2 
INDIAN TERTIARY AND POST-TERTIARY VERTEBRATA. 
of molar teeth, under the names of R. iravadicus and R. planidens ; hut it will 
he shown in the course of this memoir that both these so-called species in reality 
belong to A. perimense : in the instance of R. planidens, this has already been 
demonstrated in the preface to the first volume. 
General characters of skulls of the four species. — In the preface to the first 
volume, it has already been shown what are the leading characters of the skulls and 
dentition of the three Siwalik species of the genus Rhinoceros' and also how these 
species differ from the living Asiatic forms of the genus, with which there has lately 
been an attempt to unite them : it will not be necessary, therefore, on this 
occasion to recapitulate the statements there made. In order, however, to show the 
general form of the skulls of all the Siwalik fossil species of the family, I have 
caused to be drawn on a small scale (plates IX and X) restored outlines of their 
skulls, taken either from original specimens in the Indian Museum, or from casts of 
those in the British Museum, or from those figured in the “ Eauna Antiqua Siva- 
lensis,” Eor the purpose of comparison with these fossil skulls, there are also 
given outlines of the skulls of the three best determined living species of Asiatic 
rhinoceroses. The living and fossil Asiatic rhinoceroses, of which the skulls are 
known, 1 2 3 may be divided for our present purpose into three groups, viz., hornless 
rhinoceroses, unicorn rhinoceroses, and bicorn rhinoceroses, the figured specimens 
of which will now shortly be noticed in the above order. 
Hornless rhinoceros {Acer other ium).— The only Siwalik species of hornless 
rhinoceros, referred here to the genus Acerotherium, is A. perimense , of which the 
restored skull is drawn in figure 1 of plate IX. The form of this skull distin- 
guishes it at once from the skulls of all the other Indian species of the family. The 
molars, as will be shown below, are of a simple type, approaching those of the 
Sumatran and Javan rhinoceroses, • 
Unicorn rhinoceroses. — Of the unicorn rhinoceroses, solely composing the genus 
Rhinoceros 3 as ‘restricted by many modern writers, there are four well-determined 
recent and fossil Asiatic species of which the skulls are known ; these are figured 
on plate X. Eig. 1 is R. indicus ; 2, R.javanicus ( sondaicus ) ; 3, R. palceindicus ; 
and 4, R. sivalensis. Apart from the differences in the general outline of the skull, 
R. indicus is distinguished from all by the complex pattern of its upper molars, 
which have a large ‘ combing-plate ’ and three ‘ fossettes ’ when worn. R. palce- 
indicus and R. sivalensis are distinguished readily by the form of their upper 
molars, as is noticed in the preceding volume and in the sequel. R. palceindicus 
differs equally in this respect from R. javanicus. R. sivalensis and R. javanicus 
1 This generic term is used in the original wide sense given it by Linne. The modem sub-divisions are frequently 
inapplicable in the case of fossils. 
2 The skull of B. deccanensis (Foote) is unknown ; judging, however, from the form of the lower jaw, it is proba- 
ble that this was a bicorn species. 
3 Apparently by an oversight, Professor Cope includes the bicorn B. platyrliinus in his list of the restricted 
genus Bhinoceros (“Bui. U. S. Geol. Geog. Surv.” Vol. V, p. 229). This may have originated from a statement by 
Professor Flower (P. Z. S., 1876, p. 457) that all the Siwalik species of Bhinoceros were unicorn. 
