PLATE IX. 
(Figures 1-34, 36 by R. P. Whitfield; 35 by F. J. Swinton, emend.) 
Legend. A. 
a. 
a ' . 
D. 
C. 
j- 
Cardinal area, pedicle-valve.. 
Inner division. 
Outer division. 
Deltidium, pedicle-valve. 
Deltidium, brachial valve. 
Cardinal process. 
b. Dental sockets. 
s. Median septum. 
x. Cardinal area, brachial valve. 
t. Teeth. 
a. Adductor scars, 
r. Diductor scars. 
Genus STROPHOMENA, Rafinesque. 
Page 245. 
Strofhomena filitexta, Hall. 
(See Plate XIa, fig. 3.) 
Fig. 1. A view from the brachial valve of a large individual. 
Trenton limestone. Eastern New York. 
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 cardinal process, crural plates and undefined 
muscular impression. 
Trenton horizon. Platteville, Wisconsin. 
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 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 striae. 
For other illustrations, see Palaeontology of New York, Vol. I, pi. xxxiB, fig. 3 ; and Palaeontology 
of Ohio, Yol. I, pi. vi, fig. 5. 
Strophomena sulcata, cle Verneuil. 
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 anterior margin. 
Hudson River group. Ohio. 
For other illustrations, see Palaeontology of Ohio, Vol. I, plate v, fig. 5. 
Strophomena nutans, Janies (Meek). 
(See Plate IXa, 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 from the hinge-line. The muscular area is quadrilobate, the 
posterior scars being 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. 
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 punctse. 
