94 NEW YORK STATE MUSEUM 





Hudson past Albany and Cohoes on to the Saratoga and Schuyler- 

 ville quadrangles. 



The formation was first distinguished by the writer from the 

 " Hudson River formation " in the neighborhood of Albany (1901) 

 and partly referred to as middle Trenton shale and partly as Utica 

 shale and later correlated with the Magog shale of Canada. 

 Mainly on account of the large and distinguishing faunas obtained 

 around Albany, Green Island and Cohoes, and especially at Snake 

 hill on the shore of Saratoga lake, the formation has recently 

 (1912) been considered as a separate formation by the writer and 

 named the Snake Hill beds from the most fossiliferous outcrop. 



Lithologically, the formation is similar to the Normanskill beds, 

 but it lacks the strong development of the grits and white beds 

 as distinct divisions, though both are present in thinner intercala- 

 tions. Besides it possesses a conglomerate with characters peculiar 

 to itself. The preponderating portions of the formation, however, 

 are dark gray to black, bluish and greenish gray argillaceous shales 

 which are difficult of separation from the Normanskill shales, save 

 by the inclosed faunas. 



The argillaceous shales prevail so much in the Snake Hill forma- 

 tion that we have not observed in the belt in Albany county any 

 grits .and are aware of only one outcrop there with cherty-looking 

 silicious shales. Also on the Schuylerville quadrangle the con- 

 glomerate, the grit and the cherty beds have been observed each 

 only in a couple of outcrops, the rest all being soft shale. Thus, 

 the large area in the northeast corner of the sheet, north of Moses 

 kill, which has a rocky surface throughout, consists entirely of 

 shale. The uniform composition of the formation of shale is also 

 well shown in the new barge canal about Fort Miller, where half a 

 mile of rock exposure exhibits nothing but dark gray shales. 



Black, carbonaceous, graptolitiferous bands or seams are more 

 frequently found than in the Normanskill shale, but they contain 

 a much impoverished graptolite fauna as compared with that of 

 the Normanskill formation. On the other hand, small lamelli- 

 branchs, gastropods, brachiopods and trilobites are frequently seen 

 in the shale, while but traces of such have as yet been observed in 

 the Normanskill shale. 



The dark shales contain not infrequently thin, sandy bands and 

 still oftener intercalations of sandy limestones and also gray crystal- 

 line limestone, reaching half a foot in thickness. These bands fre- 

 quently contain a faunule of brachiopods, crinoid joints, etc., and 



