Fig-. 

 Fig. 



7. 

 8. 



Fig. 

 Fig. 



9. 

 10. 



Fig. 



11. 



Fig. 



12. 



PLATE XIV. 



(Figures 1-22 Ijy R. 1'. WiirrKIELD.) 

 Legend. D. Deltidium. a. Anterior adductors, 



j. Cardinal process. a'. Posteiior adductore. 



a. Septum. o. Ovai-ian spaces. 



1). Dental sockets. v. Vascular sinuses. 



1-, !•'. Diductor scars. 



Genus STROPHEODONTA, Hall. 



Page 284. 



Stropheodonta (Douvillina) in^quistriata, Hall. 



Figs. 1, 2, 3. Tliree views, giving the external characters of the species. 



Fig. 4. The interior of a brachial valve. 



Fig. 5. The central portion of the interioi- of the brachial valve, enlarged to show the broad. Hat postciioi- 



muscular scars and the elevated anterior muscular ridges. X 3. 

 Fig. 6. The interior of the pedicle-valve, enlarged to show the muscular impressions. X 2. 

 Hamilton group. Western Neio York. 



Stropheodonta demissa, Conrad. 



7. The exterior of a pedicle- valve ; showing the fasciculate character of the sui-face stri» near the beak. 

 A view from the brachial valve of a larger individual ; showing no evidence of deltidium on the 



striated cardinal ai-ea of the pedicle-valve. 

 A profile view of the same. 

 An enlai'gement of the cai'dinal areas ; showing the vertical stria; and complete obsolescence of 



the deltidia. X 1^. 

 The interior of a brachial valve ; showing the ci'enulated hinge-margin, the cardinal pi-ocess and 



muscular imi)reesions. 

 The interior of a pedicle-valve ; showing the muscular impressions. The center of the area has 



been broken away by the detachment of the cardinal process. 

 Hamilton group. Western New York. 



Stropheodonta in^^equikadiata, Hall. 



Fig. 13. An internal cast of the pedicle-valve ; showing the muscular impressions and vascular sinuses. 

 Fig. 14. An enlargement of tbe umbonal portion of another cast ; showing the dendritic diductor scai-s, the 

 adductors, and, at k, the filling of the cavities occupied by the branches of the cardinal process. 

 Corniferous limestone. Neio York. 



Stropheodonta Patersoni, Hall. 



Fig. 15. The exterior of a pedicle-valve ; showing, over the ^^sceral region, the undulations of the surface 

 between the primary radii. 



Corniferous limestone. Western New York. 



Stropheodonta concava, Hall. 



Figs. 16, 17. Two views, to show the general external character of the shell. 



Fig. 18. The umbonal portion of the interior of a brachial valve. From a young individual in which the 

 cai'dinal process is comparatively slender and the muscular area but slightly thickened. X 1?. 

 Hamilton group. York, N. Y. 



Fig. 19. The interior of the brachial valve ; showing the characters of the fuU-gi'Own indi\-idual. 



Fig. 20. The central cardinal portion of the brachial valve of a mature individual. The lobes of the car- 

 dinal process are of great size and deeply grooved, the ci-ural plates in a rudimentai-y condition 

 and the muscular scai-s much thickened. X 2. 



Fig. 21. A posterior view of the same specimen ; showing the ci'enulated edge.*^ of the cardinal lobes and 

 the size of the crural plates. At x the base of the cardinal process has been excavated for the 

 i-eception of the margin of the pedicle- valve. X 2. 

 Hamilton group. Cana/ndaigua Lake, N. Y. 



Fig. 22. The interior of a pedicle-valve ; showing a slight trace of the deltidium. 



Fig. 23. An internal cast of the pedicle-valve ; showing the adductor and diductor scars. 

 Hamilton group. Western New York. 



