504 
GEOLOGY OF THE FOURTH DISTRICT. 
Further examinations brought to light the Pterinea carinata, two or more species of CyprU 
cardia, a Strophomena, Cyrtolites ornatus, and the Bellerophon bilobatus, as well as the 
abundant little shell ( Orthis testudinaria ?) Orthis striatula. The latter fossil ranges through 
the Hudson river group in New-York, as it does through the Caradoc sandstone of England. 
This association of fossils, with the peculiar aspect of the limestone, and the presence of sand¬ 
stone with fucoids, seemed indubitable proof of the position of this mass. Neither the cha¬ 
racter of the rocks, nor of the fossils, indicates the Trenton limestone to which heretofore it 
has been referred. Numerous other fossils, unknown in New-York, are found at Maysville, 
the most abundant being several species of Orthis and Delthyris. 
The cliffs of Cincinnati were next examined, and the same evidence, in a higher degree, 
brought forth. At this place I met Dr. Locke, who gave me every information relative to the 
limits of the two formations, Cliff and Blue limestones, as known in Ohio, and I afterwards 
derived great assistance from his Report on the Geology of this part of the State. I was also 
fortunate in meeting, at this place, with several gentlemen who were zealously engaged in ex, 
ploring the rocks of the vicinity, and who voluntarily aided me in my objects. From Mr. J. 
G. Anthony, Mr. Clark, Mr. Carley, and Mr. Buchanan, I received many characteristic fos¬ 
sils of the locality. 
The section made there at this time presented the following features : 
On the Kentucky side of the river, at the water level, (May 8th, 1841,) the rock seen was 
a green shale with thin laminae of crinoidal limestone, containing few fossils. Among these 
the Triarthrus Beckii is the most prominent, and with fragments of Isotelus, and a few imper¬ 
fect shells, were all that I obtained. In New-York, the Triarthrus is never found below the 
Utica slate, and is a characteristic fossil of that mass ; though it does occur somewhat rarely 
in the lower part of the Hudson river group. Taken in connection with other circumstances, 
and the character of the fossils in the succeeding rocks, it seems a fair inference that this is 
the equivalent of the Utica slate, or at least not far above it. 
At low water, on the Ohio, a lower rock appears; and though the specimens I have seen 
contain no unequivocally characteristic fossils, of the Trenton limestone, yet it may exist here, 
and Mr. Vanuxem informs me that he saw it in the valley of the Little Miami, a locality which 
I did not visit.* 
Proceeding upward from the green shale with Triarthrus , we find a somewhat similar shale, 
with thin layers of sandstone, characterized by the presence of Trinucleus and Graptolites. 
Still above this we find alternations of shale, or marl, and limestone, with Orthis striatula in 
great abundance ; with this shell and above it occur Strophomena sericea, S. alternata ? 
Pterinea carinata, Cypricardia angustifrons, C. modiolaris, Cyrtolites ornatus, with a great 
* Very careful and extensive examination is often necessary, in order to identify rocks by the presence of characteristic fos¬ 
sils. In the rocks of Cincinnati, Maysville, and other places, occur fossils of the Trenton limestone. Among them are Orthis 
Striatula, Strophomena ( LepUzna) sericea, S. alternata ? Bellerophon bilobatus, Favosites lycoperdon, and others. The last named 
fossil occurs with Bellerophon bilobatus and Orthis striatula in the Caradoc sandstone of England. The Calymene of these rocks 
at the West, usually considered identical with the Trenton species, is probably distinct. 
