white.] FOSSILS OF THE FOX HILLS GEOUP. 179 



16. Actcronina prosoclieila White. 



17. Zunatia H 



18. Fasciolaria (PiestocJicilus) cuJbertsoni Meek & Hayden. 



19. Ammonites ? 



20. Plaeentieems Jenticulare Ovren sp. 



21. Lamna ? 



22. Bones and scales of teJiost fishes. 



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

 between the South Platte River on the east and the base of the Eocky 

 Mountains on the vest, and the Cache a la Poudre on the north and 

 the Saint Trains 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 Eocky Mountains in Colo- 

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

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

 name of Fox Hills Group,* and which are here, without 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 applied. 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 valley of the Cache a la Poudre, Fossil Eidge, the 

 valley of Little Thompson Creek, and the mouth of the Saint Trains 

 Eiver ; 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 OX THE FOSSILS OF THE FOX HELLS GROUP AS DEVELOPED 

 LX COLORADO, EAST OF THE EOCKY MOUNTAINS.! 



1. Halymenites major Lesquereux. 



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

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

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

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

 lar stratigraphical position. Although I am much inclined 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 Eocky 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 

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

 never been found in stata containing only fresh- water mollusks, 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, hut 

 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 equivalents 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. 



