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occur in the “Black Shales” of Ohio, U.S. On looking at 
these I at once recognized them as bodies similar to those 
met with in the Rhynchonella plewrodon bed of the Forest of 
Dean. ” 
That the spores of plants occurred in the “Black Shales” 
of Ohio was first noticed by Prof. Epwarp Orton, who referred 
to them in a Paper read before the American Association for 
the Advancement of Science, in 1882. I, therefore, wrote to 
Mr Orron, who very kindly responded ‘by sending me samples 
of the material in which they occur. But before I proceed 
further I must explain the geological position of the Black 
Shales of Ohio, and they will be found to have an interesting 
relation to the beds in the Forest of Dean in which the similar 
spores can be detected. 
Above the uppermost Devonian rocks in the State of Ohio 
comes a development of Shales of very considerable extent. 
In some parts of the State these deposits are divided into two 
divisions by a greenish blue shale, known as the “ Hrie Shales.” 
To the lowest division the name “‘ Huron” has been applied, 
and to the uppermost “Cleveland.” This division appears to 
be uncertain, and towards the west the Erie Shales disappear. 
The American Geological Survey have drawn the line between 
the Devonian and Carboniferous rocks at the Erie Shales, but, 
5 owing to this shale not being constant, Professor Orron points 
q out that the line cannot be drawn, and therefore the strata 
- becomes debatable ground. 
‘Now the “Black Shales” of Ohio are in the same position 
_as the shales at Drybrook, in the Forest of Dean. The Rhyn- 
_ chonella plewrodon bed of the latter locality is no doubt of true 
_ Carboniferous age,—the occurrence of the shell which gives the 
name is sufficient to determine that point. But below come 
other shales, followed by sandy beds, which rest on the Old 
_ Red Conglomerate. 
_ The Ohio beds are important as a source of mineral oils ; 
_ they are bituminous, and contain from eight to twenty-two 
per cent. of organic matter. To account for mineral oils 
yarious theories have been advanced. The vegetable origin has 
~ ww 
