19 Hall on the Strata and Organic Remains 
ture and condition of the organic remains, that a greater depth - 
and a more quiet state of the waters prevailed in a westerly di- 
rection. The increased number of the Brachiopoda, and their 
more perfect development, are strong facts in favor of this view, 
while the great numbers of Cypricardia and Avicula in the east- 
ern part of the State, upon the sandy mud, prove a more shal- - 
low sea and greater proximity toland. In truth, the nature and - 
condition of the deposits, with all circumstances attending them, — 
alone, proves clearly the increasing depth of water and distance — 
from shore as we progress westward. The nature of the or- - 
ganic remains proves them to have been influenced both by - 
distance from shore, depth of water, and nature of the sediment. - 
With the exception of a thin bed of limestone, all the suc- - 
ceeding deposits, as far as the Old Red Sandstone, may, for the | 
present purpose, be considered as one group, which includes | 
the Genesee slate, Portage and Chemung Groups. | 
This series consists of shales and alternations of their onal : 
layers, and flagstones, with more rarely thick-bedded sand- ! 
stones. The lower portion is mostly shale, while the arenaceous 
matter increases toward the upper part. Their calcareous 
bands sometimes occur, and these are often entirely compa 
of organic remains. : 
Towards the west there isa gradual increase of shale and a 
constant diminution i in thickness of the whole mass. In the 
mostly unlike those of the group below, though several of the 
same species are known to occur. The diminution in thick 
ness, which takes place within the State of New York, is accot 
panied by a decrease in the number of fossils. 
sils is perceptible as we proceed westward, namely, the incre a 
of the forms of Brachiopoda over those of Cypricardia, Avicul 
7 fe, or the ae and Monomyaria. True it is, howevé 
Nes MP 1 
the condition of the ocean which are accor 
