136 



UNGULATA 



ORDER VII 



Hymchyus Leidy {Colonoceras Marsh) (Fig. 173). Premolars less complex 

 than the molars, the upper ones trigonodont. Molars short-crowned. Manus 

 tetradactyl, pes tridactyl. Middle Eocene ; Bridger beds, Wyoming. 



^ y 



Fig. ]73. 



Hyraehyus eximius Leidy. Middle Eocene (Bridger beds), Wyoming. A, Last upper premolar and first 

 molar, '/i. B, Last lower molar, i/j. C, Riglit fore-foot. D, Right hind-foot. i/g. (After Cope.) 



p.' p^ fif p' rrV m^ m^ r 



Fio. 174. 



Hyracodon nehrascetisis Leidy. Oligocene (Wliite River beds), Nebraslca. J, L'pper cheek teeth from below. 



B, Lower jaw from outer side. i/o. 



Triplopus Cope. Molars with higher crowns. Manus tridactyl. Upper 

 Eocene ; Wyoming. 



Hyracodon Leidy (Figs. 174, 175). Teeth high-crowned. Three posterior 



