XO. I THE WHITE RHINOCEROS HELLER IJ 



occurred contemporaneously in America and Europe. The early 

 forms were four-toed, hornless species, which retained functional 

 lower canines as well as incisors. In America there is no evidence 

 of rhinoceroses later than the Lower Pliocene, where we find Teleo- 

 ccros, a three-toed genus with small dermal nasal horns like some of 

 the living- forms. The Pliocene and Pleistocene of Europe, Asia, 

 and Africa has supplied many species. The most recently extinct 

 species is the woolly rhinoceros, Coelodonta antiquitatis, which was 

 a northern animal contemporaneous with the mammoth and man. 

 An entire carcass of this recent species has been found preserved in 

 the ice of Siberia. The five living species of Rhino ceratidce are to-day 

 confined to Africa south of the Sahara, Eastern India, the Malay 

 Peninsula, and the Islands of Sumatra, Java, and Borneo. 



The characters which have been found of generic importance in the 

 recent and living species are : the absence or presence of functional 

 incisors and canines ; the extent of the projection of the occipital 

 portion of the skull beyond the condyles ; the union or separation of 

 the post-glenoid and post-tympanic processes forming an open or a 

 closed auditory meatus ; and the complication of the enamel folds in 

 the cheek teeth and their development in relative size of crowns into 

 brachyodont or hysodont teeth. The number of dermal horns on the 

 snout is of less importance. These have been found to show some 

 individual variation in the African species varying from one to three 

 in number in the same species. The front horn, however, is nearly 

 always the better developed and is never wanting. The characters 

 of the cheek teeth though to some extent based on the nature of the 

 food of the species, are nevertheless of much value in showing funda- 

 mental relationships. 



Ccratothcrium does not appear to be closely related to any fossil 

 species. Its nearest ally is doubtless Diceros, although the living 

 Sumatran rhinoceros, Dicerorhinus sumatrensis, is not separated any 

 more widely structurally and shares with it the character of the open 

 auditory meatus, and the dolichocephalic skull, both characters of 

 much weight. The lack of functional incisors is one of the differences 

 in dentition between Dicerorhinus and Ceratotherium, but the disap- 

 pearance of these teeth in Ccratothcrium has taken place recently. 

 The chief dental difference with these genera, however, is the com- 

 plicated enamel foldings of the cheek teeth into cement-filled enamel 

 fossettes. 



The other African genus, Diceros, shares with Ceratotherium the 

 character of the meatus and the lack of functional incisors and canines, 



