Dana, Ford, and Dwight — Fossils from the Taconic Series. 277 



II. — Emmons' Original Taconic Series. 



1. On Lower Silurian Fossils from a Limestone of the Original 



Taconic of Emmons. By J. D. Dana. 



2. Preliminary Eeport of S. W. Ford and W. B. Dwight 



upon Fossils obtained in 1885 from Metamorphic Limestones 

 of the Taconic Series of Emmons, at Canaan, New York. 

 American Journal of Science, vol. xxxi. p. 241 — 253, pi. vii. 

 April, 1886. 



PEOFESSOR DANA points out that the original and therefore 

 true Taconic system of Prof. Emmons, Which this geologist 

 propounded and described in 1842, " lies along both sides of the 

 Taconic range of mountains, whose direction is nearly north and 

 south, or, for a great distance, parallel with the boundary-line between 

 the State of New York and those of Connecticut, Massachusetts, and 

 Vermont." Emmons described it as consisting of (1) " Taconic 

 slates " in eastern New York, including the Hoosie slates ; (2) the 

 Sparry or western limestone, interstratified with the slates, west of 

 the Taconic range, and for the most part lying against the west side 

 of the range ; (3) the " talcose " or " magnesian " schist, constitut- 

 ing the Taconic range, and Greylock or Saddle Mountain, the high 

 ridge between Williamstown and Adams in the north-western angle 

 of Massachusetts ; (4) the Stockbridge Limestone, east of the range 

 of Taconic schist ; (5) Quartzite. Prof. Emmons concluded, on 

 lithological grounds, that the system was older than the New York 

 Potsdam Sandstone, and equivalent to the Lower Cambrian of Sedg- 

 wick. Subsequently, in Washington County, New York, outside the 

 typical area of the Taconic system, Emmons discovered, in black 

 slates, some Trilobites, pronounced by Barrande to be Primordial 

 species. These black shales were regarded as more recent than the 

 typical rocks, in which no fossils whatever bad been discovered, and 

 Emmons called them therefore Newer or Upper Taconic. 



But now recently fossils have been discovered in the Sparry or 

 Western Limestone, the oldest limestone of Emmons' original 

 Taconic, and in a locality in the typical area of the system. The 

 fossils are very fragmentary, and can only be examined by means of 

 thin sections and polished surfaces of the rock. They show, how- 

 ever, the presence of distinct species of Murchisonia, Pleurotomaria, 

 and Fenestella, as well as portions of Crinoids, probably of Brachio- 

 pods, and of a Trilobite. Prof. Dwight and Mr. Ford, who have 

 studied the fossils, believe that they indicate the Trenton age of the 

 limestone in which they are preserved. 



It follows from this discovery that the age of the typical Taconic 

 system of Emmons is not Cambrian or Pre-Cambrian, as stated by 

 him, and that the black shales and limestones with Primordial Trilo- 

 bites, forming his Newer or Upper Taconic system, really belong to 

 a period much older than the so-called Lower Taconic. G. J. H. 



