ON THE MOLAR SERIES OF RHINOCEROS TICHORHINUS. 529 
leptorhinus , and in the three upper molars of JR. hemitoechus (Falc.) 
from Kirkdale, in the Oxford Museum. In an example on the other 
hand of B. bicornis% it is rudimentary in the true molars, and 
well developed in the Premolar series. Thus with reference to the 
combing plates,’ the latter species stands half-way between JR. ticho- 
rhinus and B. sumatranus. 
The entrance of the anterior is at a lower level than that of the 
posterior valley, and the former penetrates more deeply than the 
latter into the substance of the tooth. The anterior A and median B 
colies advance obliquely forwards and outwards instead of at right 
angles to the median line. The posterior collis generally bears a cusp 
on its summit. The anterior (M) area is much smaller than the 
posterior (N),with the exception of m3. An oblique ridge running 
upwards and outwards from the inner side of the base traverses the 
anterior surface diagonally, forming an oblique guard. This, however, 
is not so well developed, as in the JR. leptorhinus of Cuvier and 
Professor Owen, or in the bicorn African or Sumatran species. 
The median groove cuts the base in the true, never in the pre¬ 
molars ; of the 4 fangs the inner pair are connate, in the premolar 
series ungrooved on the inner side, in the true molars always grooved 
widely and deeply. 
Among the aberrant teeth one, m 2, is remarkable for having the 
entrance of the anterior valley completely blocked up to the summit 
of the crown, which is but little worn; one, m 1 , also possesses two 
cusps, the one below the other, at the entrance of the anterior valley, 
the whole crown being at the same time considerably incurved. A 
cingulum, or ‘ bourrelet,’ is present on the exterior of one last molar. 
1. Pm 2. Of Pm 2 I have not met with any example. It is 
however figured and described by Brandt.* It is characterized by its 
small size, and the stout ridge on its anterior aspect. 
2. Pm 3. The inner base of Pm 3 regularly rounded, is unmarked 
by a vertical furrow. The second costa (K 2) is higher, broader and 
more prominent than the anterior, from which it is divided by a 
deep groove. The median groove (I) does not traverse the base of the 
exterior surface. 
JMJeamrements . 
(l) (2) (3) (4) 
Maximum 1T6 . 15 . 1'5 . . . Wookey Hole. 
Average . 1*04 . 1*44 . 1*47 . 4 61 
Minimum IT . 1*38 . 1*38 . . • Wookey Hole. 
3. Pm 4. In the unworn or slightly worn crowns of Premolar 4,, 
the exterior bears 5 costae, the second higher than the first, from 
which it is divided by a deep groove, the third narrow, sharply de¬ 
fined, and higher than the second apically, gradually dying down 
* Vide 2911. Mus. Coll. Surg. f Op. cit. p. 303. 
2 n 2 
