2 54 VISCERA OF RHINOCEROS chap. 



Rhinoceros, Ceratorli.iibus, and Atelodus. As there are so few 

 existing species the subdivision of aniniids which agree in so 

 many and such highly -characteristic features seems to be an 

 unnecessary ])rocedure. The existing llhinoceroses are but a 

 fragment of the total number of known forms from past epochs. 

 The family is very markedly on the wane. 



The genus Ehinoceros is characterised by its heavy build and 

 thick, almost smooth, skin — smooth, that is to say, so far as con- 

 cerns the slight development of hair — which is often thrown into 

 folds. There is one or there are two horns on the fore-part of 

 the head, which are, as has already been pointed out, structures 

 •s;^;' [/cneris, and not exactly comparable with the horns of other 

 living Ungulates. There are three nearly equal toes on both 

 fore- and hind-limljs. The canine teeth of existing species have 

 disappeared ; the incisors are, or are not, present ; the molars and 

 premolars are three and four in each half of each jaw. 



The visceral anatomy of the Ehinoceros has been much inves- 

 tigated so far as concerns the Asiatic forms. A curious feature, 

 which serves to discriminate some of the Asiatic species from 

 others, is to be seen in tlie small intestine. In Eh. indicus^ 

 this gut is furnished with numerous long cylindrical narrow out- 

 growths " like tags of worsted " ; in tlie allied Eh. sondaicus these 

 tags are present, but are flatter and broader ; while in the two- 

 horned Eh. sumatrcnsis there are no tags at all, but only smooth 

 valve-like folds. Another mark l)y which these species can be 

 distinguished depends upon tlie variation in the presence or 

 alisence of certain glands imbedded:^ in the integument of the foot 

 — the so-called " hoof glands." These occur in EJi. indiciis and 

 Eh. sondaicus, but are absent in Eh. siimatrensis. 



Sir W. Flower^ studied some years since the skull features 

 wliich serve to differentiate the existing forms. 



In Eh. sumatrensis the two long downward processes of the 

 squamosal bone, termed respectively post -glenoid and post- 

 tympanic, do not unite Ijelow the auditory meatus. In this the 

 species in question agrees with the African forms but not with 

 the one-horned Asiatic species, where the two processes completely 

 fuse. Again, another character, thougli perhaps less important, 



1 Garroil, Proc. Zool. Sue. lS7o, p. 92 ; ibid. 1877, p. 707. Be(idard and Treves, 

 Trans. Zool. Soc. xii. 1887, p. 183. 

 - Proc. Zool. Soc. 187tJ. p. 443. 



