6o MANAGEMENT AND BREEDING OF HORSES 



the crests of the teeth higher and more complete. Some 

 persons think that this form is not in direct line of 

 descent, and consider it a side branch. Found in -both 

 America and Europe. 



9. Parahippus and Hypohippus. — From the Middle 

 Miocene. In Parahippus the crests of the teeth are much 

 higher and the upper molars are changing in form, a 

 second pair of crescents appearing inside the outer pair. 

 Like Anchitherium, Hypohippus is off the direct line of 

 descent. The teeth of the two forms are much alike, and 

 they are often confused, though Hypohippus is much 

 larger, equaling a Shetland pony in size, a specimen of 

 this size being found near Pawnee Buttes, Colorad 

 in 1901. The forefoot has small rudiments of the first l 

 fifth toes, but there is no splint of the fifth, as in Met, 

 hippus. The second and fourth toes still touch th 

 ground, though lightly. These animals have been callc 

 the "Forest Horses," and are supposed to have lived 

 forests and on lowlands. The feet of Parahippus w 

 much like those of Hj^pohippus, with side toes smaller. 



10 and II. Protohippus and Pliohippus. — From the Mid- 

 dle and Upper Miocene. The crowns of the upper molars 

 have become much longer, the two pairs of crescents on 

 the upper molars are complete, with two half-separated 

 cusps within the inner pair. Cement fills the valleys be- 

 tween the crests, so that with the wear of the teeth th.- 

 edges of hard enamel are backed inside the dentine ana 

 outside the cement. Thus the surface of the tooth has a 

 series of enamel ridges projecting somewhat above the 

 grinding surface, due to the softer material on each side 

 wearing down into hollows, yet never breaking off, be- 

 cause they are braced so thoroughly on each side. This 

 provides an efficient instrument for grinding hard grasses. 

 In these two forms, especially Protohippus, the crowns of 

 the teeth are not so long as in the modern horse. 



The feet in these two forms have but one toe touching 

 the ground. The side toes are complete, but are more 



