PLATE XIII. 
(Figures 1-27 by K. P. Whitfield; 28 by F. B. Meek, emend.) 
Legend. H. Hinge-line. 
D. Deltidium. 
A* Delthyrium. 
t. Teeth. 
b. Dental sockets, 
s. Median septum. 
j. Cardinal process, 
a. Anterior adductors, 
a'. Posterior’adductors. 
r. Anterior diductors. 
r'. Posterior diductors. 
o. Ovarian spaces. 
Genus STROPHEODONTA, Hall. 
Page 284. 
Stropheodonta (Brachyprion) profunda, Hall. 
(See Plate XX, figs. 29-81.) 
Fig. 1. The internal cast of a pedicle-valve ; showing the muscular impressions. 
Fig. 2. A partial cast of a pedicle-valve with the shell removed from the upper portion ; showing the im¬ 
pression of the narrow area. The margin of the valve preserves the shell with its characteris¬ 
tic striae. 
Fig. 3. The central portion of a brachial valve, enlarged from a gutta-percha impression. 
Niagara limestone. Racine, Wisconsin. 
Fig. 4. The interior of a pedicle-valve having the delthyrium but partially closed, and showing the strong 
crenulations of the cardinal margin near the delthyrium. 
Fig. f>. An enlargement of the central portion of the area of the same specimen. X 2. 
Niagara group. Waldron, Indiana. 
Stropheodonta (Brachyprion) varistriata, Conrad. 
Fig. 6. The exterior of the pedicle-valve. 
Fig. 7. The interior of a similar valve. 
Fig. 8. An enlargement of a portion of the same specimen; showing the breaking of the area by the de¬ 
tachment of the cardinal process of the opposite valve. X 3. 
Fig. 9. An enlargement of the central part of the area of another specimen ; showing the character of the 
deltidium and the short row of crenulations. X 3. 
Fig. 10. An enlargement of the umbonal. portion of a pedicle-valve ; showing the character of the orna¬ 
mentation. X 3. 
Fig. 11. An enlargement of a portion of the interior of the pedicle-valve; showing the crenulations of the 
hinge and the character of the muscular impressions. X 2. 
Fig. 12. The cardinal process and crural plates. X ,2. 
Figs. 13, 15. Enlargements of the surface striae. 
Fig. 14. The exterior of a pedicle-valve. 
Fig-. 16. An enlargement of one-half of a small pedicle-valve ; showing the fasciculate striae. 
Lower Helderberg group (Tentaculite and Pentamerus limestones). /Schoharie Co., N. Y. 
Stropheodonta varistriata, var. arata, Hall. 
Figs. 17, 18. Views of two pedicle-valves ; showing the strongly fasciculate surface striae. 
Lower Helderberg group. Beer aft's Mountain, Hudson, N. Y. 
Stropheodonta profunda ? 
Figs. 19, 20. Views of a specimen which has heen referred, with doubt, to this species. 
Clinton group. Niagara county, N. Y. 
Stropheodonta varistriata, Conrad (= 8 . mipressa , Conrad). 
Figs. 21, 22. Two views of this shell; showing the depressed umbo and the great convexity in the pallial 
region. 
Lower Helderberg group. Eastern New York. 
