THE AGE OF REPTILES 57 



western Texas and New Mexico, have come many marvelous speci- 

 mens of dinosaurs, huge bipedal carnivorous dinosaurs, great spoon- 

 billed aquatic dinosaurs, armored stegosaurian dinosaurs, and many 

 kinds of the great horned dinosaurs, the Ceratopsia, so far known 

 only from these beds. Here at the very close of the Age of Reptiles, 

 at the close of the Age of Dinosaurs, are found the ultimate speciali- 

 zations of all the chief groups of dinosaurs except the long-necked 

 quadrupedal dinosaurs which gave up the ghost in Lower Cretaceous 

 times. Many were provided with horns and spines, some indeed 

 seemed to have bristled with spines throughout, a sure sign that 

 they were approaching the end of their career. The modern type 

 of crocodiles had usurped the ancient forms of the early Cretaceous, 

 and reached the largest size of their race perhaps, though but few 

 specimens are known. Here also in these beds we find the first 

 representatives of lizards and snakes in America, though snakes 

 have been described from earlier strata, perhaps, in Brazil. Those 

 archaic, old-fashioned ryhnchocephalians described on a later page 

 as the Choristodera appeared also for the first time in these beds, 

 and persisted for a little while in the Eocene, in Europe and America. 

 And with all these there has very recently been described the last of 

 the plesiosaurs, whose race went out with the dinosaurs at the very 

 close of the Mesozoic. It is needless to say that the turtles also 

 occur, for, as a general rule, wherever vertebrate fossils are found, 

 in rocks of the land or the sea, marine or fresh-water, there will 

 be some bones of turtles among them. 



With the beginning of the Cenozoic the record of the reptiles 

 becomes relatively scanty in America. In the warm waters of the 

 old Eocene lakes and rivers of Wyoming lived countless crocodiles, 

 true crocodiles of modern aspect and of large size. But, as the 

 climate of North America grew progressively colder, the crocodiles 

 retreated to the south, till, in the Oligocene, the scanty remains 

 of the last crocodiles are found in the American Tertiary. On the 

 other hand, as the open lands appeared toward the close of the Eo- 

 cene, and in the Oligocene and Miocene, the land tortoises throve 

 and grew greatly in size. In the Bad Lands of South Dakota one 

 may see their remains in almost incredible numbers. And in 

 equally great numbers are these land tortoises, in shape much like 



