ERIE COUNTY. 189 
shale designated by the first Geological Board as ‘‘the black slate,” and 
of which the outcrop forms a belt which extends entirely across the 
State, from Hrie to Scioto county. This is the shale which forms the 
banks of the Huron river at Monroeville and below. It is not here a homo- 
geneous black shale, as there are some gray, argillaceous layers inter- 
stratified with the more carbonaceous portions. The greater part of it 
is, however, black, and highly bituminous, containing ten per cent. or 
more of combustible matter. From this bitumen, by slow spontaneous 
distillation, petroleum is evolved, and flows out in oil springs at a great 
number of localities. The process of distillation also gives rise to the 
gaseous hydro-carbons, and gas springs areeven more abundant than oil 
springs over the outcrop of this formation. 
The Huron shale in some places contains many concretions of impure 
limestone, of which hundreds may be seen at Monroeville, where they 
have washed out of the river banks. These concretions are sometimes 
almost absolutely spherical; and because of their geometric regularity 
they have been collected as objects of curiosity by the inhabitants of the 
vicinity—often serving as ornamental caps to gate-posts, etc. Some of 
these concretions contain the bones or teeth of huge fishes, first discoy- 
ered in the same formation at Delaware by Mr. Hertzer, and, from its 
formidable character, called Dinichthys (terrible fish). 
_ Two species of this genus have been found in Ohio—one at Delaware, 
near the base of the Huron shale, and named after its discoverer, Dinich- 
thys Hertzert ; the other from the summit of the formation in Sheffield, 
Lorain county, and this I have named Dinichthys Terrelli, to commemorate 
the services rendered to science by Mr. Jay Terrell, to whose zeal and 
intelligence we owe all the best specimens yet obtained. Both these re- 
markable fishes will be found described in the paleontological portion of 
this report. Numerous fragments of the great bones of Dinichthys have 
been broken out of the concretions which have fallen from the shale 
banks of Huron river, but the specimens yet obtained from these are too 
imperfect to show to which species they belong. Little effort has been 
made to collect at this point, and it is probable that careful search would 
be rewarded by the discovery of some specimens of great interest. 
As nearly as we can determine, the thickness of the Huron shale in 
this part of the State is about three hundred feet. 
Hamilton Grouwp.—At Prout’s Station and Deep Cut, on the Sandusky, 
Mansfield and Newark Railroad, the base of the Huron shale is exposed, 
and beneath it are seen layers of light, cherty, and bluish, marly lime- 
stone, which are the representatives of the Hamilton group of New York. 
Here the formation has become insignificant in dimensions, compared 
