﻿C. D. Walcott — Cambrian System of North America. 147 



Classification of North American Cambrian Rocks. 



UPPER CAMBRIAN. 



Lower Calcifer- 

 ous. 



Potsdam, 

 Knox, 

 Tonto. 



MIDDLE CAMBRIAX. 



LOWER CAMBRIAN. 



Georgia. 



L'Anse au Loup, 



Prospect. 



Lower portion of the Calciferous formation of 

 New York and Canada. Lower Magnesian 

 of Wisconsin, Missouri, etc. 



Potsdam of New York, Canada, "Wisconsin, 

 Texas, Wyoming, Montana and Nevada: 

 Tonto of Arizona; Knox Shales of Ten- 

 nessee, Georgia and Alabama. The Ala- 

 bama section may extend down into the 

 Middle Cambrian. 



St. John, 

 Braintree, 

 Newfoundland, 

 Wasatch. 

 Tennessee. 



Georgia formation of Vermont, Canada and 

 New York. 



Limestones of L'Anse au Loup, Labrador. 



Lower part of Cambrian section of Eureka, 

 and Highland Range, Nevada. Upper por- 

 tion of Wasatch Cambrian section, Utah. 



Paradoxides beds of Braintree, Mass., St. 



John, New Brunswick, St. John's area of 



Newfoundland, Lower portion of Wasatch 



section, Utah. 

 jThe Ocoee conglomerate and slates of East 



Tennessee are doubtfully included. 



Survey of Newfoundland for 1865, published in 1866, by Sir 

 William LogaD, and based largelv on the paleontological work 

 of Mr. E. Billings. 



Fauna of the Cambrian System. 



As has long been well known, the Trilobita form by far the 

 largest portion of the Cambrian fauna. Of the ninety-two 

 genera and three hundred and ninety-three species known to 

 me at present from the American Cambrian, 31 genera and 226 

 species are placed under the Trilobita, and 61 genera and 167 

 species under all the other classes. The Brachiopoda come 

 next with 15 genera and 67 species ; Crustacea with 10 genera 

 and 15 species, etc. 



In the accompanying table a summary is given of the Cam- 

 brian faunas of North America, as far as known to me, up to 

 the present date. A critical study of the Upper Cambrian 

 faunas will eliminate some of the genera and species and, also, 

 add others. The study of the Lower Cambrian fauna of New 

 Brunswick is now being carried forward by Mr. Gr. F. Matthew, 

 and that of the Upper Cambrian by myself ; and probably 

 within two years the Cambrian fauna of North America will 

 include more than 100 genera and 400 species, as to-day there 

 are 92 genera and 393 species published, that I have included 

 in the fauna. There are a number of genera and species not 

 included that do not appear to be based on organic remains, or 

 are synonyms of some of those that are included. 

 Am. Jouk. Scl— Third Series, Vol. XXXII, No. 188.— August, 1886. 

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