264 BuUeti7i American Museum of Natural History. [Vol. XIII, 



2. Pleistocene and Recent Stages. 



An adaptive parallel to these types is presented in the Middle 

 and Upper Pleistocene species : R. antiquitatis resembles R. sifnus 

 (and less closely R. tieumayri) with broadly truncate nasals, 

 slender zygoma, and hypsodont, small, very narrow molar teeth ; 

 while R. hemitoechus^ resembles R. pachygnathus and R. bicornis^ 

 with brachyodont molar teeth. In both R. hemitachus and R. 

 bicornis the nasals are somewhat narrower and the upper lips 

 more prehensile and pointed. These large Pleistocene animals 

 (which co-existed for a while) thus differed in details of dentition 

 in adaptation to local differences of feeding ranges and habits, but 

 resembled each other in (i) extreme dolichocephaly, (2) back- 

 ward inclination of the occiput, (3) powerful nasal septum, (4) 

 horns on extremities of nasals. 



The existing African species, R. simus and R. bicornis, like R. 

 sumatrensis, in the Ceratorhine series, are, however, both less 

 specialized than the Pleistocene types. 



Subfamily RHINOCEROTIN^. PHYLUM VI. 



Brachycephalic or intermediate betzveen extreme dolichocephalic and brachyce- 

 phalic types ; occiput inclined forwards. Single horns upon mid-nasals ; nasals 

 pointed and generally stnooth at the extremities, Megalodine, large upper and 

 lower cutting teeth. 



No representatives of this phylum have been found in Europe. 

 In Asia, however, the Pliocene Siwaliks yield species which are 

 probably ancestral to the typical Rhinoceros unicortiis of India. 

 Lydekker ('81, PI. X) shows that R. palceitidicus leads into the 

 hypsodont or grass-eating R. unicortiis type, while R. sivalensis 

 leads into the brachyodont or shrub-eating R. sondaicus type. All 

 these four species exhibit a skull with forwardly inclined occiput, 

 concave and hornless in the frontal region, nasals with a large 

 horn in the middle portion which does not extend to the smooth 

 and pointed extremities ; well developed cutting teeth. 



The origin and relationships of this phylum are unknown ; it 

 will be noted that it is exclusively south Asiatic in distribution 

 and this (Oriental Region) may ultimately prove to be its home 

 and exclusive centre of adaptive radiation. 



' See Geol. Mag. (2), Vol. I, PI. XV, as figured by Davis. 



