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299 
the ravines, it is removed by frosts anil rains in large quantities, and 
mingled with the soil, or carried into the bottom lands, where it ferti- 
lizes the surface. Calcareous marl and tufa are formed along the water 
courses, or where water percolates through the loose partially disinte- 
tegrating shale in banks and ravines. 
This rock contains iron pyrites in nodules and irregularly formed con- 
cretions; sometimes the pyrites has, in part, replaced or invested a fos- 
sil body; and at other times fossils are studded with minute grains, or 
points, of the same mineral. Excavations for this substance, under the 
supposition that it was silver or gold, have frequently been made in the 
lake shore where it is exposed* A locality of pyrites on the bank of 
the lake in Ovid, was known to a few individuals only, and the matter 
kept a secret for several years. Large quantities of the mineral were 
taken out, always during the night, and after obtaining sufficient, as they 
supposed, to enrich themselves, one of their number was about to be 
despatched to New- York to learn the manner of extracting the metal 
from the ore*, when their dreams of fortune were suddenly ended by 
learning that their supposed gold was a compound of sulphur and iron. 
This shale is well exhibited on the Seneca lake shore, between Hath- 
away's landing and Goft's point. Some part of the mass along this dis- 
tance is black, and at first sight might be mistaken for some of the shales 
below, but the contained fossils are always a sure guide. The rock is 
also exposed by several deep ravines, which extend from the lake along 
this distance, gradually becoming smaller, to near the centre of the 
county. On the Cayuga shore this shale is exposed from near Kidder's 
ferry to within three miles of Ithaca. 
This member of the group embraces a thin mass of black slaty shale 
which contains abundance of Orbicula, a deeply grooved species of Orthis, 
and a small Leptsena. These fossils are all confined to a few feet of 
thickness, and are rarely, if at all, seen above or below. The Orbicula 
is so abundant that in one specimen in the State collection, more than 
eighty individuals are seen in a space of less than a square foot. The 
same Orbicula with the Orthis, occur in great profusion in a shale much 
higher in the series, which will soon be described. 
This shale is so well developed, and contains the fossils, particularly 
trilobites, in such great perfection, at Moscow, Livingston county, that I 
have given it that name till a more appropriate one shall be found. This 
member terminates the group, a very marked change occurring in the 
