SIWALIK RHINOCEROTnm 
37 
Sivalensis” have figured # three distinct forms of the symphysis of the mandible of 
Siwalik rhinoceroses, which they have respectively referred to the three species 
named by them from the sub-Himalaya. In the first volume of 1 his work I accepted 
these determinations, though a proviso was added in the preface that I was unaware 
on what grounds they rested. A subsequent reconsideration of the questipn has 
now convinced me that these determinations, in support of which there is no 
available evidence, are probably incorrect, and I shall accordingly proceed to show 
on what grounds they may be objected to. Before going further, however, it 
may he premised that from the remarkable similarity in the form of the lower 
molars of all species of rhinoceroses, it is a matter of extreme difficulty to speci- 
fically distinguish fragmentary fossil jaws not showing the symphysis, and accord- 
ingly only such specimens as exhibit this portion will he entirely relied upon for 
specific distinction. It appears indeed, to me, to he very problematical whether 
it would he possible to distinguish the lower molars of the living species, if re- 
moved from the characteristic parts of the mandible. 
Of the specimens figured by Bale oner and Cautley, the first is a jaw with the 
symphysis (pi. LXXIY, fig. 6), which seems to have carried no incisors, and in 
which the molar series extended far over the symphysis. 1 This specimen has been 
referred to R. sivalensis, and seems to he most nearly related to the mandibles of 
the pleistocene European and the living African rhinoceroses. The second form 
(pi. LXXIY, fig. 4) shows merely the symphysis, which carries a large pair of 
outer incisors, and apparently no median pair ; the central part of this symphysis 
forms a uniform channel, sloping regularly from before backwards as in the Javan 
rhinoceros. This specimen has been referred to R. palceindicus. The third form is 
exemplified by two specimens, one of which (pi. LXXII, fig. 4) exhibits only the 
symphysis, while the other (pi. LXXY, fig. 10) shows the rami as well. In this 
form the symphysis carries a pair of large outer incisors, and another pair of very 
small inner ones ; the central portion of this symphysis forms a channel which is 
convex in the middle of its course, as in R. indicus. This form has been referred 
to R. platyrhinus. 
In the Indian Museum the only specimens (exclusive of the mandible of Acero- 
therium perimense) of the symphysis of the mandible of Siwalik rhinoceroses are 
two ; one of these is merely a symphysis, and agrees with the form referred by 
Ealconer and Cautley to R. platyrhinus ; this specimen was obtained from the eastern 
Siwaliks in the neighbourhood of the river Jamna. The second specimen (pi. YI, 
fig. 3) agrees with the form referred by Ealconer and Cautley to R. palceindicus, and 
was obtained by Mr. Theobald from the Siwaliks of the western Punjab. 
With regard to the case of R. sivalensis, we have already shown that this is a 
unicorn species, showing great affinities in the form of its molars to the livin g 
R. javanicus. This being so, it is in the highest degree improbable that it was fur- 
1 From the description of this specimen in the index to the plates, the symphysis appears to be imperfect, and 
may have been produced into a spatulate form. 
K 
