PLATE IXa. 



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



Legend. D. Deltidium, pedicle-valve. 



C. Deltidium, brachial valve, 



t. Teeth. 



h. Dental sockets, 



c. Crural plates. 



X. Crural bases. 



Pedicle muscle. 

 Anterior adductors. 

 Posterior adductors. 

 Diductors. 

 Vascular sinuses. 



Gknus RAFINKSQUINA, gen. nov. 



Page 281. 



Rafinesquina deltoidea, Coniiul. 



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



radiating- sti-ia; 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. Jacksonhurg, N. 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. Mlddleoille, N. T. 

 This figure is from the oiiginal specimen used by Mr. Conrad, and is the subject of the drawing 

 by him reproduced in Paleontology of New Yoi'k, Vol. I, plate xxxi A, 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 tlie plate cited may be consulted. 



Fig. 



Fig. 

 Fig. 



Fig. 



Genus STROPHOMENA, Rafinesque (de Blainville). 



Page 245. 

 StROPHOMENA CoNRADI, S}). 110V. 



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

 sui'face striiB without concentric i-ugse. 



Trenton limestone. Jacksonhurg, N. Y. 



Stuophomena nutans, James (Meek). 



5. The exterior of a brachial valve. 



6. The interior of a pedicle-valve ; showing the character of the muscular impres-sions and vascular 

 markings. 



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 Palaeontology of Ohio. Vol. I, plate vi, fig. 1. 



Strophomena planumbona, Hall ( = ,S'. rugosa, Rafiiiesqiio). 



8. An enlargement of the cardinal process and crural plates. X 2. 



9. The corresponding portion of the opposite valve ; showing the irregulai-ly crenulated character of 

 the surface of the teeth. X 2. 



Hudson River gi"oup. Oxford, Ohio. 



Strophomena filitexta, Hall. 



Fig. 10. The interioi- of a brachial valve ; showing the cardinal process, muscular ai-ea, 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 jilates. 



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. 



Fig. 

 Fig. 



