178 GEOLOGY. 



heads and the smallest brains of the reptile race. They were doubt- 

 less stupid and sluggish. 



The ornithopod division was represented by Trachodon, Claosaurus 

 (Fig. 411) and kindred genera. The posterior parts of all these were 

 strongly developed, the limbs were hollow, and their footprints indi- 

 cate that they walked in kangaroo-like attitude. 



Turtles, lizards, snakes, and crocodiles. — Although it is confidently 

 believed that the Trionychia, or river turtles, one of the three or four 



Fig. 411. — A Cretaceous Dinosaur of the ornithopod division, Claosaurus annectens, 



(Restored by Marsh.) 



chief divisions of the Chelonia, had been differentiated long before, 

 the earliest known representatives of the group are from the Belly 

 River deposits of Canada. Of the true lizards which appeared in the 

 Triassic, the only other Mesozoic form known is one of small size and 

 uncertain affinities from the Laramie. True snakes made their first 

 appearance, so far as known, in the later part of the period, and all 

 were small. Among the crocodiles, the long-snouted teleosaurs (Tele- 

 orhinus) persisted, in North America at least, until well into the Cre- 

 taceous; but for the most part the order underwent a marked change 

 early in the period, developing into the modern type of crocodiles and 



