PLATE IX. 



(Figures 1-34, 36 by R. P. Whitiield; 35 by F. J. SwiNTON, emend.) 



Legend. A. Cardinal area, pedicle-valve, 

 a. Innei' division, 

 a'. Outer division. 

 D. Deltidium, pedicle-valve. 

 C. Deltidium, brachial valve, 

 j. Cardinal process. 



b. Dental sockets. 



fi. Median septum. 



X. Cardinal area, brachial 



t. Teeth. 



a. Adductor scare. 



r. Diductor scars. 



'alve. 



Genus STKOPHOMENA, Rafinesque. 



P.ige 245. 



Strophomena filitexta, HiiU. 

 (See Plate XI a, fig. 3.) 

 Fig. 1. A view from the brachial valve of a large indi\'idual. 



Ti'enton limestone. Eastern New Ym'k. 

 Pig. 2. A view of the pedicle-valve ; showing the gi'eat concavity of the ijallial region. 



Trenton horizon. Mineral Point, Wisconsin. 

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

 musculai' impi'ession. 



Trenton horizon. Platteville, Wiscon.mi. 

 Fig. 4. The interior of the pedicle-valve of fig. 2 ; showing the covered delthyrium and the character of 



the muscular impressions. 

 Fig. 5. The inteiior of a larger jjedicle-valve. 



Ti'enton hoiizon. Mi7ieral Point, Wisconsin. 

 Fjgf?. 6, 7. Enlargements of the external (fig. fi) and intei-nal (fig. 7) surface stiise. 



For other illustrations, see Palteontology of New York, Vol. 1, pi. xxxi B, fig. 3 ; and Palaeontology 

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



Strophomena sulcata, de Verueuil. 



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

 Fig. 9. A front view, to show the sinuate anterioi- margin. 

 Hudson River group. 0/iio. 

 For othei- illustrations, see Palteontology of Ohio, Vol. I, plate v, fig. 5. 



Strophomena nutans, Jtiii)e.s (Meek). 



(See Plate IX a, figs. 5-7.) 

 Fig. 11. A cardinal view of conjoined valves ; showing the area and deltidia. 

 Hudson River group. Lebanon, Ohio. 

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



Strophomena Winchelli, sp. nov. 



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

 of the surface. 



Trenton limestone. Clifton, Wisconsin. 

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

 plates, very slightly divergent fi-oni the hinge-line. The musculai' area is quadrilobate, the 

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

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

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

 Trenton limestone. Janesville, WiscOTisin. 

 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, Wisconsin. 

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



