GRAPTOLITES OF NEW YORK, PART _' 21 



stronger dynamic metamorphism ; all oi these; factors tending to obscure 

 the possible outcrops of the horizon. 



The presence of Normanskill shale in northern Maine has been made 

 known by Dodge [ 1 890 | and Ami has lately | 1005] announced the occur- 

 rence in New Brunswick of a graptolite faunule that belongs to this or the 

 following horizon. 



West of the regions just mentioned the Dicellograptus fauna has not 

 been observed again on this side of the Mississippi river. Its distribution 

 in eastern North America may therefore be said to be restricted entirely to 

 the Appalachian geosyncline and to some minor Atlantic embayments on the 

 northeastern edge of the continent. In the Appalachian province again it 

 is in the north strictly confined to the area which Ulrich and Schuchert 

 [1902 J have defined as the Levis channel, i. e. a narrow belt striking from 

 New Jersey northward between the Quebec barrier and the Green moun- 

 tain barrier to the St Lawrence, which it then follows to the St Lawrence 

 gulf. The fauna entered this channel from the north and advanced, 

 according to Ulrich and Schuchert, southward with the gradual submergence 

 of the Appalachian valley trough, apparently never reaching beyond the 

 present site of New Jersey. Its northeastern derivation is indicated by its 

 northward connection with a sea which, as shown by the other embayments 

 (Maine etc.), contained this fauna, by the European relations of the fauna 

 to be noted further on and the apparent southward restriction of its area. 



The provincial differentiation of the northern fauna from that of 

 Alabama would also seem to argue for an interruption of the connection in 

 the middle third of the Appalachian valley trough, the northern fauna 

 occupying the Levis channel or the northern third and the Alabama fauna 

 all or a portion of the Lenoir basin or southern third. Whether this sup- 

 posed invasion of the Dicellograptus fauna into the northern third was 

 preceded by a draining of the Levis channel at the close of the Chazy with 

 a subsequent resubmergence as Ulrich and Schuchert suggest, or whether 

 it resulted from a separation of the southern and northern basins by a 

 gradual elevation of the middle third would seem open to question. We 



