FOSSIL ANIMALS 



339 



devoured grasses, sedges, and other harsh vegetation which they ground 

 with lateral motion of the teeth upon one another. 



Fig. 286. — Restorations of heads of fossil elephantlike animals. Upper center, Moeri- 

 therium; below it, Palaeomastodon; upper right, Trilophodon; upper left, Dinotherium; 

 lower right, Mastodon; lower left, Elephas. {From models prepared by Ward's Natural 

 Science Establishment.) 



The appearance of the heads of the series of elephantlike animals is 

 imagined to have been as shown in Fig. 286. The ears are suggested 

 by those of modern elephants, the proboscis by modern elephants and 

 the position of the nasal openings, as 

 already indicated. The general form of 

 the head and tusks is, of course, accurate. 



Evolution of the Horse. — Most of the 

 development of the line of descent of the 

 horse took place in North America. 

 Eohippus, a lower Eocene form, is the 

 first member of the series recognizable as 

 ancestral to the horse, though it may also 

 be regarded as approximately represent- 

 ing an ancestor of the tapirs and the 

 rhinoceroses. It stood about 12 inches 

 high and had a short head and neck (Fig. 287). The hind foot 

 had three well-developed functional toes. On the outer side was a splint 

 bone representing an additional toe, and on the inner side a rudiment 



Fig. 287.— Restoration of 

 Eohippus. {From, model prepared 

 by Ward's Natural Science Ls- 

 tablishment.) 



