36 BULLETIN 16 9, UNITED STATES NATIONAL MUSEUM 



all the localities for which mammaHan material that can be identified 

 is available, and also one locality of which this is not true but which 

 is important as being the highest stratigraphicallv where mammal 

 fragments have been found. All these localities merit repeated pros- 

 pecting in the future, and any of them may turn up material of out- 

 standing importance. The same is also true, but with less probabihty, 

 of mammal localities, not especially discussed here but all given in the 

 serial locahty list, from which no identifiable specimens are now at 

 hand. 



Fort Union No. 1, or Lower Lebo 



Loc. 65.— Sec. 26, T. 6 N., R. 16 E. This is the lowest horizon at 

 which mammals have been found in this field, being only about 35 

 feet above the base of the Fort Union No. 1, or of the Lebo. It is a 

 small shale slope immediately north of the south line of the section 

 and on the west side of a wagon trail that follows the base of the Fort 

 Union No. 1, on the underlying sandstone ledge. The only identi- 

 fiable mammal yet found here is a P4 inseparable from Ptilodus 

 sinclairi, mentioned in connection with the systematic description of 

 that species. We have recently found here a few scraps of mammal 

 bones, also crocodile or champsosaur teeth and ganoid scales, but the 

 material is very scanty and poor. This is, nevertheless, the most 

 promising prospect for obtaining material near the basal contact of 

 the recognized Fort Union in this field. 



Loc. 75.— Sec. 26, T. 6 N., R. 16 E. This locahty is in the same 

 section as Loc. 65 but farther west, on the other side of a sandstone- 

 capped hill and at a higher level, about 200 feet above the base of the 

 Fort Union No. 1. The only identifiable specimen yet found at it 

 is the lower jaw made type of Chriacus pugnax. 



Loc. 9. — Sec. 35, T. 6 N., R. 15 E. This is the most promismg 

 locality for mammals in the No. 1 beds. It is a good shale exposure on 

 the west flank of the Widdecombe Creek anticline, about 200 feet below 

 the base of the No. 2 and hence probably about 300 feet above the base 

 of the No. 1, although this cannot be measured accurately. Search in 

 1935 revealed no new material. Previously the following had been 

 collected: Lower jaw fragment of fMimotricentes sp., type upper jaw 

 of Claenodon vecordensis, and two upper molars (Princeton no. 13757) 

 of Tetraclaenodon fsymholicus. 



Loc. 73.— Sec. 34, T. 6 N., R. 16 E. This locahty is in the somber 

 capping sandstone of the No. 1 beds, nearly 500 feet above their base. 

 It has yielded only one mammal, a lower jaw of Mimotricentes angusti- 

 dens in the Princeton collection. This is the only identifiable mammal 

 to be found in a sandstone in tliis field. Subsequent search has not 

 brought to light any other fragments at this locality. 



