The aperture is an opening in certain kinds of mollusc shells: it is the main opening of the shell, where the head-foot part of the body of the animal emerges for locomotion, feeding, etc.
Borysthenia naticina is a species of small freshwater snail with a gill and an operculum, an aquatic gastropod mollusc in the family Valvatidae, the valve snails.
Valvata studeri is a species of minute freshwater snail with an operculum, an aquatic gastropod mollusk in the family Valvatidae, the valve snails.
Clappia umbilicata, the umbilicate pebblesnail, was a species of small freshwater snail that had an operculum, an aquatic gastropod mollusk in the family Lithoglyphidae. This species is now extinct.
Pleurocera catenaria is a species of freshwater snail with a gill and an operculum, an aquatic gastropod mollusc in the family Pleuroceridae.
Leptoxis ampla, common name the round rocksnail, is a species of freshwater snail with a gill and an operculum, an aquatic gastropod mollusc in the family Pleuroceridae.
Marstonia olivacea, common name the olive marstonia, was a species of very small freshwater snail, an aquatic gastropod mollusc in the family Hydrobiidae. This species was endemic to Alabama, the United States. Its natural habitat was rivers. This species is now extinct.
Ladislavella utahensis, common name the thickshell pondsnail, is a species of air-breathing freshwater snail, an aquatic pulmonate gastropod mollusc in the family Lymnaeidae, the pond snails. This species is endemic to Utah Lake in the United States. The last living snails were found in the early 1930s.
The sportingoods tryonia, scientific name Tryonia angulata, is a species of small freshwater snail with a gill and an operculum, an aquatic gastropod mollusc in the family Hydrobiidae. This species is endemic to the United States.
The Utah roundmouth snail, also known as the Utah valvata or desert valvata, scientific name Valvata utahensis, is a species of freshwater snail with a gill and an operculum, an aquatic gastropod mollusc in the family Valvatidae, the valve snails.
Valvata is a genus of very small freshwater snails with an operculum, aquatic gastropod mollusks in the family Valvatidae, the valve snails.
Valvata cristata is a species of minute freshwater snail with an operculum, an aquatic gastropod mollusk or micromollusk in the family Valvatidae, the valve snails.
Valvata piscinalis, common name the European stream valvata or European valve snail, is a species of minute freshwater snail with gills and an operculum, an aquatic gastropod mollusk in the family Valvatidae, the valve snails. It is also known as Cincinna piscinalis.
Valvata macrostoma, also known as the large mouthed valve snail, is a species of minute freshwater snail with an operculum, an aquatic gastropod mollusk in the family Valvatidae, the valve snails.
Valvata sibirica is a species of minute freshwater snail with an operculum, an aquatic gastropod mollusk in the family Valvatidae, the valve snails.
Valvata lewisi, common name the fringed valvata, is a species of small freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Valvatidae, the valve snails.
Valvata tricarinata, common name the three-ridge valvata or threeridge valvata, is a species of small freshwater snail with a gill and an operculum, an aquatic gastropod mollusk in the family Valvatidae, the valve snails.
