Epiphragm
(n.) A membranaceous or calcareous septum with which some mollusks close the aperture of the shell during the time of hibernation, or aestivation.
Similar Words:
Epiphany Epipharyngeal Epipharynx Epiphonema Epiphoneme Epiphora Epiphragm Epiphyllous Epiphyllum Epiphylospermous