722 



GEOLOGY 



only three functional toes, so that they left a bird-like track; the 

 fore limbs, however, had five digits. Camptosaurus, one of the 

 largest of this group, measured about 30 feet in length, and 18 in 

 height in the walking posture. 



The stegosaurs were quadrupedal in habit, and had solid bones. 

 They were curiously armored, and formed a very remarkable group 



Fig. 494. Stegosaurus, an armored dinosaur of the Jurassic. Interpreted 

 by Charles R. Knight. (Lucas' Animals of the Past. By permission 

 of the publishers, Messrs. McClure, Phillips & Company.) 



that frequented England and Western America. They were not so 

 large as some of the preceding, but found compensation in pro- 

 tective plates, spines, and similar modes of defense. The Stego- 

 saurus of Colorado and Wyoming (Morrison beds) was one of the 

 most unique (Fig. 494). Its diminutive head and brain imply :i 

 sluggish, stupid beast, depending for protection on its bulk and 

 armor. 



Turtles, which had lived elsewhere since the Middle Trias, mado 

 their first appearance in North America in the Morrison beds, and 

 the crocodilians of the period, though still retaining the primitive 



