CHAPTER XXI 
WHITE OR SQUARE-MOUTHED RHINOCEROS 
Ceratotherium 
Ceratotherium Gray, 1867, Proc. Zool. Soc., p. 1027; type Rhinoceros simus. 
The white rhinoceros, like the black, represents a dis¬ 
tinct type of which it is the sole living member. In fact, 
it is the most highly specialized form living. Its extreme 
specialization is brought about by the lengthening of the 
skull until it has become remarkably dolichocephalic or 
long-headed. The teeth are quite as specialized as its 
skull, and in some respects parallel those of horses. Like 
the horses, the crowns have become very long or hypso- 
dont, and the cement layer has grown in thickness until 
it forms an important part of the grinding surface of the 
teeth. The teeth are no longer composed of loops which 
are separated by deep valleys and are open on the inside, 
but the loops have united and enclose the cement layer 
as islands or fossettes in the tooth. The crown is per¬ 
fectly flat and shows a complicated pattern of alter¬ 
nating folds of enamel, dentine, and cement. This tooth 
specialization has been brought about by the grass diet, 
the lengthening of the crowns and their increased surface 
being necessary in order to masticate the tough grass stems 
which form the chief part of their food. The dental appa¬ 
ratus of the other living species of rhinoceroses, which are 
chiefly browsing animals, consists of short-crowned teeth, 
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