No. 200.J 
299 
A few miles east of Rochester, we find the Pentamerus, which was 
there confined to a stratum of one foot in the lower bed of limestone, 
distributed through several feet of thickness in the limestone, above the 
upper green shale. At the Shakers' mill, in Wayne county, we find 
this fossil distributed through twelve feet in thickness of rock. This 
rock, w^hich is almost destitute of fossils at Rochester, fifteen miles far- 
ther east contains Pentamerus, Catenipora, Tubipora, Encrinites, &c. — 
The Pentamerus of the lower stratum disappears before coming to the 
Niagara river. 
The lower green shale contains but few fossils, while in the upper 
green shale we have Agnostis, Calymene, Asaphus, Producta, Orthis, &c. 
About six feet from the upper surface of this shale, we have a thin stra- 
tum, sometimes dividing into two or three, which consist almost wholly 
of fossil shells of a single species. These fossils have a beautiful pear- 
ly or testaceous lustre. 
SECTION III. 
Jlrgillaceous Iron Ore. 
The stratum of Argillaceous iron ore, mentioned in connexion with 
the rocks just described, consists of distinct concretions or flattened 
grains, having a laminated structure. Its colour is reddish brown, it has 
an unctuous feel, leaving a stain upon the fingers. In some localities, 
the mass of the ore is composed of fragments of encrinital columns, and 
other corallines, with Producta, Catenipora, &c. Many of these frag- 
ments are changed into the substance of the ore, and others still remain 
carbonate of lime. The latter mineral in seams and thin layers is of 
frequent occurrence in the ore. The ore contains sufficient argillaceous 
and calcareous matter to act as a flux, but the cinder is too fluid unless 
loam or some other earth is mixed with it. 
This stratum of ore has been described as extending from near Little- 
Falls, to thirty miles beyond the Niagara river. I have not, however, 
been able to find it between the Genesee and Niagara rivers, and I am 
quite confident that it does not exist within this limit, unless it may be 
for a short distance west of the Genesee, where the rocks are covered 
by the superficial soil. Its width, too, which has been stated at twenty 
miles, is very erroneous, it being merely the outcropping of the stratum 
where it comes to the surface. At Rochester, this stratum of ore is about 
one foot thick; fifteen miles farther east it is three feet thick, and where 
it has been worked in Wayne county it has the same thickness. This 
stratum, like the shale below, thins out west of the Genesee, and like 
that, may perhaps be found again west of the Niagara river. 
