130 F. B. Loomis — Wasatch and Wind River Rodents. 



Sciuravus depressus sp. nov. 



Type No. 432, three upper molars of the right side from the 

 Wind Hiver beds on Bridger Creek near Lost Cabin, Wyo. 

 Cotype No. 458, molar 1 of the left lower jaw, from the same 

 locality. 



This rodent is characterized by its tiny size. The upper 

 molars are rectangular, slightly longer than wide, having the 

 hypocone equally developed with the other cusps. There is a 

 front and rear marginal ridge. From each of the cusps a 

 ridge runs inward, but these do not unite to make yokes. 

 Neither protoconule or metaconule is visible in this species. 

 There is a tiny mesostyle. The lower teeth have very low 



Fig. 7. Sciuravus depressus, x 6 ; A, type, molars of the right upper 

 jaw ; B, cotype, molar 1 of the left lower jaw. 



crowns with low isolated cusps. There is no anterior mar- 

 ginal ridge, but two low folds run a short distance from the 

 protoconid, soon dying out. The inconspicuous mesostyle is 

 more isolated than usual. The lower series of molariform 

 teeth measure 8 mm . 



Plesiarctomys ? buccatus Cope. 

 U. S. Geog. Surv. West of the 100th Meridian, 1877, p. 171. 



This species, from the New Mexico Wasatch, I have not 

 seen ; but it is described and figured as having four cusps 

 developed on the upper molars, which together with its small 

 size leads me to consider it a Sciuravus. 



Amherst College, Amherst, Mass. 



