408 THE NATURAL HISTORY REVIEW, 



flattened, and at a higlier level than tlie posterior. The latter sweeps 

 regularly round from the well defined median groove. The anterior 

 valley, A, is about half the size of the posterior ; the anterior collis, D, 

 is the smallest of the three, and the median, E, the largest. The tip 

 of the third is flattened on the inner side and bent forward, leaving a 

 small process in the section aiforded by a worn tooth. 



§ 4. Permanent Dentition. — The abrasion of the enamel on 

 the anterior surface of premolar two by the pressure of premolar one, 

 proves that in the upper jaw the molar dentition consisted of I'm 4, 

 Jf 3, a point in which this species diifered from B. tichorhinus, where 

 the premolar one was not developed. It is the only megarhine tooth 

 that I have not met with. In the lower jaw the number of the 

 premolars is open to some doubt, as unfortunately the jaws present 

 only premolars three and four, and dependence cannot be placed 

 upon the isolated teeth. 



In the upper molars (Figs. 9, 10, 11), the strong development of the 

 guard, the suppression of the anterior combing plate, and conse- 

 quently of the accessory valley (vallecula accessoria of Brandt), the 

 accessory folds in the anterior valley, A, the pyramidal form of the 

 presence of first and second colles, D, E, the absence of a cusp from 

 the summit of the third, F, and of ribs from the posterior area diflferen- 

 tiate the megarhine from the tichorhine species. The grinding 

 surface also is very much more concave in the former than the 

 latter. 



The small size, the presence of a third costa on the posterior area, 

 and the excavation of the lower third of the external lamina, charac- 

 terise JB. leptorhinus, as compared with B. megarhinus. Irrespec- 

 tive of these points and of size and sculpturing, they are remarkably 

 alike. 



The fangs are four in number, the two outer being free, the two 

 inner confluent. 



The right upper jaw figured (Eig. 9) as a type specimen of the 

 British megarhine Rhinoceros contains three true and three premo- 

 lars. They occupy an alveolar length of 12.8 inches. 



§ 4. A. Upper Molar Series 2. — In Premolar two the external 

 lamina, L, is tumid, and with costa two, K 2, faintly developed. The 

 anterior valley, A, is full of involutions of enamel, and communicates 

 with the anterior surface by a deep cleft, not shown in the figure, 

 extending down as far as the cingulum at the anterior and outer angle 

 of the tooth. Its entrance on the inner side is in vain to be looked 

 for, as it is completely blocked up by the inner wall of the tooth. 



