NO, I LOWER EOCENE MAMMALIAN FAUNAS — GAZIN 55' 



with very short or almost no diastema in comparison with jaws from 

 the same horizon tentatively referred to Sinopa vulpecula. 



SINOPA, cf. MULTICUSPIS (Cope) 



(Plate 6, figure 4) 



A Bitter Creek lower jaw (U.S.N.M. No. 22459) with Mi and M2 

 preserved is tentatively referred to Sinopa mtclticuspis. The lower 

 teeth in the Bitter Creek jaw occlude very well with the upper molars 

 in the type and are not significantly different in size from teeth in 

 New Mexican specimens referred by Cope to this species, A corres- 

 pondence was also noted in size of teeth to the type of Sinopa 

 secundaria, although the latter has more slender lower jaws. On the 

 other hand, Sinopa mordax has deeper jaws and a more reduced M3 

 than indicated in the Bitter Creek specimen. Considering the wide 

 range of sizes and characters shown in materials of Sinopa and the 

 plethora of species that have been proposed, S. mordax may not 

 actually be distinct from 5'. midticuspis. A careful reexamination of 

 all the materials of Sinopa is much needed, as the present taxonomic 

 arrangement seems illogical. 



To Sinopa midticuspis is also tentatively referred a right maxilla, 

 with portions of two molars, U.S.N.M. No. 22460, from high on 

 Fossil Butte and fragments of isolated teeth from this locality and 

 from west of Elk Mountain in the Fossil Basin. 



SINOPA, cf. VULPECULA Matthew 

 (Plate 6, figures i and 2) 



The best of the Knight material (U.S.N.M. No. 19347) compared 

 to Matthew's small Lost Cabin species was described in 1952. A 

 couple of specimens that represent the same species have been added 

 to the La Barge collection but these do not furnish new information. 



Two maxillary portions, one of these with P* and the other 

 (U.S.N.M. No. 22462) with M^ and M^ from the New Fork tongue 

 are also thought to be of Sinopa vulpecula. The teeth are no larger 

 than in Sinopa multicuspis but the molar talons seem more robust. 

 In this connection it may be noted that the talonids of the lower 

 molars in the La Barge material compared to 5. vulpecula also seemed 

 relatively broader than in the various Knight materials that were 

 referred to S. midticuspis. 



SINOPA, cf. STRENUA (Cope) 

 No additional material of a larger species thought to represent 

 Sinopa strenua was encountered in the La Barge-Big Piney area, but 



