ELEPHANTS, RHINOCEROSES, AND HORSES 269 



The rhinoceroses originated at the beginning of the Miocene 

 period in North America, but all their more wonderful develop- 

 ments of bulk and horns, and their correlative loss of teeth, have 

 taken place in Europe and Asia. The rhinoceroses grew 

 gradually from out of a primitive type of Perissodactyle, not 

 far removed from the ancestral tapir, which, of course, was also 

 the stock from which tapirs and horses and other groups of 

 Perissodactyles arose. The original rhinoceros had four toes on 

 each foot, and a full set of teeth, including the normal number 

 of incisors, canines, premolars, and molars. 



It is probable that the early rhinoceroses in America were 

 hornless, though in that country had arisen even earlier a 

 marvellous group, distantly allied to the rhinoceroses in origin, 

 called the Titanotheres, nearly of the size of elephants, and pro- 

 vided with one or more pairs of " horns," represented in their 

 skulls by larger or smaller projections of bone. The rhinoceroses 

 have never grown " horns " in the direct sense of the word ; that 

 is to say, so far as the skull is concerned, there is at most 

 a great or small boss of bony matter, which acts as a support to 

 a shorter or longer projection of matted hair. The " horns " of 

 the rhinoceros are simply coalesced hair. They are not bone, 

 like the horns of giraffes or deer, nor are they hollow caps of true 

 horn (a substance like the nail or hoof, and distantly allied to 

 hair), which cap the bony projections in the skull of oxen and 

 antelopes. Increase of specialisation in the rhinoceroses caused 

 them, no doubt, to rely more and more on the mobile upper lip 

 for the collection of their food, and less on the incisor teeth for 

 this purpose ; while the development of " horns," or sharp pro- 

 jections of matted hair, replaced as weapons of offence and 

 defence the canine teeth, or tusks, which are so prominent in 

 the early rhinoceros. Consequently in the more advanced types of 

 rhinoceros, living and extinct, there are absolutely no teeth at all 

 in the fore part of the upper jaws, and indeed the fore part of the 

 jaws has ceased to exist. The teeth in these extreme types are 

 merely reduced to molars and premolars. This group is well 

 represented at the present day by the African rhinoceroses, of 



