In addition to the four groups of living Reptilia, there are a number of extinct groups. The Plesiosauria and Ichthyosauria are marine forms ranging, the former from the Trias, the latter from the Lias, to the Chalk. Their skin appears to have been naked. Ichthyosaurus is believed to have had a vertical tail fin, its intestine had a spiral valve, and some of the species were viviparous (Brit. Ass. Reports, 1880, p. 68). The neck is long in the former group; in the latter short. Both have the limbs modified into paddles. The Deinosauria are strictly terrestrial, but some of them, e.g. Iguanodon, appear to have frequented marshy ground or swamps. The group (sub-class, Marsh) comprises a large assemblage of herbivorous and carnivorous forms. Two of the sub-divisions (Stegosauria and Ornithopoda) show ornithic characters especially in the hind-limb. The group extends from Triassic strata to the Chalk (Maestricht beds in Europe). Some of the genera are gigantic in size. A very large number have been discovered in America. The Anomodontia are terrestrial forms, found in rocks of Triassic age in S. Africa, India, and the Ural Mountains. A portion of a skull has recently been obtained from a New Red Sandstone quarry near Elgin. Dicynodon and the Theriodontia (Owen, Journal Geol. Soc. 1876), etc, belong to this group.

Finally, there is a remarkable order of Flying Reptilia - the Pterodactyla, Ptero-sauria, or Ornithosauria, found in strata from the Lias to the Chalk inclusively. The fifth finger is immensely elongated, and supports the wing membrane. The toothless American genus Pteranodon is of immense size, fifteen feet from the tip of one wing to the tip of the other. Accounts of the anatomy of the Plesiosauria, Ichthyosauria, Ornithoscelida (=Deinosauria in part), Dicynodontia (Anomodontia in part), and the Pterosauria will be found in Huxley, Anatomy of Vertebrated Animals, 1871, or in Quenstedt's Handbuch der Petrefactenkunde, ed. 3, 1882-83. Some additional memoirs are noted below.

Reptilia, Hoffmann, Bronn's Klass. und Ordn. des Thierreichs, vi. Abth. 3 (in progress).

Chelonia, Strauch. Mem. de PAcad. Imp. St. Pétersbourg (7), viii. 1865. Development of Green Turtle, W. K. Parker, Challenger Reports, i. 1880. Carapace, etc.; cervical ribs, etc, Hoffmann, Niederländ. Archiv f. Zool. iv. 1877-78; v. 1879-82. Peritoneal canals, see Bridge, cited p. 279, ante.

Lacertilia. Anatomy of Lizard, T.). Parker, Zootomy, London, 1884. Skull, W. K. Parker, Ph. Tr. 170, 1879. Chamaeleon; skull, Id. Tr. Z. S. xi; changes of colour in do., Krukenberg, Vergleich. Physiol. Studien, i. Abth. 3, 1880. Amphis-baena, Bedriaga, A. N. 50. 1, 1884; Smalian, Z. W. Z. xlii. 1885.

Ophidia, see p. 72 and 73, ante.

Crocodilia, Strauch. Mem. de l'Acad. Imp. St. Pétersbourg (7), x. 1866. Skull, development of, W. K. Parker, Tr. Z. S. xi.

The fossil groups are treated principally in the following. Plesiosauria and Ichthyosauria, Owen, Fossil Reptiles of Liassic Formations, Palaeontographical Society; Id. Palaeontology, ed. 2, Edinburgh, 1861; limbs, see Baur, Z. A. ix. 1886. Anomodontia, Owen, Catalogue of S. African fossils in British Museum, 1876; Theriodontia, Journal Geol. Soc. xxxii. 1876; Dicynodon, Id. Trans. Geol. Soc. vii. 1845-56, and Ph. Tr. 1862; in Elgin, Judd, P. R. S. xxxix. 1885. Deino-sauria, Marsh, Nature, xxxi. 1884-85; Papers in American Journal of Science and Art by same; and by Cope in Proc. Philadelphia Academy, etc. For Iguanodon Dollo, Bull. Mus. Royale d'Hist. Nat. Belgique, ii. and iii.; Moseley, Nature, xxviii. 1883. Pterosauria or Ornithosauria, Seeley, J. L. S. xiii. 1878; H. von Meyer, Fauna der Vorwelt, i860; Zittel in H. von Meyer's Palaeontographica, xxix. 1882-83; Marsh, American Journal of Science, xxiii. 1882. Fossil Crocodiles, see Nature, xxxiii. 1885-86, p. 331.

Figures of many Reptilian bones will be found in Phillips' Geology of Oxford and the Thames Valley, Oxford, 1871.