3874 J. D. Dana—Limestone Belts of Westchester Co., N. Y. 
Annsville, by a fine-grained hydromica schist which looks as 
much like argillyte as the Dutchess County slates at Pough- 
keepsie that contain Hudson River fossils; and this argillyte- 
ike rock occurs at other points up Canopus Hollow, forming 
hills on its eastern side, and outcropping occasionally on the 
west side. Its feeble degree of crystallization corresponds 
with that of the limestone. Both rocks in this respect are like 
the rocks of Dutchess County, and unlike anything found in the 
Highland Archean. 
(3.) The limestone at the locality near Annsville lies uncon- 
formably against hornblendic Archean gneiss, its beds much 
contorted ; and another similar case of unconformability exists 
on the east border, half a mile northeast. In general, both in 
this valley and Peekskill Hollow, actual contacts are not in 
sight owing to the earth or alluvium of the valley ; and the 
upturning of the limestone and its associated schist has usually 
placed them in near conformity to the strike of the Archean 
rocks. Still, the unconformability is in some places distinct. 
Moreover the mica schist involved with the limestone in the 
case if the rocks were of the age of the Highland Archean. 
Inasmuch then as the Westchester rocks are newer than the 
Highland Archeean, the limestone belts of Canopus Hollow 
and Peekskill Hollow occupy Archean valleys—valleys that 
%3 The limestone of the small areas of the Verplanck peninsula, situated in the 
hornblendic and augite rocks, is often graphitic and more coarsely crystalline than 
t of the Point, 
