EEIE 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 Erie 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, bowever, 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 are even 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 bave 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 discov- 

 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 Obio — one at Delaware, 

 near the base of the Huron shale, and named after its discoverer, Dinich- 

 thys Hertzeri ; 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 .palaeontological 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 Group. — 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 



