(1):

(n.) Any species of Siphonaria, a genus of limpet-shaped Pulmonifera, living between tides, on rocks.

(2):

(n.) Any one of many species of marine shellfish of the order Docoglossa, mostly found adhering to rocks, between tides.

(3):

(n.) In a general sense, any hatshaped, or conical, gastropod shell.

(4):

(n.) A keyhole limpet. See Fissurella.