PLATE IX A. 



(Figures 1-27 by R. V. Whitfield.) 



Leg'enrl. D. Deltidium, pedicle-valvi'. 

 C Deltidium, liraohial valve, 

 t. Teeth. 



b. Dental sockets. 



c. Crural plates. 

 X. Crural bases. 



p. Pedicle muscle. 



A''. Anterior jiddui^tors. 



a. Posterior adductors. 



r. Did actors. 



V. Vascular sinuses. 



Genus KAFINESQULNA, okn. nov. 



Page 'iSl. 



Rafinesquina deltoidea, Conrad. 



Fig-. 1. The exterior of a pedicle-valve ; showing its regular convexity and deep anterior deflection, the 



radiating strije of subequal size, and the concenti-ic corrugations. 

 Pig. 2. Profile of the same specimen j showing the regular convexity from umbo to anterior margin. 



Trenton limestone. Jacksonburg, N. Y. 

 Fig. 4. An impression of the exterior surface of the brachial valve ; showing its subtriangular outline as 

 usually developed in this species, ami the flattened, scarcely concave circumbonal area. 

 Trenton limestone, Middleville, N. Y. 

 This 6gure is from the oi-iginal specimen used by Mr. Conrad, and is the subject of the drawing 

 by him reproduced in Palseontology of New York, Vol. I, plate xxxi .1, fig. S/. That figure, 

 however, gives the valve a convexity which it does not possess. For furthei- illustration of the 

 species, the other figures on the plate cited may be consulted. 



Fig. 



Genus STROPHOMENA, Rafinesque (de Blainville), 



Page 245. 



Strophomena Conradi, .sp. nov. 



3. View from the brachial valve ; showing the reversed convexity of the valves, and the fasciculate 

 surface strise without conceniric rugse. 



Trenton limestone. Jacksonburg, N. Y. 



Strophomena nutans, Jiunos (Meek). 



Fig. fi. 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. 

 Hudsou River group. Oxford, Ohio. 

 Foi other illustrations, see PaliEontology of Ohio, Vol. I, plate vi, fig. 1. 



Strophomena planu.mbona, Hall (^(S'. ni^osa, RntinesinK'). 



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 crenulate<l charactei' of 

 the surface of the teeth. X ^. 



Hudson River gr<iup. Oxford, Ohio. 



Strophomena filite.\ta. Hall. 



Fig. 10. The interior of a brachial valve ; .showing the cardinal process, muscular area, and the elevated 

 median ridges of the vascular system {i}. 



Hudson River group. IVaynesville, 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 yalve ; 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. 



