100 



GEOWGY. 



and western America. While they were less gigantic than the sauro- 

 pods, they found compensation in protective plates, spines, and similar 

 modes of defense. The Slegosaurus of Colorado and Wyoming (Como 

 beds) was one of the most unique, (Fig. 373.) The remarkably diminv • 





W&& 



>«'■: > 



Fig. 373. — Stegosaurus, an armored dinosaur of the Jurassic. Interpreted by Charles 

 R. Knight. (Lucas' Animals of the Past. By pei mission of the publishers, Messrs 

 McClure, Phillips and Company.) 



tive head and small brain imply a sluggish, stupid beast, depending 

 for protection on its bulk and armor. 



The prevalence of so many of these dinosaurs on the North American 

 and the Eurasian continents seems to imply that these lands were 

 connected, and that they were the chief dinosaurian home, though dino- 

 saurs have been identified in South Africa in beds probably Triassic. 1 



Other reptilians. — The true rhynchocephalians first made their 

 appearance during the Jurassic, in forms scarcely distinguishable 

 from the living Sphenodon, but they played no conspicuous role. Tur- 

 tles became abundant, though distinctively marine forms had not yet 

 appeared. The crocodilians, though still retaining the primitive 

 type of biconcave vertebrae, became differentiated into the marine 

 thalattosuchians, the long-headed, gavial-like teleosaurs, and the 

 short-headed, crocodile-like types which probably found much of their 



1 Broom, The Geology of Cape Colony, by A. W. Rogers, 1905, p. 244. 



