192 VIGNETTES FROM NATURE. 



towards the distinctive peculiarity of his race 

 the solid hoof, adapted to free scouring 

 over open grass-grown plains ; for one of his 

 five toes is, even at this early period, only in 

 a rudimentary condition. In the higher 

 eocenes of Wyoming and Utah we get a 

 rather more horse-like creature, prohippus, as 

 big as a fox, with four toes to his front feet 

 and three to his hind feet. Then, only about 

 a million years or so later, injihe miocene of 

 Oregon and Nebraska, we find two more 

 specialised equine animals, miohippus and 

 mesohippus, as big as a sheep, with three 

 hoofed toes on the front feet, of which the 

 middle one is distinctly the largest, being, in 

 fact, the forerunner of the one final hoof in 

 our own horses. In the pliocene, again, we 

 come upon the bones of hipparion and proto- 

 hippus, as big as this donkey, with one stout 

 middle toe, much like our modern horse's 

 hoof, and a lateral one on each side which 

 does not reach to the ground. Side by side 

 with these very horse-like forms occurs 



