74 NEW YORK STATE MUSEUM 



grains. One part of the formation is characterized by a number 

 of calcareous sandstone beds % to i foot thick, which weather into 

 a characteristic chestnut-brown sandy crust. Through the contor- 

 tions of the beds these rocks are mostly broken into strings of brown 

 boulderlike blocks. 



In the river bed where the beds are seen on edge, they appear 

 as greenish gray shales with frequent black shale bands and brown 

 calcareous sandstone beds and some thicker beds of argillaceous 

 mudrock. 



These Schaghticoke shales of Schuylerville very much resemble 

 in the alternation of the greenish gray and black argillaceous shales, 

 giving the outcrops on edge a very characteristic banded appear- 

 ance, the typical Schaghticoke shale as described by the author from 

 the bed of the Hoosic river at Schaghticoke, lacking, however, the 

 intercalated thin limestone bands observed there. They are distin- 

 guished from the surrounding Normanskill shale by the absence 

 of white-weathering chert layers and the presence of the chocolate- 

 brown weathering calcareous sandstone ; but of course none of these 

 criteria is sufficient to recognize them without the fossil evidence. 

 It is for this reason that they may be outcropping in other localities 

 without having been recognized. 



When the author described the Dictyonema flabelli- 

 forme or Schaghticoke shale,^ he followed the consensus of the 

 preceding European authors who considered the shale with Dic- 

 tyonema flabelliforme as marking the top of the Cambric. 

 Since that time stratigraphers have, especially in Sweden, advanced 

 arguments for placing the Dictyonema bed at the base of the 

 Ordovicic, a proceeding which would also seem to agree well with 

 the condition in the slate belt, since the Dictyonema shale is on 

 one hand separated by a great hiatus from the underlying Georgic, 

 but on the other by its lithologic character and probably also strati- 

 graphically is closely connected with the following Deep Kill shales. 

 Lately Ulrich ^ has also argued for the close stratigraphic connec- 

 tion of the Dictyonema flabelliforme zone with the 

 Tetragraptus zone (the lowest of the Deep Kill zones), and placed 

 the Dictyonema flabelliforme zone in his Canadian 

 system (which comprises the Tribes Hill limestone and Beekman- 

 town B-E). 



1 Ruedemann, R. Cambric Dictyonema Fauna in the Slate Belt of Eastern, 

 New York. Pal. Rep't (for 1902) 1903, p. 934. 



- Ulrich, E. O. Revision of the Paleozoic Systems, pts 1-3. Geol. Soc. 

 Amer. Bui., v. 22, no. 3, p. 678. 



