138 



specialised 



UNGULATA 



ORDER VII 



superior cheek teeth with ectoloph and two oblique transverse ridges; 

 metaloph with crochet, ectoloph usually with crista. Superior 

 and inferior premolars generally molariform. Neck short. 

 Extremities robust. Manus with four or three digits, pes 

 tridactyl. 



All members of tins subfamily were included by 



Fig. 177. 



Aceratherium tetradactylum 

 Lartet. Upper Miocene, Saii- 

 san (Gers). Left fore -foot. 

 1/5. (After Blainville.) 



Fig. 178. 



Aceratherium incisivum Cuvier sp. Lower Pliocene, Eppelsheini. Slvull. 



1/7. (After Kaup.) 



Cuvier in the single genus Rhinoceros Linnaeus; now, however, they are 



separated into a number of genera. 

 ?'%v*H (^) t'rohyracodon Koch. Bones and dentition 



%"W imperfectly known. Middle Eocene ; Tran- 



sylvania. 



Fia. 179. 



Aceratherium sp. Miocene, 

 North America. Ilisht hind- 

 foot, i/s. (After Osborn.) 



Fm. ISO. 

 Aceratherium tridactylum Osborn. Oligocene (Upper 

 White River beds), Nebraska. Skull. 1/9- (After 

 Osborn.) 



3 14 3 

 {b) Trigonias Lucas. Dental formula : YTTiT' ^"^^ upper incisor 



and second lower incisor much larger than the others. Premolars much 



