TEIASSIC FAUNA. 159 



to the tailless amphibians — frogs and toads. The true reptiles ex- 

 hibit a remarkable variety of form, and, as in the succeeding Juras- 

 sic and Cretaceous periods, constitute the most marked feature of 

 the faunal remains that have been left to us. Hence, by some 

 geologists the collective era of these three periods — the Triassic, 

 Jui-assic, and Cretaceous — or -what is generally known as the Meso- 

 zoic, has been designated the "era" or "age of reptiles." The 

 modern lizards and crocodiles had both their ancient representa- 

 tives, the former as indicated by the genera Telerpeton, Hypero- 

 dapedon, and Rhynchosaurus, and the latter by Stagonolepis, Belo- 

 don, and Parasuchus. But besides these there flourished a multi- 

 tude of reptiles belonging to several distinct and very widely 

 removed orders, which have left, to our knowledge, no traces 

 whatever of their existence in the present seas. Such are the South 

 African Anomodontia, some of whose members, as Oudenodon, 

 were totally destitute of teeth, and had their beaks encased in 

 horn, after the fashion of the modern turtles (of which they may 

 have been in part the progenitors); while others, as Dicynodon, 

 possessed the horny mandibular apparatus of the former, but were 

 provided, in addition, with a pair of huge and powerful teeth in 

 the upper jaw ; * the Theriodontia (as represented by the South 

 African Galesaurus), reptiles whose dentition partook of the char- 

 acter of that of the ordinary Carnivora, and whose earliest types had 

 already appeared in the deposits of the Permian period ; and the 

 Plesiosauria, a group of essentially sea-inhabiting reptiles, which 

 acquired a very considerable development in the Jurassic seas, and 

 whose best known exponent is the Plesiosaurus. In the animals of 

 this order the extremities of the limbs, both anterior and posterior, 

 were encased in integument, and thus converted into flippers, very 

 much like those of the whale, and admirably adapted for propul- 

 sion through the water. The most characteristic genera of this 

 period were Nothosaurus and Simosaurus. In Placodus the dental 

 armature consisted in principal part of flattened plates, resembling 

 the teeth of the pycnodont fishes, with which animals these reptiles 

 were first confounded. 



* Professor Judd has quite recently ("Nature," Oetoter 15, 1885), an- 

 nounced the discovery of dicynodont remains in the Elgin Trias of Scotland ; 

 the group of animals had hitherto been known only from Africa, India and 

 the Ural Mountains. 



