274 STANTON 



Buttes invertebrate fauna at about the same horizon the following 

 lists of fossils collected by Robert Forrester in the Laramie of south- 

 west Colorado may be given : 



Beaver Creek, T. 34 N., R. 5 W., near boundary line between La Plata 

 and Archuleta counties, Colorado. Coal measures immediately above 

 the Lewis shale. 



Anomia sp. Related to A. micronema Meek. 



Modiola laticostata White. 



Corbicula sp. Related to C. suhelliptica M. & H. 



Corhicula occidenialis M. & H. 



Corbula undifera Meek 



Melania wyomingensis Meek? 

 Yellow Jacket Creek, T. 34 N., R. 5 W., "Coal measures above Lewis shale." 



Ostrea sp. 



Unio holmesianus White 



Unio hrachyopisthns White 



Unio verrucosiformis Whitfield? 



Unio sp. Undescribed, possibly two species. 



Ttdotoma thompsoni White 



Campeloma? sp. 



Neritina sp. 



Mr. James H. Gardner, of the U. S. Geological Survey, who has 

 done detailed work in the region, verifies the identification of the 

 horizon at the localities where these collections were made. 



Area west of Rawlins, Wyoming. — At Black Buttes the marine Cre- 

 taceous and immediately overlying rocks dip gently eastward passing 

 under beds of Wasatch, Green River, and Bridger age in the broad 

 syncline of the Great Divide Basin. They again come to the surface 

 with a westward dip a few miles west of Rawlins and 60 to 70 miles east 

 of Black Buttes. A summary description of the section exposed here 

 is published by E. Eggleston Smith,''^ to which the reader is referred 

 for lithologic and areal details. The paleontologic material dis- 

 cussed below was collected in part by the field parties of Messrs. Smith 

 and Ball and in part by myself. The estimates of thickness are 

 Smith's. 



The Mesaverde formation, which is coal-bearing and about 3600 

 feet thick, is not very fossiliferous in this area, but a few marine inverte- 

 brates have been obtained in the lower part and near the top there is 



*'' The eastern part of the Great Divide Basin coalfield, Wyoming, Bull. 

 U. S. Geol. Survey, No. 341, pp. 220-242. 



