PLATE XIV. 



(Figures 1-22 by R. P. Whitfield.) 



Legend. D. Deltidiiim. a. Anterior adductors, 



j. Cardinal j)ro<>es.s. a'. Posterior adductoi-s. 



s. Sei>tuni. o. Ovarian spaces. 



b. Dental sockets. v. Vascular sinuses, 



r. r'. Di(iiictor scars. 



Genus STROPIIf:ODONTA, Hall. 



Page 284. 

 StKOPHEODONTA (DoUVILLINa) IN.EQUISTKIATA, Hilll. 

 Figs. 1. 2. 8. Tln-ee views, giving the external characters of the species. 

 Fig. 4. The interior of a brachial valve. 

 Fig. :"). The central portion of the interior of the brachial valve, enlarged to .show the liroail, flat posterioi- 



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

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

 Hamilton group. Wester7i New York. 



Stropheodonta demissa, Conrad. 



The exteiior of a pedicle-valve ; showing the fasciculate character of the surface stria; near the beak. 

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



striated cardinal area of the pedicle-valve. 

 A profile view of the same. 



An enlargement of the cardinal areas ; showing the vertical striie and complete obsolescence of 

 the deltidia. X I5. 

 Fig. 11. The interior of a brachial valve ; .showing the crenulated hinge-margin, the cardinal process and 



muscular imjn'essions. 

 Fig. 12. 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. Wester7i New York. 



Stropheodonta in^quiradiata, Hall. 



Fig. )'S. An intei-nal cast of the pedicle-valve ; showing the muscular impressions and vascular sinuses. 

 Fig. 14. An enlargement of the umhonal portion of another cast ; showing the dendritic <iiductor scars, the 

 atiductoi's, and, at k, the tilling of the cavities occupied by the branches of the cardinal process. 

 Corniferous limestone. Neio York. 



Stropheodonta Patersoni. Hall. 



Fig. 15. The extei-ior of a pedicle-valve ; showing, over the visceral i-egion. the inidulations of the surface 

 between the primary I'adii. 



Corniferous limestone. Western New York. 



Stropheodonta concava, Hall. 



Figs. 1(5. 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 

 cardinal process is comparatively slender and the muscular area but slightly thickened. X l^. 

 Hamilton group. York, N. Y. 



Fig. 13. The interioi' of the brachial valve ; showing the characters of the fidl-gi'own individual. 



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

 dinal ])rocess are of great size and deeply grooved, the crural jilati^s in a i-ndimentary condition 

 and the muvscular scars much thickened. X 2. 



Fig. 21. A postei-ior view of the same specimen ; showing the crenulated edges of the cardinal lobes and 

 the .size of the <:rural plates. At x the base of the cardinal process has been excavated for the 

 reception of the mai-gin of the pedicle-valve. X 2. 

 Hamilton grouj). Canaiidair/ua Lake, N. Y. 



big. 22. The interioi' of a j)edicle-valve ; showing a slight trace of the deltidium. 



Fig. 23. An internal cast of the pedicle-valve ; showing the adductor and diiluctor seal's. 

 Hamilton group. Western New York. 



