396 



PALAEONTOLOGY. 



beds, glacial clay, and drift. The discovery of the carcase of 

 the tichorrine rhinoceros in frozen soil, recorded by Pallas in 

 his " Voyages dans l'Asie Septentrionale," * shewed the same 

 adaptation of this, at present tropical, form of quadruped to a 

 cold climate, by a twofold covering of wool and hair, as was 

 subsequently demonstrated to be the case with the mam- 

 moth. Both the above-named fossil rhinoceroses were two- 

 horned ; but they were preceded, in the pliocene and miocene 

 periods, by a species devoid of horns, yet a rhinoceros in all 

 other essentials {Acerotherium, Kaup). 



The modifications which the upper molars of the rhinoceros 



present as compared 

 , with those of its 



antetype, the Palseo- 

 therium, will be 

 readily understood 

 by comparing fig. 

 127 with fig. 148, 

 and are as follows : 

 — The concavities 

 {ff) on the outer 

 side of the crown, in 

 fig. 127, are almost 

 levelled, and from 

 one of them a slight 

 convexity projects, 

 in some species of 

 Ehinoceros, giving a 

 gently undulated 

 surface on that side 

 of the tooth. The valley (e) is more expanded at its termina- 

 tion (i), in the Ehinoceros ; and, in some species, it bifurcates 

 and deepens, so that one branch may form an insulated circle 



* 4to, 1793, pp. 130-132. 



Fig. 148. 

 Upper molar, Rhinoceros. 



Nat. 



