531

of the cretaceous epoch. Teeth, scales, dorsal spines, and other remains of Hybodus, Acrodus, Asteracanthus, Ganodus, Eugnathus, Pachycormus, Pycnodus, Echmodus, Lepidotus, and Pholidophorus are abundant in some of the strata.*

Among the Ichthyolites that prevail in the Lias, the scales and teeth of a genus of Ganoids called Dapedius are especially abundant, and entire specimens of the fish are often met with. I am led to notice this genus more particularly, that your attention may be directed to a remarkable modification of structure observable in the Ichthyolites of the more ancient deposits, which will hereafter come under our examination. The Dapedius belongs to that division of the Lepidoids which are homocercal (equaltailed) or nearly so;† while all the genera from the palæozoic strata are heterocercal, or having tails with unequal lobes. But few of the existing genera of fishes have this latter condition of the caudal fin, while it is found in almost every fossil species below the Triassic deposits.§ 31. REPTILES OF THE JURASSIC SYSTEM. -The prevalence of animals of the reptilian class during the Oolitic era was incidentally alluded to in the course of our previous observations on the organic contents of the different members of this extensive formation. From the lowermost stratum, the Bone-bed of the Lias, to the uppermost layer of the Portland-stone, the remains of extinct reptiles have * See Medals of Creation, vol. ii. chap. xiv. xv.; and Petrifactions and their Teachings, chap. v.

It is difficult to determine whether some of the Triassic and Liassic Lepidoid fishes are really homocercal or not. Quart. Journ. Geol. Soc. vol. x. p. 368.

See Medals of Creation, p. 575; Petrifactions, p. 421.

It is worthy of remark, that in the embryotic state most fishes are heterocercal; and those species which, when arrived at maturity, have the equally-lobed tail attain this homocercal type in the progress of their development. For remarks on the heterocercality of the Salmonidæ, &c., see Mr. Huxley's observations in the "Notices of the Royal Instit." 1855, p. 84.

been found more or less abundantly in every deposit. About forty species, belonging to several genera, have been determined as occurring in the Jurassic strata of the British Islands. These have been carefully investigated and described by Professor Owen, in the Reports of the British Association for 1840 and 1841, and in the Monographs on Fossil British Reptiles published by the Palæontographical Society. Cuvier, Gervais, Hermann von Meyer, Jaeger, Burmeister, and Theodori are amongst the continental naturalists who have studied the fossil reptiles.* As I shall have occasion to recur to this subject in the sequel, it will be sufficient in this place briefly to enumerate the principal kinds hitherto discovered in the Oolite and Lias.

In addition to the reptiles of which remains have been found in the Chalk and Wealden, namely, the Megalosaurus (p. 435), Pœcilopleuron (p. 432), Cetiosaurus (p. 427), Streptospondylus, Pterodactylus, Ichthyosaurus, Plesiosaurus,—and of some of these, especially of the two last-named genera, numerous species abound in the Lias and Oolite,several other Crocodilian reptiles, with peculiar osteological modifications, also occur. These are the Teleosaurus, Steneosaurus, &c., which are characterized by their long narrow muzzles, sharp-pointed teeth, short fore-legs, imbricated scales, and doubly concave or flat-faced vertebræ : their relics are chiefly found in the Lower Oolite and Lias.

The most remarkable circumstance relating to the Ichthyosauri and Plesiosauri that swarm in the Lias is the connected state in which all the bones of the skeleton occur. The entire osseous frame-work, from the extremity of the snout to the last vertebra of the tail, often remains entire,

*See Pictet's Paléontologie, 2nd Edit. vol. ii., for a résumé of our knowledge of fossil reptiles.

+ See Medals of Creation, vol. ii. p. 679. These gavial-like reptiles are represented amongst the other extinct animals by life-like models in the Crystal Palace Gardens.

or but very little displaced from its natural position; even the bones of the paddles, with their cartilaginous appendages, are in some instances preserved.* The indigestible portion of the food of these carnivorous marine reptiles (as the scales, teeth, and bones of fishes), and their coprolites, are frequently met with in the abdominal cavity.† These facts show that the carcasses of these animals were imbedded in the soft mud at the bottom of the sea, without having been exposed to the action of the billows, or to long transport by rivers or currents. The Wealden fossils present a striking contrast in this respect; for, although bones of Plesiosauri are by no means uncommon in that formation, they are isolated and generally water-worn.

