SIWALIK RHIXOGEROTIDiE. 
3 
seem to be, on. the whole, the most nearly allied, since their teeth are constructed on 
the same general plan ; there is, however, considerable difference in the form of the 
skulls of the two species. 
Bicorn rhinoceroses. — Of the bicorn rhinoceroses, there are figured the skulls 
of two species 1 on plate IX, viz., B. platyrliinus, fig. 2 ; and R. sumatrensis , fig. 3. 
The former has molars of the complex type of R. indicus ; and the latter of the 
simpler type of R. sivalensis and R. javanicus. The latter belongs to the sub-genus 
Ceratcrhinus, and the former possibly to a modification of Atelodus. 
Value of teeth as indicating affinity. — From the above remarks, it will be seen 
that in species having the same number of horns, and closely allied in other respects, 2 
there may be very great differences in the form of the upper molars ; and it, there- 
fore, seems that the structure of these teeth cannot be considered of much value 
in the determination of the affinities of fossil species. 
Number of species of Rhinoceros and Acerotherium . — In order to avoid the 
necessity of quoting species of Rhinoceros and Acerotherium by more than one 
name, owing to the great amount of synonymy that prevails in these genera, the fol- 
lowing lists of species with the synonyms has been compiled. The names therein 
used as the names of the species will be employed in this volume, irrespective of 
the question whether they all are selected according to strict priority. Doubtful 
or insufficiently-determined species have prefixed to them a note of interrogation. 
The memoirs of Messrs. Brandt, Cope, Dawkins, Falconer, Flower, and Peters have 
been chiefly consulted in the compilation of this list. 
Genus I : ACEROTHERIUM, Kaup, 
(Including Aphelops, Cope.) 
1. Acerotherium crassum (Lefdy. sp.). Miocene (?) ; X. America. 
Aphelops (?) crassus, Cope. 
Rhinoceros crassus, Leidy. 
2. Acerotheeium croizeti (Pomel). Miocene; Europe. 
3. Acerotherium eossiger (Cope, sp.). Up. miocene; X.' America. 
Aphelops fossip er, Cope. 
4. Acerotherium goldfussi (Kaup). Mid. miocene; Europe. 
Rhinoceros bracliypus , Lart. ( teste Kaup). 
„ goldfussi, Kaup. 
5. Acerotherium lemanense (Pomel. sp.). Low. miocene; Europe. 
Acerotherium lemanense, Dawkins. 
Rhinoceros lemanensis, Filhol. 
1 There is no specimen of the skull of R. lasiotis (Scl.) available, if indeed this species be distinct from R. suma- 
trensis. 
* See Flower, P. Z. S., 1876, p. 443, et seq. 
