62 NEW YORK STATE MUSEUM 



In 1880 Professor Dwight^ added to the above from the Roch- 

 dale locality: a number of cyathophylloid corals, among them 

 Petraia corniculum, a head of Echinoencrinites 

 anatiformis, and the caudal shield! of a trilobite identified as 

 Illaenus crassicauda. The C. tenuissima was 

 identified as in part at least, Strom atopora com pacta 

 Billings (Chaetetes compacta Dawson) . This fossil is 

 now recognized as Solenopora compacta. 



The Trenton also occurs at Pleasant Valley in the railroad cut 

 just east of the Central New England station on the old Pough- 

 keepsie and Eastern road. The Trenton beds here have yielded 

 Tetradium cellulosum and great numbers of entomostraca 

 and fragments of small trilobites.^ The characteristic Trenton con- 

 glomerate carrying Solenopora compacta occurs at the 

 northeast end of the cut. The Trenton apparently has an extension 

 eastward in the village. The conglomerate carrying fossils was 

 noted by the writer at the hose house. 



It is quite probable that other Trenton localities in later years 

 were noted by Professor Dwight which were never published. 



Petrography and further description. Beds from this strip, 

 which have been referred to the Potsdam, vary from argillaceous to 

 arenaceous limestones with occasional shaly layers. It is not pos- 

 sible to say much about the extent of the P^otsdam along this strip 

 to the south. It may occur at many places for which, however, there 

 is at present no paleontologic evidence. The structural features 

 suggest that it is probably confined to the northern and central por- 

 tions of the strip and that the beds at the south are probably younger 

 The shaly limestones in the quarry west of the tunnel at New 

 Hamburg have been thought to be of Potsdam age on stratigraphic 

 grounds. 



The Beekmantown (Calciferous) of this strip is best studied at 

 its type locality at Rochdale. It is often, if not characteristically, 

 arenaceous and varies in color from a bluish gray to a gray with 

 lighter chamois-colored layers which weather very white. The two 

 are interstratified, though the writer's observations indicate that the 

 bluish beds are usually near the eastern margin and therefore in 

 the upper layers. The bluish beds carry grayish wavy markings and 

 are very tough and splmtery, breaking with conchoidal fracture. 



1 Amer. Jour. Sci., v. 19, January 1S80. 



2 (W B. Dwight) J. M. Clarke. Guide to the FossiHferous Rocks of 

 New York State. N. Y. State Museum Handbook 15. 



