338 EVOLUTION OF THE HORSE. 



and wolf, whose conformation was unsuited for predatory 

 operations in the morasses which had afforded an asylum for 

 ancestors of the horse. 



Points of Speed and Strength in the Fossil Horse. 



— At the outset of this investigation, I am met with the 

 pertinent question : what is a horse ? My natural reply to 

 this will be that the horse is an animal which has only one toe 

 to each of its legs. I might also add, for the benefit of those 

 of my readers who are interested in comparative anatomy, 

 that his teeth are plentifully supplied with crusta petrosa {see-^. 

 329) ; and that the pulley-like processes on his astragalus are 

 directed forward and outward [see p. 70). The fact of unity 

 of digit — a peculiarity which distinguishes the horse from all 

 other mammals — will probably suffice for ordinary inquirers. 

 Taking this test, we cannot with propriety apply the term 

 horse to animals further back in equine descent than the 

 Anchitherium, The Phenacodus resembles a carnivorous 

 animal (a Dandy Dinmont or otter hound) more than he does 

 one of the horse tribe. His great length of humerus must have 

 given him considerable power in raising the forehand by the 

 play of the shoulder and elbow joints, the diminution of which 

 play is compensated for in the horse by the action of the fet- 

 lock joint. His hocks and knees, like those of the dog and cat, 

 were "well let down." He miaht have had a fair "turn of 

 speed " for a short distance ; but he was too long in the body to 

 have been a stayer. There is no doubt that the ancestors of 

 the horse were of very slow pace at the time when they were 

 identical with, or nearly akin to the Paloplotherium and the 

 Hyracotherium, animals which were not far removed from 

 the rhinoceros and tapir. With the tendency to the gradual 



