Graytolites in the base of the Lower Silurian. 345 



There is little doubt but that Schmidt's Zones, 1, 2, 3 are the 

 equivalents of all the North American rocks from the base of the 

 Chazy limestone to the top of the Hudson River. Schmidt, Eich- 

 wald and others have lately greatly added to the number of species 

 in these rocks. In the lists of fossils given by Schmidt in the 

 work cited there are thirty-one species recognized as occurring in 

 the Lower Silurian of America from the Chazy upwards. None 

 of them occur below the Yaginatenkalk in Russia, and none of 

 them below the Chazy in America. In Ehstland the Cystidean 

 Sphceronites Leuchtenhergii or >S^. pomum occurs in (1). JEcM- 

 nosjjhcerites aurantium in (1), and E. aranea in (1). These 

 represent the American Chazy genera Mahcystites and Palceocys- 

 tites. The genus Bolhoporites is confined to (1) in Ehstland and 

 to the Chazy in Canada. The genus Illcenus is most abundant 

 in both countries in the same formations. Of the two Russian 

 species of Madurea, one is found in (1) and the other in (2, a). 

 UccuUomphalus Scoticus OQGurs in (1), snadE. septiferus in (l,a) 



The Orthoceratites, with large lateral siphuncles, also abound 

 more in the base of the Russian limestones than in the upper 

 strata. Taking all these facts together it seems highly probable 

 that Schmidt's No. 1 represents the Chazy and Black River of 

 North America. 



The " Chloritische Kalk," or Chloritic limestone, seems to 

 represent the Calciferous sandrock in part. This rock consists 

 of a calcareous sandstone, with green grains and small globular 



