- a part or organ serving as a lid or cover, as a covering flap on a seed vessel.
- Zoology.
- the gill cover of fishes and amphibians.
- (in many gastropods) a horny plate that closes the opening of the shell when the animal is retracted.
- zoology
- the hard bony flap covering the gill slits in fishes
- the bony plate in certain gastropods covering the opening of the shell when the body is withdrawn
- the covering of the spore-bearing capsule of a moss
- any other covering or lid in various organisms
