510 A. G. LEONARD 



From the locality on the Yellowstone, at the mouth of Cedar 

 Creek, the following marine shells were secured, from the upper 

 fifty feet of the Pierre : 



Avicula nebrascana M. and H. Scaphites nodosus Owen vars. brevis 

 Avicula linguaeformis E. and S. and plenus. 



Inoceramus sagensis Owen. Limopsis parvula M. and H. 

 Inoceramus cripsi var. barabini Mor- Yoldia evansi M. and H. 



ton. Lucina subundata M. and H. 



Modiola meeki E. and S. Protocardia subquadrata E. and S. 



Veniella subtumida M. and H. Dentalium gracile M. and H. 



Callista deweyi M. and H. Vanikoro ambigua M. and H. 



Anchura americana E. and S. Margarita nebrascensis M. and H. 



Haminea occidentalis M. and H. Fasciolaria (Piestocheilus) culbert- 

 Pyrifusus newberryi M. and H. soni M. and H. 



Lunatia concinna M. and H. Baculites ovatus Say. 

 Scaphites nodosus var. quadrangu- Nautilus dekayi Morton. 



laris M. and H. Chlamys nebrascensis M. and H. 



The beds which outcrop at the latter locality on the Yellow- 

 stone, twelve miles above Glendive, Montana, are brought above 

 river level by an anticlinal fold, the dip of the strata here being 

 2o° S. 52 W. The Bowman County outcrop is probably caused 

 by the same anticline, since the strike of S. 38 E. shows that the 

 fold so well exposed on the Yellowstone, if continued in that direc- 

 tion, would include the Little Beaver Creek locality. That the 

 two areas of outcrop are continuous seems probable from the fact 

 that ammonites and other marine shells are reported to have 

 been found at several intervening points on Cabin and Cedar 

 creeks. 



There are extensive outcrops of Pierre shale along the Missouri 

 River and its tributaries in the northeastern corner of Montana, 

 in Dawson and Valley counties. At the mouth of Big Dry Creek, 

 fifteen miles south of Glasgow, the shale rises 200 feet above the 

 river, and it is also well shown on most of the creeks entering the 

 Missouri from the south for a distance of eighty or one hundred 

 miles west of the Big Dry. Among these is Hell Creek, on which 

 150 feet of Pierre are exposed above creek level. Among the most 

 common fossils occurring in the calcareous concretions of this 

 locality are ammonites and baculites. 



