Limestone Belts of Westchester County, N.Y. ~ 4655 
of the thick covering of Triassic, east of Ramapo, and beyond in 
the large limestone area of Pepack. These “ magnesian lime- 
stones” have not yet afforded fossils, but their Lower Silurian 
age is unquestioned. 
New Jersey thus throws light upon Westchester rocks as 
well as those of Dutchess County; and, in fact, into all Green 
Mountain geology, for these New York and New Jersey beds 
are but western and southwestern prolongations from the 
Green Mountain region. 
CONCLUSIONS. 
From the distributional, stratigraphic and paleontological 
facts which have been presented the conclusion appears to fol- 
low that— 
The limestone of Westchester County and New York Island 
and the conformably associated metamorphic rocks are of Lower 
Silurian age. 
Should it be made certain that all the magnesian limestone 
of the New Jersey Lower Silurian is Calciferous, there will be 
some reason for the inference that the limestone of West- 
chester County, since it is magnesian, is Calciferous or of the 
earlier part of the Lower Silurian. The schists may be either 
earlier or later than the limestone. 
Finally, in view of all the facts from the length and breadth 
of the Green Mountain region which are brought out in this 
and previous papers, comes the broader conclusion : 
The limestone and the conformably associated rocks of the Green 
Mountain region from Vermont to New York Island are of Lower 
Silurian age. 
e evidence which has been adduced, though then but 
partly discerned, led Professors W. B. and H. D. Rogers and 
Professor W. W. Mather, forty years since,* nearly to the re- 
sult here reached. The discoveries of fossils, together with 
Lower Silurian. ine. 
It remains to add a few words on the origin of the rocks of 
the “ Cortlandt Series.” 
* Professors Rogers, Amer. Phil. Soc., Jan. 1, 1841, and this Jour., iv, 1872, p. 
363; Mather, Rep. Geol. N. York, 4to, 1842, pp. 438, 464, 628, and this Jour., 
xvii, 388, 1879. 
