WILLIAM B. DWIGHT. 209 
Wappinger creek, from the main valley road, near 
schoolhouse No. 12, a few rods southeast of the latter 
building, makes a sharp turn to che north as it crosses 
the summit of the limestone ridge, here quite low. Ex- 
actly at this turn, both in the road itself and in the 
fields of Mr. Paul Flagler’s farm, on either side, the 
rock, consisting of calcareous shales, passing into com- 
pact arenaceous limestone, yields excellent Potsdam 
fossils. So far as examined, these consist of Lingu- 
lepis pinniformis, and an undescribed brachiopod. 
No trilobites have as yet been found here. These 
primordial strata evidently continue for over half a 
mile to the northward, exposed in ledges along the 
higher parts of the ridge. They are then mostly con- 
cealed under drift, but they reappear in a narrow layer 
of shales, yielding Lingulepis pinniformis, lying at 
the eastern base of the bold precipice of Trenton and 
Calciferous (7) limestones at the southern end of Wal- 
lace’s quarry. These potsdam layers are two or three 
rods west of the farmhouse occupied by Mr. Tabor at 
the point where the road suddenly turns east to cross 
the Wappinger creek. This fact adds a complication to 
the already difficult problem of the stratigraphy in the 
neighborhood of this most interesting quarry. 
It is now my impression that there is a considerable 
breadth of outcrop of primordial strata between Salt 
Point and Pleasant Valley ; at the same time it must be 
noted that there is abundant evidence by fossils of the 
presence of a considerable ampunt also of the higher 
limestones of this vicinity. 
It remains now to note the discovery of primordial 
strata of yet lower horizon than the Potsdam. During 
the last week of October, and the first week of Novem- 
ber, 1886, Mr. Charles D. Walcott, of the United States 
geological survey, and the writer, made several joint 
trips of observation to various points of interest in the 
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