epiphragm
noun
ep·i·phragm ˈe-pə-ˌfram 
: a closing membrane or septum (as of a snail shell or a moss capsule)
Example Sentences
Recent Examples on the Web In addition to keeping the snails safely secured to surfaces, this temporary adhesive, known as the epiphragm, retains moisture and prevents their bodies from drying out. 
Meilan Solly, Smithsonian, 20 June 2019
Meilan Solly, Smithsonian, 20 June 2019 Word History
Etymology
borrowed from New Latin epiphragma, borrowed from Greek epíphragma "lid, cover," from epiphrak-, stem of epiphrássein "to block up" (from epi- epi- + phrássein, Attic phráttein "to fence in, enclose, block," of obscure origin) + -ma, resultative noun suffix
First Known Use
circa 1854, in the meaning defined above