Fragile brown shell but quite plump. Sculpture of fine concentric rings. Muscle scars and pallial line weak.
- Margin of shell is not crenulated
- Small shell (up to about 0.3cm)
- No lateral teeth but three cardinal teeth in each valve
Lived attached by byssus threads in crevices on rocky shores. In places densities of 60 000 per cubic metre have been recorded. Feeds by filtering phytoplankton. In reproduction the females produce gelatinous capsules and attach them to their byssus. These capsules contain a few large embryos that develop directly into young bivalves (ie. No larval stage)
Occurs from the north of Norway down to the Mediterranean