CHAPTER II. 



THE HORSE AND ITS NEAREST EXISTING RELATIONS. 



The tapirs (Family Tapiridce} Characters, species, geograph- 

 ical and geological distribution The rhinoceroses (Fam- 

 ily Rhinocerotidce) The horses (Family Equidce) Their 

 immediate predecessors The hipparions or three-toed 

 horses of Europe and America Existing species of horses 

 The horse (Equus caballus) Wild, domesticated, and 

 feral horses Wild asses Equus liemionus of Asia and its 

 varieties The African wild ass and the domestic ass 

 (Equus asinus) Striped members of the equine family 

 Zebras and quaggas (Equus zebra, E. lurclielli, E. grevyi, 

 and E. quagga) Hybrids or mules Aptitude for domes- 

 tication only found in certain members of the family. 



As shown in the last chapter, the Perissodactyle 

 ungulates, by various and gradually progressing de- 

 viations from the common original type, began at a 

 very early age to break up into several groups, some 

 of which, after undergoing a considerable degree of 

 specialization, have become extinct, without leaving 

 successors ; but three of these modified types, already 

 distinct at the close of the Eocene period, have con- 

 tinued up to the present day, gradually, as time ad- 

 vanced, becoming more and more divergent from each 



