SIWALIK EHIN OCEEOTIDiE. 
15 
mentioned, it is on this identification that the specific determination of the cranium 
and other teeth of this species depends. The tooth figured by Falconer is cfrawn of 
half the natural size, and is slightly smaller than our specimen. The former further 
differs from the latter, in that the ‘ cingulum ’ is not distinctly crenulated, and that 
on the inner side it bends outwards into the entrance of the c median valley,’ in 
place of passing straight across it. These, .however, are trifling differences, and a 
specimen of the corresponding tooth figured hy myself in the preceding volume of 
this series 1 is intermediate in these respects between the other two homologous 
teeth, the ‘ cingulum ’ being partly crenulated, and extending a short distance into 
the ‘ median valley.’ In the figure in the previous volume last referred to, two 
molars are drawn, and these were originally considered to be respectively the last 
premolar and the first true molar, in place of the second and third premolars. The 
grounds of this determination were, firstly , that the serial position of Falconer’s 
figured premolar was unknown ; and, secondly , that of my own two figured specimens, 
the smaller, or anterior tooth, as is stated on page 51 (33) of the first volume, is 
less worn than the larger and succeeding tooth (right side of figure). In normal 
cases this would indicate that the smaller tooth was the last premolar, and the 
larger the first true molar, and accordingly the teeth were so reckoned. The 
present complete specimen of the dentition has, however, shown that this determina- 
tion was erroneous, and that consequently the degree of relative wear of the two 
teeth figured in the first volume must be due to some abnormality in the time of 
their appearance above the gum. The teeth figured in the first volume being 
reckoned, respectively, as the last premolar and the first true molar, it was on that 
supposition totally impossible that the true molars referred in that volume to 
R. planidens could belong to Aeerotherium perimense, and they were accordingly 
assigned to a new species. 
Another incomplete specimen of a second upper premolar, which has been 
referred to Aeerotherium perimense , is drawn in figure 6 of plate VI of volume I. 
This tooth was originally described as belonging to an unknown species of Rhinoceros, 
and was obtained from the lower Manchhar rocks of Sind. It stiows a wavy but 
uncrenulated cingulum passing entirely across the entrance to the ‘median valley,’ 
as in the specimen figured in this volume. It, however, presents a distinct ‘ crochet,’ 
which is Wanting in the other figured specimens, though there seems, judging from 
other teeth, to be some range of variability in this respect. The determination of 
this tooth is, therefore, still open to a certain degree of doubt. The first of the two 
upper molars of a fossil rhinoceros from Burma figured by Mr. Clift, 2 and already 
referred to, corresponds in general form with the second upper premolar of A. peri- 
mense, and is consequently referred to that species ; 3 the second tooth in Mr. Clift's 
figure will consequently be the third upper premolar. In the second premolar, as 
far as can be inferred from the figure, the ‘ cingulum’ is less developed in both teeth 
1 PL VI. fig; 5. 2 “ Trans. Geol. Soc.,” 2nd Ser., vol. II., pi. XL., fig. 1. 
3 This determination was first made in the first volume of this series (p. 52), but the serial position of the two teeth 
was incorrectly determined. 
