HISTORY OF THE PERISSODACTYLA 327 



wealth of material and the admirable preservation of much 

 of it, it is extremely difficult to find a clew through the mazes 

 of this labyrinthine genealogy. From the standpoint of the 

 existing geographical distribution of animals, few mammals 

 could seem more foreign and exotic to North American life 

 than do the rhinoceroses, and yet for a very long time that 

 continent was one of the chief areas of their development, 

 so far, at least, as that development can be followed. It is 

 even probable, though not clearly demonstrable, that the 

 family originated here and subsequently spread to the Old 

 World, but not to South America, where no member of it 

 has ever been found. The later history of the rhinoceroses ran 

 its course in the Old World entirely, and the highest speciali- 

 zations within the family are to be found there ; in North 

 America these animals are not known to have persisted beyond 

 the lower Pliocene, and if they did survive, it was only as a few 

 stragglers in out of the way places. 



The modern rhinoceroses are restricted to Africa, southern 

 Asia and some of the larger Malay islands, Borneo, Sumatra 

 and Java, and within these wide geographical limits are to be 

 found the terminal representatives of at least three separate 

 and quite distinct phyla, the African, Indian and Sumatran 

 genera respectively (Opsiceros, Rhinoceros, Dicerorhinus) . It 

 will be advisable to begin the study of this peculiarly interesting 

 family with a brief examination of its modern members, even 

 though none of these are found in the western hemisphere. 



All the existing rhinoceroses are large and massive animals, 

 ranging from four feet to six feet six inches in height at the 

 shoulder, and all have solid dermal horns, except in most 

 females of the Javan species ^ {R. sondaicus). The Indian 

 and Javan species have a single horn on the nose, while those 

 of Africa and Sumatra have, in addition to the nasal horn, a 

 second one on the forehead. The horns, thus, do not form a 



' The names, Javan and Sumatran rhinoceroses, are somewhat misleading, 

 since both of these species are also found on the mainland of India. 



