CORALLINE LIMESTONE. 321 



CORALLINE LIMESTONE OF SCHOHARIE AND THE BASE OF THE HELDERBERG. 



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. Vantjsem), a character which is here 

 very conspicuous, and pervading the entire rock, but which is also 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 



