What is "epiphragm"

Epiphragm \Ep"i*phragm\, n. [Gr. ? a covering, lid, fr. ? to block up.] (Zo["o]l.) A membranaceous or calcareous septum with which some mollusks close the aperture of the shell during the time of hibernation, or estivation.

n. A dry layer of mucus used by a snail or mollusk to seal itself inside its shell during hibernation.

An epiphragm is a temporary structure which can be created by many species of shelled, air-breathing land snails, terrestrial pulmonate gastropod mollusks. It can also be created by freshwater snails when temporary pools dry up.

In most species the epiphragm is made of dried mucus and although it is elastic, it is fairly easily torn when forcibly removing a snail from its substrate. In a few species the epiphragm is thick and quite rigid, being reinforced with calcium carbonate. This kind of epiphragm is very strong and may be difficult to break.