DESCRIPTION OF PLATE XVIII. 



Rhinoceros leptorhinus (R. megarhinus), Rhinoceros 



HEMITCECHTJS, AND RHINOCEROS BICORNIS. 



Figs. 1 and 2. Represent the two varieties of the last upper premolar, 

 right side, of Rhinoceros leptorhinus {R. megarhinus, Christ.), 

 referred to at page 328 of the text, in one of which (fig. 1) 

 there is a very pronounced basal bourrelet, while the other 

 (fig. 2) is entirely free from it. These two figures have been 

 copied from the illustrations of De Christol's memoir in the 

 Ann. des Sc. Nat. 2me. Ser. torn. vi. Zool. PI. III., figs. 10 

 and 4. In both, the 'combing plate ' (K) is seen converging di- 

 agonally to meet the plane of the crochet (T) nearly at a right 

 angle. The drawings are about two-thirds of the natural size. 



Fig. 3. Represents the penultimate true molar, upper jaw, right side, 

 of Rhinoceros leptorhinus {R. megarhinus, Christ.), two-thirds 

 of the natural size. The section of the crochet is wedge-shaped, 

 thinning from a broad base to a sharp edge, and it forms a 

 very open angle with the disc of the posterior colline. This 

 specimen is referred to at page 331, and the figure has been 

 copied from Plate III., fig. 3 (not fig. 5, as stated in text), of De 

 Christol's memoir above referred to. 



Fig. 4. Penultimate upper molar, left side, of R. leptorhinus (i?. me- 

 garhinus'), yielding precisely the same characters as fig. 3. It 

 is about two-thirds of the natural size and has been copied 

 from the ' Paleontologie Francaise,' by Gervais, PI. II., fig. 5. 

 It is referred to at page 33 1 . 



Fig. 5. Last upper molar of Rhinoceros hemitachus, two-thirds of the 

 natural size, showing an abnormal condition of the crochet. 

 The specimen is believed to have been procured from Grays 

 Thurrock, and is now in the Museum of the College of Surgeons. 

 Dr. Falconer's reasons for regarding this tooth as belonging to 

 R. hemitachus, rather than to R. leptorhinus, will be found at 

 page 337. 



Figs. 6 and 7. Two views of a germ of last upper molar, left side, of the 

 existing species, Rhinoceros bicornis, two-thirds of the natural 

 size. Fig. 6, inner side. Fig. 7, crown, a, anterior colline ; 

 b, longitudinal colline ; c, continuation of longitudinal colline, 

 which is the homologue of the posterior transverse colline ; d, 

 the crochet ; e, anterior barrel ; f, anterior basal bourrelet ; g, 

 posterior barrel; /(, small tubercle at posterior inner angle; i, 

 the vertical groove of the anterior outer angle. (See page 335.) 

 The specimen is now in the British Museum. 



