26 INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
inferior and external surfaces are rounded : tlie tooth is strongly curved upwards, 
and extends above the plane of the grinding surfaces of the molars. A slight frac- 
ture of the portion of the symphysis between the two large incisors shows that no 
small median incisors were present. The hone of the jaw itself is so decayed and 
mixed up with the closely adherent matrix that it is no easy matter to detect its 
true form. The ramus is very noticeable for its great vertical depth; and the 
symphysis seems to be much like that of the Javan rhinoceros, except that the 
enormous size of the incisives renders its borders more swollen and protuberant. 
Of the molar series, the three last premolars and the first true molars, as 
already stated, are shown in the portion of the right ramus (fig. 1) : the fragment 
of the associated left ramus, represented in figure 2 of the same plate, shows two 
teeth, which, from their condition of wear, seem to he, respectively, the first and 
second true molars. The teeth of the molar series resemble those of living species 
of rhinoceros, with the exception that at the base of their external surfaces they 
carry a narrow hut distinct ‘ cingulum,’ thereby showing, as is pointed out by M. 
Gaudry in the passage already cited, an affinity with older forms of the order, like 
P alceotherium. 
Comparisons and dimensions . — Of the three forms of lower jaws of rhinoceros 
exhibiting the symphysis, figured in the “ Eauna Antiqua Sivalensis,” the only 
one which agrees with the present specimen in the number of its anterior teeth is 
the one represented in figure 4 of plate LXXIV, which is there referred to R. 
palceindicus. A more perfect specimen of a similar lower jaw is represented in 
figure 3 of plate VI of this volume, and is inferred, like the first specimen, to belong 
rather to R. sivalensis. The much smaller size of these specimens, with the absence 
of a £ cingulum ’ on the molars, at once distinguishes them from the specimen before 
us. The dimensions of that specimen are as follows : — 
Depth of ramus at last premolar 4'5 
Length of symphysis 6’4 
Vertical diameter of incisor 1’8 
Transverse „ „ „ 2 - 4 
Length of remaining protruded portion of incisor 3'5 
„ of three premolars 5‘1 
„ of 1st true molar 2'65 
„ of 2nd „ 2'8 
Young jaw. — In figure 1 of plate III of this volume, there is represented an 
unworn tooth-germ of a rhinoceros in its alveolus. This specimen is contained in 
a fragment of the left ramus of a mandible from which the other teeth have dis- 
appeared. The figured tooth, of which the anterior crescent has been somewhat 
injured, from its large size not improbably belongs to the present species. It was 
obtained by Mr. Theobald from the Siwaliks of the Punjab, in company with 
numerous other remains of Acerotherium perimense. Behind the figured tooth there 
exists in the jaw the empty alveolus of a still larger tooth : from the small dimen- 
sions of the jaw, it is probable that the tooth remaining is the first true molar. Its 
