30 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



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. — Length of lower molar series is about 13 per- 

 cent less than in the type of Thryptacodon dcmari and lower jaw 

 much shallower. Upper and lower molars similar to those in T. de- 

 mari, except that M3 is relatively much narrower. 



Discussion. — In addition to the type there are two other specimens 

 representing this species in the University of Wyoming collection and 

 about nine in the collections of the National Museum. No difficulty 

 was encountered in distinguishing these materials from that repre- 

 senting Thryptacodon danari and upon completing the segregation of 

 the species it was found that all the material except one specimen 

 of T. belli was derived from the saddle locality at the south rim, 

 whereas all but two of the specimens of T. demari were from the 

 localities farther to the west, and apparently a little higher strati- 

 graphically. 



MEASUREMENTS IN MILLIMETERS OF TEETH IN TWO NEW SPECIES OF ThryptaCodon 



M\ anteroposterior diameter buccally : transverse 



diameter 5.7 : 6.2 



M", anteroix5sterior diameter buccally : transverse 



diameter 6.5 ": 8.0 



P4, anteroposterior diameter : transverse diameter 

 Ml, anteroposterior diameter : transverse diameter 

 M2, anteroposterior diameter : transverse diameter 

 M3, anteroposterior diameter : transverse diameter 

 ' Approximate. 



Arctocyoninae 



The approximately 30 specimens of claenodonts in the Bison basin 

 collections nearly run the gamut in size of teeth from a little smaller 

 than in Clacnodon procyonoides to possibly a little larger than in the 

 largest Claenodon ferox, as represented in the Torrejon collections. 

 No one, I believe, would seriously contend that a single species is rep- 

 resented, nor does it seem possible to arrange them logically, with the 

 material at hand, into less than about four species. Possibly a larger 

 collection would show a different distribution as to species and would 

 probably represent not more than three. Simpson (1936) has shown, 

 for example, that the amount of material now known from the Tor- 

 rejon in New Mexico has resolved the complex there into only two 



