PLATE XV. 



(Figures 1-36 by R. P. WHITFIELD.) 



Legenii, v. Pedicle-valve. j. Ctiiilinal process, 



d. Brachial valve. c. Ci-uva. 



A. Cardinal area. s. Median septum. 



D. Deltidiuni. r. Diductor scai-s. 



A. Delthyrium. a. Anterior adductors. 



t. Teeth. a'. Po.sterior adductors, 



b. Dental sockets. 



Genus STROPHEODONTA, Hall. 



Page 284. 



Stropheodonta corrugata, Conrad. 



Vig. 1. The exteiior of a pedicle-valve ; showing the corrugations along the car<linal margin. 

 Clinton gi'oup. Western JS'tw York. 



Stropheodonta (Leptostrophia) perplana, Conrad. 



View of the tirachial valve ; showing the cardinal area of the opjiosite valve. 

 Corniferous limestone. Western New Yorli. 

 3. The peiiicle-valve of a smaller specimen. 



Hamilton group. Western New York. 

 The exterior of a pedicle-valve ; showing the alternation in size of the stris. 

 An enlargement of the striae from the same specimen. 



Hamilton group. NeiD Buffalo. Iowa. 

 A similar enlargement where the stri;e are of equal size. 



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

 tulose lateral margins of the muscular ai'ea. 



Hamilton gi-oup. Westerti New York. 

 The interior of a pedicle-valve retaining similar characters. 



Hamilton group. New Buffalo, Iowa. 

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

 cess and latei-al niusculai- ridges. X -. 



Hamilton group. Canandaigu,a Lake. N. Y. 

 Fig. 10. The cardinal process, enlarged to show the grooving of the posterior surface of the lobes foi- the 



attachment of the diductor mu.scles. X 3. 

 Fig. 11. The cardinal areas of both valves; showing the unintei-rupted striated surface. X 14- 

 Fig. 12. A longifuiiinal axial section of the two valves ; showing the normal curvatui-e 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, var. nervosa, Hall. 



Fig. 14. A poi-tion of a pedicle-valve; showing the irregular character of the stria". 

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



Fig. 17. A specimen showing the wrinkled striae and extended cardinal angles. 

 Chemung group. Steuben county, N. Y. 



Stropheodonta (Leptostrophia) Junia, Hall. 



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

 Hamilton group. Canandaigua Lake, N. Y. 



Stropheodonta (Douvillina) Cayuta, Hall. 



Fig. 18. An internal cast of the pedicle-valve ; showing the short, transverse, shar|)ly defined muscular 



scar. 

 Fig. 19. An enlai-gement of the muscular area of the same specimen. X 2. 

 Chemung group. Steubeti county, N. Y. 



