. Amblyurus, 143. Ambonychia, 57. Ammonites, 86. Amoeba, 9. Amphibichnites. 163. Amphicoelia, 271. Amphicyon, 340. Amphidotus, 36. Amphilestes, 303. Amphitherium, 303. Amphiura, 33. Aniplexus, 23. Anacanthini, 148. Anauchydes, 34. Anastoma, 79. Anatinid®, 57.
Ancyloceras, 86.
Andrias, 284.
Annulata, 39.
Anomia, 58. Anomodontia, 235. Anoplotherium, 332. Anthocrinus, 31. Anthozoa, 21. Anthracotkerium, 367. Antlirocosia, 66. Antipathes, 21.
Apateon, 168.
I Aphis, 47.
I Apioceras, 83. Apiocrinus, 30. Aporrkais, 73.
Apteryx, 294.
Apus, 45.
I Aptvchus, 86.
J Arachnida, 48.
Arbacia, 36.
Area, 61.
Arcella, 9.
Archseocidaris, 35. Archteoniscus, 45. Archegosaurus, 168, 177. Archiacia, 36. Archimedipora, 20. Arthraster, 34.
Asaphus, 44.
Ascidia, 27.
Ascoceras, 83.
Asilus, 47.
Aspidiscus, 25.
Aspidura, 33.
Astartidse, 57. Asteriadae, 33. Asteropterichius, 104. Astrsea, 36. Astrogonium, 34. Athyris, 50.
Atlanta, 72.
Atrypa, 50.
Aturia, 82.
Aulacanthus, 105.
Aves, 286.
Aviculid®, 60. Aviculopecten, 57.
Axinus, 57.
Bacillaria, 14, 16. Bactrites, 85.
Baculites, 86. Bakewellia, 60. Balsenodon, 342. Balanophyllia, 26. Balanus, 40.
Batistes, 100.
Baphetes, 184. Bathygnathus, 252. Batracliia, 283. Batrachopus, 166. Belemnites, 92. Belemnitella, 93. Belemnoris, 90. Belemnosepia, 91. Bellerophon, 72. Bellinurus, 42.
Belodon, 251. Beloptera, 90. Beloteuthis, 90.
“ Berg-mehl,” 15. Berosus, 47.
Beyrichia, 42. Bifrontia, 77.
Bison, 370.
Blastoidea, 30. Blattidse, 47.
Borsonia, 75.
Bos, 370.
Bothrioconis, 6. Botliriolepis, 132. Bourgetocrinns, 29, 34. Brachiolites, 8. Brachiopoda, 49. Brissus, 36. Brontozoum, 290. Bryozoa, 27.
Bubalus, 370. i Buecinum, 71, 97. Buprestis, 47. Byssacanthus, 103.
Calceola, 53. Callorhynchus, 116. Calymene, 42.
416
Calyptroeida?, 77. Camarophoria, 51. Camaroceras, 83. Camelopardalis, 388. Campanularia, 17. Campylodiscus, 15. Cance'llaria, 76. Cantharidas, 47. Capitosaurus, 196. Caprina, 63. Caprinella, 64. Caprotina, 64. Carabidas, 47. Careharodon, 111. Cardiadse, 65. Cardiomorpha, 64. Cardiola, 60. Cardium, 65. ■ Carinaria, 73. Carnivora, 376. Carolia, 58. Caryoorinus, 31. Cassidaria, 76. Cassidulida?, 36. Cassis, 76. Catantostoma, 78. Catopygus, 35. Caturus, 139. Caturidse, 139. Cellepora, 28.
“ Celts,” 401. Centriscus, 103. Centrodus, 138. Cephalaspis, 122. Ceratiocaris, 43. Ceratites, 82. Cercomya, 68. Cercopis, 47. Ceromya, 68.
Cervus, 371.
Cerylon, 47. Cestracion, 106. Cetiosaurus, 272. Chama, 62. Cheiracanthus, 131. Cheirolepis, 131. Cheirotherium, 163. Chelonia, 281. Chelydra, 282. Chemnitzia, 77. Chenendopora, 7. Chimasra, 116. Chiton, 77.
Choanites, 7. Choeropotamus, 367. Clioetites, 23. Chondrosteus, 145. Chonetes, 53. Chrysaora, 28.
Chry sodom us, 97. Chrysomelidaj, 47. Cicada, 47.
Cidaris, 35.
Cimicid®, 47.
INDEX.
