332 



RHINOCEROS. 



forwards and parallel to the crochet, corresponding with 

 what was described above of the same process in the last 

 premolars. The origin and connection of this ' combing 

 plate ' are explained by the mammillary processes seen above 

 the ' crochet ' in the terminal expansion of the transverse 

 valley in m. 2 of fig. 1 (PL XVI.). These denticuli are con- 

 nected with the bottom of the fissure and with its outer wall. 

 It is obvious that if the abrasion of the crown were carried a 

 little further they would run together into a continuous 

 plate, which would project into the valley parallel to the 

 crochet, reproducing the pattern seen in p.m. 4 of the 

 same figure, and in the last true molar, m. 3 of fig. 2 

 (PI. XVI.). When this occurs a very complex pattern is 

 the result. Cuvier has figured no examples, but in the 

 additions to Vol. iii. of the ' Oss. Fossiles,' he refers to some 

 teeth procured by Mr. Pentland in Tuscany, ' dont la colline 

 posterieure, an lieu d'un seul crochet, en donne plusieurs 

 petits en avant; ce que fait paraitre cette colline dentelee 

 vers sa base quand elle commence a s'user.' He adds, ' ce 

 caractere pourra servir a reconnaitre cette espece (referring 

 to Rhin. leptorhinus) par ces molaires.' Professor Owen had 

 his attention directed to the same peculiarity in a fossil 

 which he describes ' as the germ of the antepenultimate 

 molar of a Rhin. leptorhinus from Grays, in Essex, in which 

 many smaller processes are sent off into the principal valley, 

 in addition to the large promontory,' but he was not disposed 

 to place much stress upon this as a specific character. In 

 Rhin. megarhinus, these ' combing plates ' are not directed 

 forwards, but converge from the anterior outer angle towards 

 the crochet. I have lately ascertained, by the examination 

 of the cast of a cranium with teeth contained in the Museum 

 at Pisa, that Rhin. hemitoechus occurred in the Fauna of the 

 Val d'Arno, 1 and the teeth so briefly yet pointedly noticed by 

 Cuvier in the passage cited above in all probability belonged 

 to this species. In the penultimate (m. 2) of the ' Bacon 

 Hole' specimen (PL XVII. fig. 1), although not much ad- 

 vanced in wear, the denticuli of the ' combing plate ' have 

 run together and it is projected forwards parallel to the 

 ' crochet,' thus confirming the constancy, of the character. 



The penultimate and antepenultimate upper true molars 

 differ so little from each other, except in dimensions and some 

 trivial details of proportion, that it is unnecessary to describe 



1 This cranium of a Rhinoceros, with 

 a partial bony septum, was subsequently 

 determined by Dr. Falconer to belong to 

 Rhin. Etrusms (p. 359). Mention, how- 

 ever, is made in his note-books of a lower 



jaw of Rhin. heniitcechus in the Pisa 

 Museum. The existence of the latter 

 species in Italy is also mentioned in his 

 letter to M. Lartet, already referred to, 

 p. 309.— [Ed.] 



