Description: A thin, brittle shell with an inflated appearance and a mostly elliptical outline. The anterior end of the shell forms a beaked shape, and at the posterior end there is a permanent pedal gape. At their largest they can measure over 15 cm in length but are more frequently found at smaller sizes. The exterior of the shell is white to pale grey, and may have some of the bored material stuck to it, or discolouring the shell. The periostracum is a pale yellow and may cover parts of the external shell surface. The shell has around 24 (occasionally more) prominent ridges and around 40 radiating ribs on the outer surface, and where these intersect sharp spines are formed. Interior of the shell is a glossy white with some of the external structuring visible. The pallial line is thick, and the pallial sinus deep.

Habitat: Bores into sand. peat, maerl, wood, chalk, sandstone, shale and slate.

Distribution: Recorded from most coasts of Britain and Ireland, but seems to have a more southern distribution and is absent from northernmost coasts.

Similar Species: May potentially be confused with the American piddock Petricolaria pholadiformis, Barnea parva or Barnea candida.

Key Identification Features:

• Inflated appearance and broadly elliptical outline.
• Anterior end of shell forms a beaked shape.
• Gapes at posterior end.
• Structure of 24 ridges and 40 radiating ribs.
• Where these intersect there are sharp spines.

Distribution Map from NBN: Pholas dactylus at National Biodiversity Network mapping facility, data for UK.

iNaturalist: Pholas dactylus at iNaturalist World Species Observations database.

GBIF data for Pholas dactylus

WoRMS: Pholas dactylus at World Register of Marine Species. Accepted name: Pholas dactylus Linnaeus, 1758. AphiaID: 140770.

Classification: Biota; Animalia; Mollusca; Bivalvia; Autobranchia; Heteroconchia; Euheterodonta; Imparidentia; Myida; Pholadoidea; Pholadidae; Pholadinae; Pholas