PLATE IXa. 
(Figures 1-27 by R. P. Whitfield.) 
Legend. D. Deltidium, pedicle-valve. 
C. Deltidium, brachial valve, 
t. Teeth. 
b. Dental sockets. 
c. Crural plates, 
x. Crural bases. 
p. Pedicle muscle. 
a / . Anterior adductors, 
a. Posterior adductors, 
r. Diductors. 
v. Vascular sinuses. 
Genus RAFINESQUINA, gen. nov. 
Rafinesquina deltoidea, Conrad. 
Fig. 1. The exterior of a pedicle-valve; showing its regular convexity and deep anterior deflection, the 
radiating stria? of subequal size, and the concentric corrugations. 
Fig. 2. Profile of the same specimen ; showing the regular convexity from umbo to anterior margin. 
Trenton limestone. ' Jaclcsonburg, iV. Y. 
Fig. 4. An impression of the exterior surface of the brachial valve; showing its subtriangular outline as 
usually developed in this species, and the flattened, scarcely concave circumbonal area. 
% Trenton limestone. Middleville, N. Y. 
This figure is from the original specimen used by Mr. Conrad, and is the subject of the drawing 
by him reproduced in Palaeontology of New York, Vol. I, plate xxxiA, fig. 3/. That figure, 
however, gives the valve a convexity which it does not possess. For further illustration of the 
species, the other figures on the plate cited may be consulted. 
Genus STROPHOMENA, Raeinesque (de Blainville). 
Page 245. 
Strophomena Conradi, sp. nov. 
Fig. 3. View from the brachial valve ; showing the reversed convexity of the valves, and the fasciculate 
surface striae without concentric rugae. 
Trenton limestone. JacJcsonburg, N. Y. 
Strophomena nutans, James (Meek). 
Fig. 5. The exterior of a brachial valve. 
Fig. 6. The interior of a pedicle-valve ; showing the character of the muscular impressions and vascular 
markings. 
Fig. 7. The central cardinal portion of the brachial valve; showing the bilobed cardinal process, the 
curved crural plates, and the muscular impressions. X 3. 
Hudson River group. Oxford, Ohio. 
For other illustrations, see Paleontology of Ohio, Vol. I, plate vi, fig. 1. 
Strophomena planumbona, Hall ( = S. rugosa, Rnfinesque). 
Fig. 8. An enlargement of the cardinal process and crural plates. X 2. 
Fig. 9. The corresponding portion of the opposite valve; showing the irregularly crenulated character of 
the surface of the teeth. X 2. 
Hudson River group. Oxford, Ohio. 
Strophomena pilitexta, Hall. 
Fig. 10. The interior of a brachial valve ; showing the cardinal process, muscular area, and the elevated 
median ridges of the vascular system (?). 
Hudson River group. Waynesville, Ohio. 
Fig. 11. The interior of a pedicle-valve ; showing the limitation of the muscular area by an elevated bor¬ 
der, which is continuous from the dental plates. 
Fig. 12. Exterior of a brachial valve ; showing the tendency to plication of the surface. 
Fig. 13. A cardinal view of a specimen retaining both valves, and showing the resupination of the shell. 
