2 54 VISCERA OF RHINOCEROS 



Rliinoeeros, Ceratorhinus, and Atclailus. As there are su few 

 existing species tlie subdivision of animals whicli agree in so 

 many and sucli highly -cliaracteristic features seems to be an 

 unnecessary procedure. The existing Ehinoceroses are but a 

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

 The family is very markedly on the wane. 



The genus Rhinoceros is characterised by its heavy l^mild 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 

 sia f/eneris, and not exactly comparable with the horns of other 

 living Ungulates. There are three nearly equal toes on both 

 fore- and hind-limbs. 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 the small intestine. In Eh. indicus ^ 

 this gut is furnished with numerous long cylindrical iinrrdw out- 

 growths " like tags of worsted " ; in the allied Rli. soiidaicus these 

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

 liorned Rh. sumatrensis there are no tags at all, but only smooth 

 valve-like folds. Another mark by which these species can be 

 distinguished depends upon tire variation in the presence or 

 absence of certain glands imbedded in the integument of the foot 

 — the so-called " hoof glands.'' These occur in Rh. indicus and 

 RIi. sondiiicits, but are absent in Rh. sicmatrensis. 



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

 which serve to differentiate the existing forms. 



In Rh. sumatrensis the two long downward processes of the 

 squamosal bone, termed respectively post -glenoid and post- 

 tympanic, do not unite below 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. .Vgain, another character, though perhaps less important, 



' GaiToil, Proc. Zool. Soc. 1873, p. 92 ; ibid. 1S77, p. 707. Beddard and Treves, 

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

 = Froc. Zool. Soc. 1876, p, 443. 



