Operculum synonyms

Above the mouth is the lid (operculum), which varies in size from a small narrow process to a large heartshaped expansion.

Spire of shell much reduced; two bipectinate ctenidia, the right being the smaller; no operculum.

Very usually, but not universally, the metapodium carries an operculum.

Cyclostoma, shell turbinated, operculum calcareous, British.

Foot divided into two, posterior half bearing the operculum; a wide epipodial velum; shell turbinated.