Description: This bivalve has a thin, brittle shell that is broadly oval and up to 2 cm in length. It is white to pale yellow, sometimes with pink, red or brown radiating rays which can be irregular, but clearer at the margins. The periostracum is thin, glossy and transparent. There are evenly spaced, concentric ridges on the valves but growth stages are not clear. Inside of the shell is white to yellow, but sometimes the pink to brown rays on the outside are visible. Both valves have 2 cardinal teeth, the posterior is bifid on the right, the anterior on the left, and a weak anterior and posterior lateral tooth. On the right valve the anterior lateral tooth is long and thin.

Habitat: Deep offshore silty sand from 150-500 m.

Distribution: Rarely recorded around Britain and Ireland.

Similar Species: Could be confused with some other superficially similar bivalves. Careful inspection of diagnostic features such as cardinal and lateral teeth, pallial sinus and overall shape and appearance of the shell should help to distinguish.

Key Identification Features:

• Small brittle bivalve up to 2 cm.
• White to pale yellow with irregular, radiating rays in pink, red or brown.
• 2 cardinal teeth on each valve, posterior bifid on right, anterior on left.
• Anterior lateral tooth on right valve is long and thin.

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

iNaturalist: Arcopella balaustina at iNaturalist World Species Observations database.

GBIF data for Arcopella balaustina

WoRMS: Arcopella balaustina at World Register of Marine Species. Accepted name: Arcopella balaustina (Linnaeus, 1758). AphiaID: 491643.

Classification: Biota; Animalia; Mollusca; Bivalvia; Autobranchia; Heteroconchia; Euheterodonta; Imparidentia; Cardiida; Tellinoidea; Tellinidae; Arcopagiinae; Arcopella