RHINOCEEOTID^. 



91 



tallest in Elasmotherium. One or more dermal horns may be attached 

 to the fronto-nasal region. The digits on the pes are apparently 

 always three, but they may be either three or four in the manus. 



Genus RHINOCEROS, Linn. 1 



Including 2 : — Aceratherium, Kaup 3 . 

 Atelodus, Pomel 4 . 

 Ceratorhmus, Gray 5 . 

 Diceratherium, Marsh 6 . 

 Zalabis, Cope 7 . 

 Aphelops, Cope s . 

 Peraceras, Cope 9 . 

 C&nopus, Cope 10 . 



Following Flower's n arrangement of the living Ehinoceroses in a 

 single genus, there seems no good reason for excluding the hornless 

 forms 12 , in some of which the number of digits in the manus is four, 

 and in others three ; canines and incisors, as in the horned forms, 

 vary in number 13 . 



Dentition :— I. g=g, C. ~^ y Pm. \, M. |. In the adult the first 



premolar may be absent in both jaws ; pm. 1 is sometimes a true 

 dent de remjjlacement u . The upper cheek-teeth ia have two transverse 



1 Syst. Nat, ed. 12, vol. i. p. 104 (1766). 



2 For the numerous genera adopted by Cope, see Proc. Amer. Phil. Soc. 

 vol. xix. p. 393 (1881). 



3 Isis, 1832, p. 904. 



4 Ann. Soc. Lit. Auvergne, vol. xxvi. p. 114 (1853). 



5 Proc. Zool. Soc. 1867, p. 1006. 



6 Amer. Journ. ser. 3, vol. ix. p. 242 (1875). 



7 Amer. Nat. vol, xiii. p. 771b (1879). (Founded on an error.) 



8 Ann. Eep. Chief of Engineers, vol. ii. p. 991 (1875). Also occurs in pri- 

 vately published Paheont. Bull. No. 14, p. 1 (1873). 



9 Amer. Nat. vol. xiv. p. 540 (1880). 



10 Amer. Nat. vol. xiv. p. 611 (1880). 



11 Cat, Vert, Anim. Mus. E. Coll. Surgeons, part ii., Mammalia, pp. 415-432 

 (1884). 



12 The female of R. sondaicus (the so-called B. inermis of Lesson) appears to 

 be hornless in some instances. The genus Aceratherium was retained for the 

 fossil forms by the writer in the ' Palasontologia Indica,' ser. 10, vol. iii., and in 

 his ' Catalogue of Siwalik Vertebrata in Indian Museum,' part i. (1885), Cal- 

 cutta. 



13 The outermost lower cutting-tooth is here reckoned as a canine. 



14 See a paper by the present writer in the Journ. As. Soc. Beng. vol. xlix. 

 pt, 2, p. 135, pi. vii. (1880). 



15 For the explanation of the terms employed in describing the upper cheek- 

 teeth of this family, see woodcut on page 116, and ' Pakeontologia Indica,' ser. 

 10, vol. ii. p. 8. 



