Limestone Belts of Westchester Co., New York. 451 
hem. 
Now, to the north in the western half of Vermont, where 
these limestones and schists are least crystalline, they have 
afforded many fossils, including Corals, Crinoids, Brachiopods, 
Gasteropods and Trilobites, of Trenton, Quebec and Calciferous 
age, so many kinds and under forms so little disguised by 
metamorphism that the Lower Silurian age of the limestone 
and of the associated schists is placed beyond reasonable ques- 
tion.+ Again, along what may be called the middle of the 
range, in its western half over Dutchess County, where again 
the limestones and schists are least crystalline, that is, least 
altered, the limestones have afforded, at various points between 
Poughkeepsie and the Taconic range, numerous Trenton and 
Caleiferous fossils—Corals, Crinoids, Brachiopods, Gasteropods, 
Orthocerata, Receptaculites and Trilobites ;{ and, besides, the 
associated schists of Poughkeepsie have yielded several species 
of Hudson River Brachiopods;§$ so that a Lower Silurian age 
for the limestones and schists has become a certainty. In addi- 
tion to the facts already. published I have learned from Profes- 
sor W. B. Dwight, in a letter dated October 26th, of his recent 
discovery of fossils (Orthis testudinaria, O. pectinella, Cheetetes 
compacta, crinoidal columns, ete.) in the Wappinger valley lime- 
stone three miles directly south of Vassar College. 
* Percival’s limestone areas often embrace, as has been explained, large areas 
of comformable schist (all that are contained within the outer limits of the lime- 
stone); and in the Ridgefield part of the map the positions of the areas, as a 
bese lly fail to indicated. are similar itions of 
schist in his broad Canaan area; but these follow the line of strike of the area, 
other season; and, at the same time, to attempt to map the Archeea’ 
n W. exists 
in isolated areas to the south of Canaan, and is the occasion of the abnormally 
in the vicinity of Danbury and Ridgefield. 
7 
curving co sin 
+ This Journal, TI, xiii, 332, 1877. eA 
Dana, ibid., xvii, 378; W. B. Dwight, ibid., xvii, 393, xviii, 50, 1879. 
elson Dale, ibid., xvii, 57, January, 1879.—It cannot be inferred from 
T. Ni | , 
these fossils from the vicinity of Poughkeepsie that the hydromica and mica schists 
or slates of Dutchess County, or even the argillyte-like kinds, are wholly of the 
Hudson River group; on the contrary, part may be Primordial. 
