Translations:AY Honors/Shells - Advanced/Answer Key/111/en
From Pathfinder Wiki
The operculum, meaning little lid, (plural: opercula or operculums) is a corneous or calcareous structure which exists in some groups of marine, freshwater, and land snails or gastropods. It is present in most but not all gastropods that have shells and gills. Pulmonate snails do not have opercula, but some terrestrial species are capable of secreting an epiphragm.
