248 STANTON 



U. retusoides Whitf . 



U. percorrngata Whitf. 



U. posthiplicata Whitf. 

 ft/, aldriclii White 

 f Z7. holmesianus White 



U. vetustus Meek 

 ft/, cryptorhynchus White 

 *£/. biesopoides Whitf. 



U. cylindricoides Whitf. 

 *f/. letsoni Whitf. 

 *f/. gibbosaides Whitf. 

 *t/. pyramidatoides Whitf. 



U. subtrigonalis Whitf. 



Spharhim planum M. & H. 



Corbicula subelliptica M. & H. 

 "f^Campelorna jnultilineaia M. & H. 

 ^Campeloma vetida M. & H. 



Campelomu producta White 

 ■\Viviparns plicapressus White 

 ^Cassiopella turricula White 

 *Thauniastus limnmformis M. & H. 



Bulimus rhomboideus M. & H. 



Species marked * occur in "Ceratops beds" of Converse County. 

 Species marked t occur at Black Buttes. 



On the faunal and stratigraphic evidence Brown's correlation of 

 the "Hell Creek beds" with the " Ceratops beds" of Converse County, 

 Wyoming, is fully justified. The flora is relatively meagre and accord- 

 ing to Knowlton shows closer relationship with the overlying Fort 

 Union. Of 13 identified species 2 are recorded in the Laramie, 

 3 in the Denver, and 8 in Fort Union and later formations. 



Between the "Hell Creek beds" and the typical "yellow beds" of 

 the Fort Union there are 100 feet of lignite-bearing strata in which no 

 dinosaurs have been found and which were tentatively assigned to 

 the Fort Union for this reason, though the few plants obtained from 

 them are included in the census just given. 



Areas in North and South Dakota. — Along the little Missouri River 

 in the southwest corner of North Dakota A. G. Leonard has studied 

 a section similar to that on Hell Creek and his description of it is 

 published by Knowlton." The base of the section is a marine 

 Cretaceous shale referred to the Pierre which is overlain by 80 feet 



'* Proc, Wash. Acad. Sci., vol. .\i, Xo, j;, lyog, p. 201. 



