123—36 CRANIA OF RUMINANTS FROM THE INDIAN TERTIARIES. 
On referring to the table of the frontal measurements of the skulls of the 
Indian Oxen, given below, it will he seen that the transverse diameter of the 
forehead of this specimen exceeds the antero-posterior diameter by three and a 
half inches — a proportion which makes the supra-nasal portion of the cranium 
considerably shorter than the nasal and infra-nasal portions, and gives to the upper 
part of the skull a great preponderance in wddth over the lower part. 
The horn-cores are widely separated at them bases, and are placed on a ridge 
which is considerably below the highest point of the cranium ; the superior border 
of this intercornual ridge is concave ; when seen from in front, the summit of the 
superior curved line or crest of the occiput projects above and between the bases 
of the horn-cores, whereas in a similar view of the crania of the genera Bos, Bihos, 
and Bubalus, no portion of the occiput will he seen. The whole of the above characters 
show that the cranium belongs to the genus Bison. 
The horn-cores are compressed antero-posteriorly ; their anterior surface is flat 
from above downwards and concave from within outwards ; their posterior surface is 
convex in both directions ; each horn-core is marked by a longitudinal groove along 
the superior border ; a similar groove is found in the horn-core of Bison {PoepJia- 
gus) grunniens into which is fitted a projecting ridge on the inner surface of the 
horn ; this ridge and groove arrangement doubtless affords additional strength to 
the union of the horn with the horn-core, and renders the former less liable to he 
knocked off by any sudden blow. The direction of the fragment of horn-core 
which remains attached to the skull is at first upwards, backwards, and outwards, 
gradually curving until its direction becomes upwards, forwards, and outwards ; the 
whole direction of the horn-cores was probably very similar to that of the horn-cores 
of the living Yak, though in the fossil species the inchnation forwards was probably 
somewhat less ; the horn-cores diminish gradually and regularly in diameter ; their 
anterior surface is concave, and their posterior surface convex. 
The frontals are somewhat crushed on the left side of the cranium ; they are 
slightly hollowed between the upper angles of the bases of the horn-cores, and 
below the intercornual ridge become still more hollowed out ; this frontal hollow 
is somewhat in the form of the letter H, having one transverse portion and two 
lateral vertical portions as seen in the figure ; the median portion of the lower half of 
the frontals immediately above the apex of the nasals, is prominent and swelling ; 
a ridge, concave on its outer side, descends from the outer angle of the base of the 
horn-core to the superior border of the orbit. The supra-orhital foramina are 
widely separated and are situated on the narrowest line of the frontals ; they 
pierce the bone at right angles to its surface ; the sulci are entirely below the 
foramina, and are nearly vertical and of considerable depth and width as far down 
as the superior border of the orbit ; below tliis point they become much shallower 
and converge. Between the orbit and the base of the horn-core, the cranium 
})ecomes considerably narrower from side to side, and the orbit and the base of the 
horn-core are separated only by a short interval. The orbit is salient, of small size. 
