372 RHINOCEROS. 



4. A fragment of a left lower jaw with the penultimate and ante- 

 penultimate true molars. 



Of the last true molars, the best preserved, A, (PL XXXII. fig. 6), 

 resembles very much in form, size, and amount of Avear, the specimen 

 of R. megarhinus, which I got from Gervais, from the marine sands of 

 Montpellier. It is deficient only at the outer angle, where the grooved 

 portion is broken off by a fracture sloping from the inside outwards. 

 The crown presents the characteristic V-shaped outline. The posterior 

 barrel is somewhat compressed, and at the posterior inner angle (where 

 the rudimentary valley of R. hemitcechus is seen), there is a broad ad- 

 pressed basal tubercle with an obscurely crenated edge, very considerably 

 larger than the tubercle on the Montpellier cast (PI. XXXI. fig. 2). This 

 tubercle leaves a neck between it and the enamel of the crown, filled 

 up with cement ; but there is nothing resembling the pit in R. hemitce- 

 chus ; and there is no decurrent groove ascending from it. The prin- 

 cipal differences between it and the Montpellier specimen are : 1st, 

 that the A'alley is more open, with a wider fissure, from more advanced 

 wear, and that there are no remains of the crochet process intruding 

 into the valley (only a sinuous line), nor of a combing plate from the 

 outer angle causing the ' duck's head ' pattern of the Montpellier crown, 

 which is seen also in Gervais' drawings. The termination of the valley 

 forms a large oval fossa, which contracts into the fissure, that opens 

 between the barrels. 2nd, that there is a basal tubercle between the 

 barrels, appended to the posterior barrel. 3rd, that there is a well- 

 marked layer of cement, which is abundant in the valley near the 

 intercolumnar tubercle. 



The second specimen, B, is nearly in the same stage of wear, but it is 

 mutilated by a fracture, which has removed a portion of the inner side 

 of the last barrel, while the outer angle, mutilated in A., is entire. It 

 corresponds very exactly in form with the other. The posterior barrel 

 shows the same kind of tubercle, adpressed and near the base, but the 

 greater part of it is removed by the fracture. The transverse valley is 

 more contracted in consequence of part of the crochet remaining. The 

 termination is triangular, and a good deal like Gervais 1 fig. G, 1 but is 

 more triangular and has less of the ' duck's bill ' pattern. This spe- 

 cimen very fortunately presents the outer angle entire. It resembles 

 the Montpellier cast exactly in form, i.e. it is broad and salient, with a 

 well pronounced vertical groove, and the lobes of the emargination sub- 

 equal, being very different in form from the R. hemitcechus molar ; 

 where the angle is narrow, the groove shallow, the lobes unequal, the 

 anterior being much the higher. There is no intercolumnar tubercle 

 in B., but the barrel is broken at that point. 



From the annexed comparative measurements, I am satisfied that 

 these Roman specimens, including Lyell's Ponte Molle specimen, are of 

 the same species, as the Montpellier one, i.e. R. megarhinus of 

 Christol. Lyell's specimen shows much cement at the mouth of the 

 valley, but the outer angle of the chevron is mutilated and rolled, and 

 the posterior barrel is rolled below where the posterior basal tubercle is 

 placed. The enamel in all is thin and smooth. 



1 Paleontologie Franijaise, PL ii. — [Ed.] 



