F. B. Loomis — Hyopsodidce. v 421 



Hyopsodus poioellianus Cope.* 

 This, the largest species of the Hyopsodidos, occurs but 

 infrequently, being known by parts of the lower jaw only. 

 The teeth are low and wide with stout, low cusps and no cingu- 

 lum. The metaconid is simple and widely 

 separated from the protoconid. The hypo- 

 conulid is small, even on the last molar. 

 The protolophid is low and the metalophid 

 lacking. On the last molar the entoconid „ „ 



• i -, n Fig. 4. Hyopsodus 



region is occupied by two small cusps. powellianus. xf. 



The three lower molars measure to- 

 gether 18 mm . In the Amherst collection the species occurs but 

 twice, both specimens coming from the basal beds of the 

 Wasatch of the Gray Bull River, Wyoming. 



Hyopsodus laticuneus Cope.f 

 A single specimen represents this species, on which the 

 genus Diacoclexis also hangs. The specimen included both 

 upper and lower teeth, but Matthew has removed the lower 

 premolars and assigned them to Eohippus index, leaving the 

 upper molars which are characteristic of the genus Hyopsodus, 

 and a last lower molar which is distinguished by low broad 

 crown with obtuse cusps, lack of an external cingulnm and the 

 entoconid region occupied by two small cusps, and lastly by 

 the metaconid being bifid. This last character alone distin- 

 guishes the species from H. powelliamis to which it is equal 

 in size. The. specimen came from the Wasatch in the neigh- 

 borhood of Gray Bull River. 



In the Wind River horizon, four species are known, three 

 of which are here described for the first time. This horizon 

 is marked by a slight advance in the development of the genus. 

 The hypoconulid is stronger, especially on the last molar, and 

 in the entoconid region there is only a single strong cusp, the 

 entoconid. The metalophid is universally present. 



In the locality found by the Amherst party the specimens 

 of Hyopsodus formed fully a third of the collection. 



Hyopsodus wortmani Osborn.J 



The type specimen (including an upper and a lower jaw) 

 was first figured by Cope among H. vicarius specimens, and 

 was later by Osborn removed and used as the type of this 

 species, the description however being very meager. 



The teeth are moderately wide with rather low cusps and a 

 cingulum along the front only. On the fourth premolar the 

 protoconid and deuteroconid are connected by a sharp ridge ; 

 the basin behind is wide, and on the outer side of the rim is a 



*Rep. U. S. Geol. Surv., iii, 235, 1884. 

 fProc. Amer. Phil. Soc, xx, 181, 1881. 

 + Bull. Amer. Museum Nat. Hist., xvi, 185, 1902. 



