38 BULLETIN?" 169, UNITED STATES NATIO^^AL MUSEUM 



almost barren exposure at a small pointed hill and east of this a flat 

 and poor but richer exposure where the following mammals were 

 found: 



tPtilodus gidleyi: 1 lower premolar. 



Ptilodus montanus: 2 lower premolars. 



Metachriacus provocator: Associated upper and lower jaw fragments and I 



isolated lower. 

 Anisonchus sectorius: 1 lower jaw. 



Loc. 81. — Sec. 23, T. 6 N., R. 15 E. This is in the extreme northern 

 part of the field where the steep monocline swings into the Widde^ 

 combe Creek Anticline, It is in the lower half of the No. 2 beds, 

 probably about 300 feet above their base. Mr. Silberling found this 

 excellent shale exposure years ago, but nothing was found in it until 

 1935, when a small rich pocket of fossil mammals, most of them still 

 in place, was discovered. Extensive prospecting failed to uncover 

 anything else, and despite its richness this seems to have been a very 

 local pocket, only 2 or 3 feet in diameter. The material is in the 

 American Museum collection and includes the following forms: 



Aphronorus fraudator: Upper premolar. 



Prothryptacodon ffurens: 1 lower jaw. 



Metachriacus provocator: 1 upper and 3 lower jaws. 



Mimotricentes flatidens: 1 upper and 1 lower jaw, possibly associated. 



Didymictis cf. haydenianus: 1 upper jaw. 



Loc. 5^.— Sec. 23, T. 5 N., R. 15 E. This locaHty is at a large shale 

 exposure immediately north of the Gidley Quarry. Fossils have been 

 found here at two levels, one about the same as that of the Gidley 

 Quarry and designated as Loc. 54, and the other, Loc. 52, about 50 

 feet lower. Numerous scraps have been found here, but the only cer^ 

 tainly identifiable specimen is apparently associated right and left 

 M2 and other fragments of Claenodon montanensis. 



Loc. 4' — The Gidley Quarry occurs at this level relative to th,e other 



localities. It is discussed elsewhere. 



Loc. 5.— Sec. 33, T. 6 N., R. 16 E.l ^, ,, ^ ,. 



r n o o/m/>AT-n-.^T^r Thcse are the two discovery 



Loc. 6. — Sec. 34, T. 6 N., R. 16 E.j "^ 



localities, where Douglass found the first Fort Union mammals in 1901. 



They are at nearly the same level, about 1,200 feet above the base of 



the Fort Union (No. 1), and 125 to 150 feet below the basal No. 3: 



sandstone, about the same level as the Gidley Quarry. Loc. 5 is a 



relatively large shale exposure on the west side of Bear Butte near its 



northern end, readily recognized as being opposite (across the county 



road from) a small, tepee-shaped outlier of the main butte. Loc. 6 is a 



smaller shale exposure about quarter of a mile northeast of Loc. 5 and 



just east, or slightly southeast, of the extreme northern end of Bear 



Butte (see plate 3). Douglass' material from the two localities (with 



identifications slightly amended in the light of later knowledge) was as 



follows: 



