ISBN: | 978-5-5137-5901-0 |
High Quality Content by WIKIPEDIA articles! The operculum, meaning little lid, (plural: opercula or operculums) is a corneous or calcareous anatomical structure which exists in many (but not all) groups of sea snails and freshwater snails, and also in a few groups of land snails. In other words, this structure is found in some marine and freshwater gastropods, and in a minority of terrestrial gastropods, including the families Helicinidae, Cyclophoridae, Aciculidae, Maizaniidae, Pomatiidae, etc.