RHINOCEROS TICHORHINUS. 



337 



summits by attrition, is not so soon blended into one con- 

 tinuous tract as in the Palseothere (fig. 116), but long 

 remains insulated by a complete boundary ridge of enamel 

 in each lobe, as shown in the lower molar tooth of the 

 Rhinoceros tichorhinus (fig. 127). This tooth was discovered 

 in the drift gravel, over-lying the Fig. 127. 



London clay, during the opera- 

 tions of digging the Eegent's Canal, 

 and is now in the British Museum. 

 It shows also the deeper internal 

 excavation, and the unequal height 

 of the two crescentic lobes, which 

 distinguish the lower molars of the 

 Rhinoceros from those of the 

 largest Palseothere. 



In the lower jaw of the Rhino- 

 ceros tichorhinus, represented in 

 figures 123 and 124, five molar 



, , . j j i Fifth molar, right side, lower 



teeth are Shown in SltU, and the j aw , nat. size ; Rhinoceros tichor- 



socket of a small premolar in front. 



The lower jaw, discovered at Montpellier, figured by M. 

 Christol in his Memoir on the species of fossil Rhinoceros, 

 in the ' Annales des Sciences' 1 for 1835, pi. ii. figs. 1 and 2, 

 and referred by that author to the Rhinoceros tichorhinus, 

 is described (p. 46) as having all its molars, " munie de 

 toutes ses molaires," of which teeth the figures exhibit six, 

 corresponding in number with those of the specimen from 

 Wirksworth. I have, however, obtained good evidence, 

 from British specimens, of the accuracy of M. Adrien 

 Camper's statement, cited by Cuvier, ' Ossemens Fossiles, 1 

 1822, torn. ii. pt. 1. p. 61, that the tichorhine Rhinoceros 

 had seven molar teeth on each side of the lower jaw, like 

 the existing species ; and that the smaller number in the 



