Marsh Collection, Peabody Museum. 139 



gracilis. It is possible that the tooth pertains to the small 

 species described as Omomys Ameghini, but I do not think it 

 likely. 



The locality is not clearly indicated on the label, but the 

 specimen was associated with other fragments from Dry Creek, 

 which gives it an upper middle position in the Bridger horizon. 



Enryacodon lepidus Marsh. 



Euryacodon lepidus Marsh, this Journal, August and September, 1872, p. 

 33, Separata. 



Professor Marsh in describing this genus and species says : 

 " A small mammal, doubtless an insectivore, is represented by 

 a fragment of an upper jaw containing the last two molars in 

 perfect condition. Our collections contain other characteristic 

 fossils which appear to be specifically identical with this speci- 

 men. The teeth preserved agree nearly in the composition of 

 their crowns with the molars described by Dr. Leidy under the 

 name Palmacodon verus, but each has. its inner margin pro- 

 duced into a small tubercle. In the penultimate upper molar, 

 this tubercle is especially prominent. The outer margin, also, 

 of these molars has but a single faint indentation between the 

 external cusps. Both teeth are surrounded by a distinct basal 

 ridge. The specimens preserved indicate an animal about as 

 large as a weasel." 



Besides the type, there are in the collection four other ex- 

 amples which I refer to this species. One of these is a fragment 

 of an upper jaw bearing the second and third molars, just as 

 in the type ; and three lower jaw fragments, which, however, 

 in no instance are associated with the upper molars. The 

 reference of the latter to this species, therefore, contains an 

 element of uncertainty. 



The upper molars, figure 133, resemble those of Omomys 

 Carteri. In the second molar of this latter species, however, 

 figure 123, the anterior internal cingular cusp is not devel- 

 oped, while in Euryacodon lepidus it is strong. The last 

 molar, moreover, in the latter species is a little less reduced 

 and the crown is not so narrow and pointed, especially on its 

 internal or lingual side. The external cusps are rather conical, 

 and the intermediates are moderately well developed. The 

 homologue of the main postero-internal cusp has a somewhat 

 more external position, and this portion of the crown has a 

 distinctly less rectangular outline than the corresponding tooth 

 in Omomys Carteri. 



In the lower jaw, figure 134 (if the specimens are correctly 

 referred to this species), the molars only are known. The 

 structure of their crowns is quite different from that of any 

 species of Omomys. The anterior cusp of the trigon is well 



