ERIE COUNTY. 193 
Of Macropetalichthys the only portion yet found is the cranium. This 
is composed of a number of geometrical plates of which the external 
surface is beautifully tubercled. It is known to most of the quarrymen, 
and by them it is generally regarded as the carapace of a turtle. It is, 
however, in fact, the cranium of a large fish, as any one will plainly see 
if they will take the trouble to compare with it the cranium of our 
common sturgeon. No teeth have been found connected with the cranial 
bones of Macropetalichthys, though many heads apparently complete have 
been discovered. J have, therefore, been led to conclude that, like the 
sturgeon, this fish was toothless. 
Onychodus was an equally large fish, of which the cranial bones were 
much more numerous and easily separated, so that they are generally 
found detached and scattered through the rock. The jaws of this fish 
are not unfrequently met with. They are a foot or more in length, and 
are studded with teeth along the upper margin. The most singular fea- 
ture in the structure of this fish is formed by a crest of seven large, 
curved, pointed teeth, which, attached to an arch of bone, were inserted 
between the extremities of the under jaw, apparently acting like the 
prow of aram. These teeth are quite abundant in the Sandusky lime- 
stone, the smaller and more curved ones somewhat resembling the claw 
of some of the cat tribe, a resemblance which suggested the name I have 
given to the genus—claw-tooth. 
Oriskany Sandstone.—Beneath the Corniferous limestone, on the Penin- 
sula, and near Castalia, a thin band of sandstone is visible. This holds 
the position of the Oriskany sandstone in New York, and though it has 
here yielded no Oriskany fossils, they are said to have been obtained 
from it in Indiana; and there is little doubt, therefore, that it should be 
regarded as the equivalent of the Oriskany sandstone. 
Waterlime.—The upper portion of the Silurian system is, in Ohio, rep- 
resented by the Waterlime and Salina formations. Of these, the Water- 
lime is the uppermost and by far the most conspicuous. It underlies a 
larger portion of Ohio than any other formation except the Coal Meas- 
ures. It composes all of Catawba Island, Put-in-Bay, and the other 
islands of that group. LHrie county just reaches the edge of the Water- 
lime area, and, as has been mentioned, it is in this rock that the subter- 
ranean channel is excavated through which flows the stream of water 
that forms Castalia Spring. 
The Waterlime group is probably about one hundred feet in thickness. 
The upper portion is a nearly pure dolomite, the lower an argillaceous 
limestone, some of which is well adapted to the manufacture of hydraulic: 
lime. 
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