Solid wedge shpaed shell up to about 10cm in length. The outside is purple, blue or brown in colour; the inside is pearl white bordered with purple or blue. The surface is sculptured with concentric rings.
- Umbones turn downwards to make the basal line of the shell concave
- Mantle edge is dark blue or purple
Lives attached by byssus threads to any suitable hard substrate. Feeds by filtering phytoplankton.
Distributed from the south of Britain to the Iberian Peninsula and into the Mediterranean.