906 WAPPINGER LIMESTONES AND ASSOCIATE STRATA. 
however, equally tenable on the supposition of a solid 
globe. Unequal contraction of such a globe cannot fail 
to produce displacement and fracture. 
DECEMBER 15, 1886.—FIFTIETH REGULAR MEETING. 
William G. Stevenson, M. D., chairman, presiding. 
The following paper was read : 
PRIMORDIAL ROCKS OF THE WAPPINGER VALLEY LIME- 
STONES AND ASSOCIATE STRATA. 
BY PROF. WILLIAM B. DWIGHT. 
In a paper read before the Section last spring (see 
page 130 of this vol.), a description was given of Pots- 
dam strata discovered early in 1885 on the farm of Mr. 
A. K. Smiley near the driving-park. 
The lack, at that time, of sufficiently extended paleon- 
tological evidence, left it very uncertain what propor- 
tion of the width of the western of the three parallel 
limestone belts might be primordial, and what portion 
might be occupied with the higher limestone strata of 
the vicinity. The only evidence on this point was the 
presence of a narrow strip of fossiliferous Trenton along 
the extreme eastern margin, at R. J. Kimlin’s farm. 
As the result of continued field-work, it is now in my 
power to present very material and important additions 
to our knowledge of the primordial rocks in Dutchess 
county. 
I may describe first the points of information gained 
with reference to the above mentioned western belt lying 
south of the driving park. A ledge of Potsdam, con- 
taining a few specimens of Lingulepis pinniformis, has 
been found on R. J. Kimlin’s farm. It is a few rods 
east of the road, and a little north of his barn. It is 
thus near the eastern margin of the belt, and only a 
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