72 NEW YORK STATE MUSEUM 



bay; and likewise the top in a bed of magnesian limestone with 

 many streaks of sand grains and few fossils. Five feet of this 

 limestone are exposed in the point boundmg ^lullen bay on the 

 east. 



Black River group. ^ The Chazy is followed in the Crown 

 Point section by 5 feet of dove-colored limestone which in part 

 strikingly resembles the " Birdseye " or Lowville limestone to the 

 south and west of the Adirondack plateau and also contains the 

 characteristic vertical worm tubes (Phytopsis tubulosus 

 Hall). This bed which is exposed outside the fort at the north 

 entrance has been considered as representing the Lowville for- 

 mation in the Champlain basin. Since, however, the writer found 

 15 feet above its top, in a bed of the " Black River formation," 

 numerous typical specimens of Tetradium cellulosum- 

 which in the Black River and iMohawk regions is the most char- 

 acteristic fossil of the Lowville limestone, and as far as we know 

 is there restricted to it, it is possible that the 5 feet of dove- 

 colored limestone represent only a part of the Lowville formation 

 and that a portion or all of the " Black River " of this section is 

 equivalent to the Lowville. Indeed, it is claimed by Dr Ulrich 

 that all of the " Black River '^ limestone of the Champlain valley is 

 older than the Watertown limestone and is to be correlated with 

 the Lowville formation. Li the Westport area the dove-colored 

 limestone has not been found. 



A careful section of the " Black River " of Crown Point penin- 

 sula with fossil lists is given by Dr Raymond in the before cited 

 paper. Two zones are distinguished, one, 7 feet of lumpy, black 

 and heavy bedded limestone with a pelecypod fauna, and a 

 second, 55 feet of lighter colored rock containing a brachiopod 

 and crustacean fauna. The lower 24 feet of the latter portion are 

 coarse grained while the remainder is fine grained. The lowest 

 15 feet of these beds in this section were found by us to contain 

 chert in numerous nodules and even in continuous layers and the 

 inference itself suggests that this " Black River *' corresponds to 

 the cherty limestone or the Leroy member of the Lowville for- 

 mation. 



1 The Black River group, as now understood by this survey, comprises the 

 Lowville liroestone, the Watertown limestone (formerly the Bl?.ck River 

 limestone^and the Amsterdam limestone\. 



2 Not nsted by Raymond. There occur also in this horizon H o r m o - 

 ceras tenuifilum, Lituites and Oncoceras sp. ; also not listed in the 

 previous publications. 



