32 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I44 



tinus and Knight O. sheai, it does not form an intermediate stage 

 between them. It is of further interest to note that the talonid basins 

 in the lower molars of all the Wasatchian Omomys materials are 

 somewhat elongated, but rather less so than in Bridgerian materials. 

 They do not appear, however, to be relatively so short as in upper 

 Wasatchian Loveina (pi. 2, fig. i). The trigonid pattern clearly 

 separates O. minutus from Anemorhysis. 



OMOMYS, cf. VESPERTINUS Matthew 

 (Plate s, figure a) 



A lower jaw fragment with Mi and M2 in the University of 

 Wyoming collection (No. 1647) from the Red Desert locality east 

 of Steamboat Mountain is a little larger than Omomys sheai. M2 is 

 very much like that in 0. sheai, but its length is nearly the same as 

 that in Graybullian Omomys vespertinus, which is more nearly 

 equivalent in age. The width of the talonid portion of the tooth, 

 however, is a little less than in O. vespertinus, and relatively a little 

 narrower than in 0. sheai, although the difference here is less evi- 

 dent. Suggestive of O. vespertinus is the somewhat higher outer 

 wall of the lower molars than in O. sheai. 



MEASUREMENTS IN MILLIMETERS OF LOWER MOLARS 



IN WASATCHIAN SPECIES OF Omomys 



O. vespertinus 0. minutus O. sheai 



A.M.N.H. A.C.M. U.S.N.M, 



No. No. No. 



1683s 336s 22384 



Type Type Type 



M1-M3 length 7.8 5.8 



Ml, anteroposterior diameter : 



transverse diameter 2.6:2.0 2.0: 1.6 ■ 



Ms, anteroposterior diameter: 



transverse diameter 2.4 : 2.0 1.9 : 1.6 2.2 : 1.8 



M», anteroposterior diameter: 



transverse diameter 2.7 : 1.7 2.2 : 1.3 2.6 : 1.5 



• Approximate. 



CHLORORHYSIS KNIGHTENSIS Gazin 

 (Plate 2, figure 2; plate 12, figure 10) 



This interesting omomyid in the La Barge fauna was described in 

 1958 from the anterior portion of a lower jaw exhibiting C-P4, but 

 the molars were not then known. It was considered close to Loveina 

 but differences in P3 and P4, particularly in the absence of a postero- 

 internal crest extending from the primary cusp of P3, and in the 



