6i2 NORTH AMERICAN INDEX FOSSILS. 



Dome formation 355 ft. 



Howell formation 435 ft. 



Spence formation 20 ft. 



Langston (?) 205 ft. 



Lower Cambric. 



Pioche formation 125 ft. 



Prospect Mountain formation 1,200 ft. 



Base unknown. 



In the foregoing sections, the following definite correlations are 

 made: Pioche and Mt. Whyte; Spence and Stephen; Notch Peak, 

 St. Charles and Sherhrooke. 



In central Nevada (Eureka district) the following section occurs : 



SUPERFORMATION. 



Pogonip limestones (Lower Or- 



dovicic) 3,000-5,000 ft. 



Upper Cambric. 



Lower part of Pogonip limestone. 



Dunderberg shale 350 ft. 



Middle Cambric. 



Hamburg limestone (partly per- 

 haps Upper Cambric) 1,200 ft. 



Secret Canyon shale 1,600 ft. 



Upper Eldorado limestone. 



Lower Cambric. 



Lower Eldorado limestone 3^050 ft. 



Prospect Mountain quartzite. . . . 1,500 ft. 



Base unknown. 



In west British Columbia and the Yukon Territory, the Cambric 

 appears to be represented by the Adams Lake series (25,000 ft.) 

 and the Nisconlith series (15,000 ft.) of schists, conglomerates and 

 volcanic material, and phyllites with some limestones and quartz- 

 ites. In Alaska, several more or less metamorphic series are doubt- 

 fully referred to the Cambric. These are the Birch Creek schists of 

 the middle and lower Yukon region ; the Totsen series of schists of 



