PALEONTOLOGY OF THE BOULDER AREA 103 



FOX HILLS 



The Fox Hills formation is generally so friable that it is difficult to 

 obtain good specimens of most species, though a few, such as Cardium 

 speciosum, are found in very good condition. East of the big White 

 Rock fault the following species have been found : 



Mactra alta Tellina scitula 



Mactra warrenana Nucula sp. 



Pteria haydeni ? Dentalium sp. 



Cardium speciosum Cylichna scitula 

 Pholodomya subventricosa 



Further north a single specimen referred to Pholodomya subven- 

 tricosa has also been found. 



A poorly preserved undescribed Mactra labeled Marshall is in the 

 collection, but the exact locality is unknown. 



At the south end of the Weisenhorn Mesa, south of Weisenhorn or 

 Boulder Lake, the following species are found intermingled : 



Mactra formosa Nucula sp. Pyrifusus sp. 



Mactra warrenana Ostrea glabra Melania wyomingensis 



Callista sp. Dentalium sp. Undetermined gastero- 



Cardium speciosum Lunatia sp. pods 



It is worthy of notice that in this list at least two Laramie species, 

 Ostrea glabra and Melania wyomingensis, are associated with strictly 

 marine Fox Hills species. Dr. Stanton writes: "Similar occurrences 

 of these same Laramie species in Fox Hills beds have been noticed else- 

 where, especially on the Coffin Ranch four miles east of Longmont, Colo., 

 and near Point of Rocks, Wyoming." 



The Laramie is the coal-bearing formation. Leaf impressions, fossil 

 wood, and sea-weed casts are common, but we have no determined 

 material on hand from this locality. Ostrea glabra occurs in great 

 quantities at various points, particularly near Marshall. 



