162 NEW YORK STATE MUSEUM 



some more marked differences in the fossils of their lower, middle, 

 and higher portions, on account of which they have been separ- 

 ated and described under the successive divisions of the Mar- 

 cellus, Hamilton, Genesee, Portage, Chemung and Catskill. 



Hamilton group 



The Hamilton group, named from its exposure at Hamilton, 

 Madison county, consists of the following sub-divisions. 



Group Stage 



f Genesee 

 I Tnlly 



Hamilton l ( ^ 08C0W shale 



' Hamilton \ Encrinal limestone 



Marcellus 



Ludlow ville shale 



Marcellus Shale 



The lowest division, resting immediately on the Upper 

 Helderberg limestone, was named from the village of Marcellus, 

 near which it is well exposed. It is a mass of dark, fissile, short- 

 fractured shale, one or two hundred feet in thickness, in most 

 places containing layers of impure limestone and rounded con- 

 cretions of similar material in its lower part. 



At the village of Stafford in Genesee county, a thin limestone 

 is well exposed about 40 feet above the base of the Marcellus. 

 It has been called by Prof. J. M. Clarke, the Stafford Limestone, 

 and extends from central New York to Lake Erie. 



In Onondaga county the Goniatite limestone replaces the Staf- 

 ford limestone. 



These shales closely resemble those of the coal formation 

 and sometimes contain thin seams of coaly or bituminous 

 matter, which have misled many persons to spend consider- 

 able sums in digging and boring in them, with the illfounded 

 expectation of finding useful layers of coal. This is an idle hope: 

 for they lie thousands of feet below the Carboniferous system, 

 beneath which no valuable coal strata have ever been found. 



