6o6 NORTH AMERICAN INDEX FOSSILS. 



4. Paradoxides lamellatus zone. 

 3. Protolenus zone. 



Lower Cambric. 



2. Etcheminian-Holmia broggeri zone (including the 



Smith Point limestones and shales). 

 I. Coldbrookian. 



SUBFORMATION. 



Precambric formations. 



Zones 3 to 12 inclusive, together with some of the succeeding 

 Ordovicic bed, were grouped by Canadian geologists as the St. 

 John Formation. On lithologic grounds Matthew divided this into 

 Div. I, or Acadian (zones 3 to 6 inclusive), Div. 2, Johannian 

 (zones 7 to 8 inclusive), and Div. 3, Bretonian (zones 9 to 12 

 inclusive), and the overlying basal Ordovicic. 



In eastern Massachusetts the lower Cambric is represented by 

 the Nahant limestones and argillites, the Weymouth shales, and 

 the North Attleboro limestones. All of these carry the Holmia 

 fauna and are of Etcheminian age. The middle Cambric is repre- 

 sented by the Braintree phyllites, with Paradoxides harlani, rep- 

 resenting zone 5 of the Atlantic series. Upper Cambric rocks are 

 known in eastern Massachusetts only from boulders. 



The Pacific province has as a subprovince the Appalachian belt, 

 which extends from the Gulf to Labrador. Its faunas were dis- 

 tinct, throughout earl} md middle Cambric time, from those of the 

 Atlantic province, but became confluent with them in late Neo- 

 Cambric time. 



Only lower Cambric strata are so far known from the northern 

 part of the Appalachian area. Here the base of the series is 

 formed by the Vermont quartsite, succeeded by the Stockhridge 

 dolomites. These include the Georgia shales in the type section at 

 Georgia, Franklin County, Vermont, and the Troy limestones and 

 Washington County shales in eastern New York. In southeastern 

 New York the Wappinger limestone carries lower middle and upper 

 Cambric fossils and extends into the base of the Ordovicic. On 

 the western border of the Appalachian trough in the Adirondack 

 region, the Potsdam sandstone alone represents the Cambric. It 

 is the highest Cambric zone, equivalent according to Matthew to 



