PLATE XII. 
(Figures 1-5, 8-21 by It. P. Whitfield; 6, 7 by F. B. Meek.) 
Legend. H. Hinge-line. 
|D. Deltidium, pedicle-valve. 
C. Deltidium, brachial valve. 
a. Cardinal area, outer portion, 
j. Cardinal process, 
i. Lobes of cardinal process. 
b. Dental sockets, 
t. Teeth. 
a. Anterior adductors, 
a'. Posterior adductors, 
r. Diductors. 
Genus STROPHONELLA, Hall. 
Page 290. 
Strophonella (-) striata, Hall. 
Fig. 1. The exterior of a brachial valve. 
Fig. 2. The interior of a pedicle-valve; showing the extension of the dental lamellae along the sides of 
the muscular area, and the crenulations of the cardinal margin near the delthyrium. 
Fig. 3. An enlargement of the central portion of the brachial valve; showing the cardinal area, its 
crenulated margin, and the deltidium enveloping the lower portion of the lobes of the cardinal 
process. In this drawing the specimen is viewed with the cardinal area nearly at right angles 
to the line of vision ; the groove between the lobes of the cardinal process is, therefore, much 
foreshortened, and made to appear shallow; the crural ridges are also to be regarded as re¬ 
treating rapidly into the background. 
Niagara group. Waldron, Indiana. 
Strophonella semifasciata, Hall. 
Fig. 4. The exterior of the concave pedicle-valve. 
Fig. 5. An enlargement of the central portion, of the area of both valves; showing the development of 
the deltidia and the oblique striae on the broad triangular space enclosed by the lines a, a, a. 
[This space should be defined by lines extending from the apex to the limit of the figure on 
each side, and which may be obscure in some of the figures.] 
Niagara group. Waldron, Indiana. 
Strophonella Leavenworthana, Hall. 
Fig. 6. The exterior of a brachial valve. 
Fig. 7. A profile of the same ; showing the concavity in early growth-stages, followed by great convexity 
and strong geniculation. 
Fig. 8. The interior of the brachial valve; showing the crenulations of the cardinal margin, the cardinal 
process, slightly developed crural plates, and the adductor impressions. 
Fig. 9. The interior of the pedicle-valve; showing the crenulations of the hinge-margin, the closed del¬ 
thyrium, and the arrangement of the muscular scars. 
Lower Helderberg group. Albany county, N. Y. 
Strophonella punctulifera, Conrad. 
Fig. 10. The exterior of the brachial valve; showing the concavity in the umbonal, and convexity in the 
pallial region. 
Fig. 11. An internal cast of a brachial valve ; showing the muscular imprints and the crenulations in the 
matrix left by the removal of the hinge. 
Fig. 12. The cardinal areas of both valves of fig. 10 ; showing the narrow convex deltidium closing the 
delthyrium in each valve. X 11- 
Lower Helderberg group. Near Clarksville, N. Y. 
Strophonella ampla, Hall. 
Fig. 13, An internal-cast of a pedicle-valve; showing the muscular impressions and marks of the strongly 
pustulose interior surface. In the imprint left by the cardinal area are seen the crenulations 
of the hinge-line, and the mark of the small, linear convex deltidium. 
Schoharie grit. Albany county, N. Y. 
Fig. 14. The interior of a pedicle-valve in which external evidence of the deltidium is lost and the crenula¬ 
tions of the hinge extend more than half the length of the area. The margin of the area on 
each side of the deltidium has been broken away by the detachment of the cardinal process of 
the other valve. 
Corniferous limestone. Onondaga Valley, N. Y. 
Fig. 15. An enlargement of the surface striae. 