I Cirripedia, 40. i Cirrus, 78. Cladacanthus, 104. Cladodus, 108. Cladyodon, 251. Clavagella, 69. Clavella, 75. Cleodora, 71.
Cliona, 8.
Climatius, 103. Clymenia, 83. Clypeaster, 36. Cnemidium, 7. Coccinella, 47. Coccosteus, 123. Coccoteuthis, 90. Cochliodus, 109. Coelacanthi, 131. Ccelogenys, 386. Coelorhynchus, 148. Coenites, 20.
Coleia, 45.
Cololites, 39. Colonodns, 138. Colossochelys, 283. Coluber, 280. Columbellarina, 73. Colymbetes, 47. Comatula, 29, 34. Conchiosaurus, 214. Conchorhynchus, 86. Conocardium, 57, 65. i Conoclypeus, 36.
| Conodonts, 97.
I Conorbis, 75.
; Conularia, 71.
Copris, 47.
Corallium, 21.
Corax, 111. Corbicula, 66.
Corbis, 65.
Corbula, 68. Cordylodus, 96. Cornulites, 46. Coryphodon, 322. Corystes, 47. Coscinodiscus, 13, 16. Cosmacanthus, 103. Crania, 55. Crassatella, 66. Crenella, 62. Cribrispongia, 7. Crinoidea, 29. Crioceras, 89. Cristellaria, 12. Crocodilia, 271. Crocodilus, 273. Crossostoma, 74. Crotalocrinus, 30. Crustacea, 41. Cryptangia, 26. Cryptoceras, 82. Cryptodon, 65. Ctenacantlius, 100.
Ctenodonta, 57. Ctenognathus, 96. Ctenomys, 386. Ctenoidei, 146. Cucculsea, 59. Cupularia, 28. Cupulispongia, 7. Curculionidse, 47. Cuvieria, 72. Cyathophyllum, 23. Cyathina, 26. Cyathocrinus, 31. Cvclas, 42. j Cycloidei, 147.
I Cyclolites, 25. Cyclopthalmus, 48. Cyclostoma, 79. Cyclostrema, 77. Cymba, 76.
Cyphon, 47. Cyprseidse, 76. Cyprida, 46. Cyprinidse, 57. Cypris, 42.
Cyi tis, 50. Cyrtoceras, 83. Cyrtolites, 72. Cyrena, 65. Cvstoidea, 30-32. Cytherea, 67. Cytheridse, 42.
Dapedius, 142. Davidsonia, 53 Defrancia, 28. Dendrerpeton, 182. Dendrodus, 133. Dendrophyllia, 26. Dendropupa, 79. Dentalina, 11, 12. Dentalium, 77. Ileshayesia, 75. Diastopora, 28. Diatomacese, 13, 16. Dibranchiata, 90. Iliceras, 62, 64. Dichobune, 336. Dichodon, 333. Dicynodonts, 236. Didacna, 65. Didelphis, 341. Didus, 295. Didymograpsus, 20. Difflugia, 9. Dikelocephalus, 157. Dimeracantlius, 103. Dimorphodon, 246. Dinornis, 293. Dinosauria, 257. Dinotherium, 352. Diplacanthus, 130. Diploctenium, 25. t Diplodonta, 65.
( Diplograpsus, 20.
INDEX.
417
Diplopterus, 130. Dipriacanthus, 104. Diprotodon, 394. Dipterus, 129. Disaster, 35. Discinid®, 56. Discoidea, 36. Discosorus, 84. Dithyrocaris, 42. Ditrupa, 40. Dolichosaurus, 278. Dolium, 74.
Donacia, 47.
Donax, 68. Dorypterus, 138. Dreissenia, 61. Dromatheriuin, 302. Dromilites, 46. Dryopithecus, 350.
Echimys, 386. Echinarachnius, 36. Echinodermata, 29. Echinoidea, 34. Echinolampas, 36. Echinopsis, 35. Edaphodas, 117. Edmondia, 57. Elasmodus, 117. Elasmotherium, 387. Elater, 47.
Elephas, 360. Elonichthys, 138. Einvs, 282 Enallostega, 11. Lncrinus, 30. Entalophora, 28. Entomostega, 11. Entomostraca, 41. Entomoconclius, 42. Entosolenia, 11. Eopithecus, 341. Epiaster, 36 Epiornis, 294. Erismacanthus, 104. Eryon, 46.
Eschara, 28.
Estheria, 42.
Etyus, 46.
Eucalyptocrinus, 31. Eudea, 7.
