NO. 6 PALEOCENE FAUNAS OF BISON BASIN GAZIN 2$ 



Ml, anteroposterior diameter : greatest transverse 



diameter 3.0 : 3.0 3.2 : 3.0 



Mj, anteroposterior diameter : greatest transverse 



diameter 3-3 : 3-2 3-3 : 3-2 



M3, anteroposterior diameter : greatest transverse 



diameter 4.4 : 2.9 



Carnivora 



ARCTOCYONIDAE 



Creoclonts are well represented in the collections, comprising a 

 diversity of forms not hitherto recorded in the Tiffanian. Most of 

 the forms are of arctocyonid types, and among these are species of 

 Tricentes and Claenodon, suggesting affinities with the earlier Tor- 

 rejonian faunas, together with Thryptacodon better known in later 

 horizons. Chriacus, having a comparatively great range in geologic 

 time, is represented by a species rather similar but possibly a little 

 more progressive than that of the Torrejon. So far as Claenodon is 

 concerned, although the species are difficult to distinguish from those 

 of the Torrejon, undescribed material of the genus has been obtained 

 from Paleocene deposits as late as Clarkforkian, and the presumably 

 descendant Anacodon is, of course, found in the lower Eocene. 



OXYCLAENINAE 



TRICENTES FREMONTENSIS,s new species 



Plate 5, figure 4 



Typc.—Leh ramus of mandible with Mx-Mg, U.S.N.M. No. 20582. 



Horizon and locality. — Bison basin Tiffanian, saddle locality at 

 south rim of Bison basin, sec. 28, T. 27 N., R, 95 W., Fremont 

 County, Wyo. 



Specific characters. — Teeth close in size to those of Tricentes suh- 

 trigonus but anterior portion of lower dentition reduced, with trigonid 

 of Ml narrow and premolars smaller. 



Discussion. — The above new specific name is proposed with some 

 hesitancy, as the Torrejon species, Tricentes subtrigomts, shows an 

 astonishing amount of variation in characters of the lower teeth. Vari- 

 ation in size, relative proportion of teeth, and cusp development makes 

 any attempt at detailed comparison nearly futile. Marked variability 

 was also noted in the material of Tricentes jremo}itensis. Neverthe- 

 less, P3 and P4, as observed in U.S.N.M. No. 20584, are smaller than 

 in any of the specimens of T. subtrigonus I have examined, and in 



8 Named for Fremont County, Wyo. 



