28 NEW YORK STATE MUSEUM 



supported by accumulative evidence — where one has to deal with faunas 

 of obviously world-wide distribution. This does not exclude that there 

 existed slight provincial differences between these pelagic faunas of the 

 oceanic basins — a fact which we have already emphasized in the discussion 

 of the distribution of the Deepkill graptolite faunas — and a possible 

 concomitant exchange of forms that originated in the different basins. 



The Normanskill graptolite shales of the Appalachian geosyncline and 

 those of the basins of Arkansas, Indian Territory and of the Rocky moun- 

 tain region are separated by the vast expanse of synchronous Trenton lime- 

 stones extending across the intervening area. The Normanskill shale and 

 the Trenton limestone not only approach so closely along the Quebec 

 barrier as to come practically into contact, but they seem actually to 

 overlap each other at times as indicated by the occurrence of Trenton 

 conglomerate on Rysedorph hill and by certain observations of the writer 

 in Saratoga and Washington counties. It would then seem that the 

 Normanskill graptolite fauna of the Levis channel would have had, at least 

 occasionally, ample opportunity to spread westward across the barrier and 

 it should be expected, in traces at least, in the Trenton limestone. 



The Trenton limestone has furnished the following faunule : 



i Dictyonema neenah Hall 4 Diplograptus amplexicaulis ( Hall) 



2 Dictyonema canadensis (Whiteaves) 5 Climacograptus typicalis Hall 



3 Thamnograptus affinis Whiteaves 



Of these the first two are forms not represented in the Normanskill 

 shale, the first is from the "Trenton limestone" of Wisconsin, the second, 

 third and fifth are from the Galena-Trenton limestones of the Lake \\ inni- 

 peg region which according to Whiteaves [1897, p. 135] "most probably 

 represent the whole of the Utica and Trenton formations, inclusive of the 

 Galena." This would explain the appearance of C 1 i m a c g r a p t u s 

 typicalis in the list. The Trenton limestone of New , \ ork has fur- 

 nished the single species of D i p 1 o g r a p t u s a m p 1 e x i c au 1 i s which 

 occurs quite frequently in certain layers of the middle and upper Trenton 

 at Trenton Falls and Middleville and is characteristic of a /one that is 



