Extinct. 



190 EEPTILIA. 



The class Reptilia is divided into the following ten orders, 

 of which the first four are represented by living forms, 

 whilst the remaining six are extinct : — 



1. Chelonia (Tortoises and Turtles). \ 



2. Ophidia (Snakes). [ 



3. Laccrtilia (Lizards). 



4. Crocodilia (Crocodiles and AUigatois) 



5. Ichthyopterygia. 



6. Sauropterygia. 



7. Anomodontia. 



8. Pterosauria. 



9. Deinosauria. 



10, Thei^iodontia. j 



As regards their general distribution in time, the Eeptilia 

 attained their maximum of development in the Mesozoic 

 period, which has hence often been called the " Age of 

 Eeptiles." If the Elgin Sandstones, containing the remains 

 of Tdcrpeton and Stagonolcpis, be of Triassic age — as seems 

 almost certain — then no Eeptile has as yet been discovered 

 in the Devonian rocks. In the Carboniferous rocks, the 

 place of the true Eeptiles seems to have been taken by the 

 Amphibian group of the Labyrinthodonts. It is possible, 

 however, that the little Hylonomus, of which three species 

 were discovered in the Coal-strata of Nova Scotia by Dr 

 Dawson, may be Lacertian in its affinities. It is also 

 possible that the vertebrae from strata of the same age 

 described by Professor Marsh under the name of Eosaurus 

 Acadiensis, may belong to a marine reptile allied to Ichthyo- 

 saurus. In the Permian rocks the first undoubted Eeptilian 

 remains occur, the Proiorosaurus of this period being a La- 

 certilian, and other forms being known as well from deposits 

 of the same age. 



Throughout the whole Mesozoic series, Eeptilian remains 

 are abundant and belong to numerous and strange types. 

 Chelonians and true Crocodiles, with Lizards allied to exist- 

 ing forms, make their first appearance in deposits belonging to 

 this period. The extinct orders of the Icldhyoptcrygia, Saurop- 

 tcrygia, Anomodontia, Pterosauria, Theriodontia, and Deinosau- 

 ria, not only first appear in Mesozoic deposits, but are exclu- 



