EVIDENCE FROM PALEONTOLOGY 111 



bone in the skeleton declares its affinities with the 

 rhinoceroses. 



The second branch, though of American origin, 

 spread to the Old World and has been found in 

 France. The short, low and very broad skull had no 

 horns, but large tusks provided effective weapons of 

 defence. In marked contrast to the cursorial type, 

 these animals were presumably aquatic in habit and 

 though rather low, were very massive in build and 

 had four toes in the front-foot; aside from the head, 

 they must have been quite hippopotamus-like in 

 appearance. 



The third branch, the true rhinoceroses, has had a 

 far more complicated history, because of the number 

 of distinct series within the group, which passed 

 through parallel courses of development; Professor 

 Osborn recognizes no less than seven of these series in 

 the Old and New Worlds. The terminal members of 

 three series are the modern African, Indian and 

 Sumatran species. While the structure of the true 

 rhinoceroses underwent very considerable changes in 

 that part of their history of which the record has been 

 discovered, the changes are much less radical than 

 those which took place in the horses in the same 

 length of time and, for the most part, they affected 

 the skull and dentition. The true rhinoceroses are 

 characterized by the peculiar development of the 

 front teeth (incisors and canines); in the modern 

 African species these teeth have been entirely sup- 

 pressed, but in the Indian and Sumatran and the 



