WHITE.] FOSSILS OF THE FOX HILLS GROUP. 179 



16. Act(ronina prosocheila White. 



17. Lunatia ? 



18. Fasciolaria {PiestocJieilus) culhertsoni Meek & Hayden. 



19. Ammonites ? 



20. FUwenticeras Icnticulare Owen sp. 



21. Lamna ? 



22. Bones and scales of teliost fislies. 



The district which I have thus traversed, and which is embraced 

 between the Sonth Phitte Itiver on the east and the base of tlie llocky 

 Mountains on the west, and the Cache a la Pondi-e on the north and 

 the Saint Vraius on the south, probably presents the best exemplifica- 

 tion of the Cretaceous groups, more especially of the Fox Hills Group 

 and its fauna, that is to be found east of the Kocky Mountains in Colo- 

 rado. The strata with which I am now more immediately concerued are 

 those to which I have in my report for last year applied the single 

 name of Fox Hills Group,* and which are here, withont doubt, both the 

 stratigraphical and paleontological equivalent of all those in the Upper 

 Missouri Eiver region, to which both the names Fort Pierre Group and 

 Fox Hills Group, Upper and Lower, have been ai:)plied. Those northern 

 divisions are no doubt sufficiently characteristic there, but their recogni- 

 tion as indicating seperate epochs of geological time is impracticable here. 

 Therefore, in the following discussion of the species I shall consider as 

 belonging to only one category all that have been separately enumerated 

 as coming from the vallej' of the Cache a la Pondre, Fossil Eidge, the 

 valley of Little Thompson Creek, and the mouth of the Saiut Vrains 

 River ; but 1 shall discuss the subordinate horizons that are indicated 

 by certain of the species, in connection with their separate consideration, 

 in the following notes : 



NOTES ON THE FOSSILS OF THE FOX HILLS GHOUP AS DEVELOPED 

 IN COLORADO, EAST OF THE KOCKY MOUNTAINS.f 



1. Hali/menites major Lesquereux. 



The only localities east of the Rocky Mountains at which I obtained 

 this fucoid is at the mouth of the Saint Vrains, and in the valley of 

 Platte River some eighteen miles east of Greeley, but Dr. Hayden and 

 others report it at several locaUties in that region, and as holding a simi- 

 lar stratigraphical position. Although I am luuch inchned to regard 

 this as a Laramie fossil, I discuss it in connection with the Cretaceous 

 fossils of this region as a matter of convenience. Its upward range west 

 of the Rocky Mountains is to the very summit of the Laramie Group, 

 where I have found it near Black Buttes Station, in the valley of Bitter 

 Creek, Wyoming. Even here, however, it was in or beneath strata that 

 contaiu brackish- water invertebrate fossils. So far as I am aware, it has 

 never been found in stata containing only fresh-water moUusks, but it 



*Mr. Clarence King, in his map of the Green River Basin, applied the name Col- 

 orado Group to the equivalents of not only the Fort Benton and Niobrara Groups, but 

 he included with them the equivalent of the Fort Pierre Group also, leaving the Fox 

 Hills Group to stand alone, as Hayden and Meek did originally. There are excellent 

 paleontological objections to such a division between the eqiiivalents of Fort Pierre 

 and Fox Hills Groups, but not between those of the Fort Pierre and Niobrara Groups. 



t All the invertebrate fossils of this list, unless otherwise stated, are figured in vol. 

 ix of the United States Geological Survey of the Territories. This applies not only to 

 the species originally described by Meek and Hayden, but to those of other authors 

 also. 



