REPORT OF THE STATE PALEONTOLOGIST I903 349 



dictya frondosa and is designated as the Ptilodictya 

 frondosa zone. This hmestone by reason of its distinctive 

 lithologic and faunal features can not be confused with any other 

 bed. No outcrop of this rock has been observed in New York. 



5 Decker Ferry. The 15 feet of limestones and shales lying 

 above the red crystalline limestone have no characteristic fossil 

 to mark it as a distinct zone. Rhynchonella? lamellata 

 occurs abundantly, but this fossil has a considerable vertical range 

 and in some sections extends up into the Rondout. This zone may 

 be regarded as transitional into the Cobleskill limestone. Its 

 stratigraphic position is that of the lower cement bed of the 

 Rondout section, but in the Nearpass section there are no cement 

 beds. 



6 Cobleskill formation. Six feet of limestone characterized by an 

 abundance of corals, such as Prismatophyllum ine- 

 q u a 1 i s Hall, Halysites catenulatus Linne. This zone 

 by reason of similarity in lithologic features and fossil con- 

 tents may be definitely correlated with the Cobleskill limestone 

 of Schoharie county v^here it is typically developed, with a thick- 

 ness of 6 feet. 



7 Cobleskill formation? Above the 6 feet of limestone desig- 

 nated the Cobleskill there are 4 feet of limestone in thin beds 

 separated by shaly layers. Though containing Cobleskill fossils, 

 the abundance of ostracodes present indicates a change in the 

 nature of sedimentation, due perhaps to the introduction of brackish 

 water conditions which lasted throughout Rondout time. 



8 Rondout formation. Above the Cobleskill limestone in the 

 Nearpass quarry section there are 39 feet of shales and lime- 

 stones. In general lithologic features this formation resembles 

 the Rondout as developed in New York State, but the cement 

 bed so characteristic at the base of the formation farther north 

 is absent here. With the exception of several species of Leper- 

 ditia, fossils are extremely rare. Future studies may show that 

 the 4 feet of limestones and shales at the base of this formation 

 and which have been provisionally included with the Cobleskill 

 belong to the Rondout. 



