490 NEW YORK STATE MUSEUM 



For English as well as American geologists, therefore, the Swedish beds, 

 which are found in undisturbed or slightly altered position, must remain the 

 standards of succession. 



The identity of a considerable number of forms from the Arenig beds of 

 the Lake district in north England and of Wales Avith species described by 

 Hall from the Quebec beds, and of English Llandeilo graptolites mth those 

 of the Normanskill fauna, was early recognized, and these American terranes, 

 accordingly, roughly correlated with English formations. 



Kegarding the succession of the minor divisions of the known graptolite 

 terranes of eastern North America there prevailed, however, in consequence of 

 their disturbed position, certain wrong conceptions ; and these, having received 

 Hall's authoritative confirmation, enjoyed for a long time an unhesitating 

 acceptance. One of these was the placing of the " Hudson river shales " as a 

 mass with their Normanskill and other faunas in the uppermost Lower Siluric, 

 above the Utica shales. 



When Lapworth [1886] was given an opportunity to study a collection 

 from various localities in Canada, he recognized in them the Cambric Dictyo- 

 neraa zone, the Phyllograptus anna zone, the Normanskill zone and 

 the Utica zone, and by reference to the succession of the zones in Europe he 

 asserted that the Phyllograptus zone must correspond to a part of the lowest 

 Lower Siluric, and the Normanskill zone should be placed provisionally 

 between the Chazy and Trenton, at any rate below the Utica. Ami [1890] 

 inclined to a similar correlation of the Normanskill shale on account of its 

 association with rocks of apparently Lower Trenton aspect in the Quebec 

 fault block; and Gurley, after an investigation of the North American 

 graptolites, concluded that "the vertical succession of the American graptolites 

 represents a complete parallel to the range in other countries." 



The present writer has shown [!.901] that in the so called "Hudson river 

 shales " of the neighborhood of Albany there can be discerned a number of 

 faunal zones, running parallel to the strike of the beds, from which the 

 succession, in ascending order, of the Normanskill fauna, the Utica and 

 Lorraine faunas ^vith several transitional f annul es can be established [see 



