46 
INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
Theobald from the Siwaliks of the Punjab. The specimen figured is from the 
right side of the skull, and from its size is probably the last of 'the premolar series. 
With the exception of having been somewhat rolled on the outer surface, the speci- 
men is perfect, and has been but slightly abraded by use. Erom a comparison of the 
figure with the figures of the upper premolars of Acerotherium perimense and 
Rhinoceros sivalensis , this tooth would seem not to belong to either of those 
species, the premolar of the former being characterised by its large c cingulum,’ 
and that of the latter by the greater development of the anterior ‘ costa,’ and 
consequently greater flexure of the external surface. The last premolar of R. 
platyrhinus is distinguished by the presence of a distinct ‘ combing-plate.’ It 
seems, therefore, not improbable that the tooth before us may be the last upper 
premolar of R. palceindicus ; but as these teeth seem so liable to variation, it is not 
possible to be certain on this point. The tooth is characterised by the sub-equal 
size of the two ‘ colles by the presence of a small and slightly bifurcate c crochet ’; 
and by the absence of any distinct ‘ combing-plate ’: the external surface has two 
equal-sized ‘costae,’ which have been somewhat worn away by rolling. As regards 
form, the tooth appears to agree with the last upper premolar drawn in figure 1 of 
plate VI, but is of larger size, and must have belonged to an animal of the dimen- 
sions of Ealconer’s type specimens. If this tooth be a premolar of R. palceindicus , 
it is quite evident that the detached tooth figured by Ealconer as such, and already 
noticed, must be, as here considered, a true molar. 
Tipper milk-molars. — In figures 1, la, lb, 1 c of plate LXXIV of the “ Eauna 
Antiqua Sivalensis ” are given four views of a young skull of a Siwalik rhinoceros, 
referred by the authors of that work to R. palceindicus : the general form of the skull 
seems to indicate that such determination is probably correct. In the post-humous 
descriptions of the plates, the specimen is said to show the permanent dentition, and 
this determination was originally accepted in the first volume of this work, 1 but was 
subsequently shown to be erroneous, 2 and that the four teeth present in the skull are 
really milk-molars. In figure 3 of plate VII of this volume, a view of the inner 
aspect of these teeth is given, taken from a cast of the skull, the original being 
in the British Museum. It is on the authority of Ealconer’s reference of this 
skull to R. palceindicus that the milk-molars described above 3 are assigned to R . 
sivalensis, since they differ considerably from those in the skull under consideration. 
It will, perhaps, be simpler to show in what respect the latter differ from the milk- 
molars referred to R. sivalensis, than to describe them in detail. 
The two sets of teeth belong to the two opposite sides of the skull, and the set 
referred to R. palceindicus contains the first milk-molar, which is wanting in the 
set referred to R. sivalensis. The second milk-molar (mm. 2) in the former is dis- 
tinguished by having a very distinct median “ costa ” on the external surface, 
which does not occur in the corresponding tooth of R. sivalensis; the antero- 
external angle of the crown of the latter is more produced, and tends more towards 
1 Page 24. 3 Page 10. 3 PI. VI, fig. 2. 
