RHINOCEROS HEMITCECHUS. 337 



Rhin. hemitcechus is presented by a specimen in the Museum 

 of the College of Surgeons, of which the precise origin has 

 not been recorded, but which is believed to have been procured 

 from Grays Thurrock, or some other of the fluviatile deposits 

 in the Valley of the Thames. It is represented two-thirds of 

 the natural size by fig. 5 of PI. XYIII. In this case the 

 crochet forms a wall across the valley, insulating its upper 

 portion and connecting the two barrels. It is united to the 

 middle of the anterior colline, and above it, a parallel, short, 

 stout, ' combing plate ' juts into the insulated fossette. The 

 general form, angular offset of the crochet, enormous coat of 

 cement, and details of the characters prove it to be of Rhin. 

 hemitcechus. 1 



That this peculiar confluence of the crochet with the ante- 

 rior barrel is abnormal in the true molar is proved by the 

 extreme rarity of the instances which have been observed of 

 it in any species of Rhinoceros. Cuvier has figured one (Oss. 

 Toss. Rhinoc. PL XIII. fig. 4), a penultimate, being the 

 Crozes specimen already referred to (supra, p. 830). I have 

 examined, in the Museum of the Faculty of Sciences of Mont- 

 pellier, other specimens from the Departement du Gard, which 

 agreed with the figure of this specimen in every essential 

 respect except the irregular connections of the crochet, and 

 they appeared to me all to belong to the Rhin. megarhinus 

 of Montpellier. If the form of the crochet, its offset, and the 

 acute angle which it makes with the posterior colline in 

 m. 2 of fig. 2, Plate XVI., are compared with the same points 

 in the Crozes specimen, the differences are very obvious. 

 No other instance of a bridge-crochet in a true molar has, so 

 far as I am aware, been figured. In the milk molar it is by no 

 means of rare occurrence, and is often seen in those of Rhin. 

 bicomis. This appearance must not be confounded with the 

 cohesion between the crochet and the ' combing plate,' which 

 gives rise to the third fossette so characteristic of Rhin. 

 tichorhinus. 



The most significant peculiarity in the last true molar of 

 Rhin. hemitcechus remains to be described. From the marked 

 triangular outline of the crown in plan, and the V-shaped 

 confluence of the terminal ridges, it might have been ex- 

 pected that the posterior fossette would be entirely suppressed, 

 as in Rhin. bicomis and other species in the same category. 

 But at the posterior angle of the hind barrel, and dislocated 

 from its ordinary position in the other true molars, a well- 

 defined fossette is placed close to the base of the crown. It is 

 of a triangular form, with a gaping rim, which is deeply 



1 On tlio drawing of this spccimon Dr. F. has written ' R. megarhinus'} ' — [Ed.] 

 VOL. II. Z 



