epiphragm

300px|thumb|right|Helix pomatia using a simple transparent epiphragm made of dried mucus

An epiphragm (from the Ancient Greek ἐπί, epi " upon, on, over " and φράγμα, -phrágma "fence") 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.