402 



UNGULATA 



Family Rhinocerotid.e. 



Although the existing members of this family are readily dis- 

 tinguished from the other living representatives of the suborder 

 by the simple crescentoid form assumed by the ridges of the lower 

 cheek-teeth, yet it is exceedingly difficult to give a definition by 

 which they can be distinguished from the Lophiodontidce, from some 

 members of which they are, indeed, probably derived. The outer 

 columns of the upper molars (Fig. 167) are, however, so excessively 



/„ flattened as to produce 



a continuous thick and 

 nearly straight outer 

 wall, which is often pro- 

 duced in advance of 

 the anterior transverse 

 ridge ; both transverse 

 ridges being but little 

 curved, and intimately 

 connected with the 

 outer wall. The upper 

 premolars are in most 

 cases nearly or quite as 

 complex as the molars, 

 and the ridges of the 

 lower cheek-teeth are 

 crescentoid. The last 

 lower molar has no 

 third lobe. The height 

 of the crowns of the 

 cheek-teeth is variable. 

 The skull is large, with 

 the orbit confluent with 

 the temporal fossa. 

 There are either three 

 or four digits in the manus, and three in the pes. One or more 

 dermal horns are attached to the fronto-nasal region of the skull 

 of existing forms, but these were wanting in some of the fossil 

 species. 



Rhinoceros. l — Incisors variable, reduced in number, often quite 

 rudimentary, and early deciduous. Upper canines absent. Molar 

 series, consisting of the full number of four premolars and three 

 molars above and below, all in contact and closely resembling each 

 other, except the first, which is much smaller than the rest and 

 often deciduous ; and the last, in Avhich the hinder lobe is partly 

 1 Linn. SysL Nat. 12th ed. vol. i. p. 104 (1766). 



Fig. 167. — A partially worn second right upper molar of 

 Rhinoceros antiquitalis. Letters as in Fig. 105 (p. 375), ex- 

 cept Tc, which indicates a prolongation of the median valley. 

 (After Owen.) 



