LOWER SILURIC SHALES OF THE MOHAWK VALLEY 45 



Eusarcus triangulatus C. & R. (r) 



Dolichopterus frankfortensis C. & R. (c) 



Hughmilleria magna C. & R. (c) 



Pterygotus prolificus C. & R. (c) 



In following the dip of the rocks, a long series of outcrops were 

 found beginning at Duanesburg, about ten miles west-southwest 

 from Schenectady, and extending about four miles along the rail- 

 road to Delanson. The dip is too small to measure accurately, dif- 

 ferent measurements giving from i° to 2°, but it is safe to assume 

 that these outcrops which are halfway between the lower beds at 

 Schenectady and the top of the formation at the Helderbergs are 

 1000 feet above the base. 



In a bluestone quarry just above the station at Duanesburg about 

 40 feet of thicker and thinner, partly coarser sandstone beds with 

 intercalated gray, argillaceous and often also arenaceous shales are 

 exposed. The sandstone beds are distinctly lenticular, rapidly thin- 

 ning out and swelling up in the quarry face and carrying numerous 

 mud pebbles near their surfaces. The shaly layers show fine cases 

 of mud-flow and the whole character of the beds indicates a rather 

 shallow, current or wave-swept sea. The shale seams are profusely 

 filled with seaweeds and fragments of eurypterids. 



The following species were obtained: 



Sphenophycus latifolius (Hall) (cc) 



Climacograptus bicornis Hall (r) 

 Camarotoechia sp. fragments 



DoHchopterus frankfortensis Clarke & Rued. . (c) 



Eusarcus triangulatus C. & R. (c) 



Stylonurus ? limbatus C. & R. (r) 



Hughmilleria magna C. & R. (c) 



Pterygotus prolificus C. & R. (c) 



P. Pnasutus C. & R. (r) 



The beds can be followed along the Schenectady branch of the 

 Delaware & Hudson Railroad in a continuous exposure to Delanson, 

 without any change in lithic or faunal character. Following then 

 the southwest dip no outcrops are met with until the Schoharie 

 valley is reached, where a number of small exposures are observed 

 in the river bank above Schoharie Junction. These represent the 

 uppermost portion of the Schenectady beds and can not be more 

 than 300 feet below the top, or the boundary with the Brayman 

 shales in the hills to the east and west of the valley. The beds are 

 still the same alternating thick impure sandstones and dark gray to 



