8 Hall oa the Strata and Organic Remains. 
that State, is scarcely foünd to the west of the Genesee River. 
In Ohio, Indiana, and even in the "Territory of Iowa, on the 
west side of the Mississippi River, this fossil abounds, but often 
so associated with calcareous strata as apparently to be a fossil 
of the next group; and I am by no means quite satisfied that 
it does not ascend into the Niagara Limestone. This fact 
proves conclusively that the Pentamerus oblongus lived in 
great numbers in the central part of New York, while over an 
immense area, between this point and the western part of Ohio 
and the Peninsula of Upper Canada, it did not exist. At the - 
same time fragments of Crinoidea, apparently identical with 
those of the Clinton Group in New York, occur in various 
places in Ohio and in the same position. 
The Niagara Group consists of a shale and limestone, and is 
one of the most interesting groups in the State of New York. 
The shale is highly fossiliferous, containing corals, crinoidea, 
shells and trilobites, while the limestone abounds in corals, 
almost to the exclusion of all other forms. | 
This group, at the west, appears asa great mass of limestone, - 
the shale, so characteristic of itin New York, having entirely — 
disappeared. The fossils of the limestone at the west are also - 
corals, with few of any other character. The fossils of the shale | 
are consequently absent over all the great tract of country occu- - 
pied by the States of Ohio, Indiana, Kentucky, Illinois, Wis- 
consin and Iowa. 3 
There is here evidence of a vast augmentation of calcare- - 
ous matter in a westerly direction ; for this group, which, in - 
the centre of New York, is but a Pus feet in thickness, gradu- - 
ally increases in that direction until, at Niagara Falls, it is about - 
two hundred and fifty feet, including the shale ; while a at the * 
west it has acquired a. thickness little less than one thot : 
feet. Sam it will also be remembered, is mally limestones, 
Adis ditio k may require qualification, for I have recently seen es 
Crinoidean from E Ee is known in New York only in the — he 
; NM Group. June 3d : 