In the Kimmeridge Clay, the relics of a very large marine saurian, allied to the Plesiosaurs, but distinguished by certain osteological characters, have been met with: this extinct reptile is named Pliosaurus. Bones of Flying-Saurians, or Pterodactyles, occur more abundantly in the Oolite and Lias than in any other series of deposits; more than twelve species have been found in the Solenhofen and other Bavarian quarries. In the Stonesfield-slate the bones of one species (Pterodactylus Bucklandi), and in the Lias of Lyme Regis, a considerable part of the skeleton of another (P. macronyx), have been discovered. The Mammalia of Stonesfield have already been noticed (p. 508).

The general character of the Jurassic or Oolitic formation, as derived from its organic remains, is therefore that of a series of oceanic deposits, accumulated in a depression of great extent, through a period of immense duration. The sea teemed with marine invertebrate animals, belonging to genera and species most of which became extinct before the

* See Medals of Creation, vol. ii. p. 669.

+ Consult Dr. Buckland's Bridgwater Treatise, p. 198; and Geol. Trans. 2 ser. vol. iii. p. 223.

Tertiary epoch; and with these were associated multitudes of peculiar Fishes and Reptiles. The dry land, as attested by the remains drifted into the basin of the sea, was inhabited by a few reptiles and marsupial mammals, and was clothed with tree-ferns, cycadeous plants, and coniferous trees; and insects, pterodactyles, and possibly birds,* flew above its surface.

* The Rev. Mr. Dennis's microscopical evidences (Microscop. Journ, vol. v. p. 63) only require further patient investigations to substantiate the fact of the existence of Birds' remains in the Stonesfield slate. The same observant naturalist has brought forward very probable evidences of the mammalian character of some bones from the "Lias Bone-bed' of Lyme Regis (ibid. vol. iv. p. 261).

LECTURE V.

PART II.-THE TRIAS AND PERMIAN FORMATIONS.

The Trias and Permian Formations. 2. Geographical Distribution of the Trias and Permian. 3. Rock-Salt and Brine-Springs. 4. Origin of Rock-Salt and Gypsum. 5. The Cheltenham Waters. 6. Conglomerates of the Trias. 7. Organic remains of the Trias. 8. Crustacea, Mollusca, and Crinoidea. 9. Fishes of the Trias. 10. Reptiles of the Trias. 11. The Labyrinthodon. 12. The Rhynchosaurus. 13. The Dicynodon of Africa. 14. Foot-prints on stone. 15. Ornithichnites. 16. Triassic Mammal. 17. The Permian System. 18. Magnesian limestone or Zechstein. 19. Permian of Germany and Russia. 20. Organic Remains of the Permian System. 21. Invertebrata of the Permian. 22. Fishes of the Permian. 23. Reptiles of the Permian. 24. Reptiles. 25. Chelonians or Turtles. 26. Crocodiles. 27. Enalio-saurians or Marine Reptiles. 28. The Plesiosaurus. 29. Pterodactyles, or Flying Reptiles. 30. Ophidians and Batrachians. 31. Review of the Age of Reptiles. 32. Objections considered. 33. Concluding Remarks.

*

1. THE TRIAS AND PERMIAN FORMATIONS.-Beneath the Lias there is a series of strata, many hundred yards in total thickness, which was formerly known in geology as the New Red Sandstone Formation, and divided into two groups, namely the Upper and the Lower. But later investigations having shown, that, of the fossils found in the lowermost group, scarcely a species is known in the upper series, nor in any newer strata, this system is now separated, under the name of " Permian," from the former, and regarded as the uppermost or terminal group of the Paleozoic or primary series; while the Upper New Red is ranked as the lowermost of the Mesosoic or secondary formations.† The name of Trias, or Triassic System, by which the Upper New Red is now distinguished, relates to the well-marked triple sub

*See Phillips's "Manual of Geology," 1855, p. 246, 247

See the "Synoptical Arrangement," p. 203.