76 
AUG. F. FOERSTE 
between the beak and the anterior margin of the shell. Judging 
from the concavity of the inner side of this valve, the maximum 
convexity of its exterior was about 9 mm. from the hinge-area, 
and it equalled about 3 mm. From this point the convexity 
continued quite evenly as far as the lateral and anterior margins 
of the valve. The radiating striae on the outer surface of the 
shell were very fine and even, and numbered about 10 to 12 in 
a width of 3 mm. 
Locality and formation.' — Quarry J a mile northeast of Cen- 
terville, Ohio; in the argillaceous strata immediately beneath 
the Brassfield limestone. 
Remarks .' — Br achy prion stropheodontoides Savage is figured 
and described as rather strongly convex in the median portion 
of the ventral valve, and as most strongly convex in its umbonal 
region. There is no corresponding accentuation of the convexity 
of this valve in its median parts in the Centerville species here 
described. 
Whitfieldella cf. ovoides Savage 
Plate XIV, fig. 14 
Whitfieldella ovoides Savage, Bull. Geol. Surv. Illinois, 23, 
1913, p. 90, pi. 5, figs. 13-15; pi. 7, fig. 13. 
Shell 16.5 mm. long, about 14 mm. wide, and estimated to 
have been about 10 mm. thick. The pedicel valve is considerably 
deeper than the brachial valve, and arches strongly over the 
latter at its beak. The shell tends to be broadest at its postero- 
lateral margins, about 7 mm. anterior to the beak of the pedicel 
valve. Anteriorly the lateral outlines converge. The anterior 
margin is rounded. The median part of the pedicel valve is 
grooved rather narrowly. Casts of the interior of the pedicel 
valve are fairly common, and exhibit casts of the cavity beneath 
the beak enclosed by the convergent dental lamellae, and 
casts of the impressions left by the diductor scars. The latter 
are striated or ridged longitudinally. The surface of both valves 
is rather strongly marked in a concentric manner by striae 
or ridges indicating successive stages of growth. Possibly these 
