14 
INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
American acerotheria. — In the foregoing list of the species of the genus 
Acerotherium (with which is combined the genus Aphelops of Professor Cope) 
there are enumerated ten American species of rhinoceros provisionally referred to 
that genus, namely, A. crassum, A. fossiger, A. jemezanus, A. malacorliinus, 
A. megalodus, A. meridianum, A. mite, A. occidentale, A. pacificum and A. 
truquianum } But few of these American species of acerotheria appear to he 
represented by complete crania, and any comparison between them and the Indian 
representative of the genus must consequently he deferred till the upper molars of 
the latter have been described. 
Upper molar dentition. — The fine specimen of the left upper maxilla of a 
rhinoceros, of which the dentition is represented in plate II, was obtained by 
Mr. Theobald in the Siwaliks of the Punjab, and is the specimen already alluded to. 
As noticed above, the molar teeth in this jaw correspond exactly with those of the 
skull just described; but being less worn, and in a better state of preservation, have 
been selected for figuring. The specimen exhibits the four teeth of the premolar 
series, in the last of which the outer wall has been somewhat damaged ; and the 
first, and a considerable portion of the second, true molar. In advance of the first 
tooth of the molar series, the section of the jaw exhibits the root of an incisor tooth. 
The second, third, and fourth teeth (counting from the left) are seen to belong to 
the premolar, and not to the milk-molar series, from the fact of the fourth tooth 
being less worn than the fifth,: — the first true molar. 
1st premolar. — The first tooth is of an irregularly triangular shape, and of 
relatively large size ; its crown is considerably more worn down than that of the 
succeeding tooth, and the whole tooth is more elevated above its alveolus than any 
of the others. It is, therefore, not improbable that this tooth in reality is the first 
of the milk-molar series, which has never been replaced by a premolar ; it is, how- 
ever, more convenient to refer to it as the first premolar. 2 
2nd premolar. — The second premolar has an approximately square-shaped 
crown : the £ anterior collis ’ is smaller than the posterior, and there is no distinct 
‘ crochet ’ in the e median valley.’ A very well-marked sinuous and crenulated 
e cingulum ’ surrounds the greater part of three sides of the crown : this ‘ cingulum ’ 
on the inner side rises high above the entrance to the * median valley.’ The c dorsum,’ 
or external surface of the crown, is nearly flat, hut presents a slight tendency to 
be thrown into vertical folds at its antero-external angle. This tooth corresponds 
almost exactly to the left upper premolar figured in the “ Eauna Antiqua Siva- 
lensis” 3 under the name of Rhinoceros {Acerotherium) perimense, and, as already 
1 In his last paper on the extinct rhinocerotidse of America ( loc . cit.,) Professor Cope omits some of the above 
mentioned species ; it is, however, not stated on what grounds these omissions are made, and they are accordingly all 
mentioned in this work. As well-established species like It. deccanensis and A. perimense are likewise omitted from 
the same list, it may he that the other omissions are due to want of care, though this seems strange, seeing that several 
of them were named by the author of the paper in question. 
2 For the homology and replacement of this tooth, see the above-quoted paper by the author in the “ Journal of the 
Asiatic Society of Bengal,” Vol. XLIX, pt. II, p. 135. 
3 PI. LXXV, fig. 15 (numbered 14 in description of plate). 
