l6 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I49 



floristic environment or food supply for the herbivores is not at hand. 

 A comparison of the mammalian faunas, however, reveals other and 

 apparently related discrepancies that are surely significant. Certain 

 of the differences, nevertheless, while provoking speculation, cannot 

 be fully credited because of the sparsity of remains upon which 

 presence was established. 



Perhaps the most striking feature revealed in the faunal com- 

 parisons made is the seeming incompatibility of Meniscotherium and 

 Phenacodns. This is most noticeable in the difference between the 

 faunas of the Big Horn Basin and those of the Green River basin. 

 Exception to this relates to the smaller form or forms of Menisco- 

 therium which, as well as being found in more paludal sediments, 

 is associated, though very sparsely, with Phenacodus in both the 

 Clark Fork and Bitter Creek localities. It may be further noted, 

 however, that in the more abundant materials of the Four Mile 

 fauna, which is close in time to Bitter Creek, some diversity of 

 phenacodonts is represented, but no Meniscotherium. Unfortunately, 

 the relative stratigraphic position for much of the Cope collection 

 from the San Juan Basin is not known. Nevertheless, it would seem 

 from Granger's and Simpson's collecting that Phenacodus is essen- 

 tially characteristic only of the Almagre, although one of the 

 specimens mentioned (Granger, 1915) came from the Largo or Menis- 

 cotherium facies. In the Wind River Basin Phenacodus but not Menis- 

 cotherium occurs in the Lysite, whereas in the Lost Cabin beds 

 both are recorded although Meniscotherium is very scarce. More- 

 over, there is no reported information on the relative stratigraphic 

 position of these, so that no certain conclusions can be drawn. In 

 the Piceance Creek Basin, of the approximately 25 Chicago Natural 

 History Museum specimens certainly identified as Phenacodus, only 

 1 was from the Roan Cliffs area yielding M. chamense. Except for 

 three from localities not pinpointed, however, the remainder were 

 from the area southeast of the Colorado River, often in association 

 with M. tapiacitis. Finally, Phenacodus but no Meniscotherium is 

 reported (Peter Robinson, MS.) for the Wasatchian of the Huerfano 

 Basin in Colorado. 



Among other elements that seem foreign to the Meniscotherium 

 environment are Homogalax and Ectocion, although the evidence 

 here may not be so convincing, inasmuch as these two are rather 

 sparsely represented outside the Big Horn Basin. For example, 

 Ectocion is found in the Clarkforkian beds at Buckman Hollow, 

 Four Mile Creek, and Lost Cabin, and Homogalax at Bitter Creek, 