Eugeniacrinus, 31, 34. Eugnathus, 140. Eulima, 77. Euompiialus, 72. Eupatagus, 86. Eurynotus, 138. Eurypterus, 43. Exogyra, 58.
Fascicularia, 29. Favosites, 23. Favositid®, 23.
Felis, 376.
Fenestrella, 20, 28. Ferussina, 75, 79. Firolid®, 72. Fistularid®, 102. Flabellina, 6, 12. Flabellum, 26. Flustra, 29. Foraminifera, 9. Fungid®, 25. Fusulina, 6, 12. Fusus, 76.
Gailt.onella, 14. Galecynus, 376. Galeocerdo, 111. Galerites, 34.
Galeus, 111. Gauocephala, 168. Ganodus, 117. Ganoidei, 118. Gastornis, 291. Gastroch®na, 68. Gavialis, 273. Geocrinus, 31. Geoteuthis, 91. Gervillia, 59. Gilbertsocrinus, 31. Gitocrangon, 45. Glandina, 79.
“ Glenotremites,” 32. Globiconeha, 80. Globigerina, 10. Globulus, 77. Globulodus, 138. Glyphea, 45. Glypticus, 36. Glvptocrinus, 81. Glyptolepis, 131. Glyptodon, 392. Glyptopomus, 132. Gnathodus, 96. Goniatites, 84. Goniodiscus, 34. Goniomya, 67, Gouiopholis, 271 . Gorgonid®, 21. Grammvsia, 57. Graphuiaria, 20. Graptolites, 19. Grateloupia, 67. Gryph®a, 58. Guettardia, 6, 8. Gulo, 341. Gyracanthus, 104. Gyrinus, 47. Gyroceras, 84. Gyropristis, 104. Gyrosteus, 139.
I-Ialysites, 23. Hamites, 86. Haplacanthus, 103. Harpalus, 47. Helicerus, 94.
2 E
Helicoceras, 89. Helicoidea, 11. Helicostega, 11. Heliolites, 23.
Flelix, 75, 79. Helopborus, 47. Hemerobioides, 47. Ilemiaster, 36. Hemicidaris, 35. Hemipneustes, 85. Hemipristis, 111. Heterocercal fish, 119. Heteropoda, 72. Heterostcus, 119. Ilimantopterus, 43. Hinnites, 59. Hippalimus, 7. Hippocrena, 73. Hippohyus, 367. Hippopotamus, 364. Hippopodium, 67. Hippurites, 64. Hippuritid®, 58. Histiophorus, 148. Holaster, 36. Holectypus, 36. Holocystis, 25. Ilolopella, 77. Holoptyobius, 132. Holostomata, 76. Holothurioidea, 37. Flomaeantbus, 103. Homosteus, 119. Hoplopygus, 138. Hornera, 29.
Human remains, 401. Iluronia, 84.
Ifyama, 384.
Ily®nodon, 339. FIyal®a, 71.
Hvalonema, 21. Hybodus, 105, 108. Ilydrophilid®, 47. Ilydrozoa, 19. Hylasosaurus, 264. Hymenocaris, 43. Hyopotamus, 367. Hystrix, 386.
Janira, 59.
Ian thin a, 77.
Iclmology, 152. Icbthyopterygia, 198.
“ Ichthyodorulites,” 104. Ichthyosaurus, 200. ldmonea, 28. Iguanodon, 265.
Ilbenus, 42.
Indusial Limestone, 48. Infusoria, 14. Inoceramus, 8, 59. insecta, 47.
Invertebrata 17. Jouannetia, 69.
418
INDEX.
Ischiodus, 117.
Isis (Isisina), 21.
Isoarca, 59.
Isodus, 138.
Kellia, 65.
Labyrintthoi>ontia,183. Lacertilia, 278. Laccopbilus, 47.
Lagena, 11.
Lagomys, 386. Lagostomus, 386. Lamellibranchiata, 57. Lamna, 112.
Leda, 61.
Leiacanthus, 104.
Leiodon, 279.
Lepadidas, 41.
Leperditia, 42.
Lepidaster, 33. Lepidoganoidei, 129. Lepidosteus, 119. Lepidotus, 144. Lepracanthus, 104. Leptmna, 54. Leptaoanthus, 104. Leptoclieles, 43. Leptolepis, 144. Leptopleuron, 255.
Lenita, 36.
Libellula, 47.
Liraanomia, 58.
Limnsea, 79.
Liranius, 47.
Limopsis, 67.
Limulus, 43.
