MARINE MOLLUSCA OF THE UNITED STATES. 93 



Shell ovate or oblong ; apex posterior, oblique, submarginal ; aperture 

 elongated, polished within, the posterior half covered by a horizontal 

 testaceous lamina. Crepidula, Lam. 



Genua CRTJCIBULTJM, Schumacher. 

 Essai d'un Nov. Syst. 182. 1817. 

 1. C. STRIATUM, Say. Fig, 186. 



{Dispotoea.') Jouru. Philada. Acad. Nat. Sci. v. 216. 1826. 

 Shell moderately solid, conical, with numerous equidistant, 

 elevated radiating lines. Summit smooth, obtusely pointed, sub- 

 spiral, inclining towards the left side and posterior end. Internal 

 cup attached at one side, and terminating above near the inner 

 apex of the shell. White. 



Height 12.5, diam. 20 mill. 



New England to New Jersey. 



Undetermined Species. 

 Infundibulum depressum. Say. 



Journ. Acad. Nat. Sci., Phila., v. 209. 1826. 



Shell depressed, fragile, with small concentric irregular wrinkles ; 

 volutions three ; suture not profoundly indented ; apex not cen- 

 tral ; base oval, almost orbicular; umbilicus oblong; internal 

 plate small. 



Diameter 5 -|- mill. 



South Carolina. 



Genus CREPIDULA, Lamarck. 

 Prodromus. 1799. 

 1. C. FORNiCATA, Linuseus. Figs. 181, 188, 189. 



{Patella.) Syst. Nat. Edit., xii. 1357. 1767. 

 Crepidula glauca, Say, Journ. Philad. Acad., ii. 226. 1822. 

 Crepidula convexa, Say, ibid., 227. 1822. 



Shell varying in convexity, with one side more oblique than 

 the other; apex turned to one side ; surface transversely wrinkled. 

 Partition smooth, slightl}' concave. White, or greenish, or red- 

 dish, with longitudinal undulated chestnut-colored lines, some- 

 times broken up into spots. 



Length 1 to 2 inches, width .7 to 1.3 inch. 



Inhabits the entire coast. (Eur.) 



C. glaiica (Fig. 189) is the young shell when flattened; if the 

 growth is normally convex, however, the young is the G. convexa 

 (Fig. 188). I have satisfied mj^self that these two- forms are both 



