IIOLAE TEETH AND OTHER REMAINS OF MAMMALIA. 
23 
expected that further researches will bring to light more perfect specimens for future 
examination and description. The lower molars of this species are unknown, as we 
have none of these teeth from Burma in the Indian Museum. 
R-hinoceros planidens, n. Sp. nobis. Plate 4, figs. 7, 9. 
The two upper molars of this species (plate figs. 'I and 9) were collected 
by Mr. Theobald in the Siwaliks ; the specimen drawn in fig. 9 is from the 
left side; that in figure 7 is from the right side. Eig. 9 shows the median 
collis, and posterior and median valleys, with the adjoining half of the anterior 
collis; figure 7 comprises the whole of the internal half of the crown; the 
summit of the median collis is broken off ; unfortunately neither of the speci- 
mens show the dorsum. The teeth present a good many points of resemblance 
to the Burmese specimens, but also show other points of divergence, which, taken 
together with the wide distance between the localities from which they were 
obtained, fully justify specific distinction. 
The median valley is wide at the entrance, and, as in the Burmese and the other 
Siwalik species, becomes deeper as it passes outwards ; so that the worn-crown would 
present an isolated enamel pit. The crochet is blunt and simple, and does not extend 
more than half-way across the median valley. The antecrochet is much larger than 
in the Burmese species, bounded by a deep vertical groove at its internal border. 
The tubercle at the entrance to the median valley is much wider than in Rhino- 
ceros iravadicus, and its inner border is nearly on a line with the inner border of the 
tooth, instead of being considerably external to it ; the outer side of this tubercle 
descends suddenly to the bottom of the valley ; externally to the antecrochet the 
valley is continued as a mere line between the bases of the colles, which are conti- 
guous, the broad floor of the valley of the Burmese specimens being absent. This 
narrowness of the bottom of the valley is caused by the greater proportionate size 
of the median collis, the two colles being nearly equal in diameter ; the diameter of 
the base of the anterior collis is ‘9 inch, and that of the median collis ’8 inch. 
The anterior valley ( seen on the right side of fig. 7 ) forms in this species a 
distinct cavity, instead of a flat surface as in R. iravadicus ; the cavity is triangular 
and bounded by the continuation of the cingulum ; externally to this valley the 
enamel of the crown is sharply folded on itself, and is of the same thickness as on 
the inner side of the tooth. On looking at the corresponding part of the Burmese 
tooth (the centre of the left side of fig. 1, plate 2), the enamel is seen to have 
almost entirely disappeared at this point, and to have no trace of the fold. The 
folded portion of the enamel of the Siwalik specimen forms a thick isolated ledge on 
the side of the tooth, at a point where there is no appreciable coating of enamel at 
all in the Burmese specimen. 
The cingulum commences in the middle ofi the anterior surface of the tooth, 
and is continued as a distinct ledge round the whole of the anterior collis (right 
( 41 ) 
