CRANIA OF RUMINANTS FROM THE INDIAN TERTIARIES. 39—126 
P. grunniens are given in Mr. Hodgson’s Memoir on the Mammals of Nepal a figure 
of the cranium of Bison urns is given in Owen’s “ British Fossil Mammals and 
Birds” (p. 491). 
From the table of frontal measurements given below, it will he seen that 
the diflerences between the two diameters of the forehead of this species and that of 
Poephagus grunniens are identical ; hut allowing for the smaller size of the present 
specimen, the breadth is stiU greater in proportion to the length than in the Yak. The 
orbits are rather more prominent than in the Yak ; the interval between the orbits 
and horn-cores are nearly the same in the two species ; and the form and direction 
of the horn-cores are also approximately similar in both species. The prominence of 
the orbits in the Siwalik cranium is like the orbits of Bison americanus. In a front 
view of our specimen, the summit of the occipital crest, as seen between the horn- 
cores, occupies only the middle two-thirds of the intercornual interval, as in the Yak, 
and does not occupy nearly the whole of this interval as in Bison prisons and B. 
americanus. The concave upper boundary of the intercornual ridge of our specimen 
differs from the straight boundary of the same in Bison americanus and Poephagus 
grunniens ; the supra-orbital foramina and sulci have the same form in all the 
species. The frontals of the Siwahk species are slightly concave, whereas in the 
others they are as slightly convex. The occipital crest of the Siwalik species does 
not extend quite so high up on the plane of the occiput as does that of the Yak, 
in which the crest forms a higher and narrower arch than in this species. 
Comparing the occiput of this species with that of the fossil Bison prisons of 
Europe, we find the occipital crest of the latter considerably wider and flatter at its 
summit, though situated at the same relative height on the occipital surface, and 
having the same relation to the temporal fossae ; in consequence of the greater width 
of the summit of this crest, the interval between the extremities of the temporal 
fossae is somewhat greater than in the Indian fossil species ; the shghtly concave in- 
tercornual line, and the great interval between the bases of the horn-cores, is a 
character common to the two species. In both, the occipital crest splits at the ex- 
tremity of the temporal fossa, so as to inclose the upper half of the fossa on both 
sides with a prominent ridge of bone. The occipital crest in both species is of great 
thickness, and is rounded off. 
I have retained the Siwalik species in the genus Bison, and not placed it in the 
genus Poephagus, chiefly because the distinction between the two genera or sub-genera 
is founded mainly on external characteristics, of slight classificatory value, and not 
on important cranial differences. We have, of course, no means of knowing the ex- 
ternal characters of the Indian fossil species, and I have therefore retained it in the 
original or type genus. On distributional grounds, it might perhaps he considered 
right to refer it to the sub -genus Poephagus if that genus is really sufficiently dis- 
tinguished from Bison ; the characters of the Siwalik cranium seem to be interme- 
diate between the true Bison and Poephagus. 
^ Jourual of the Asiatic Society of Bengal. Vol. X, P- 471. 
