Review of the New York Geological Reports. 57 
coon Creek, where it is quarried for millstones and sold under the 
name of the Racoon Creek burr; they are however, for the most 
part, too soft, owing to the presence of calcareous matter. ‘This 
is, very likely, the western equivalent of the porous part of the 
Schoharie grit. 
- Onondaga Limestone.-—Though not exceeding ten or fourteen 
feet in thickness, this rock is wonderfully persistant. In conse- 
quence of the absence of the strata which intervene between it 
and the Onondaga salt group, through a great part of Western 
New York, this limestone often rests on the impure hmestone, 
the terminal mass of the salt group, with sometimes a few inches 
of sandstone, or a band of non-fossiliferous bluish grey limestone 
intervening. 
The Onondaga limestone is, for the most part, a pure calcare- 
ous rock, with thin partings of greenish shale between the beds, 
often made up of the fragments of Crinoidea and. corals, partic- 
ularly species belonging to the genera Cyathophyllum and Fa- 
vosites. "These are not unfrequently of a pink or reddish color, 
which gives the rock a pretty variegated appearance, and renders 
it well suited for a marble. ‘When thinly laminated by these 
seams of shale, and the surface covered with encrinital columns 
and plates, as it usually is,” Hau informs us, “the rock bears 
most striking resemblance to the Wenlock limestone of England, 
as seen in some specimens from Wenlock which were presented 
by Mr. Lyexz. So complete is the resemblance in some instan- 
ces, that one might almost be mistaken for the other. . Judging, 
however, from the general character of specimens and the de- 
scription of Mr. Murcuitson, there is a greater amount of shale 
intermixed with _ Wenlock limestone, than with our rocks at 
the same peri 
“The ieee or even identity of specimens from Dudley i in 
England with those from the Niagara group, has been remarked ; 
if this inference be correct, of which there seems no doubt, then 
. We find a wide separation here between rocks which in England 
constitute one group. That such is the fact appears plain; for 
there are many fossils of the limestones above the salt group, 
which are identical with the Wenlock formation, while the iden- 
tity of so many species of the Niagara group leaves no doubt of 
perfect correspondence. We are therefore to look upon the salt 
group as a formation, on this continent, eetieng in at a period du- i. ; 
Seconp Series, Vol. 1, No. 1.—Jan. 1846. 
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