148 



UNGULATA 



ORDER VII 



surrounded by a basal cingulum ; the cusps either isolated or only in- 

 distinctly united by a ridge. Premolars trigonodont. Last inferior molar 

 with single cusped talonid. Lower Eocene ; England. H. leporinum and 

 cunicuhis Owen. 



Propacliynolophus Dep6ret. Cheek teeth less bunodont than in Hyraco- 

 theriimi, with distinct ridges. P. maldani and gaudryi Lemoine. Lower 

 Eocene ; Rheims and Erquellines. 



Eohippus Marsh {Protoroliippus Wortman ; Hyracotherium Cope) (Figs. 

 194-196). M distinctly lophodont. Upper P simpler than M. Upper 





Pig. 194. 



Eohippus I'enticolus Cope sp. 

 Lower Eocene (Wasatch beds), 

 Wyoming, A, Left fore foot. B, 

 Left hind foot, i/s- (After Cope.) 



Fig. 195. 



Eohippus tapirinus Cope. Lower Eocene (Wasatch beds), Wyoming 

 A, Upper and B, lower cheek teeth, '/i- (After Wortman.) 



^, ^, A /^j A /?' 



Fig. 196. 



Eohippus cristonensis Cope. Lower Eocene (Wasatch beds), Wyoming 

 Left lower dentition, i/i. (After Cope.) 



molars with subcrescentic external cusps ; mesostyle absent and hypostyle 

 weak. Scapula with well -developed coracoid process. Eadius and ulna 

 distinct. Fifth metacarpal shorter than the second. Femur with broad 

 third trochanter. Lower Eocene (Wasatch beds) ; E. cristonensis, tapirinus, 

 index Cope, E. validus Marsh ; Wind River beds, E. craspedotus, venticolus Cope. 



Orohippus Marsh (Orotherium, Helotherium Cope) very similar to 

 Pachynolophus. P^ fully, P'^-^ partly molariform. Superior molars with hypo- 

 style. Manus tetradactyl. Middle Eocene ; Bridger beds, 0. pumilus Marsh, 

 0. osbornianus Cope. 



Pachynolophus Pomel. Superior molars with two pyramidal external 

 cusps joined to a moderately arched ectoloph, with a vertical weak mesostyle 

 and parastyle ; the two internal cusps conical and subequal. Fourth 

 premolar somewhat lower crowned than first molar, but otherwise similar to 

 it; hypocone distinctly developed. Inferior molars composed of two sharply 



