Preliminary Notes on Cincinnatian Fossils 213 
the crest of the Cincinnati geanticline. Strophomena maysvillensis 
is always identified as Strophomena planoconvexa to which it is 
undoubtedly closely related. It is a much more abundant form 
than the latter and is believed to be sufficiently distinct from the 
same to warrant a separate name. 
Typical specimens of Strophomena planoconvexa are figured 
by Meek in volume I of the Ohio Paleontology. 
Strophomena concordensis, sp. nov. 
{Plate IV, Fig. 6 A. B.) 
At the top of the Arnheim bed is a bluish clay, often indurated 
and weathering into so-called nodular masses. This layer is char- 
acterized at numerous localities in the more southwestern counties 
in the Ordovician areas of Ohio by the presence of great numbers 
of Strophomena concordensis. This species occurs also at the 
same horizon at Concord, in Kentucky. Three miles south of 
Maysville, at the deep cut on the railroad, it occurs in limestone 
at the top of the Arnheim. 
This species belongs to the same group as Strophomena nutans, 
but it is larger than typical specimens of that species, and the 
interior of the pedicel valve is never thickened as strongly or 
abruptly as in that form. The thickening of the interior of the 
pedicel valve, in fact, usually is only moderate, and is crossed by 
vascular markings which are more conspicuously parallel or mod- 
erately radiating along the anterior border than in any other spe- 
cies. The brachial valve usually is more or less nasute anteriorly, 
and the view of the shell from the side of the pedicel valve is more 
or less triangular. The convexity of the brachial valve varies 
considerably, but usually is rather strong. The flattened part of 
the valve extends only from 6 to 9 millimeters from the beak, but 
the rapid downward part of the curvature often does not begin 
until 15 millimeters from the hinge line. The radiating stria- 
tions are of the type found in Strophomena planumbona. The 
types are from Concord, Ky. 
Dalmanella emacerata, Hall. 
I Thirteenth Report, New York State Cabinet of Natural History, 
i860, p. 121. 
No illustrations accompany the original description. In the 
