1869.] MR. G. BUSK ON FOSSIL REMAINS FROM BORNEO. 413 
nary fossil or extinct forms, all except R. etruscus. All the other 
characters, moreover, would equally exclude these species ; I shall, 
therefore, at present advert only to the latter three above named. 
Fig. 4. 
Crown surface. 
1. If we regard the entire dentition of Rhinoceros sondaicus*, it 
is of course at once distinguished from R. sumatranus by the size of 
the outer incisor, and by the conformation in many respects of nearly 
all the teeth, and especially of the premolars; but as we are now 
concerned only with the second upper molar, I will limit what I have 
to say to that tooth alone. 
As regards the dorsum (fig. 5, p. 414), the resemblance between 
this surface in R. sondaicus and in the Sarawak tooth is obvious at 
first sight ; the only difference, so far as 1 can perceive, is in the cir- 
cumstance that the anterior costa (ac) is not prolonged quite to the 
base of the crown ; but this, I think, may be explained by the imma- 
ture condition of the Sarawak specimens. But by this surface alone 
it would not be easy, I conceive, or even possible, in some cases, to 
distinguish between R. sondaicus and R. sumatranus, as shown in 
figure 6 (p. 414), which represents the dorsal surface of the same 
tooth in R. swmatranus. The chief points upon which I should 
rely, as showing the identity of the Sarawak teeth with those of R. 
sondaicus, are :—1, the wide angle at which the crochet (c) is given 
off (fig. 7, p. 415); 2, the emargination and absence of a denticle 
on the posterior vallum; 3, the comparatively greater transverse as 
compared with the longitudinal diameter of the crown,—since in R. 
sumatranus. the crochet springs at a right angle or even less from the 
hinder column (fig. 8, p. 415), and the posterior vallum, which has 
a more or less crenate edge, presents a very distinct and constant 
* Under this name I include R. nasalis, R. stenorhynchus, and R. floweri of 
Dr. Gray, not because I would venture at present to decide as to the true rela- 
tions of these forms to each other, but because the dental characters at any rate, 
so far as I can perceive, afford no sufficient distinctions between them ; and one 
thing appears abundantly clear, that, as contrasted with other well-marked spe- 
cies, they all constitute a group apart which I should myself regard as specific. 
