56 Review of the New York Geological Reports. 
of Indiana, apparently in an isolated position,* a fine grained, 
white and yellowish siliceous sandstone, evidently very similar 
to the Oriskany sandstone, and which cannot be far removed from 
the same geological horizon; yet, since this Fall Creek rock is 
particularly characterized by casts of Pleurorhyncus, (one of 
which is, probably, the ewneaius;) and postabdomens of a Caly- 
mene, that it is the western representative of the Schoharie grit. 
It is not at all improbable, however, that here are blended togeth- 
er the three adjacent sili formations of the Helderberg series, 
—the Oriskany sandstone, and overlying Cauda-galli and Scho- 
harie grits; for we find that though the upper layers in which 
the Pleurorhyncus occurs, effervesce with acids, there is beneath 
a whiter variety, of quite a different appearance, destitute of cal- 
careous matter, in which, as yet, no fossils have been observed. 
The eastern shore of Cayuga is a good locality for collecting 
the fossils of the Oriskany sandstone. 
The purer varieties of this rock are used in the manufacture of 
glass at Vernon. Some iron ore has been procured in the ferru- 
ginous layers near Perryville; but all that has hitherto been ob- 
tained, was found to be too much contaminated with sand to be 
of economical value, as is too often the case where hydrated ox- 
ide of iron has been infiltrated amongst sandstones. 
Caudi-galli Grit—This and the succeeding formation are of 
limited extent and of little importance; so that we shall pass 
them over with only a few remarks. The Caudi-galli grit is an 
argillo-calcareous sandstone, usually of a drab color or brownish 
hue, containing remarkable plumose impressions, supposed to be 
Fucoides, which have given name to the rock. 
Schoharie Grit, is a calcareous sandstone, which, when weath- 
ered, becomes porous and colored with ferruginous stains. “It 
abounds in a species of Pleurorhyncus and Orthoceras, along 
with many corals, and is well developed at Schoharie and the 
Helderberg. 
~ Besides the siliceo-calcareous, Pleurorhyncus rock above cited, 
as occurring in the middle of Indiana, there is a porous siliceous 
rock full of casts of corals found in the southern part of the same 
State, particularly near Vernon, in Jennings County, and on Ra- 
'* The extensive drift formation of this part of Indiana, renders it difficult to as- 
emam the area over which these siliceous rocks prevail. 
