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I Assembly 
occor in short , interiiipted layers that are localj being subordinates of 
the slaty shale rocks which commence from the Seneca limestone. This 
limestone I did not see at Auburn j the alluvial and Tillage covering 
the space between the cornitiferous and the black slaty shale or pyriti- 
ferous slate.-' 
The Seneca limestone^ I first met with in Seneca county; it is there 
separate from all other masses of limestonej and could be confounded 
with no other; hence its name. 
This limestone contains but few species of fossil shells^ one of which 
I have only seen in this rock. Another^ the Strophomena lineata, 1 dc 
not remember to have met w^ith in any rocks belowj and is highly 
characteristic of this limestone^ for though it is found in the shales, 
which are several hundred feet above it, yet it rarely occurs in any oi 
the limestones; and in some localities of the Seneca, the individuals are 
so numerous as to present almost as much shell as stone. 
We have now, in this report, and in the one of last year, noticed in brief 
the whole of the groups and roc c masses, great and small, which occui 
geologically betw^een the gneiss of Little-Falls and the upper layers oi 
the great east and west limestone range of of .Nev/-York, and in the or- 
der in which they follow or rest upon each other — the order of their 
age. The thickness of the whole, taking the measure of each rock and 
group where its thickness is greatest, exceeds 2,000 feet. All the dif- 
ferent groups, containing organic remains, are readily identified by them, 
causing no difficulty to those acquainted with the fossils in assigning 
each group, rock or specimen containing them, to the place which it 
holds in the series. 
Of the rocks to be noticed, there remains from 12 to 3500 feet before 
completing the whole of the series of the Third District. All which 
are anterior in origin to the coal. We had intended to have given the 
different groups into which this great mass is divided, from observations 
made with Mr. Hall, along the line of Cayuga lake to Pennsylvania: 
but the length to which this report extends, leaves but a few pages for 
the products which belong to the northern section of the counties, and 
therefore must be left for the subsequent one. 
The Seneca limestone, in many of its localities, is of so dark a colour 
from carbonaceous matter as to be almost black, which is the case with 
the mass below it, but not in so great a degree. So great is the quan- 
tity of carbonaceous or coaly matter which colours the slaty shale, or 
the " pyritiferous slate" which rests upon the Seneca limestone, that it 
