SIWALIK AND NARBADA EQUIDiE. 
23—89 
molar seems always to be worn very unequally, being more abraded in front than 
behind in the latter the wear of this tooth is equable. In the former, again, the 
first milk-molar is of much smaller size than in the latter, and comparatively 
seldom persists. The larger form of E. sivalensis indicates an animal of, at least, 
fifteen ‘ hands ’ in height. 
In E. onager , of north-western India and Persia, the anterior c pillar ’ in all the 
molars is of large size, and is larger in the last premolar than in any of the true 
molars. The first milk-molar, if developed, seems to be always shed at a very 
early period. 
In Equus hemionus, or the kiang, of Tibet, the upper molars in the matter of 
form are extremely close to those of E. sivalensis , and it seems to me that it is 
doubtful whether we could distinguish the molar series of the two forms if both 
were found in the fossil state. The molars of the living species do not, however, 
ever attain to the dimensions of the larger individuals of the fossil species. In the 
kiang, moreover, the first milk-molar is alway very minute, and in all the skulls that 
have come under my observation is shed before any of the premolars appear. 
These, however, are but slight differences, and I cannot but think that there is a 
very intimate relationship between these two species, an inference which is support- 
ed by the characters of the crania of the two forms. 
Cranium.— The specimens of the cranium which can with certainty be referred 
to this species are two, viz., the one already referred to in the “ Eauna Antiqua 
Sivalensis,” and the one in the Indian Museum to which the molar dentition in 
figure 2 of plate XIV belongs. Both these specimens have lost their premaxillse. 
A third skull of a Siwalik horse, in the Indian Museum, exhibits these bones, but, 
as all the molar teeth, except the two last, are wanting, I am not quite sure of the 
species to which that specimen belongs, though from the form of the skull I am 
inclined to refer it to E. sivalensis. The premaxillse in that specimen are intermediate 
in length between those of the domestic horse and the kiang, but approach nearer 
to those of the latter, the interval separating the molar series from the incisors 
being very much less than in Equus caballus. 
A specimen of the extremity of the premaxillse of a Siwalik horse, of the 
species of which I am uncertain, in the Indian Museum 1 shows that the incisors 
are placed very obliquely. The specimen represented in figure 5 of plate LXXXII 
of the “ Eauna Antiqua Sivalensis ” exhibits the same character. This oblique 
position of the incisors is a character distinguishing EquUs caballus from E. 
onager and E. hemionus. Unfortunately I am unable to say whether any of these 
specimens of the premaxillse belong to E. sivalensis or to the next species. 
The cranium of E. sivalensis figured in the “ Eauna Antiqua Sivalensis ” is of 
great breadth across the orbits, a character which it possesses in common with the 
1 No. C. 186. This specimen is described by Falconer on page 187 of vol. I of the “ Palaeontological Memoirs,” 
No. 805, as the mandible 
