Solid shell up to about 20cm in length. Dark blue or purple in colour bu this is generally obscured by dark brown periostracum. The inside of the shell is white. The surface is sculptured with fine concentric rings and ridges.
- Periostracum is not 'hairy' except in juveniles where the hairs are smooth
- Dark blue or purple shell with no rays
- The beaks are a slight distance from the extreme end of the shell
Lives on muddy gravel attached by byssus threads where it feeds by filtering phytoplankton. It can occur in very dense communities.
CommonNorway south to the Bay of Biscay