80 
MOLAH TEETH AND OTHER REMAINS OE MAMMALIA. 
of that species he discovered, it cannot he said that it does not. Possibly, however, 
from its very aberrant form, it belongs to yet another nndescribed Siwalik species. 
The premolars of R. platyrhimis have each two costae on the dorsum. The ultimate 
premolar of B, palceindicus has a large median costa on the dorsum, but no 
combing-plates. In Ealconer’s figure of a premolar of this species there is no 
costa on the dorsum. 
The tooth figured in Plate 6, Eigure 9, was collected by Mr. Theobald in the 
Siwaliks ; it is probably either the milk molar or a premolar of the left maxilla of 
a species of BMnoceros. The crown is perfect with the exception of a few chips 
out of the enamel ; it is about a third worn down. 
The configuration of the crown surface presents some very remarkable pecu- 
liarities which I have not seen in any other specimens of BMnoceros molars. The 
crown surface is approximately square, with a slightly produced antero-external 
angle ; the external surface or dorsum is nearly plane, having only a very slight 
costa half-an-inch behind the anterior border. On the anterior surface {the left 
side of the figure) a slight cingulum occupies the internal half; between this and 
the external side of the anterior collis {left lower angle of the figure) there is a 
small oval anterior valley {the pit on the left side of the figure) placed more exter- 
nally than usual. The anterior and median colles are of nearly the same diameter : 
their internal walls are nearly vertical, with no trace of any cingulum on them. 
The anterior collis {left of figure) has a somewhat triangular cross-section. 
Instead of being connected by a column of dentine with the dentine of the outer 
wall of the tooth, the anterior collis forms a completely isolated pillar, there 
being a narrow pass on its outer side connecting the anterior and median valleys. 
This pass is so low that it would not be touched by wear until the crown became 
worn down to the level of the cingulum. I have seen no other specimen, either 
recent or fossil, in which the anterior collis is isolated in a similar manner. 
The entrance to the median valley {middle of lower border of figure) is by a 
narrow pass, slightly higher than the level of the cingulum, and without any 
tubercle at the entrance. Externally to the pass the descent into the valley is very 
abrupt and steep ; the extremity of the valley is nearly half-an-inch below the 
level of the pass. 
The median collis {right lower angle of figure) is united to the external 
dentine wall by a very narrow neck of dentine, running at first forwards and 
outwards, and then bent back on itself. On its anterior side this neck gives off 
a very small bifurcate crochet, projecting about half-way across the median valley. 
On its posterior side the dentine neck gives off another bluntly conical process, 
projecting into the posterior valley {the pit on the right side (f the figure) ; the 
narrowness of this dentine neck and the posterior process are quite unusual. 
In consequence of the narrowness of this neck, the posterior valley is of large 
diameter : its external wall is nearly vertical, and its anterior and posterior walls 
sloping : the pass into this valley is very sharp and abrupt. 
( 48 ) 
