The Rise of the Mammals 



sidered to have been partly formed in lakes 

 and broad streams, and partly by the heaping 

 up of earth on the wind-swept lowlands. They 

 form a great cemetery of ancient animals which 

 has yielded scores of species and thousands of 

 specimens, and its possibilities in the way of 

 fossils seems to be by no means exhausted. 



Skull of a Titanothere, Brontotherium ingens. (After Marsh.) 



The giants among these animals were the 

 Titanotheres, the largest of which attained al- 

 most the bulk of an elephant, though propor- 

 tionately less heavily built and standing some- 

 what higher on their legs. Their most striking 

 peculiarity, however, lay in the saddle-shaped 

 skull with its blunt horns, one on either side of 

 the nose. It does not seem probable that these 



237 



