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. 
Genus CRUCIBULUM, Schumacher. 
Essai d’un Noy. Syst. 182. 1817. 
1. C. stRIATUM, Say. Fig. 186. 
(Dispotea.) Journ. 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. rornicaTa, Linneus. Figs. 187, 188, 189. 
(Patelia.) Syst. Nat. Edit., xii. 1257. 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, slightly 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. (Hur.) 
C. glauca (Fig. 189) is the young shell when flattened; if the 
growth is normally convex, however, the young is the C. convexa 
(Fig. 188). I have satisfied myself that these two forms are both 
