442 N. H. DARTON PALEOZOIC AND MESOZOIC OF WYOMING 



feet. In. the first can3'oii south of South fork of Horse creek the rocks 

 are. mostly hard, buff sandstone, the upper third slabby and including 

 some buff to greenish sandy shales. On South fork of Horse creek are 

 60 feet of slabby buff to gray sandstone, sandy shales, and grayish green 

 shales lying on a 50-foot bed of massive gray sandstone, supposed to be 

 the top of the Chug-water formation. South of Horse Creek canyon the 

 lower 30 feet or more are greenish, sandy shale, above which are 10 feet 

 of bright buff, soft sandstone extending to base of Morrison formation. 

 Near Iron Mountain station there are two members : An upper one, 30 

 feet thick, of soft, slabby sandstone, gray at base and biiff toward top, 

 with ripple-marked layers and much intercalated shale; and a lower 

 member, 50 feet thick, mostly of green to gray shale, with layers of soft, 

 thin-bedded, greenish gray sandstone. 



Fossils and equivalency. — The formation contains abundant fossils of 

 middle to upper Jiirassic age, and it is believed to be equivalent to the 

 Sundance formation of the Black Hills region. The following are the 

 principal fossils : Belemnites densus, Gryphcsa calceola, var. nebrascensis, 

 Campectonites hellistriatus, Eumicrotis curta, Trigonia ehgantissima, T. 

 americana, T. conradi, T. montanensis, and Pentacrinus asteriscus. 



In Freezeout hills the following fossils are reported by W. IST. Logan^° 

 in section given on page 441 : Bed number 10, Pseudomonotis curta; bed 

 number 12, remains of Ichthyosaurus and Plesiosaurus ; bed number 13, 

 abundant Belemnites densus throughou.t, and in the concretions Pinna 

 hingi. Pinna sp. Cardioceras cordiforme, Avicula heedei, Astarte paclcardi, 

 Pentacrinus astericus, Tancredia huTbosa, T. magna, Lima lata, Qoniomya 

 montanaensis, Avicula mucronatus, Pleuromya subcompressa, Cardinia 

 wyomingensis, Pseudomonotis curta, Belemnites densus and B. antus, and 

 also remains of plesiosaurs and ichthyosaiirs ; bed number 14, Campto- 

 nectes bellistriatus, C. extenuatus, Ostrea densa, and 0. strigilecula; in a 

 sandy limestone bed in base of bed number 15, Pentacrinus astericus, As- 

 terias dubiuni, Pseudomonotis curta, Avicula macronatus, and Ostrea 

 strigilecula. 



Ceetaceous System 



morrison formation 



General relations. — The Morrison formation extends throughout east- 

 em and central Wyoming, presenting all the features which characterize 

 it in the type locality in Colorado and in the Black hills and Bighorn 

 mountains. It outcrops along the east side of Wind Eiver mountains, 



"Loc. cit, pp. 112-113. 



