91—4 CRANIA OR RUMINANTS RROM THE INDIAN TERTIARIES. 
The second fossil Indian species of the genus, Buhalus platyceros, is from the 
Siwaliks, and differs in the form of its cranium from that of any living species of 
the genus ; this difference mainly consists in the long upward prolongation of the 
frontals between the bases of the horn-cores and in the want of the high and 
vertical occiput ; by these peculiarities it shows an affinity to the Antelopes which 
Professor Rutimeyer regards as the progenitors of the true Oxen. 
Among the fossils from the mammaliferous beds of the Irawadi River now 
contained in the Collection of the Indian Museum, there are several fragments of 
cylindrical horn-cores of small size, together with a single upper molar tooth ; these 
specimens evidently belonged to a species of Bovoid Ruminant ; but they are of 
course too fragmentary, even for generic distinction ; it wRl be. interesting if more 
complete remains should hereafter be discovered to determine whether or no the 
fossil ox of the Irawadi beds was at all related to Bibos banting now inhabiting 
the same regions. 
The crania of nearly all the species of fossil Indian cattle show certain modi- 
fications of form which render them more or less aberrant from the living types of 
their respective genera, making it a matter of considerable doubt in some cases 
whether to refer them to the existing genera or to make new genera or sub-genera 
for their reception. When possible, I have generally placed the fossil species under 
the recent genus, if there were several important characters common to the living 
and fossil types ; not unfrequently, however, the fossil species will not bear a rigid 
interpretation of all the characters of the genus under wliich it has been placed ; 
this will be found to be the case with Bos namadicus. Bos acutifrons, and Bubalus 
platyceros. A difficulty of this kind must always be expected to arise when we 
have to deal with a large series of recent and fossil forms, and is one which tends 
to do away with some of the sub-genera of modern Zoologists which are only 
founded on minute and unimportant points of detail. 
The Siwalik being one of the largest fossil Bovine fauna hitherto described, it 
would not be unreasonable to suppose that it would be also the most rich in the 
number of genera ; this we find in fact to be the case ; the three chief groups of 
living oxen, viz., Bos, Bison, and Bubalus, being each represented by one or more 
species, and there are, besides, several extinct genera or sub-genera unknown in 
other deposits. In no region of the world at the present time are the three above- 
mentioned genera found living together, though there is the nearest approach to it 
in modern India, where Bibos (representing Bos) and Bubalus are found in the 
plains, and Bison represented by Boepliagus in the Himalayas, the latter separated, 
however, completely from the genera of the plains. 
The crania of the fossil Indian oxen tend to do away with the distinctions 
which separate the genus Bibos from Bos ; the three genera. Bos, Bison, and 
Bubalus, are found to have possessed their most important craniological distinctions 
in Siwalik times, and to have preserved them with some slight modifications up to 
the present day. This is quite in accordance with the discoveries of Palaeontologists 
