Epiphragm

noun

1. In botany: The disk-like apex of the columella of Polytricheæ, which extends over the mouth of the capsule below the operculum.
2. A delicate membrane closing the cup-like receptacle of the Nidulariacei.
3. In conchology, the plate of hardened mucus secreted by a gastropod, as a snail, to plug up or seal the opening of the shell during hibernation; a sort of temporary or false operculum, sometimes hardened by calcareous deposit. See clausilium.
4. A membranaceous or calcareous septum with which some mollusks close the aperture of the shell during the time of hibernation, or estivation.
5. A dry layer of mucus used by a snail or mollusk to seal itself inside its shell during hibernation.