THE RHINOCEROT. 309 



In some s-peoies. oi Hhinoceros there are |^ incisors in tlie 

 milk detention, and ^—^ or {^ incisors in the permanent denti- 

 tion. In the latter the upper incisors are large, long-crowned 

 teeth, very unlike the lower ones, of which it seems probable 

 that only one pair, in any case, are permanent teeth. In some 

 Rhinoceroses, as has been already stated, the adult is devoid 

 of incisor teeth. 



There are no canines in either dentition. Of the four milk- 

 molars, the first, as in the Horse, is smaller than the others, 

 and is not replaced. The structure of both the upper and the 

 lower molars is substantially the same as in the Horse, but the 

 roots are developed much sooner ; the laminoe of the upper 

 molars take a much more transverse direction ; the laminas of 

 the upper molars do not develop pillars, though accessory 

 crests may be developed from the two faces of the posterior 

 lamina ; the lower molars have no pillars ; and the cement 

 does not fill up the valleys between the wall and the laminsB. 



The cardiac division of the simple, though large stomach, 

 is lined by a white callous epithelium, as in the Horse. The 

 small intestine presents large processes or tags, half an inch 

 long or more, upon which the true villi are borne. The 

 csecum is very large, and the colon enormous. There is no 

 gall-bladder. The heart and brain are very similar to those 

 of the Horse. 



The male can hardly be said to have a scrotum, as the 

 testes lie close to the abdominal ring. A prostate, vesiculas 

 seminales, and Cowper's glands, are present. The long penis 

 has a mushroom-shaped glans, and the animal is retromingent. 

 The cornua uteri are proportionately longer than in the mare. 

 The teats are two and inguinal in position. The characters 

 of the fcetal membranes and the nature of the placentation are 

 unknown. 



At the present day the genus Rhinoceros is confined to 

 Africa and Asia. The African species all have two horns, 

 a nearly smooth skin, and the adult has no incisors. The 

 Asiatic species have one horn only (except that of Sumatra, 

 which has two). The skin is marked out by deep folds into 

 shields, and the adults have well-developed incisors. 



Rhinoceroses are known in the fossil state as far back as 

 the miocene epoch. R. tichorhinus^ with the nasal septum 

 ossified, and a covering of long woolly hair, inhabited Europe 

 and Asia during the cold of the glacial epoch., R. incisiviis 

 had four digits in the manus, and larger incisor teeth than any 



