1847.] SHARPE ON THE PALZOZOIC ROCKS OF N. AMERICA, 151 
ceding ; but they are seldom found in a condition which admits of 
their being identified. 
3. Chazy Limestone, Bird’s-eye Limestone and Black-river 
Limestone. 
Mr. Hall enumerates 77 species of organic remains from these 
beds, of which the most remarkable are the Orthocerata in the 
Black-river limestone, which are sometimes above ten feet long. I 
have seen no specimens of European species, but Mr. Hall gives 
three :— 
Illeenus crassicauda ? Lituites convolvens, Hisinger. 
Columnaria alveolata, Goldf. 
4. Trenton Limestone. 
Utica Slate. Blue Limestone of Ohio. 
Hudson River group. 
These beds furnish an abundant and interesting supply of fossils, 
and usually in a condition in which they can be studied with great 
advantage. We here begin to find many species which are common 
in Europe, where they characterize the middle part of our Lower 
Silurian formation, thus giving us the first good term of comparison 
with the American beds. In Mr. Lyell’s collection I have found the 
following European species, and it is probable that a larger collection 
would supply more, as the American authors give long lists of British 
species from those beds :— 
Leptena alternata. Spirifer biforatus. 
depressa. Terebratula bidentata. 
—— imbrex. reticularis ? 
sericea, Strophomena grandis. 
Orthis parva. Bellerophon bilobatus. 
testudinaria. Porcellia ornata. 
5. Grey Sandstone. 
Oneida Conglomerate. 
Medina Sandstone. 
Clinton Group. 
Also part of the Cliff Limestone of Ohio. 
The organic remains in the sandstones are few, and I have not 
recognized any European species among them. The Clinton group 
is rich in fossils, but unfortunately Mr. Lyell’s cabinet is poorly 
supplied with them. I have only been able to identify Pentamerus 
oblongus in the Clinton group, and Pentamerus levis in the Cliff 
limestone: these are regarded in America as one species, but they 
are clearly distinct. In Mr. Hall’s Report the following are added 
from the Clinton group :— 
Atrypa hemispheerica. Leptzna depressa. 
—— aflinis. Spirifer radiatus. 
Both in fossils and mineral character the Clinton group forms a 
passage between the Lower Silurian sandstones below it and the lime- 
stone series above it: the latter is clearly referable to the epoch of our 
