Description: This bivalve has two solid equal valves and a distinctive inflated, elongated irregular oval outline, which gapes at both ends. The valves are mostly white but often discoloured and may have some material attached. It can reach almost 4 cm in length. Outer surface may be covered in part by the light yellow periostracum. There are concentric ridges and radiating ribs, which get more pronounced towards the rear of the shell. Shell interior is glossy white and some of the external ridges and rays are visible. Pallial sinus is deep and extends beyond the midline. The margins of the shell are smooth aside from at one end, where projections give it a notched outline.

Habitat: Bores into soft rock such as chalk, lignite, mudstone, lias (includes limestone) and red sandstone, as well as slate and maerl. Found from the intertidal to around 5-6 m depth.

Distribution: Seems to be a southern species. Most records are from south of Britain with a few records in Scotland. Currently no records from the island of Ireland.

Similar Species: Could be confused with Barnea candida, which has a more brittle shell with a more regular shape and less inflated appearance. See also the American piddock Petricolaria pholadiformis and common piddock Pholas dactylus.

Key Identification Features:

• Solid valves.
• Distinctive elongated irregular oval outline.
• Concentric ridges and radiating rays on outer shell surface.
• Rays more pronounced towards rear of shell.
• Deep pallial sinus, extending beyond midline.

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

iNaturalist: Barnea parva at iNaturalist World Species Observations database.

GBIF data for Barnea parva

WoRMS: Barnea parva at World Register of Marine Species. Accepted name: Barnea parva (Pennant, 1777). AphiaID: 140768.

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