4 SMITHSONIAN MISCELLANEOUS COLLECTIONS VOL. I3I 



for a few feet immediately above. The ledge locality would seem 

 almost certainly to be stratigraphically much higher than the saddle. 

 The locality is nearer the rim, hence topographically higher, and the 

 dip of the beds may be a little more southwesterly than at the saddle 

 so that the ledge would appear to be stratigraphically higher than any 

 portion of the escarpment above the saddle. A considerable extent, 

 however, of the exposures between the two localities is obscured by 

 talus and vegetation, and so the relationship could not be determined 

 precisely. 



The locality that I am informed Mr. Bell discovered, and from 

 which the University of Wyoming secured upper teeth of Titanoides 

 primaevus, is still farther west, about midway north and south in the 

 eastern half of adjacent section 29. The general locality is in the 

 southwestern part of the basin and just west of the most westerly of 

 the wagon trails crossing the south rim of the basin. Fossils, though 

 comparatively few, were found ranging from very near the top of the 

 escarpment to 30 or 40 feet stratigraphically lower. The beds here 

 appear to have a greater southerly dip than at the saddle or ledge lo- 

 calities, and the stratigraphic position relative to the more easterly 

 localities is not readily evident from field relations, as much of the 

 escarpment between this locality and the ledge is obscured. The 

 faunas discussed in the following part of this paper would suggest 

 that it is still higher. 



The most westerly locality is an east-facing gravel-capped exposure 

 at the west end of the basin, evidently about midway east and west 

 across section 29, close to the northern line. Fossils were discovered 

 here in a very restricted zone around a low hill set out from near the 

 base of the exposure and at about its most southeasterly extent. Jaws 

 and isolated teeth were encountered over an area of only a few hun- 

 dred square feet on the slopes extending out from the base of this hill. 

 The west-end exposure is well isolated by grass and sagebrush slopes 

 from the Titanoides locality to the south, but there seems no doubt 

 from the dip at the latter locality that the west-end site must be con- 

 siderably lower stratigraphically, unless the intervening rock is com- 

 plicated by changes in dip or faulting. The relative position of the 

 horizon represented with respect to that at the ledge or saddle is un- 

 certain, but there is some evidence from the fossils that it may not be 

 far removed in time from that represented at the ledge. 



THE BISON BASIN FAUNAS 



The following tabulation pertains to the four principal localities in 

 the Bison basin from which collections were obtained. The figures 



