ONONDAGA LIMESTONE. 
133 
There are many fossils by which this rock is readily recognized, and are characteristic of 
it, besides the Encrinites laevis. Among them is the Elongated pentamerus (No. 1 of the 
wood-cut). This fossil is generally diffused in this rock, and so far as our knowledge of it 
extends, is confined to it. Some of the specimens show a considerable size, being about 21- 
inches in depth or thickness, and 4$ inches in length. The Undulated delthyris, which 
resembles the Thick-ribbed delthyris, is also found in it; but the ribs are not so round, and 
the surface is covered with undulations in the direction of the lines of growth, whence its 
name. It contains also the Consimilar hipparionix (No. 3 of the wood-cut), which is also 
found in several localities. It is the only rock in which the Gigantic cyathophyllum (C. 
gigantea) is found; one of which, in the State Collection, is over eight inches in length and 
two and a half in diameter. There are four other species of this genus in the collection 
from this rock; about three species of the Platyceras, three of the Platyostoma, and several 
other fossils which are new, among which is the fish-bone (No. 4 of the wood-cut). This is 
the first rock in the district, in which any thing of the kind had been seen or heard of. In 
the State Collection there is another one from the fourth district, but very imperfectly pre¬ 
served, found by Mr. Hall in the Oriskany sandstone, the lowest position in which any 
remains in the State have been discovered of an animal higher in the scale of organization 
than Crustacea, or the class to which crabs, lobsters, etc. belong. There are fish bones of 
like character in the State Collection, obtained from the next rock in succession in both dis¬ 
tricts ; all which seem to have served a common purpose, appearing to be the major spine of 
the back or dorsal fin. 
The layers and courses of this limestone, as usual with limestone rocks, are separated by 
shale, which is of a greenish color, but in small amount. It is coextensive with the rock, a 
fact of some importance in the theory or cause of the color of rocks ; for the less the crystal¬ 
line action, the more the red, black and yellow colors predominate, crystallization favoring a 
lower degree of oxidation of the metallic coloring matter. 
The Onondaga limestone, though generally nearly pure, in some localities contains nume¬ 
rous nodules of flint, and in parallel layers. Its vertical joints are very regular in two direc¬ 
tions, at nearly right angles to each other, often dividing the layers into convenient sized 
masses: direction of the joints, N. 33° to 35° E., and S. 55° to 57° E. 
It is one of the most valuable building stones in the Helderberg division. It is largely 
quarried near Syracuse for the canal, and is more or less used as a marble throughout the 
district. Its power to resist the action of air, water and frost, is shown from the fact of its 
being the bottom rock of streams which no longer exist; and it is the rock generally over 
which the water flows north, forming the falls great and small at the west end of its range, 
the most noted of which are those of Perryville and Cazenovia. 
This limestone forms a conspicuous ledge of about twelve feet thick to the right of the road 
from Fort-Plain to Cherry-Valley, the surface of the rock being uncovered for some extent. 
It continues to the village, but is concealed in part of its course by alluvion thrown up into 
low hills. It forms the surface of the valley, and is uncovered in many parts above the road 
which crosses the valley towards the lower part of the village. The north projecting end 
