163—22 INDIAN TERTIARY AND POST-TERTIARY YERTEBRATA. 
Hyopotamus giganteus. 
palseindicus. 
americanus. 
gresslyi. 
(?) vectianus. 
velaunus. 
bovinus (type ). 1 
Mandible. — The three fragmentary specimens of mandibles of hyopotamids from 
the Bhiigti hills, represented in plate XXV. of this memoir, have been already 
partially discussed under the head of Antliracotherium hyopotamoides ; the specimen 
represented in figure 1 being provisionally referred to that species, and that in figure 
3 being considered to possibly belong to the same. The specimen represented in 
figure 2, comprising the same portion as that represented in figure 1, but differing 
from it in form, is provisionally referred to the present species, and its distinction 
from the mandible assigned to Anthracotherium hyopotamoides will now be pointed 
out. 2 The specimen represented in figure 2 comprehends the hinder portion of the 
right ramus of the mandible, perfect for the length of the last true molar, but in 
front only showing the lower half of the ramus for a length of some three inches, 
and posteriorly the anterior part of the surface for the attachment of the masseter 
muscle. The specimen shows the half-worn last true molar, which is perfect, with 
the exception of a portion of the enamel of the third barrel. 
The tooth in this jaw cannot be distinguished by any satisfactory characters 
from that of the jaw represented in figure 1, but the differences in the jaws them- 
selves are considerable, and will now be pointed out. In figure 1 the whole jaw is 
deeper, the notch on the inferior border more distinctly marked, while the diminution 
in depth anteriorly, as far as can be judged from the portion remaining, is less rapid 
than in figure 2. Again, in figure 1 the prominence for muscular attachment on the 
anterior border of the masseteric fossa (seen in the middle of the curved line to the left 
of the figure) , is placed much nearer to the molar than in figure 1 (seen on the left side 
of the inferior border of the figurej. On the superior aspect the portion below the 
hinder part of the molar, on the outer side, forms a more distinctly separate surface 
in figure 1 than in figure 2 : while on the external surface, the specimen represented 
in figure 1 is much more curved than the other. Some of the above differences are 
indicated more clearly by the following table of measurements. 
J & Fig. 1. Fig. 2. 
Depth at second column of molar 3'22 3-05 
„ ,, first ,,,,,, . 2-9 
Interval between prominence on anterior border of masseteric fossa & molar 2-24 1 '7 
Greatest thickness 1’5 1-56 
Length of molar 2 ’08 
Width „ „ 1-2 1-19 
1 It may be mentioned that a species has been described under the name of Hyopotamus helveticus , Kiit, from the miocene of 
Switzerland, which is probably the same as one of the species given in the previous list. 
2 When these specimens were figured it was considered that they belonged to the same species : if the present view as 
to their distinctness had be,en then entertained, the specimen represented in figure 1 would have been viewed from the same 
aspect as that in figure 2. The reader who is desirous of verifying the differences pointed out here, can do so by comparing 
the casts of the specimens in the British Museum. 
