58 NEW YORK STATE MUSEUM 



the Oneida conglomerate in the Frankfort section. It then is proba- 

 ble that the Frankfort shale is the source of this pyrite and that the 

 pyritiferous layer capping the Frankfort, Schenectady and Indian 

 Ladder beds is a residual clay representing the long hiatus that cor- 

 responds to the remainder of the Ordovicic and the greater part of 

 the Siluric. The thickness of the Brayman shale, its lithic character 

 and overlapping distribution argue in favor of its residual origin. 

 In that case the presence of the pyrite in both the Brayman shale 

 and the top sandstone of the Schenectady shale would lose its 

 force as a connective of the two formations and the exact age 

 determination of the shale again becomes impossible from that 

 criterion. 



But the facts remain that the Brayman shale, where it is thickest 

 and typically exposed, rests upon Schenectady beds, or beds as old 

 as the upper Trenton age and that there is apparently, as pointed 

 out by Grabau, no erosion interval observable between the top 

 sandstone of these Schenectady beds and the Brayman shale; and 

 the conclusion is hence permissible that the Brayman shale should 

 be correlated with some part of the Upper Ordovicic (i. e., the Cin- 

 cmnatian) rather than the Salina. My correspondence has shown 

 that Doctor Ulrich and the author had reached the same conclusion 

 independently at their separate visits to the Schoharie region, and 

 Doctor Ulrich has in the Revision of the Paleozoic Systems corre- 

 lated the Brayman shale with the Frankfort (title 69, plate 27). 



Snake Hill beds 



The separation of the Canajoharie beds from the Utica formation 

 necessitates the recognition and definition of a further unit in the 

 slate belt of the upper Hudson River region. A large fauna had 

 been collected from these beds by the author about the mouth of 

 the Mohawk river and published in 1901 in New York State 

 Museum Bulletin 42. The principal localities were the east and 

 north shores of Green island, Van Schaick island, Block island, 

 Mechanicville, and Brothers' quarry at Troy. On the strength of 

 these faunules the shales had been referred to the lower and middle 

 Trenton (Watervliet, Port Schuyler), Utica and Lorraine. In 

 Memoir n, page 29, this belt of shale has, ori the evidence 

 from the graptolites, been correlated with the upper Trenton and 

 the name Magog shale from the graptolite locality Magog in Quebec 

 applied to it. Investigations since carried on in this slate belt about 

 Saratoga lake have furnished a large addition to the fauna hitherto 



