PLATE IX. 



(Figures 1-34, 36 by R. P. Whitfield; 35 b>- F. J. Swinton, emend.) 



Legend. A. Cardinal area, pedicle-valve, 

 a. Inner division, 

 a'. Outer division. 

 D. Deltidium, jiedicle-valve. 

 C. Deltidium, brachial valve, 

 j. Cardinal process. 



Fig. 

 Fig. 



b. Dental sockets. 



s. Median septum. 



X. Cardinal area, brachial valve. 



t. Teeth. 



a. Adductor scars. 



1-. Diductor scars. 



Hall. 



Fig. 



Fig. 

 Fig. 



Fig. 

 Fig. 

 Figs. 



Genus STROPHOMENA, Rafinesque. 



I'nge 245. 



Stroi'homena filitexta, 



(See Plate XIa, fig. 3.) 



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



Trenton limestone. Eastern New Ywk. 



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



Trenton horizon. Mineral Point, TViscun»in. 



3. The intei-ior of a large bi-achial valve ; showing the cardinal process, crural plates and undefined 



muscular impression. 



Trenton horizon. Platteville, Wisccmxin. 

 The interior of the pedicle-valve of fig. 2 ; showing the covered delthyrium and the charaiter of 



the muscular impressions. 

 The intei-ior of a larger pedicle-valve. 



Trenton horizon. Mineral Point, Wismisin. 

 7. Enlargements of the external (fig. 6) and internal (fig. 7) surface strife. 



For other illustrations, see Palaeontology of New York, Vol. I, pi. xxxi b, fig. 3 ; and Palaeontology 

 of Ohio, Vol. I, pi. vi, fig. 5. 



4. 



5. 



6. 



Strophomena SULCATA, de Vcnieuil. 



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



9. A front view, to show the sinuate anterior margin. 



Hudson River group. Ohio. 

 For other illusti-ations, see P.alseontology of Ohio. Vol. I, plate v, fig. 5. 



Strophomena nutans, James (Meek). 



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

 Fig. 11. A cai'dinal view of conjoined valves ; showing the area and deltidia. 

 Hudson River group. Lebanon, Ohio. 

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



Strophomena Winchi;lli, sp. iiov. 



Fig. 10. The exteiior of the brachial valve ; showing its great convexity anil the fine filiform radial striae 

 of the surface. 



Trenton limestone. Clifton, Wisconsin. 

 Fig, 12. The interior of a brachial valve ; showing the slender bilobed cai'dinal process and the crural 

 plates, very slightly divergent from the hinge-line. The mus('ular area is quadrilobate, the 

 posterior scars being broailer 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. Janemiille, Wi.'iconsin. 

 Fig. 13. The interior of a pedicle-valve ; showing the character of the muscular area, and the thickening 

 about the margins of the shell. 



Trenton limestone. Clifton, Winronsin. 

 Fig. 14. An enlargement of a somewhat exfoliated surface; showing the distribution of punctae. 



