Three Great Fossil Placoderms of Ohio, — Claypole. 89 
nodosodosatus, Aviculopecten carbon {ferns, Fusulina robusta, 
Archceocidaris aculeatus. 
Fossils similar to the above have been obtained from near 
the mouth of the Big Nemaha and at Hillsdale, Nebraska. 
The character of the beds and certain Brachiapoda, including 
Productus semireticulatus var. calhounianus with Meekella 
striatocostata, resemble very much the lower Permian of Elk, 
Cowley and Greenwood counties, Kansas. But at Kansas 
City, within less than 100 feet of the base of Upper Coal 
Measures, we do find certain fossils which are very much like 
some Permian fossils, as Aviculopecten and En microtis. But 
the limestones are very different in other respects. 
THE THREE GREAT FOSSIL PLACODERMS OF 
OHIO. 
By E. W. Claypole. 
The discoveries of the past few years have brought to our 
knowledge a large fish-fauna whose existence was previously 
unsuspected. The great shale-mass of Ohio has yielded little 
of interest to the early research of the palaeontologist. It was 
consequently regarded as very barren ground. So barren, 
indeed, had it been in almost all its exposures that evidence 
wits lacking to determine its precise age and position, and it 
has. therefore, been divided at various levels between the De- 
vonian and the Carboniferous systems. This great Ohio Shale. 
the marginal, or rather, the off-shore deposit of all but the 
earliest ages of the Devonian era in Ohio, crops out from 
north to south through the middle of the state, from the 
lake to the river. At its southwestern outcrop it is only from 
300 to 400 feet in thickness, but it gradually thickens south- 
ward and eastward until near lake Erie it reaches about 1,000 
feet, at Cleveland 1.801). in the Tuscarawas valley I. SOU. and 
on the river its bottom has not been reached at 2,500 feet. So 
great a mass of one material indicates a long continuance of 
almost unchanging conditions of deposit and. indeed, this 
-hale is tlie equivalent of all the sediments in Pennsylvania 
from the to]> of the Corniferous Limestone to the top of the 
< ;tt skill Sandstone, a distance, sometimes, of 7,000 or S.ono 
feet. 
