Il8 NEW YORK STATE MUSEUM 



Ulrich^- has placed it above the typical Chazy and below the Low- 

 ville and Raymond^^ has correlated it with the Upper Chazy. The 

 zone of Corynoides gracilis may then correspond to the Lowville 

 and Leray periods. The later distinction of the Canajoharie and 

 Snake Hill shales (see below, p. 122) has made it, at any rate, quite 

 certain that all the Normanskill shale belongs below the Trenton. 



Deep Kill Shale 



In 1902 the writer^* described the graptolite shales of Beekraan- 

 town age which he had discovered along Deep kill in Rensselaer 

 county, N. Y., as the Deep Kill shale. These were divided into the 

 following zones in descending order : 



c Zone of Diplograptus dentatus and Cryptograptus antennarius. 



b Zone of Didymograptus bifidus and Phyllograptus anna. 



a Tetragraptus-zone. 



In the correlation table (op. cit., p. 575) these zones were corre- 

 lated with the Main Point Levis and Levis zones of Gurley and 

 the St Anne zone of Lapworth, all in Quebec; the lower and upper 

 Tetragraptus zones and Ellergill beds of Great Britain; and the 

 Tetragraptus shale and the zones with Phyllograptus typus and 

 Didymograptus bifidus, and that of Glossograptus and Didymo- 

 graptus geminus in Sweden. 



Schaghticoke Shale 



In 1903, the presence of the zone of Dictyonema flabelHforme in 

 the shale belt of New York was announced,^^ the beds being desig- 

 nated as Schaghticoke beds. The Zone of Dictyonema flabelHforme 

 has a wide extension in northern Europe, notably Great Britain, 

 Scandinavia and the Baltic provinces of Russia. It was there cur- 

 rently considered as marking the closing stage of the Cambrian, 

 and this view was adopted by the writer. In the shale belt of New 

 York it is the lowest graptolite horizon observable and the Schagh- 

 ticoke beds rest directly upon the lower Cambrian. The occurrence, 

 in the absence of other fossils, afifords therefore no direct evidence 



" E. O. Ulrich, Revision of the Palaeozic Systems. Bui. Geol. Soc. of 

 America, 22: 512. 1911. 



^ Percy E. Raymond, Expedition to the Baltic Provinces of Russia and 

 Scandinavia, pt i. The correlation of the Ordovician strata of the Baltic 

 basin with those of eastern North America. Bui. Mus. Comparative Zool., 

 Harvard College, 56: 237. 1916. 



" R. Ruedemann, Graptolite Facies of the Beekmantown Formation in 

 Rensselaer County, N. Y., N. Y. State Mus. Bui. 52, 1902. 



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

 New York, N. Y. State Mus. Bui. 69, 1903. 



