116 INDEX TO THE STRATIGRAPHY OF NORTH AMERICA. 



Cambrian period. This very interesting transition fauna is the first recorded from this region 

 to show in any way a passage from the Lower to the Middle Cambrian. 



Shaler and Foerste'^^^^ found other localities of occiorrence of Cambrian strata 

 at North Attleboro, Mass. The fossils belong to the Olenellus zone and occur in 

 red shales and limestone. At the several separate localities the following forms 

 have been collected : 



Locahty 1, Hyolithes princepsf, Hyoliihes micans, H. liUingsi, Stenoiheca rugosa var. pauper, 

 SaltereUa curvata, Pleurotomaria (Raphistoma) attlehoroensis, Fordilla troyensis. In red shale 

 near by occurred Agraulus strenuus. 



At locality 2 were found : Oholella atlantica Walcott, OioleUa crassa Hall, SceneUa reticulata 

 Billings, Stenofheca curvirostra S. & F., Stenoiheca rugosay&v. ahrupta S. & F., Platyceras pri- 

 mievum BilHngs, Hyolithes americanus, Hyolithes communis var. emmonsi Ford, Hyolithes 

 quadricostatus S. & F., Microdiscus hellimarginatus S. & F., M. hiatus Hall, Olenellus walcotti 

 S. & F. (probably a young form of some known species), Ptychoparia attlehoroensis S. & F. 

 (probably the young form of some species of trilobite), Agraulus strenuus? Billings. 



K-L 12-13. WYOMING. 



Cambrian strata which outcrop around the crystalline rocks of the Bighorn 

 Mountains constitute the Deadwood formation. They consist of sandstones, shales, 

 and limestones from 850 to 1,050 feet in thickness. 



Darton^'°* gives many details of local variation in character. The following 

 is a representative section: 



Section of Deadwood formation in Wolf Creelc canyon, west of Sheridan, Wyo. 



White massive sandstone at base oJf Bighorn limestone. Feet. 

 Thin-bedded limestone, gray, greenish, and pinkish tints, with flat-pehble limestone conglomer- 

 ate and glauconite 300 



Gray and greenish shale with thin limestones and sandstones 300 



Brown to buff massive sandstone ; many fossils 50 



Thin-bedded brown and gray sandstones 50 



Gray sandstones and shales "T. 35 



Hard brown cross-bedded sandstone t't 6 



Brown sandstone and sandy shale .- .- so 



Dirty-buff to brown and reddish soft cross-bedded sandstone; much glauconite; many fossils. . . 20 



Soft greenish-gray sandstone , 12 



Buff sandstone with fossils 8 



Dark-gray and greenish shales with thin sandstone beds above 200 



Coarse-grained cross-bedded buff to brown, massive sandstone 30 



The distribution of the Deadwood formation in central Wyoming has recently 

 been described by Darton ^*** as follows : 



General relations. — ^The sandstone of the Deadwood formation is at the base of the sedimen- 

 tary series in northern and central Wyoming. It thins out to the southeast and apparently 

 ceases at no great distance east of longitude 107°, so that in Converse, Albany, and Laramie 

 counties the Carboniferous rocks lie directly on pre-Cambrian granites and schists. In the 

 Shirley Hills a hard, massive sandstone and conglomerate underlying Madison limestone may 

 be Deadwood. On the West Fork of Troublesome Creek, 9 miles northwest of Difficulty post 

 office and about Leo, this sandstone, 30 feet or more thick, is hard and in part conglomeratic. 

 Near North Platte River, north of the mouth of the Medicine Bow, it is about 100 feet thick. 

 Whether in these areas it is a shore deposit of Madison age or the Deadwood formation was 

 not ascertained. In the basal sandstone in the gorge of North Platte River, 3 miles northeast 

 of Pathfinder, Mr. Walcott found a few fragmentary fossils which he regards as Cambrian. 



