18 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
In figure 4 of the same plate are drawn two upper milk-molars of a rhinoceros, 
which were also considered in the preface to belong to the same species as the 
true molars. It will be shown in the sequel that these teeth also may probably be 
referred to A. perimense, so that the name R. iravadicus must be withdrawn. As 
will be seen from an inspection of the figures, the upper molars of A. perimense 
from Burma are of considerably smaller size than those from the Punjab; and, 
as the same will subsequently be shown to be the case with the milk-molars, it may 
not be improbable that there existed a smaller Burmese race of the species. 
Last upper true molar. — Of the last upper true molar of Acerotherium peri- 
mense, a specimen from the right side is drawn in figure 5 of plate III. This 
specimen is one of an associated set of upper molars from Mr. Theobald’s Punjab 
collection. The anterior teeth are in general characters precisely similar to those 
already figured, and, therefore, need no further mention. The last true molar 
shows a large ‘cingulum’ surrounding the ‘anterior collis,’ the latter being of 
great size and thickness. A large tubercle, which may be considered as a detached 
portion of the e cingulum,’ obstructs the entrance to the ‘ median valley.’ The 
‘posterior collis’ is thin, and gives off a distinct ‘ crochet’ projecting into the 
‘ median valley.’ The antero-external angle is produced into a strong ‘ buttress.’ 
Dimensions of upper molar series . — Having now passed in review the whole 
of the upper series of molar teeth of this species, we may firstly give the dimen- 
sions of the figured specimens, and then proceed to institute comparisons between 
them and the molars of other species of the genus. The following table gives the 
dimensions of the five complete anterior teeth drawn in plate II, and of the two 
later teeth in figures 3 and 5 of plate III : — 
Length of first premolar 1'3 
Width of „ „ 1-15 
Length of 2nd „ . . . . 1’6 
Width of „ „ . ■ T9 
Length of 3rd „ 1’9 
Width of „ „ 2 8 
Length of 4th „ 2 2 
Width of „ „ 3-2 
Length of 1st true molar 3‘2 
Width of „ „ 3'2 
Length of 2nd „ ........... 3'35 
Width of „ „ 3-3 
Length of 3rd „ 3'2 
Width of „ „ 32 
General characters of upper molars. — The foregoing descriptions, with the 
accompanying plates, will have shown that the teeth of the upper molar series of 
Acerotherium perimense are formed on the general plan of those of the living 
Sumatran and Javan rhinoceroses (R. sumatrensis and R. javanicus ). 
They are characterised by a ‘buttress’ at the antero-external angle; by a more 
or less complete ‘ cingulum,’ which always forms a tubercle at the entrance to the 
1 median valley ’ ; by the presence of a ‘ crotchet,’ and by the normal absence of a 
