Wincliell.] -^'^^^ [Jan. 4, 



There are several specimens of this form, and they differ from speci- 

 mens of P. Cooperensis from Burlington, Iowa, jDrincipally in a mnch 

 shallower ventrol sinus and a larger size. In size, and in the peculiar ar- 

 rangement of the granulations of the inner surface, they resemble P. du- 

 pHcostaia, Win., but the costaj are less developed, and there are fewer 

 spines distributed over the genei'al surface. These forms resemble, not 

 a little, P. mminalis, Hall, from the Burlington Limestone, but the cos- 

 tffi are less pronounced, and the ventral valve enlarges less rapidly. This 

 is possibly the species vphich has sometimes been referred to P. Cora, 

 D'Orb. 



Pkodtjcta gracilis? Win. (Proc. Acad. N. Sci., Phil., July, 18G5.) 

 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- 

 vula, and the ventral valve is not sufficiently produced. It is desirable 

 yet to make comparisons vrith specimens of P. minuta, Shum. 



Producta morbilliana. Win. (PhiL Proc, July, 1865, p. 113.) From 

 bed No. 4, Sciotoville, Ohio. 



Producta arcuata. Hall (Iowa Rep. 518, pi. vii, fig. 4, a. b). Quito 

 abimdant in bed No. 5, Rockville, Ohio. Quite identical forms occur also 

 at Granville, O. 



Choketes MULTicosTA, Win. (Proc. A. K 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. Safford's collection. They agree 

 with this species, except that the strise 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. 



Chonetes PULCHELLA, Will. (Proc. A. N. Sci., Phila., Sept., 1862.) 

 A single ventral valve occurs among the specimens from Tennessee. Ifc 

 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. 



Chonetes Fischeri, N. & P. (Jour. A. N. S., Phil., vol. I). From dark 

 bituminous shales, Tennessee. 



Chonetesgeniculata"? 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 seraetimes re- 

 ferred with doubt to C. geniculata. I suspect tliey may all prove to be C. 



