operculum
Pronunciation: /ə(ʊ)ˈpəːkjʊləm/
noun ( plural opercula /-lə/)
Zoology & Botany- a structure that closes or covers an aperture, in particular:
- technical term for gill cover.
- a secreted plate that closes the aperture of a gastropod mollusc’s shell when the animal is retracted.
- a lid-like structure of the spore-containing capsule of a moss.
Origin:
early 18th century: from Latin, literally 'lid, covering', from operire 'to cover'