954 NEW YORK STATE MUSEUM 



typus and Tetragraptus serra, to the Beekmantown, 

 the Gape Rosier Dictyonema sociale zone should, in 

 our opinion, on the evidence adduced above from northern 

 Europe and specially in view of the fact that in the St John 

 basin it is found in the same beds with Cambric trilobites, be 

 retained in the Cambric system. Dr Ells correlated this zone 

 with divisions 2 and 3; as division 2 however contains Lower 

 Cambric fossils, the Dictyonema zone should be expected at a 

 much higher level, and we surmise that, if it is ever found in the 

 Quebec region or Cape Rouge section, it will appear in the 

 lower or middle part of division 4, or just below the line, where 

 Walcott would terminate the Cambric system. 



We have already stated in the report on the Levis beds of the 

 slate belt that Professor Dale 1 recognized the presence of a 

 terrane (horizon F) of ca, 85 feet of " gray, calcareous or very 

 quartzose, finely bedded shales or black shales, with thin lime- 

 stone beds", which he referred to the Beekmantown. Dr Gurley 

 identified in the suite of fossils submitted to him for this ter- 

 rane, Bryograptus, Dichograptus, Callograptus salteri? 

 cf . Dendrograptus sp. and Dictyonema flabelli- 

 forme. In regard to this fauna it is said : " Several of these 

 are regarded as probably of Calciferous age, which would place 

 the horizon in the lowest part of the Ordovician. The European 

 species of Bryograptus come from the Upper Cambrian. 

 Dictyonema ranges from the Ordovician into the Devonian." 

 The cited list of determinations gives us the impression that 

 Gurley had before him fragmentary representatives of both the 

 Cambric Dictyonemia and Lower Siluric Phyllograptus zones. 

 There is no doubt that, with his thorough knowledge of the 

 graptolites, Dr Gurley would not have failed to recognize the 

 zones mentioned, if such complete collections as the writer has, 

 had been at his disposal. But any one who is at all acquainted 

 with the slate region of Vermont and eastern New York, knows 

 the extreme difficulty of securing anything but fragmentary col- 

 lections in the intricately folded and mostly strongly cleaved 

 beds. Exceptionally fortunate circumstances are necessary to 

 permit the collection of superior material. 



U. S. Geol. Sur. 19th An. Rep't 1899. p. 185. 



