C. D. Walcott — The Taconic System of Emmons. 241 



sive-bedded sandstone.* The sandstone is of Potsdam age, and 

 contains typical fossils in its extension north in the valley of 

 Lake Champlain : in Washington County I found, at Dewey's 

 Bridge, south of Whitehall, fossils in the Potsdam sandstone, 

 and at Whitehall, numerous Potsdam fossils in the limestone 

 layers resting upon the sandstone and beneath the Calciferous 

 formation. The Calciferous formation was subjacent to the 

 Chazy limestone. 



In Dutchess County Professor Dwight found the Potsdam 

 fauna in a limestone, three species of which are identical with 

 those at the Saratoga and Washington County localities. This 

 proves the presence of the Potsdam fauna in Dutchess County, 

 not far distant from the sandstone and limestone carrying the 

 Georgia fauna. Although no direct stratigraphic connection 

 is yet known at this point between the limestone carrying the 

 Potsdam fossils, and the limestone resting on the the sandstone 

 carrying the Georgia fossils, there is little doubt, from the 

 known succession of faunas elsewhere, that the Potsdam forma- 

 tion was deposited in its usual position, between the Georgia 

 and Calciferous formations, and that it has been displaced by 

 the subsequent faulting of the strata. 



In Saratoga County, the Calciferous-Trenton terranes are 

 superjacent to the Potsdam, and, also, in Dutchess and Wash- 

 ington counties. In all the sections given in Bulletin 30, IT. S. 

 Geological Survey, the Potsdam is superjacent to the Georgia 

 Terrane ; and I find that Terrane No. 5, beneath the 2,000 

 feet of greenish schistose shales of Terrane No. 2, is character- 

 ized by the Georgia or Middle Cambrian fauna. I think, then, 

 that we may conclude that Terrane No. 2 represents the Pots- 

 dam horizon : also, that the latter may be represented in part 

 by sandstone or quartzite on the west side, near the limestones, 

 or, if the same conditions prevail as in Dutchess County, the 

 lower portion of the limestone ; the shales and schists beneath 

 the limestone all belong to the Middle Cambrian. To the 

 east of the limestone, the Potsdam Terrane may be repre- 

 sented in part by either (1) the upper part of the quartz- 

 ite of Terrane No. 1, (2) the lower part of the limestone of 

 Terrane No. 3, or (3) the hydromica shale between the quartz- 

 ite and limestone, or Terrane No. 2, or by the combination of 

 two or more of these parts. 



Terrane No. 5. — In my field work of 1886- ? 87, I studied 

 with . care the slates, shales and interbedded limestones and 

 sandstones that form Terrane No. 5. On the map an inter- 

 ruption is shown midway, by the presence of a broad belt of 



* Bull. IT. S. Geol. Survey, No. 30, pp. 21, 22, 1886.— T found several species of 

 this same fauna (Dicellocephalus, Ptychaspis, etc.) in sandstone in the upper beds 

 of the Potsdam sandstone, in the vicinity of Chiteaugay Chasm, Franklin County, 

 N. V. ; also in a calciferous sandrock of the Potsdam Terrane, at Whitehall, N. Y. 



