32$ 
I Assembly 
to the force which produced the undulations, the upper part slipped over 
the lower, and at this point partook of the elevation south; while the 
lower was affected only by the uplifting to the north. The point of the 
greatest depression is a short distance south of this locality. In this 
quarry was found the only specimen yet seen of a fern of the genus 
Sphenopteris; and through the liberality of Mr. Sexton, to whom I am 
farther indebted, I am enabled to place this specimen in the collection 
of the State. With the exception of the curved fragments of Fucoides, 
the upper part of this group is nearly destitute of fossils. 
Chemung group. The tops of the hills and high grounds in the towns 
of Erin, Veteran, and Catlin, display a group of rocks and fossils very 
distinct from those last described. The essential difference is the litho- 
logical characters of the sandstone of this group in the absence of argil- 
laceous matter in most of the layers, these being nearly a pure siliceous 
rock, harsh to the touch, and generally of a porous texture; while still 
a large proportion of the mass consists of compact shales and argillace- 
ous sandstones of a softer texture than those below. The surface of the 
sandstone layers is rough, while those below are smooth and glossy, and 
being never rippled, prove that the rocks were deposited in a quiet sea. 
A great variety of beautiful and characteristic fossils occur in the 
sandstone as well as the shale; many different from those of the group 
below, while several species exist in both. The principal ones are a 
species of Delthyris, the shell on each side extending into a wing, 
(D. Alata?) a Leptaena, Orthis, and a species of Avicula or Pterinea, 
ribbed like the common Pecten; besides several others of genera and 
species not before seen in the upper rocks. 
The most northern extension of this group appears on the top of Buck 
mountain, near Millport, and on the high ground farther west; whence 
it is traced in the same direction to the valley of Port creek, on the 
western boundary of the county. The same rocks are found on the 
hills in Erin, and loose masses from above are scattered through all the 
low grounds hence to the Chemung river. 
At about the latitude of Horseheads, in the northern part of the towns 
of Elmira, and Bigflatts, this lower portion of the Chemung group ap- 
proaches nearly to the level of the valley. At Mayber's quarry, a mile 
and a half east of Horseheads, the rocks are quarried for the sandstone 
which is used for flagging, step stones, &c. These layers are highly si- 
liceous and compact; and sometimes contain a few fossils. They al- 
ternate with thick masses of shale; often several layers of the former 
