NO. 6 



PALEOCENE FAUNAS OF BISON BASIN — GAZIN 



"O bo m 



Mammalia — continued "^ "§ fe 



Carnivora — continued ^ 



Claenodon, z{. procyonoldcs (Matthew) 3 



Claenodon, ci. montanensis (Gidley) 5 



Claenodon, cf. jerox (Cope) 5 • • 3 



Claenodon acrogenius, new species 6 I 



Dissacus, sp 2 



Didymictis, near D. tenuis Simpson i 



Condylarthra : 



Promioclacnus pipiringosi, new species I 



Cf . Promioclaenus pipiringosi, new species 2 



Promioclaemis ? sp I 



Litomylus scaphicus, new species 2 i 



Litomyliis scapliiscns, new species i 2 



Haplaletes pelicatus, new species 4 



Haplaletes serior, new species 



Protoselene? novissimus, new species 2 



Litolestes lacunatus, new species 



Cf. Litolestes lacunattis, new species i 



Gidleyina ivyoiningensis, new species lO 



Gidleyina, cf. Wyoming ensis, new species 5 • • • • 3 



Phetiacodns? bisonensis, new species 28 2 



Phenacodus? sp. (large) I i 2 



Pantodonta : 



Titanoides primaevus Gidley I 



Caenolambda pattersoni, nevf genus and species. .. . I 



a. Caenolambda pattersoni, new genus and species, i i 

 Pantodont, undet. (tooth frags.) 2 5 3 i 



* Two of these are from the vicinity of the saddle locality but approximately so feet 

 higher. 



ENVIRONMENT AND RELATIONSHIPS BETWEEN THE 

 BISON BASIN FAUNAS 



Although differences are noted between the faunas represented at 

 the four principal localities, all four faunas appear to be Tiffanian, 

 and for the most part, if not all, a comparatively early part of this 

 time interval. Whether these differences are essentially a matter of 

 chance collecting, of facies or environmental differences with time as 

 a minor factor, or of change resulting in part from evolution of cer- 

 tain persisting kinds, but complicated by migration involving the in- 

 troduction and disappearance or local extinction of others, is not en- 

 tirely clear. Each, though, is likely to have contributed to the picture. 



Chance collecting is unquestionably an important factor where the 

 number of specimens of each form is small, but it cannot be predicted 

 with any assurance that further collecting would increase the faunal 



