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of division between the two being sufficiently marked. The shale of 
this group frequently alternates with thin layers of sandstone, and from 
slaty becomes more compact. The whole mass consists of alternations 
of slaty and compact shale, with an argillaceous sandstone in layers 
from an inch to eight inches thick. The surfaces of the sandstone lay- 
ers are frequently covered with fucoides, but in Seneca county the most 
abundant remains are fragments of terrestrial vegetables, which in some 
cases are so numerous as to cover the surfaces of the thin strata. Some 
of these fragments are several feet long and half a foot wide, present- 
ing externally the vegetable structure, while the interior is changed to 
coal. These seams of coal are from a quarter of an inch to one or two 
inches in thickness. Their occurrence has frequently induced explora- 
tions for coal, on the supposition that the thin seams were leaders which 
communicated with extensive beds of that mineral. It is needless to 
say that there is no foundation for such belief, all the carbonaceous mat- 
ter being derived from detached fragments of vegetables deposited with 
the sediment forming the rocks, and in no case presenting evidence of 
any large accumulations of the same material. 
About four miles south of Lodi village an excavation for coal has 
been made in the mass. The principal inducement in this case appears 
to have been pyrites and the sulphurous odor of the water, which is 
covered with a film so common in water flowing through pyritous or 
other rocks. Petroleum also occurred in globules on the lower surfaces 
of the slaty layers, which circumstance was considered by an " old mi- 
ner," who directed the excavation, as a sure indication of coal. When 
I saw the place the original excavation was filled with dirty water, and 
the shales thrown out were nearly dissolved into soil. 
Some tolerable flag stones are obtained from this group in the town of 
Lodi, and Mr. Wycko{F has used the same in the construction of a mill 
at Lodi falls. 
A portion of this group is characterized by certain fossils, some of 
which differ from any above or below; these fossils are a large Ortho- 
cera, Cyrtoceras, Lingula, Posidonia, and a peculiar grooved or ribbed 
shell, either Avicula or Pterinea. 
This group is exposed in many of the ravines south of Lodi village, 
on the Seneca lake shore, and also in the same latitude on the Cayuga 
shore, in the south part of Covert, and in the ravines extending towards 
the middle of the county. The group is also well developed a short 
distance south of the county line at Goodwin's falls, as will be mention- 
