PLATE XV. 



(Figures 1-36 by K. P. Whitfield.) 



Legend, v. Pedicle-valve, 

 d. Biachial valve. 

 A. Cardinal ai-ea. 

 D. Deltidium. 

 A. Delthyrium. 

 t. Teeth. 

 b. Dental sockets. 



Genus STROPHEODONTA, Hall. 



Page 284. 



Stropheodonta corrugata, Ci)nriul. 



Fig. 1. Tile exterior of a pedicle-valve ; showing the corrugations along the cardinal mai-gin. 

 Clinton group. Western New York. 



Stropheodonta (Leptostrophia) perplana, Conrad. 



Fig. 2. View of the brachial valve ; showing the cardinal area of the opposite valve. 



Coi-nifei-ous limestone. Western New York. 

 Fig. 3. The pedicle-valve of a smaller specimen. 



Hamilton group. Weatei'n New York. 

 Fig. 4. The exterior of a pedicle-valve ; showing the alternation in size of the striae. 

 Fig. 5. An enlargement of the striae from the same specimen. 



Hamilton group. Neio Buffalo, Iowa. 

 Fig. 6. A similar enlargement where the sti'ise are of equal size. 



Fig. 7. The interior of a pedicle-valve ; showing the iminterrupted cardinal area and the thickened pus- 

 tulose lateral margins of the muscular area. 



Hamilton group. Wester7i New York. 

 Fig. 8. The interior of a pedicle-valve retaining similar characters. 



Hamilton group. New Buffalo, Iowa. 

 Fig. 9. An enlargement of the interior umbonal portion of the brachial valve ; showing the cardinal pro- 

 cess and lateral musculai' I'idges. X 2. 



Hamilton gi-oup. Ca7iandaigua Lake, N. Y. 

 Fig. 10. The cardinal process, enlarged to show the groo\-ing of the posterior surface of the lobes for the 



attachment of the diduetor muscles. X 3. 

 Fig. 11. The cardinal areas of both valves; showing the uninterrupted sti-iated surface. X H- 

 Fig. 12. A longitudinal axial section of the two valves ; showing the normal curvature of the shell and the 



position of the cardinal process. 

 Fig. 13. An enlargement of the surface as left by the removal of the shell. 

 Hamilton group. Western New York. 



Stropheodonta perplana, Conrad, vai-. nervosa, Hall. 



Fig. 14. A portion of a pedicle-valve; showing the irregular character of the sti-iie. 

 Fig. 15. An enlargement of a portion of the same. 



Fig. 17. A specimen showing the wrinkled stris and extended caidinal angles. 

 Chemung group. Steuben county, N. Y. 



Stropheodonta (Leptostrophia) Junta, Hall. 



Fig. 10. A portion of the pedicle-valve ; showing the crenulated area and partially covered ilelthyrium. 

 Hamilton group. Canandaigua Lake, N. Y. 



Stropheodonta (Douvillina) Caydta, Hall. 



Fig. 18. An internal cast of the pedicle-valve ; showing the short, transverse, .sharply defined musculai- 



scar. 

 Fig. 19. An enlargement of tbe muscular area of the same specimen. X 2. 

 Chemung group. Steuben county, N. Y. 



