Description: A thin, solid bivalve, reaching around 3 cm. It is broadly circular in shape, although slightly longer than it is broad. It is white with a light yellow to brown periostracum. There are fine concentric ridges and a few very pale radiating rays. Each valve has 2 cardinal teeth, the anterior is bifid on the left, while the posterior is bifid on the right. There are single posterior and anterior lateral teeth on each valve. Shell interior is white. Anterior adductor scar comma-shaped and close to pallial line.

Habitat: Muddy sand and gravel. Offshore, from around 5-70 m depths.

Distribution: Scattered records from all around Britain and Ireland, but seems to be most common on south and southwest coasts of Ireland and Britain.

Similar Species: There is only one species in this genus found in Britain and Ireland.

Key Identification Features:

• White bivalve with fine concentric ridges.
• 2 cardinal teeth, anterior bifid on left valve, posterior on right valve.
• Comma-shaped anterior adductor scar, close to pallial line.

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

iNaturalist: Diplodonta rotundata at iNaturalist World Species Observations database.

GBIF data for Diplodonta rotundata

WoRMS: Diplodonta rotundata at World Register of Marine Species. Accepted name: Diplodonta rotundata (Montagu, 1803). AphiaID: 141883.

Classification: Biota; Animalia; Mollusca; Bivalvia; Autobranchia; Heteroconchia; Euheterodonta; Imparidentia; Venerida; Ungulinoidea; Ungulinidae; Diplodonta