C. D. Walaott — The Taconi'c System of Emmons. 399 



should refer to the data given in that Bulletin, and decide indi- 

 vidually upon the value of the correlations made in the table. 





Lower 

 Calciferous. 



Lower portion of the Calciferous formation of New 

 York and Canada. Lower Magnesian of Wis- 

 consin, Missouri, etc. 



Upper 

 Cambrian. 



Potsdam. 

 Knox. 

 Tonto. 



Potsdam of New York, Canada, Wisconsin, Texas, 

 Wyoming, Montana and Nevada; Tonto of Ari- 

 zona ; Knox Shales of Tennessee, Georgia and 

 Alabama. The Alabama section may extend 

 down into the Middle Cambrian. 



Middle 

 Cambrian. 



Georgia. 



L'Anse au 

 Loup. 



Prospect. 



Georgia and " Granular Quartz" formations of Ver- 

 mont, Canada, New York and Massachusetts. 



Limestones of L'Anse au Loup, Labrador. 



Lower part of Cambrian section of Eureka and 

 Highland Range. Nevada. Upper portion of 

 Big Cottonwood Canon Cambrian section. Utah. 



Lower 

 Cambrian. 



St. John. 

 Braintree. 

 Newfound- 

 land. 

 Uinta ? 



Paradoxides beds of Braintree, Mass., St. John, 

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

 land ; Lower portion of Big Cottonwood Canon 

 Cambrian section, Utah. Uinta? (The Ocoee 

 conglomerate and slates of East Tennessee are 

 doubtfully included.) 



Description of the Map and Section. 



The map shows the geographic distribution of the strata re- 

 ferred to the " Ta conic System " in eastern New York and 

 western Vermont, Massachusetts and Connecticut. The data 

 for it are taken from the Geological map of Vermont and New 

 Hampshire, by Professor C H. Hitchcock, 1877 (Geol. North- 

 ern New England) ; the maps published by Professor Dana, 

 on the geology of the region studied by him in western Massa- 

 chusetts and Connecticut, and eastern New York ; and the map 

 of southwestern Vermont, published by Professor Dana on the 

 result of Rev. A. Wing's field studies (Am. Jour. Sci., 3d 

 ser., vol. xiii, 1877); and for Washington and Rensselaer 

 Counties, N. Y., as mapped from field work done by myself 

 in 1886-87. 



The line of contact of the Cambrian and pre-Cambrian rocks 

 on the east, in Vermont, is tentative, as it is known to be in- 

 correct in details ; the data for correcting it have not been ob- 

 tained. 



Certain changes in the identification of the strata, as com- 

 pared with the older maps, have been rendered necessary by 

 the correlations made in this paper ; and the shales, in the 

 vicinity of the limestones south of the Rensselaer county line, 

 have not been colored, as it is yet undetermined whether they 

 belong to the Hudson or Cambrian Terrane. The shales im- 

 mediately beneath the limestone (3) are shown as a distinct 



