6io NORTH AMERICAN INDEX FOSSILS. 



SUBFORMATION. 



Pre-Cambric crystallines. 



The Madison sandstone and Mendota beds of Wisconsin are cor- 

 related by Winchell with the Jordan and the Saint Lawrence beds 

 respectively, the former carrying Dikellocephalus osceola and the 

 latter D. minnesotensis. The Franconia is correlated by Hall and 

 Sardeson with the Potsdam of New York. 



In the Black Hills and the Front Range region, the Palaeozoic 

 begins with Upper Cambric Deadwood sandstone, where not over- 

 lapped by later formations. West of the Front Range, the forma- 

 tion is known as the Sawatch quartzite. It carries a Dikellocepha- 

 lus fauna. 



In Montana and the Canadian extension, only Middle Cambric 

 deposits occur, the lower being overlapped and the upper (if de- 

 posited) removed by post-Cambric erosion. The basal bed is the 

 Flat-head quartzite, succeeded by the Gallatin limestone, the two 

 together constituting the Barker series} 



The entire Cambric series is well developed in Nevada, Utah, 

 Idaho and the Canadian Rockies.^ 



The section in the Canadian Rockies, with thicknesses, mostly 

 at Mt. Bosworth is as follows : 



SUPERFORMATION. 



Lower Ordovicic Hmestones. 



Upper Cambric. 



10. Sherbrooke formation Ij375 ft. 



9. Paget formation 360 ft. 



8. Bosworth formation ij855 ft. 



Middle Cambric. 



7. Eldon formation 2,728 ft. 



6. Stephen formation 640 ft. 



5. Cathedral formation 1,595-1,800 ft. 



5 Little Belt Mt. Folio. 



® Walcott, " Nomenclature of Some Cambrian Cordilleran Formations," Smith- 

 sonian Miscellaneous Collection, Vol. 53, No, 1809; "Cambrian Sections of the 

 Cordilleran Area," ihid., Vol. 53, No. 1812. 



