FOSSIL ANIMALS 



341 



In Merychippiis, a INIiocene animal, the feet were all three-toed (Fig. 

 290), vestiges of the fifth toe being present in some specimens and wanting 

 in others. The lateral toes, however, were high above the ground; the 



Fig. 290. — Fore feet of fossil horselike animals; from left to right, Orohippus, Meso- 

 hippus, Miohippus, Meryehippus, Pliohippus. Of each type there are represented the 

 bones and the restoration in the fiesh. (From, models prepared by Ward's Natural Science 

 Establishment.) 



entire weight of the body was borne upon the middle (third) toe. The 

 permanent molar teeth had moderately high crowns, and the upper sur- 

 face was worn down to a flat grinding surface marked by sharp ridges of 

 enamel set among dentine and cement (Fig. 288). Meryehippus was 

 evidently a grazing animal, whereas its predecessors must have fed upon 

 succulent herbage which was crushed, not ground. The skull was 



Fig. 291. — Skull of Mesohippus, about J^fo natural .size. (From photograph of specimen 

 in Museum of Geology, University of Michigan.) 



enlarged (Fig. 292), and the lower jaw was heavier in evident relation to 

 the change of the teeth. The orbit of the eye occupied a more posterior 

 position relative to the teeth, making the face longer. The orbit was 

 also completely closed behind by a bar of bone which in the earlier 



