1847.] SHARPE ON THE PALHOZOIC ROCKS OF N. AMERICA. 153 
mineral character, and containing so many fossil species in common, 
that they must be regarded as one group, however convenient these 
divisions may be for local examination. A large proportion of their 
shells correspond with those of our Wenlock formation, and there 
can be no doubt that they must be classed with that deposit. But 
it is not a little remarkable that we find mixed with these species of 
the Middle Silurian age some forms which we are accustomed to con- 
sider of the Devonian, or even of the carboniferous epoch: the most 
marked of these are Orthis resupinata, a small Productus and a large 
unnamed Spirifer, which if found apart from other known species 
would have been enough to have caused the beds to be classed in the 
carboniferous system. 
The species identified with ours are the following :— 
Avicula naviformis. Pentamerus galeatus. 
Atrypa tumida. Spirifer plicatus. 
didyma. Strophomena pecten, 
Leptena depressa. Terebratula borealis. 
Orthis hybrida. reticularis. 
orbicularis. Stricklandi. 
—— resupinata. ——— n. 8, found in Wenlock shale. 
9. Oriskany Sandstone. 
Cauda-galli Grit. 
Schoharie Grit. 
These beds are locally distributed ; the first, of no great thickness 
m New York, becomes of more importance in Pennsylvania and Vir- 
ginia: it is however everywhere of great moment geologically, as in 
entermg it we lose all those species which are considered here as 
peculiar to the Wenlock formation: the species which are common 
to the Oriskany sandstone and the beds below it are either carboni- 
ferous forms, or such species as have as great a range vertically. 
Mr. Hall places these beds and the limestone series next to be 
mentioned as No. 10, in the Wenlock formation, adding, however, 
that there are many reasons for classing them in the Ludlow forma- 
tion. The evidence which I have had before me does not justify 
either of these views, but leads me to class both these and the fol- 
lowing beds in the same great formation as the Hamilton and Che- 
mung groups, the whole giving us what appears to be an enormous 
development of the Devonian system ; for I cannot find im any of the 
New York beds any equivalent of the Ludlow formation of England, 
The species from the beds No. 9, identified as European, are,— 
Spirifer arenosus. Terebratula reticularis. 
— Urii. 
10. Onondaga Limestone. 
Corniferous Limestone. 
The fossils of the lower bed are mostly corals; in the apnea are 
found the following :— 
Leptzna depressa. Terebratula reticularis. 
Orthis resupinata. 
