PLATE XVII. 



(Figaros 1-15, 18-29, 33-46 by li. P. Whitfield; 16, 31, 32 by F. B. Meek; 47-51 copies.) 



Legend. A. Cardinal ai-ea. j. Cardinal process. 



D. Deltidium, pedicle-valve. v. Brachial Hdges. 



C. Deltidium, brachial valve. a. Anteiior adductors, 



t. Teeth. a'. Posterior adductors. 



b. Dental sockets. r. Diductors. 



Genus PRODUCTELLA, Hall. 



Page 328. 



Peoductella subaculeata, (Mufchibon) Hall. 



Fig. 1. The exterior of a pedicle-valve. 



Cornifei-ous limestone. Falls of the Ohio. 

 Fig. 2. The inteiior of a brachial valve ; showing the cardinal process. 



Coruiferous limestone. East Victor, iV. Y. 



Produotella 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. 



Peoductella Shumardiana, Hall. 



Pig. 7. A pedicle-valve with distinct spinferous costje. This figure is fi-om one of the original specimens 

 of the species. 



Yellow sandstones. Burlington, Iowa. 



Produotella navicella, Hall. 



Figs. 8, 9. Views of the Interioi' and exterior of the pedicle-valve. 

 Hamilton group. Westes'n Neio York. 



Genus STROPHALOSIA, King. 



(See Plates XVb, XVI.) ' 

 Page 314. 



Strophalosia truncata, Hall. 



(See Plate XVb, figs. 24-36.) 

 Fig. 10. The interior of a brachial valve ; showing the cai'dinal 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. 

 Pigs. 12, 13. Two views of a pedicle-valve ; showing the truncation of the beak. X 2. 



Marcellus shales. Westei-n New York. 



Pig. 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 nMy, N. Y. 



Fig. 15. An enlargement of the cardinal process ; showing its simple, uncoalesced lobes. X 6. 



Marcellus shales. We,itern Neiv York. 



Genus PRODUCTELLA, Hall. 



Page 328. 



Peoductella subalata, Hall. 



Fig. IB. Exterior of the pedicle- valve ; from one of the original specimens. 

 Hamilton g-roup. Mock Island, Illinois. 



