CORALLINE LIMESTONE. 
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CORALLINE LIMESTONE OF SCHOHARIE AND THE BASE OF THE IIELDERBERG. 
In the neighborhood of Schoharie, and extending along the base of the Helderberg mountains 
and along the Hudson river, there is a thin mass of limestone, characterized by an immense 
number of corals, chiefly favosites, and which forms a band so distinct from any other limestone 
that it has been for many years known by this name. Besides the corals, it contains other 
fossils peculiar to it, and which in some localities are sufficiently characteristic in the absence 
of corals. 
In its western extension, this limestone can be traced as far as Herkimer county; but being 
only a few feet thick, its continuity further westward has not been ascertained in a satisfactory 
manner. 
This limestone, at Schoharie, rests upon a green shale, which appears to be the only repre¬ 
sentative of the various masses of which the Clinton group, in its full development, is composed; 
and in its farther extension ^westward, it is clearly traced above that group of rocks. At 
Schoharie, and elsewhere, it is succeeded by a shaly ash or drab-colored limestone, which I 
regard as the Onondaga-salt group, but which has thinned out to a very insignificant mass 
of fifteen or twenty feet thick. 
Both the coralline and the drab-colored limestone, which is nearly destitute of fossils, have 
been included with the tentaculite limestone above, as the “ Water-lime group ; though the 
fossils of the upper and lower members are entirely dissimilar, and the few known in the 
central portion are unlike either. 
I believe it can be conclusively shown that this coralline limestone is no other than the 
Niagara limestone, and indeed representing the entire Niagara group. In the first place, it holds 
the same position, being above the Clinton group and below the Onondaga-salt group. The 
Niagara group can be traced continuously from the western line of the State to Oneida county, 
where it has become very thin, and contains but a few fossils. The limestone has become 
entirely concretionary or brecciated (as shown by Mr. Yanuxem), a character which is here 
very conspicuous, and pervading the entire rock, but which is Slso a feature at the west 
where the mass is thicker. Over a part of Oneida county and the western part of Herkimer, 
there is a space where no representative of the Niagara group has been traced continuously; 
not that the place where it should occur has been examined, and it found to be wanting, but 
because there are no good exposures of the strata which enable one to examine and determine 
satisfactorily the presence or absence of a thin bed like this one. In tracing the same line 
eastward, however, into Herkimer county, there is a thin mass of limestone holding the same 
place, but more closely united perhaps with the drab limestone above, which is the thinned 
Onondaga-salt group. Here it has been united with the Water-lime group as elsewhere, though 
really without sufficient reason. In Herkimer county it contains numerous: corals, among 
which is Catenipora escharoides, a coral that*has never been seen above the Niagara group 
