CRANIA OF RUMINANTS FROM THE INDIAN TERTIARIES. 79—166 
the three allied genera. In his Memoir on Bramatherium, Mr. Bettington considers 
the frontal horns of that genus, which arise from a common base, to he homologous 
with the -small and conical anterior horns of Sivatherium, wliich arise by a distinct 
base close above the orbits ; according to this view the posterior horns of both 
genera will also be homologous. The position of the common base of the horns of 
Hydaspitherium, which is placed high up on the frontals, and only a short dis- 
tance from the occipital crest, seems, however, clearly to show that these horns are 
homologous with the posterior horns of Sivatherium ; and I think no one will 
doubt but that they are also homologous with the anterior horns of Bramatherium, 
which latter will then also be homologous with the posterior horns of Sivatherium. 
According to this view, the small anterior horns of Sivatherium have no repre- 
sentative in the other genera ; and the posterior horns of Bramatherium are also 
unrepresented in the cranium of Sivatherium ; the base of the horns of Hydas- 
piotherium is so large that I think it quite probable that higher up it may have 
divided into two pairs of horns, which would then be homologous with the two 
pairs of horns of Bramatherium ; only in the one case the two pairs take origin 
from a common base, and in the other the anterior pair only take origin from 
a common base, wliile the posterior pair rise from distinct bases. The supraorbital 
horns of Camelopardalis giraffa are probably homologous with the posterior horns 
of Sivatherium, while the azygos mesial bony elevation on the frontals of the 
former genus is, although not a true horn, perhaps homologous with the anterior 
horns of Sivatherium ; the two pairs of horns of Tetraceros quadricornis are res- 
pectively homologous with those of Sivatherium ; Helladotherium has no horns. 
The accompanying diagram represents these relationships. 
Homology of horns of Sivatheridce and Camelopardalis. 
Turning now to the skull of Sivatherium, we find very considerable structural 
differences between it and the skull of the present genus ; the first striking difference 
is the absence of any anterior horns near the orbit in Hydaspithermm ; next we 
may notice there is only a very short and shallow contraction above the orbits 
in the cranium of Sivatherium, while above this contraction the skull expands 
