20 
INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
mation of the bases of the two ‘ colles. 5 The ‘cingulum’ in R. deccanensis 
appears to exist as a more distinct ledge than in the Perim acerothere, and is 
not crenulated ; — the latter character, however, seems to be a variable one. The 
‘ crochet’ is strongly developed in the third premolar of the Deccan rhinoceros, 
and the buttress at the antero- external of both premolars and molars is very slight, 
in which respect this species differs from the Perim acerothere. In the dilapidated 
condition of the molars of the former, a close comparison would be difficult. 
The two species were, however, in all probability widely different in their anterior 
teeth; R. deccanensis had certainly no incisors in the lower, and probably 
none in the upper jaw; while A. perimense probably possessed these teeth in 
both jaws. 
Comparison with European aeerotlieria . — It will be unnecessary to institute 
a comparison between the upper molars of Acerotherium perimense and those of 
fossil European species of Rhinoceros , since the difference in the crania affords 
abundant ground of distinction ; the comparisons are, therefore, confined to the 
genus Acerotherium. The molars of A. incisioum / apart from their greatly inferior 
size, are distinguished by the ‘cingulum’ being much smaller, more closely applied 
to the tooth, never crenulated, or interrupted, and not forming a large and distinct 
tubercle at the entrance to the ‘ median valley.’ The premolars are also more equal 
in size than are those of the Perim species, and there are numerous minor differ- 
ences in the form of the teeth of the two species, which can be best understood 
by an inspection of the figures. The most important of these minor differences is 
the tendency to the formation of a third, or ‘ accessory fossete,’ in the worn pre- 
molars of A. incisivum, which is totally wanting in A. perimense. Of the upper 
teeth of A. goldfussi , the best figure available is that of a molar given by Kaup 2 
This tooth appears to have a less completely developed ‘ cingulum ’ than the teeth 
of A. perimense figured here, but agrees in this respect more nearly with this part of 
the teeth of the latter figured in plate VI., figure 5 of volume I. The small figures 
of upper molars of A. goldfussi given by Kaup 3 indicate no tubercle at the entrance 
of the ‘ median valley :’ and no cingulum in the last true molar. The upper molars 
of A. minutum 4 and A. eroizeti, 5 are sufficiently distinguished from those of the 
present species by their inferior size, as well as by their possessing no distinct 
£ cingulum ’ on their inner surface. The molars of A. eroizeti and A. lemanense 
are, according to M. Eilhol, 6 distinguished by the absence of the ‘ crochet.’ 
Dentition of American acerotheria. — Of the ten species of American rhino- 
ceroses provisionally referred to the genus Acerotherium noticed above, the upper 
true molars of A. crassum 7 have no distinct tubercle at the entrance to the 
‘median valley.’ In A. fossiger 8 there is no ‘cingulum’ to the true molars. 
1 Kaup. “ Oss. Foss. d. Mus. d. Darmstadt,” pi. xiv., fig. 5. 2 Loc. cit., pi. xii., fig. 12. 
3 “ Beit, zur naher Kennt. d. urwelt. Sauget.,” pt. I, pi. Jl. 4 “ Oss. Foss. d. mus d. Darmstadt." 
5 Filhol. op. cit. 6 Op cit. 7 “ Journ. Acad. Nat. Sci. Philad.,” 2nd ser., vol. vii., pi. xiii. fig. 8. 
8 “ Bui. U. S. Geol. Geog. Surv.,” vol. v., p. 237. 
