LANCE FLORA OF EASTERN WYOMING 



89 



abundant marine invertebrates, which include Veniella humilis Meek and Hayden, 

 Discoscaphites conradi (Morton), D. cheyennensis (Owen), and the diagnostic zone 

 index Sphenodiscus lenticularis (Owen), 



The thickness of the Fox Hills sandstone in the region has been variously esti- 

 mated at between 300 and 750 feet. Discrepancies in thickness appear to be the 



R 65 W. 



Rg^W. 



T 



36 

 N 



X PLANT LOCALITY OOIL WELL 



OLIGOCENE PALEOCENE UPPER .CRETACEOUS 



• OIL TANK 



OROUP 



m 



FORT UNION 

 fOHMATION 



D' 



ANCe 

 F0RMA7I0N 



FOX HILLS 

 FOBMATION 



H 



flERHC SH/M.C 



FiG. 2 — Areal geology of Lance Creek area, showiiig locations of plant localities 



result of difficulties involved in properly placing the contact with the overlying 

 Lance formation. The practical sokition to these difficulties has been ably stated 

 by Dobbin and Reeside: 



"In general, minor individual lithologic units are not persistent in either the Fox Hills or the 

 Lance. On the other hand, largcr Hthologic units, aggregations of these smaller, variable units, 

 persist over large areas and are trustworthy features for identification. In some places, however, 