Lingula, 56.
Litharsea, 26. Lithocardium, 65, 67. Lithodendron, 23. Lithornis, 291. Lithostrotion, 23. Litorinidas, 77.
Lituites (Breynius), 84. Lituola, 6, 12. Loligosepia, 91. Lophiodon, 329.
Loricula, 46.
Loxonema, 71.
Lucinidae, 65.
Lucinopsis, 67.
Luidia, 33.
Lunulites, 28.
Lutraria, 68.
Lyrodesma, 57, 62.
Maceli.odus, 279. Machairodus (Bander)
fish, 98.
Machairodus (Kaup) mammal, 382. Macluvea, 71. Macrauchenia, 393.
Macrochilus, 71. Macrodon, 61. Macropetalichthys, 100. Macropoma, 144. Macropus, 394.
| Macropthalma, 46. Macrospondylus, 271. Macrotherium, 346. Mactra, 67.
Malacostraca, 45.
! Mallotus, 150. j Mammalia, 295.
- Geological distribu¬ tion of, 407. Mammillopora, 6.
Manon, 6.
Marginula, 15. Marsupites, 30.
Martesia, 69. Massospondylus, 271. Mastigophora, 91. Mastodon, 353. Mastodonsaurus, 195. Megaceros, 372. Megachirus, 46. Megalodon, 63. Megalosaurus, 258. Megaspira, 79. Megatherium, 390. Melania, 77.
Melanopsi3, 77. Melocrinus, 31. Melolontha, 47. Menopoma, 185. Merycotherium, 387. Mesopithecus, 351. Mesostylus, 47.
Metopias, 196.
Meyeria, 45.
Michelinia, 24. Micrabacia, 25.
Micraster, 36. Microconchus, 40. Microlestes, 301. Microtherium, 338. Millericrinus, 31. Milleporidsa, 23.
Mitra, 75.
Modiola, 62.
Modiolopsis, 61. j Mollusca, 48.
1 Monodacna, 65.
| Monopleura, 64. Monostega, 11.
Monotis, 60.
Montlivaltia, 25. Mosasaurus, 279. Murchisonia, 71. Muricidae, 73.
Mya, 6S.
Myacid®, 58.
Myacites, 68.
Myalina, 57.
I Myliobates, 105.
Mylodon, 389. Myopara, 62. Myophoria, 62. Myoxus, 385. Myriapoda, 48. Mystriosaurus, 271. Mytilidse, 61,
Narcodes, 103. Natica, 75.
Naulas, 103.
Nautilus, 75. Nautiloceras, 84. Navicula, 14.
Neaera, 68.
Nebalia, 43.
Neithea, 59. Nemacanthus, 104. Nepadse, 47.
Neptunia, 76.
“ Nereites,” 39. Nerinrea, 74.
Nerita, 78.
Neritoma, 74.
Nestor, 399.
Nodosaria, 12. Notagogus, 144.
| Nothosaurus, 210, 231. Nothosomus, 144. Notidanus, 110. Notopocorvstes, 46. Notornis, 294. Nototherium, 395. Nucleobranehiata, 72. Nucleolites, 36. Nucula, 61.
Nucunella, 62. Nummulites, 6-13.
j Onor.us (Ungula), 53.
! Oculina, 26. Odontacanthus, 103. Odontaspis, 111. Odontosaurus, 196.
| Oldhamia, 20, 28. Oliva, 75.
Onchus, 100, 103. Onychoteuthis, 91.
! Operculina, 12. j Ophidia, 279. Ophioderma, 33. Ophiopsis, 144. Ophiura, 34.
| Opbiurella, 33. Ophiuridae, 33.
Opis, 67.
; Opisthocoelia, 272.
Oracanthus, 104.
J Orbitoides, 6, 12.
; Orbitolites, 12. Oreaster, 34. Ornithichnites, 288.
! Orodus, 108. Orognathus, 138.
INDEX.
419
Ortliacanthus, 104. Orthis, 53.
Orthoceras, 85. Orthonotus, 61. Orthophlebia, 47. Osteolepis, 130. Osteoplax, 138. Ostracoda, 42. Ostracostei, 118. Ostreidfe, 58. Otozoum, 165. Oudenodon, 238. Ovibos, 401.
Ovulites, 6, 12.
Pachycormus, 140. Pachygyra, 25. Pachyrisma, 66.
