196 NEW YORK STATE MUSEUM 



the name of Poughquag quartzite. This name, originally sug- 

 gested by Dana, was adopted in the New York city folio as a 

 substitute for the name Lowerre previously used by the writer 

 and for the name Cheshire which had been, for some time, used 

 in New England as a designation for this basal deposit. One of 

 the reasons for this substitution was, that in the railroad cut 

 southeast of Poughquag station, a Lower Cambrian fossil, 

 HyoUthes sp. was found in the quartzite by Professor Dale and 

 collections of it were made there hj the man who acted as 

 collector for Professor Dale. The name Poughquag has, there- 

 fore, a chronologic value as a designation for this formation 

 because this locality has yielded Lower Cambrian fossils while 

 at Cheshire Mass., no organic forms have jet been discovered. 



The geologic structure in this area is not complex and the 

 relations of the formations are clearly suggested by the map. 

 The long contact of schist and gneiss was regarded by Professor 

 Dale as a fault line but careful study of the region by the writer 

 leads him to the opinion that it is more probably a case of overlap. 



Professor Dale's party made no special study of the gneiss and 

 schist and detailed petrographic examinations of these rocks in 

 this district have not yet been made. The latter is a fine grained, 

 hydromica schist and, at a point one half mile east of the con- 

 tact, contains a considerable percentage of carbon in the form of 

 graphite. The Precambrian gneiss in this region has some dis- 

 tinctive characters which are described as follows : 



During the past 20 years the writer has been occupied, in the 

 intervals of other work, with the study of the crystalline rocks 

 of southeastern New York. The first task^ accomplished was 

 the differentiation of the principal members of the crystalline 

 area and the determination of the structural relations of the 

 quartzose and micaceous rocks to the great crystalline limestone 

 which for many years was the only member accurately differ- 

 entiated. With the identification of the Hudson schist and 

 Poughquag quartzite came the recognition below the limestone of 



^Am. Jonr. Sci. 3. 39:383-92. 



