2. (Anat.)
(a) Any lidlike or operculiform process or part; as, the
opercula of a dental follicle.
(b) The fold of integument, usually supported by bony
plates, which protects the gills of most fishes and
some amphibians; the gill cover; the gill lid.
(c) The principal opercular bone in the upper and
posterior part of the gill cover.
3. (Zo["o]l.)
(a) The lid closing the aperture of various species of
shells, as the common whelk. See Illust. of
{Gastropoda}.
(b) Any lid-shaped structure closing the aperture of a
tube or shell.