PLATE IX. 



(Figures 1-34, 3« by R. P. Whitfield; 35 by F. J. SwiNION, emend.) 



Legend 



Fig:. 



FifT. 



Fiff. 



Fiy. 



A. Cai-iliiial area, jiediclc-valve. 

 a. Inner division. 

 a'. Outer division. 

 D. Deltidium, pedicle-valve. 

 C. Deltidinm, bi-achial valve, 

 j. Cardinal process. 



b. Dental sockets. 



s. Median septum. 



X. Cardinal area, brachial valve. 



t. Teeth. 



a. Adductor scars. 



r. Diductor scars. 



Genus STROPHOMENA, Kafinesque. 



P.age 245. 



Strophomena filitexta, Hall. 

 (See Plate XIa, fig'. 3.) 

 Fig. 1. A view from the brachial valve of a large individual. 



Trenton limestone. Eastern New Yc^rk. 

 Fig. 2. A view of the pedicle-valve ; showing the great concavity of the pallial region. 



Trenton horizon. Mineral Point, Wisconsin. 

 Fig. 3. The interior of a large brachial valve ; showing the cai-dinal process, crui-al plates and undefined 

 muscular impression. 



Trenton horizon. Phitteinlh, Wisconsin. 

 Fig. 4. The inferior of the jiedicle-valve of fig. 2 ; showing the covei'ed delthyrium and the character of 



the muscular impressions. 

 Fig'. 5. The interior of a larger pedicle-valve. 



Trenton horizon. Mineral Point, Wisconsin. 

 Figs. 6, 7. Enlargements of the external (fig. 6) and internal (fig. 7) surface striiE. 



For other ilbustrations, see Palaeontology of New York, Vol. I, pi. xxxi B, fig. 3 ; and Palseontology 

 of Ohio, Vol. I, pi. vi, fig. ft. 



Strophomena sulcata, de Veriieiiil. 



Fig. 8. A view of the brachial valve ; showing the area and deltidium of the opposite valve. 

 Fig. 9. A fi'ont view, to show the sinuate anterior mai'gin. 

 Hudson River group. Ohio. 

 For other illustrations, see Palaeontology of Ohio, Vol. I, jilate v, fig. 5. 



Strophomena nutans, J;uue.s (Meek). 

 (See Plate IXa, figs. 5-7.) 

 Fig. H. A cardinal view of conjoined valves ; showing the area and deltidia. 

 Hudson River group. Lebanon, Ohio. 

 For other illustrations, see P.aheontology of Ohio, Vol. I, plate vi, fig. 1. 



Strophomena Winchelli, 



SI), nov. 



valve ; showing its great convexity and the fine filiform radial strise 

 Clifton, Wisconsin. 



10. The exterioi' of the brachial 

 of the .surface. 



Trenton limestone. 



12. The interior of a brachial valve ; showing the slender bilobed cardinal process and the crural 



plates, very slightly divergent fi-orii the hinge-line. The muscular area is quadrilobate, the 

 posterior scars lieing broader and having a faintly dendritic surface, the anterior pair being 

 narrow and elongate, and striated close to the median line. The figure gives an inaccurate idea 

 of the structure of the muscular area, which is correctly shown in figure 26, plate xx. 

 Trenton limestone. Janesville, Wisconsin. 



13. The intei-ior of a pedi(!le-valve ; showing the character of the musculfir area, and the thickening 



about the margins of the shell. 



Trenton limestone. Clifton, Wisconsin. 



14. .\ii enlargement of a somewhat exfoliated surface ; showing the distribution of punctse. 



