MEDINAN, NIAGARAN, AND CHESTER FOSSILS 
47 
mens, have a considerable vertical range in the Niagaran, and 
the specimens found so far at different localities and horizons in 
Ohio are regarded as inadequate for purposes of exact correlation. 
For the present, therefore, the so-called Laurel limestone of 
western Ohio must be regarded as identified lithologically, rather 
than paleontologically with the typical Laurel of Indiana. 
The same statement can be made regarding the so-called Os- 
good clay shale of Ohio. This has been identified lithologically 
with a clay shale band well exposed in the upper part of the 
quarries southwest of Laurel, Indiana, but the fauna found in 
these so-called Osgood clay shales in Ohio is that of the under- 
lying Dayton limestone, and not that of the typical Osgood 
formation in Ripley and Jefferson counties, in Indiana. 
In the large quarry northwest of Lewisburg, Ohio, the top of 
the Dayton limestone contains the species usuall 3 ^ identified as 
Enter olasma caliculum (Hall), Atrypa reticularis Linnaeus, 
Spirifer radiatus (Sower by) , and a Spirifer intermediate between 
between niagarensis (Conrad) and eudora (Hall) in the number 
of its radiating plications. The middle part of the Dayton 
limestone here contains Enterolasma caliculum, Orthis flahellites 
Foerste, Plectamhonites transversalis, Spirifer plicatellus Lin- 
naeus, Schuchertella subplana (Conrad), and a small species of 
Whitfieldella, similar to the one most common in the Osgood and 
Laurel limestones of Indiana. 
At Rocky Point, 3 miles northeast of Eaton, on the road to 
Lewisburg, the Osgood clay, overlying the Dayton limestone 
is 4 feet 3 inches thick, and contains the following species: En- 
terolasma caliculum, Atrypa reticularis, Leptaena rhomboidalis, 
Orthis flabellites, Schuchertella subplana, and the same species 
of Spirifer as that cited from the top of the Dayton limestone 
at the quarry northwest of Lewisburg. 
From Trotwood 2^ miles southward and d miles east, the 
following fossils are found in the Dayton limestone: Enterolasm'i 
caliculum, Rhinopora sp., Clathrodictyon vesiculosum, Camaro- 
toechia neglecta, Leptaena rhomboidalis, Orthis flabellites, Platy- 
strophia daytonensis, Platystrophia reversata, and Rhipidomella 
hybrida. 
