WHITE.J CRETACEOUS FOSSILS OF ASIILEY's FORK. 229 



In the valley of Brush Creek I observed several more or less massive 

 layers of sandstone distributed in the softer layers of the Colorado Group, 

 the like of wliicli I have not seen elsewhere in that group. Just north 

 of Dodds's Kanch, in the valley of Ashley's Fork, a high hogback ot 

 sandstone rises uj) toward the flank of the mountains from the valley- 

 plain of that stream. As one approaches it by going uji the valley it has 

 the appearance of the usual hogback of the Dakota Group, which appears 

 almost everywhere at the flanks of the mountains, especially as the plain 

 IS known to be in part, and so fax as the lithological characters of the 

 strata can be observed beneath the siuiace debris it ax^pears to be 

 wholly, occupied by the strata of the Colorado Group. In fact, however, 

 as proved by the fossils, a large part of the valley-plain is occupied by 

 strata of the Fox Hills Group which are as soft and easily eroded as those 

 of the Colorado Group are; and the hogback referred to constitutes the 

 lower portion of the former group. From the strata of this hogback I 

 collected the following fossils : 



LIST OF CRETACEOUS FOSSILS AT DODDS'S RANCH ON ASHLEY'S FORK, 



UTAH. 



1. Inoceranms liowelU Wliite. 



2. Car (Hum spceiosum Meek & Hay den ? 



3. Mactra {Cymhopliora) ivarrenana Meek & Hayden. 



4. Anchura "I 



NOTES ON THE CRETACEOUS FOSSILS FROM ASHLEY'S FORK. 



1. Inoceramus howelli White. 



This species was originally discovered by Mr. E. E. Howell in South- 

 ern Utah, and was described by me in Powell's Eeport on the Geology 

 of the Uinta Mountains, p. 114, where it was referred to a much lower 

 horizon than it is now believed to occujjy. It is redescribed and illus- 

 trated in another part of this volume. 



2. Cardium speeiosum Meek & Hayden. 



Some casts of a Cardium in soft sandstone were found among the 

 other specimens that seemed to belong to this species, but they are too 

 imperfect to allow of satisfactory determination. If they really belong 

 to this species it has here as low a range in the Fox Hills Group as it 

 was found to have in Eastern Colorado, which, however, is not improb- 

 able. 



3. Mactra ( Cymhophora) ivarrenana Meek & Hayden. 



Although the examples foimd here are in the form of casts, their iden- 

 tity with tliis species seems hardly questionable. For fiu'ther remarlts 

 on this and the next i)receding species, see notes on the fossils of the 

 Fox Hills Group in Colorado, east of the Eocky Mountains. 



4. Anchura ? 



Some casts only of this species were found, and they are too imperfect 

 for specilic determination. They probably belong to A.fnsiformis Meek. 



These fossils, although imperfect, are too clearly characteristic of the 

 Fox Hills (}roup to admit of doubt as to the age of the strata containing 

 them. To the north of the hogback, composed of these strata, those of 

 the Colorado and Dakota Groui^s are seen to rise successively, and to rest 

 in order upon the Jura-Trias. Both the Colorado and Dakota Groups, 

 especially the former, are here of much less than their usual thiclmess, 



