the acorn, in zoology; a genus belonging to the order of vernes testacea. The animal is the triton; the shell is multivalve, unequal, fixed by a stem or siphon. There are several species, of which the most remarkable is the anatifa, consisting of five shells depressed, affixed to a pedicle and in clusters. It adheres to the bottom of ships by its pedicles. The tentacles from its animal are feathered; and have given the old English historians and naturalists the idea of a bird. They ascribed the origin of the barnacle goose to these shells. See Plate CCLXXXIII.