ILLUSTRATIONS. 



Page. 

 Plate I. Map showing the distribution, by geologic provinces, of the Cam- 

 brian strata as shown by surface outcrops in North America 358 



II. Map to illustrate geologic provinces and relative thickness of the 

 Cambrian rocks of North America, with theoretic sections of the 



Cambrian group at the close of Cambrian time 365 



HI. Hypothetical map of the North American continent at the beginning 



of and during Lower Cambrian time 368 



Fig. 1. Typical sections of the Atlantic Coast Province 274 



2. Typical sections of the Appalachian Province 31 1 



3. Typical sections of the Rocky Mountain Province 32i) 



4. Typical sections of the Interior Continental Province 357 



5. Typical sections of the Interior Continental Province 358 



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