BENTON FORMATION' 681 



Cyrena securis Meek. 

 Volutoderma ambigua (Stanton). 

 Scaphites ventricosus M. & H. 



vermiformis M. & H. 



oonf. larviformis M. & H. 

 Baculites asper Morton. 



conf. gracilis Shumard. 



Highwood River, near Ing's and Pocaterra's ranches, mouth of Sulli- 

 van Creek and Trap Creek Benton. 



Inoceramus simpsoni Meek. 



exogyroides M. & H. 

 gilberti White. 

 Pecten sp. nov. x. 

 Scaphites ventricosus M. & H. 

 vermiformis M. & H. 

 Baculites asper Morton. 

 Prionocyclus wyomingensis Meek. 



North Fork of Willow Creek, near Dick's ranch Benton. 



Inoceramus labiatus (Schlotheim). 



deformis Meek. 



simpsoni Meek. 



exogyroides M. & H. 

 Pecten sp. nov. x. 

 Ostrea congesta Conrad. 

 Scaphites vermiformis M. & H. 

 Baculites gracilis ? Shumard. 

 asper Morton. 



The large majority of the species collected from the Benton formation 

 are Upper Colorado forms. A few species, such as Inoceramus labiatus 

 (Schlotheim), Prionocyclus wyomingensis Meek, Scaphites warreni M. & 

 H., and Volutoderma ambigua (Stanton), indicate lower horizons. It is 

 regrettable that the exact stratigraphic position in the Benton formation 

 can not be given for each lot of fossils listed. The repeated faulting and 

 complex folding make this a detailed work calling for more time than 

 was available for this work. 



Belly Eiver Formation 



As far as the Sheep Eiver, the Elbow River, and the rest of our area is 

 concerned, it is difficult to subdivide the sediments above the Benton for- 

 mation. These rocks are a great development of brackish and fresh- 

 water sandstones of uncertain thickness. In part they represent the west- 

 ward boundary of marine basins, such as the Bearpaw. The separation, 



