The River Snail (Viviparus viviparus) is a freshwater gastropod commonly found in slow-moving rivers, canals, and lowland lakes across much of Europe, including the British Isles. Recognisable by its smooth, conical shell with gently rounded whorls, this snail typically displays a glossy olive-green to brown colouring, often with faint spiral bands. Adult shells can reach up to 4 cm in height and possess a robust operculum that seals the aperture when the snail retracts, offering protection from predators and desiccation.

A notable characteristic of the River Snail is its method of reproduction. Unlike many other molluscs, Viviparus viviparus is ovoviviparous—a term that describes animals which produce eggs that hatch inside the parent’s body. Rather than laying eggs externally, the female retains them until they are ready to hatch, giving birth to fully formed, miniature snails. This increases the likelihood of survival for the young, offering them protection during their earliest and most vulnerable stage.

The species is also equipped with gills lined with cilia—tiny, hair-like structures that create water currents to assist in both breathing and feeding. These adaptations enable the snail to tolerate low-oxygen environments commonly found in silty or sluggish waters.

The River Snail plays a key role in maintaining ecological balance in freshwater systems, grazing on algae and contributing to nutrient cycling.

Collected in Barton in August of 1911.