Pate ister, 33. Palffichinus, 35. Palaeoerangon, 45. Palseocyclus, 25. Palaeoniscus, 137. Palasophrynos, 283. Palaeophys, 280. PaUeopyge, 157. Palaeosaurus, 249. Palaeospongia, 6. Palseoteuthis, 81. Palaeotherium, 33 Palapteryx, 294. Paleryx, 280. Paludina, 77. Pamphagus, 9. Pandora, 08. Panopjea, 68. Parasmilia, 25. Parexus, 103. Passalodon, 117. Patella, 79.
Pecten, 58. Pectunculus, G2. Pelagosaurus, 271. Pelorosaurus, 272. Pentacrinus, 29, 30. Pentamerus, 50. Pentremites, 30. Perna, 60.
Petricola, 67. Pezophaps, 295. Phacops, 42. Phascolomys, 395. Phaseolotherium, 304. Phcenicopterus, 292. Pholadomya, 68. Pholas, 69. Pholidophorus, 143. Phragmoceras, 83. Phryganea, 47. Phyllodus, 149. Phyllolepis, 132. Phyllopora, 28. Physa, 79. Physonemus, 104.
Pileolus, 74.
Pisces, 99.
Pisodus, 149. Pistosaurus, 214, 230. Placodermata, 118. Placodus, 216. Placoganoidei, 118. Placoidei, 118.
Placuna, 58. Placunopsis, 58. Plagiaulax, 319. Plagiostoma, 59. Plagiostomi, 99. Planorbis, 79. Platemys, 282.
PI aty acanthus, 104. Platycrinus, 31. Platysomus, 138. Plesiosaurus, 223. Plectrodus, 101. Plectrolepis, 138. Pleuracanthus, 103. Pleuraster, 33. Pleurophorus, 57, 66. Pleurosternon, 2S1. Pleurotomaria, 78. Plicatilia, 15.
Plicatula, 59. Pliolophus, 3'25. Pliopilhecus, 350. Pliosaurus, 232. Pododus, 138. Podopilumnus, 46. Poecilopleuron, 271. Pollicipes, 41. Polycystine®, 10, 13. Polvgastria, 14.
Polypi, 19. Polypothecia, 7. Polytremaria, 78. Polyptvchodon, 235. Polythalamia, 11. Porarabonites, 51. Porcellia, 71.
Poromya, 68. Posidonomya, 12, 57. I’otamides, 77. Poteriocrinus, 30. Prionus, 47.
Procoelia, 273. Producta, 53. Propterus, 144. Prosoponiscus, 45. I’rotaster, 33. Protemys, 281. Protichnites, 159. Protopithecus, 393. Protornis, 291. Protorosaurus, 253. Protovirgularia, 20, 39. Protozoa, 5. Psammosteu.3, 138. Pseudocrinus, 30. Psittacodus, 117.
Pteraspis, 101. Pterichthys, 119.
Pterinea, 60.
Pterocera, 73.
Pterocoma, 31. Pterodactylus, 246. Pterodonta, 80. Pteroperna, 60.
Pteropoda, 71. Pterosauria, 244. Pterotheca, 72. Pterygotus, 43. Ptilodictya, 20.
Ptilopora, 20, 28. Ptyacanthus, 103. Ptychoceras, 89. Ptyckodus, 110. Ptychognathus, 238. Pulmonifera, 70. Pulvinites, 60.
Purpurina, 73. Pycnodontes, 140. Pycnodus, 142.
Pygaster, 34. Pygocephalus, 45. Pygopterus, 168. Pyramidella, 76.
Pyrina, 36.
Pyritonema, 21.
Pythina, 65.
Radiata, 19.
Radiolites, 63.
Raia, 115.
Raiidse, 113. Eamphorhvnehus, 246. liana, 284.
Ranella, 73.
Raniceps, 183. Raphiosauius, 278. Raphistoma, 77.
Rastrites, 20.
Reptilia, 168.
- Geological distribu¬ tion of, 285. Requienia, 63.
Retzia, 52.
Rhabdoidea, 11. Rhinoceros, 366. Ilhinodon, 98.
Rhizodns, 132. Rhodocrinus, 31. Riiizopoda, 8.
Rhombus, 149. lihyncholites, 86. Rhynchonella, 51. Rhynchosaurus, 239. Rhynclioteuthis, 81. Rimella, 73.
Ringicula, 80.
Ilissoa, 62.
Rodentia, 385.
Rosalina, 12.
Rostellaria, 73.
420
INDEX.
Rotalina, 12. Ruminantia, SC8. Rytina, 346, 400.
