The Common Piddock (Pholas dactylus) is a distinctive burrowing bivalve mollusc found along the eastern Atlantic coastline, from the British Isles to the Mediterranean. Easily recognised by its elongated, oval-shaped shell, the Common Piddock exhibits a chalky-white exterior marked with ridges and rows of rasp-like teeth that aid in boring into soft substrates such as clay, chalk, and soft limestone. Adults typically measure up to 12 cm in length and are well-adapted for life spent almost entirely within the substrate.

One of the most remarkable features of the Common Piddock is its ability to bore into rock using both mechanical and chemical means. As the mollusc matures, it gradually creates a permanent burrow in which it remains for life. Despite this sedentary existence, the piddock can extend its siphons beyond the burrow to filter-feed on plankton and organic matter suspended in the water column.

Common Piddocks inhabit intertidal to shallow subtidal zones, often in sheltered coastal areas. Their presence is often revealed by oval or flask-shaped holes in exposed rock surfaces, especially at low tide. While not commonly consumed today, piddocks were once eaten in some coastal communities, and their unique habitat-forming behaviour continues to be of ecological interest.

Originally part of the MBA collection. Collected from Rum Bay in 1898.