1902.] Mattheiv, The Skull of Hypisodus. 3^3 



Family HYPERTRAGULID^ Cope, 

 (leptomerycid^ Scott.) 



Leptomeryx Lcidy. 



Dentition, \\ C-yi- Pf Mf. Lower canine incisiform, first premolar 

 small, caniniform, with a long diastema in front of it and a somewhat 

 shorter one behind. Upper canine small or absent. Second, third, 

 and fourth premolars in series with molars, p* with two crescents, p*"* 

 with anterior, posterior, and internal accessory cusps. Mesostyle 

 prominent on upper molars. Second, third, and fourth lower pre- 

 molars in series with molars, trenchant, with anterior basal cusp, 

 basin heel, and accessory ridges from the protoconid. Last molar 

 with heel composed of a large posteroexternal crescent and a small 

 anterointernal flattened cusp (as in Palceomeryx) . 



Skull of moderate length, muzzle slender, elongated, orbits not very 

 prominent. Prelachrymal vacuity diamond-shaped, situated rather 

 above than in front of the 

 lachrymal. Bullae small, not 

 filled with cancellous tissue. 



Ulna and radius separate; 

 tibia and fibula separate; navi- 

 cular and cuboid united. Man- 

 US of four usable digits, the 

 lateral pair smaller, no cannon- 

 bone. Pes with cannon-bone 

 and no lateral digits (? the p^g^ Dentition oi Leptomeryx. 



small proximal splints of me- 

 tatarsals II and V fused to the cannon-bone). Hoofs small, pointed. 



1. L. evansi Leidy. White River (Oreodon Beds). S. Dak. 



Leidy, Ext. Mam. Dak. and Neb., p. 165, pi. xiv, figs. 1-8. — Scott, 



Jour. Morph., V, Dec. 1S91. Scott, Trans. Wagn. Inst. Sci., 

 1899. 15. 



2. L. mammifer Cope. White River (? Titanotherium 

 Beds), Swift Current Creek, Canada. 



Cope, Rep. Geol. and Nat. Hist. Surv. Canada, I, 1885 (1886), 84c. 



One and a half times the linear dimensions of L. evansi. 

 Prof. Cope distinguished it by the presence of a separate 

 cusp between the entoconid and the heel of ni3; this appears, 

 however, to be only the anterointernal cusp common to all 

 species of Leptomeryx. 



