FISHES OF THE CARBONIFEROUS SYSTEM, 127 
a general though gentle dip toward the east, rising westward to the great 
arch of the Cincinnati axis. From Cleveland to Berea this rise is quite 
conspicuous, and in the early days of our geological explorations it was 
supposed to continue toward the west. Later, however, it was found that 
a broad arch was formed in the vicinity of Berea, and thence westward the 
Waverly series dipped rapidly down to the valleys of Black River and the 
Vermilion. This dip misled us, and the thinning of the Erie shale, bringing 
the Cleveland down near to the Huron, caused these two to be confounded, 
and led to the supposition that the fish-bearing black shales which form the 
lake shore in Lorain County were the upper part of the Huron; hence all 
the great Placoderms discovered by Mr. Terrell were at first referred to that 
‘formation. his matter was, however, cleared up by an excursion made by 
the writer westward from Cleveland in 1886, and it is now definitely estab- 
lished that all the outcrops of black shale in Cuyahoga and Lorain Counties 
belong to the Cleveland shale, and that none of the fossil fishes described 
from northern Ohio should be credited to the Huron. 
From the Cleveland shale we have now obtained the remains of more 
than twenty species of fossil fishes, some of which in magnitude and interest 
surpass any others known. This has rendered the determination of its 
precise geological age a matter of special importance. In the reports of 
the Geological Survey of Ohio it was made a part of the Waverly series 
chiefly on the testimony of Mr. Andrew Sherwood, one of my assistants, 
who brought to me fragments of an earthy limestone which he claimed to 
have found in the valley of Tinker’s Creek, near Bedford, Ohio, ‘beneath 
the Cleveland shale.” These specimens contained numerous Waverly fossils, 
among which Syringothyris typus was conspicuous. Subsequently, when a 
question was raised in regard to the accuracy of these observations, efforts 
made to rediscover the stratum of limestone reported by Mr. Sherwood were 
without success, and we are compelled to depend for the time being upon 
other evidence as to the age of the deposit. 
As a general rule the Cleveland shale is very barren of fossils, many 
of its exposures having yielded nothing but the imprints of sea-weeds. 
Aside from the great fishes which are its characteristic fossils, and which, 
being all new species, do not decide this question, we have not a great array 