Saocosoma, 31. Salenia, 35. Saurichthyidse, 138. Saurillus, 279. Sauropsis, 140. Sauropterygia, 209. Sauropus, 167. Saurostomus, 140. Saxicava, 69. Scalaria, 77.
Scalites, 77 Scalpellum, 41. Scaphites, 89. Scelidosaurus, 258. Scelidotherium, 391. Schizaster, 36. Schizodus, 62. Sciurus, 385. Scoliostoma, 71. Scutella, 34. Scutellina, 36. Scyphia, 6. Semionotus, 143. Semiophorus, 146. Sepia, 90.
Septifera, 61. Seraphs, 73.
Serpula, 40.
Siluridse, 100. Simosaurus, 214. Siphonia, 6. Siphonotreta, 53. Sivatherium, 387. Smerdis, 147. Solecurtus, 68. Solemya, 62. Solenella, 62. Solenidse, 68. Soroidea, 11. Sowerbya, 67. Spalacotherium, 315. Sparella, 97. Sparsis]iongia, 6. Spatangidre, 35. Sphseronites, 30. Sphagodus, 100. Sphenacantlms, 104. Sphenotrochus, 26. Sphinx, 48.
Spinax, 105. Spiniferit.es, 8. Spinigera, 74. Spirifera, 50. Spiroglyphus, 40. Spirorbis, 40.
Spirula, 90. Spirulirostra, 90. Spondylus, 59. Sponges, 5.
Squalid®, 110. Staganolepis, 257. Steganodictyum, 6. Stellaster, 33. j Stellispongia, 7. j Steneosaurus, 271, 274.
Stephanopliyllia, 26.
| Stereognathus, 308. Stichostega, 11. Strepsidura, 75. Streptospondylus, 272. Stringocephalus, 50.
; Stromatopora, 6.
Strombus, 73.
J Strophalosia, 55.
1 Strophomena, 53. i Sturionidoe, 145. Stylina, 25. Suchosaurus, 271.
Sus, 368.
Synapta, 37. Syndosmya, 68. Synocladia, 28. Syringopora, 23.
Tancredia, 67. Tanystropheus, 220. i Teleosaurus, 271, 274.
) Tellina, 67.
Tellinidse, 58. Telephoridse, 47. Temnopleurus, 36. Tentaculites, 46. Terebellaria, 28. Terebellum, 73. Teredina, 69. Terebralia, 77. Terebratella, 49. Tetragonolepis, 142. Teuthidse, 90. Textularia, 15. d'hamniscus, 28. Thecidium, 50. Tkecodontia, 248. Theeodontosaurus, 248. Thecosmilia, 25.
Thetis, 68. Thryssonotus, 140. Thylacoleo, 396.
Tinea, 48.
Tornatella, 80. Toxaster, 36. Toxoceras, 89. Toxodon, 393.
Tragos, 6.
Trematosaurus, 195. Trelosternon, 281. Trichiles, 61. Triconodon, 318. Tridacna, 65. Trigonellites, 86. Trigon, 105.
Trigona, 67. Trigoniad®, 58, 62. Trigonoceras, 83. Trigonosemus, 50. Trilobites, 44. Trinucleus, 42. Trionyx, 282.
“ Tripoli,” 14.
I Triton, 76.
Trivia, 76.
Trochidse, 77. Trocbocyathus, 26. Trocbotoma, 74. Trogontheriunr, 386. Tropidaster, 33. Tropifer, 45. Trystichius, 104. Tubina, 71. Tubulipora, 29. Tunioata, 17. Turbinolia, 25. Turbo, 62.
Tun-ilites, 89. Turritella, 77. Tylostoma, 80.
Uxcites, 50.
| Unicardium, 65.
Unionid®, 62.
; Uronemus, 138.
| Ursus, 384.
Vagineli.a, 75. Yarigera, 80. Venerid®, 58. Yenerupis, 67. Ventriculites, 6, 8. Vermetus, 40. A7ermicularia, 40. Vermilia, 40. Verruca, 41.
I Yerticellopora, 7. j Verticordia, 62.
Volutidoe, 76.
; Volutilithes, 75. Volvaria, 75.
Waldheimia, 49. Webbinn, 12. Woodocrinus, 31.
Xantiiidium, 8. j Xestorrhytias, 196.
! Xiphias, 148.
I Xiphodon, 337.
Yoldia, 62.
Zaphrentts, 23. Zeugloilon, 344. Zygobates, 114. Zygosaurus, 196.
1
date due
304309