DETAILED STRATIGRAPHIC DISTEIBUTION. 



137 



Detailed stratigraphic distribution of Cambrian and Ordovician Brachiopoda — Continued. 



Uissourl. 



Montana and Wyoming. 



The sedimentation in Montana and northwestern Wyoming exhibits so many peculiarities that correlation is 

 difficult, even between sections only a few miles apart. The Wolsey shale occupies a position immediately above a 

 sandstone in the Little Belt Mountains and is Middle Cambrian in age. It can thus be closely correlated with the 

 similarly situated Flathead shales of Peale, which are also Middle Cambrian. On Dearborn River, however, a shale 

 which occupies the same stratigraphic position [see Walcott, 1908f, pp. 202-203] carries a typical Lower Cambrian 

 fauna in its lower part and Middle Cambrian in its upper layers. The sandstone underlying the Dearborn River shale 

 horizon is Lower Cambrian in age, and that underlying Peale's Flathead shales has been found to contain a fairly well 

 developed Middle Cambrian fauna. 



The Gallatin formation of Peale has a very wide geographic distribution, and collections have been made at many 

 localities. The various horizons can not be differentiated, but the faunas show clearly that his Gallatin is in part 

 Upper Cambrian and in part Middle Cambrian. A limestone in the Phillipsburg quadrangle that is believed to be the 

 equivalent of the Yogo limestone of the Little Belt Mountains has been found to contain both Middle and Upper 

 Cambrian fossils. 



The localities (see index for numbers) give all the known data as to the stratigraphy of the different collections. 



Nevada: Barrel Spring. 



Barrel Spring section. 

 [Walcott, 1908t, pp. 188-189.] 



Localities and species in the Barrel 

 Spring section. 



Other Lower ft Cambrian localities and 

 species in Nevada and California 

 shown in their approximate strati- 

 graphic position. 



A section of Lower Cambrian strata studied by Mr. F. B. Weeks 

 near Barrel Spring, 16 miles south of the town of Silver Peak, 

 Nevada, is much like that east of Waucoba Springs, and has 

 about ttie same fauna at various horizons in it. 



LOWER CAMBRIAN. 



a It has been agreed, but too late for any other correction than the insertion of this footnote, that the " Edgewise beds" should be placed in 

 the Upper Cambrian. 



6 Three scattering localities have been identified as Middle Cambrian, and eight locahties were collected from the Emigrant formation (Upper 

 Cambrian) of Turner in the Silver Peak district. See index for locality numbers. 



