240 C. D. Walcott — The Taeonic System of Emmons. 



Geol., pt. 2, pp. 73-77, 1856). He studied the section, 

 where it is very much broken and disturbed, and found evi- 

 dence that sustained his view. If he had gone a mile to the 

 north, he might have discovered that the shales pass conform- 

 ably beneath the limestone and, also, that shales occur con- 

 formably above it. Fossils were abundant at a point one mile 

 north, northwest of Hoosick Falls, and the following species 

 were recognized : Solenopora compacta, Maclurea spJ, Litu- 

 ites sp. ? (ngs. 8 and 9), and Orthoceras sp. undet. 



On the map the localities, where fossils have been found in 

 this terrane, are indicated by the letter F. 



Resume.- — The stratigraphic and paleontologic evidence unite 

 to prove that the limestones and marbles of Terrane No. 3 are 

 the geologic equivalent of the Calciferous-Chazy- Trenton lime- 

 stones of the Champlain and Hudson valleys, and belong to 

 the system of strata characterized by the second fauna of 

 Barrande. 



Terrane No. 4. — This terrane directly overlies and rests in 

 synclinals of the limestones of Terrane No. 3, at Grayloek and 

 at other points ; and there is no apparent reason to differ from 

 Professor Dana in referring it to the Hudson Terrane. 



In regard to the graptolites found in it, near Hoosick, N. Y., 

 I wish to state that I visited that locality and collected speci- 

 mens of the flattened and distorted graptolites from the 

 smooth shales. On comparing the specimens with those of 

 Diplograp>t%is pristis, from the Hudson Terrane, at Fort 

 Edward, N. T. and, also, from the Hudson Terrane in the 

 western part of the township of Greenwich, Washington 

 County, N. Y, I fully concur with the opinion given by Pro- 

 fesssor James Hall, in 1847 (Pal. N. Y., vol. i, pp. 321,322, 

 pi. 72), that the Hoosick shale graptolite is identical with the 

 Diplograptus pristis found in the Hudson Terrane, within the 

 Hudson valley. 



Terrane No. 2. — In speaking of this terrane as the shale 

 above the quartzite of Terrane No. 1 and beneath the lime- 

 stone of Terrane No. 3, it was assumed that it represented the 

 Potsdam horizon {ante) ; and we now have to search for 

 the evidence of that horizon between the recognized Georgia 

 horizon of Terrane No. 1, and the Chazy-Trenton horizon of 

 Terrane No. 3. Unfortunately, on the east and west sides of 

 the synclinal, on the line of the section, the shales beneath the 

 limestones are unfossiliferous ; but, from the data afforded by 

 the Potsdam or Upper Cambrian strata of Saratoga, Dutchess 

 and Washington counties, N. Y., we obtain a fairly satisfactory 

 identification of the Potsdam horizon in the Taeonic area. 



In Saratoga County a section occurs where a pure limestone, 

 carrying a well-marked Potsdam fauna, rests directly on a mas- 



