Winchell.] 
250 
[Jan. 4, 
There are several specimens of this form, and they differ from speci¬ 
mens of P. Cooperensis from Burlington, Iowa, principally in a much 
shallower ventral sinus and a larger size. In size, and in the peculiar ar¬ 
rangement of the granulations of the inner surface, they resemble P. du- 
plicostcUa, Win., but the costae are less developed, and there are fewer 
spines distributed over the general surface. These forms resemble, not 
a little, P. mminalis, XJaffl, from the Burlington Limestone, but the cos¬ 
tae are less pronounced, and the ventral valve enlarges less rapidly. This 
is possibly the species which has sometimes been referred to P. Cora , 
D’Orb, 
Producta gracilis? Win. (Proc. Acad. N. Sci., Phil., July, 1865.) 
From bed No. 4, Sciotoville, Ohio. 
The numerous casts from this locality do not preserve the striations as 
strongly as the types of this species ; but they are too broad for P. par- 
mila , and the ventral valve is not sufficiently produced. It is desirable 
yet to make comparisons with specimens of P. minutco, Shum. 
Producta morbilliara, Win. (Phil! Proc., July, 1865, p. 113.) From 
bed No. 4, Sciotoville, Ohio. 
Producta arcuata, Hall (Iow r a Rep. 518, pi. vii, fig. 4, a. b). Quite 
abundant in bed No. 5, Rockville, Ohio. Quite identical forms occur also 
at Granville, 0. 
Choretes multicosta, Win. (Proc. A. N. S., Phil., Jan., 1863, p: 5.) 
In yellowish-brown calcareo-argillaceous beds and dark bituminous shales 
in Hickman and Maury counties, Tennessee. 
There are two dorsal valves in Prof. Salford’s collection. They agree 
with this species, except that the striae are considerably more obscure 
than even in the typical specimens ; and the external surface is minutely 
granulated. 
This species ranges from the base of the Yellow Sandstones, at Burling¬ 
ton, Iowa, into the base of the Burlington Limestone. 
Ciionetes pulchella, Win. (Proc. A. N. Sci., Pliila., Sept., 1862.) 
A single ventral valve occurs among the specimens from Tennessee. It 
exposes only the inside, and hence the number of ribs cannot be satisfac¬ 
torily ascertained. A slightly divergent spine appears at each extremity 
of the hinge line. 
Several clearly marked specimens from Newark, Ohio, occur in Prof. 
Andrews’ collection. These exhibit, however, three or four hollow spines 
each side of the beak. 
Other specimens from near Shafer’s, on Oil Creek, Pa., are almost per¬ 
fectly identical with these. 
Choretes Fischeri, N. & P. (Jour. A. N. S., Phil., vol. I). From dark 
bituminous shales, Tennessee. 
Choketes geniculata? White (Proc. Bos. Soc. N. Hist. IX, 29). From 
bed No. 5, Rockville, Ohio. 
The few imperfect specimens in the collection agree with forms occur¬ 
ring at Burlington, Iowa, in the Yellow Sandstones, and sometimes re¬ 
ferred with doubt to C. geniculata. I suspect they may all prove to fie C. 
