THE GEOLOGICAL RECORD. 99 



swimming-paddles. Neither group persisted beyond the 

 Cretaceous epoch. Among the most interesting extinct 

 reptiles are the Dinosauria. First appearing in the Tri- 

 assic, they flourished in the Jurassic and Cretaceous, but 

 became extinct before the beginning of the Eocene epoch. 

 Often of gigantic size as for instance Cetiosaurus and 

 Diplodocus these remarkable animals were the lords of 

 the earth in later Mesozoic times. Some were adapted 

 to a herbivorous vegetable diet, like the huge Iguano- 

 don ; while others were aggressive carnivores, like 

 Ceratosaurus and Megalosaurus. But in spite of every 

 effort, so to speak, to succeed in all possible directions, 

 in spite of elaborate adaptations, terrible weapons, 

 formidable defensive bony plates, horns, and spines, 

 these splendid Dinosaurs all foiled in the struggle for 

 existence by the end of the Cretaceous epoch (Figs. 4 

 and 5). 



Some representatives of the large order Crocodilia still 

 persist in the tropics ; but the Ehynchocephalia survive 

 at the present day only in the single species Sphenodon 

 punctatum, preserved by special legislation on certain 

 small islands off the coast of New Zealand. The Ptero- 

 sauria, admirably specialised for flight as they appear to 

 have been, had but a short success in later Mesozoic 

 times. On the other hand, the Chelonia (tortoises and 

 turtles), modestly taking refuge in their bony shell, are 

 fairly flourishing in warm countries even at the present 

 day. But of the vast array of reptilian forms the 

 Lacertilia (lizards) and Ophidia (snakes) are the only 

 two orders which have really increased and spread in 

 recent times. A few other orders linger on in reduced 

 numbers ; the majority have failed altogether (Figs. 4 

 and 5). 



But although the reptilian type, once so successful and 

 widespread, has failed so signally in the struggle for 

 existence, it has given rise to other types which have 

 replaced it. The birds are doubtless descended from 



