PLATE XIV. 



(Figures 1-22 by R. I'. WHITFIELD.) 

 Legend. D. Deltidium. a. Anterior afiiiuctors. 



j. Cardinal process. . a'. Posterior adductors, 



s. Septum. o. Ovarian spaces, 



b. Dental .sockets. v. Vascular sinuses, 



r, v'. Diductor scars. 



Genus STROPIIEODONTA, Hall. 



P.ige 284. 



Stroi'heodonta (Douvillina) in^quistriata, Hall. 



Figs. 1, 2, 3. Three views, giving thi^ external characters of the species. 



Fig. 4. The interior of a brachial valve. 



Fig. 5. The central portion of the interior of the hi'achial valve, enlarged to show the hro.id, flat posterior 



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

 Fig. t). The interior of the pedicle-valve, enlargeil lo show the muscular imjiressions. X 2. 

 Hamilton group. WeMern New York. 



StROPHEODONTA DEMIS.SA, CoiUUtl. 

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

 Fig. S. A view fi'om the brachial valve of a larger individual ; showing no evidence of deltidium on the 



striate<i cardinal area of the pedicle-valve. 

 Fig. 3. A protile view of the same. 

 Fig. 10. An enlargement of the cardinal areas ; showing the vertical striic and complete obsolescence (f 



the deltidia. X 1^ 

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



muscular impressions. 

 Fig. 12. The interior of a pedicle-valve ; showing the muscular impressions. The center of the area has 



been bi'oken away by the detachment of the cardinal process. 

 Hamilton group. Western Neio York. 



StROPHEODONTA IN^QUIRADIATA, Hilll. 



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

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

 adductoi-s, and, at k, the tilling of the cavities occupied by the branches of the cardinal process. 

 Corniferous limestone. New York. 



StROPHEODONTA PaTERSONI, Hall. 



Fig. 15. The exterior of a pe<licle-valve ; showing, over the visceral 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 liriichial valve. From a yoiuig indiviiiual in which the 

 cardinal pi-ocess is (comparatively slender and the muscular area but slightly thickened. X 14- 

 Hamilton group. York, N. Y. 

 Fig. 19. The interior of the brachial valve ; showing the charactei-s of the full-grown imlividual. 

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

 dinal ])rocess are of great size and deeply grooved, the crural plates in a rudimentary condilioii 

 an<l the muscular scars much thicketied. X 2 

 Fig. 21. A posterior view of the same .specimen j showing the crenulateil edge." of the cardinal lot)es and 

 the size of the crural plates. At x the ba.se of the ('ardiual j)rocess has been excavated for the 

 reception of the margin of the pedicle-valve. X 2. 

 Hamilton gronj). Cananilai;/iia Lake, N. Y. 

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

 Fig. 23. An internal cai't of the pe<ii(tle-valve ; showing the lulductoi' and diductor scars. 

 Hamilton group. Western New York. 



