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NEW YORK STATE MUSEUM 



molds and casts. Such material formed the basis of the list of 

 species given by Clarke in his description of the section along 

 the West Shore tracks near Port Ewen station [1900, p. 73]. 



A certain superficial resemblance exists between the Port 

 Ewen and the New Scotland beds, and as this resemblance may 

 lead, and indeed has led, to confusion on the part of students 

 and others who make hurried visits to the region, it may be 

 well to describe some of the characters by which the two forma- 

 tions may be distinguished. 



The New Scotland beds are alternating series of bands of shale 

 and limestone, with lines or seams of nodular chert in the lower 

 portion, and the entire series is replete with organic remains. 

 The basal New Scotland is a shaly, blue gray limestone, abound- 

 ing in the shells of Gypidula gal eat a. The upper portion 

 of the New Scotland gradually changes from a dark gray shaly 

 limestone to a bluish gray limestone, and finally merges into the 

 heavy beds of the Becra ft through gradual increase in the thick- 

 ness of the purer limestone seams and a corresponding diminu- 

 tion of the shale content of the mass. The Port Ewen beds, on 

 the other hand, commence with an impure limestone, without 

 chert, little different from the upper part of the Becra ft, which 

 by increase in frequency and thickness of the undulating seams 

 of yellowish shaly material, and corresponding loss or diminu- 

 tion of the lime seams, assumes within 20 feet above the top of 

 the Becraft the typical character of the Port p]wen beds. This 

 typical character is that of massive dark gray, impure limestone 

 that weathers brown and that contains lines of nodules of purer 

 limestone which form cavities in the weathered rock surfaces. 

 Toward the top of the Port Ewen beds the rock changes from 

 the even grained dark limestone, which persists through a thick- 

 ness of about 100 feet, and seams of black chert become intereal- 

 cated in the layers of limestone. These chert layers increase in 

 thickness, the limestone diminishes in thickness, and finally lay- 

 ers of pebbles appear to indicate the proximity of the overlying 

 Oriskany sandstone. The chert layers, aggregating 11 feet. 3 

 inches, in the Port Ewen section, and of slightly greater thick- 

 ness toward the south near Whiteport, seem to mark the upper 

 pari of* Ihe Port Ewen beds at all points where this formation 



