32 



THE HORSE 



continued practically unchanged since the Miocene 

 times ; while almost all other mammalian forms which 

 existed then have either become extinct or undergone 

 extensive modification. In the structure of their feet 

 they scarcely differ from Hyracotherium. They are, in 

 fact, typical old conservatives, which have scarcely 

 departed in any way from the manners, customs, or 

 structure of their ancestors. They appear to be 

 animals tending to extinction, for, though formerly 

 having a wide range of distribution through the con- 

 tinents of America, Europe, and Asia, they are now 

 only found at two rather isolated parts of the world — 

 i.e., South and Central America and the Malay region 

 — and they are by no means numerous either in species 

 or individuals. 



A second branch of the group can be traced 

 through such forms as Hyracodon, Aceratheriiim, and 

 Aphelops to the modern rhinoceroses, which in many 

 respects are more specialised than the tapirs. They 

 have but three toes upon each foot, and the teeth have 

 been considerably changed, some species having lost all 

 the incisors or cutting teeth of the front of the mouth. 

 They have, moreover, acquired the peculiarity of wearing 

 one or two large horns upon their noses, which the early 

 species of the family did not possess. 



Somewhat allied to the rhinoceroses were some 

 remarkable animals which flourished in the early Mio- 



