PLATE XVII. 
(Figures 1-15, 18-29, 33-46 by R. P. Whitfield; 16, 31, 32 by F. B. Meek; 47-51 copies.) 
Legend. A. Cardinal area. j. Cardinal process. 
D. Deltidium, pedicle-valve. v. Brachial ridges. 
C. Deltidium, brachial valve. a. Anterior adductors, 
t. Teeth. a'. Posterior adductors, 
b. Dental sockets. r. Diductors. 
Genus PEODUCTELLA, Hall. 
Page 328. 
Productella subaculeata, (Murchison) Hall. 
Fig. 1. The exterior of a pedicle-valve. 
Corniferous limestone. Falls of the , Ohio. 
Fig. 2. The interior of a brachial valve ; showing the cardinal process. 
Corniferous limestone. East Victor, N. Y. 
Productella spinultcosta, Hall. 
Figs. 3, 5. Two views of a pedicle-valve. 
Corniferous limestone. Louisville, Kentucky. 
Fig. 4. The exterior of a pedicle-valve. 
Marcellus shales. Western New York. 
Fig. 6. A pedicle-valve referred with doubt to this species. 
Yellow sandstones. Burlington, Iowa. 
Productella Shumardiana, Hall. 
Fig. 7. A pedicle-valve with distinct spinferous costae. This figure is from one of the original specimens 
of the species. 
Yellow sandstones. Burlington, Iowa. 
Productella navicella, Hall. 
Figs. 8, 9. Views of the interior and exterior of the pedicle-valve. 
Hamilton group. Western New York. 
Genus STKOPHALOSIA, King. 
(See Plates XVb, XVI.) J 
Page 314. 
Strophalosia truncata, Hall. 
(See Plate XVb, figs. 24^26.) 
Fig. 10. The interior of a brachial valve ; showing the cardinal process. 
Fig. 11. The exterior of a brachial valve; showing the convex umbo corresponding to the truncation of the 
apex of the opposite valve. X 2. 
Figs. 12, 13. Two views of a pedicle-valve; showing the truncation of the beak. X 2. 
Marcellus shales. Western New York. 
Fig. 14. An impression of the external surface of the brachial and part of the pedicle-valve ; showing the 
cardinal areas and minute deltidia. X 2. 
Hamilton group. Near Tully, N. Y. 
Fig. 15. An enlargement of the cardinal process; showing its simple, uncoalesced lobes. X 6. 
Marcellus shales. Western New Yo?'k. 
Genus PEODUCTELLA, Hall. 
Page 328. 
Productella subalata, Hall. 
Fig. 16. Exterior of the pedicle-valve; from one of the original specimens. 
Hamilton group. Bock Island, Illinois. 
