Abra alba (W Wood, 1802)Tellinoidea : Semelidae
To size: To 25mm. Shell Structure: Thin, brittle. Equivalve: Almost equivalve. Equilateral: Inequilateral, beaks to the posterior. Tumidity: Not tumid. Outline: Subtrigonal, posterior dorsal margin almost straight sloping to a rounded posterior margin, anterior dorsal margin slightly longer and slopes slightly less steeply to a broadly rounded anterior margin. Twists to right slightly.
Sculpture: Fine concentric lines, growth stages clear. Margin: Smooth. Ligament: External small brown, arched band, internal ligament in a small triangular chondrophore. Hinge: LV one small cardinal and single weak laterals; RV two cardinals and single laterals. Pallial Musculature: Deep pallial sinus, confluent with pallial line for most of its length. Cruciform muscle scars visible in some specimens. Periostracum: Light brown. Colour: Dirty white.
Distribution & Ecology
Lives in a wide range of substrates but most often in fine, silty sand, less frequent in mud or gravel
Distributed all around the coasts of Britain and Ireland, occurring from the lower shore to the shelf edge.
Continental Shelf (to 200m)
Juveniles & Similar Species
Hyaline, transparent, similar to adult but outline in very small shells more symmetrical.
Key Features & Similar Species
Often confused with Abra nitida, but the outline of A. alba is more inequilateral, more broadly subovate with a less pointed posterior and lacks the distinct depression associated with the external ligament. Some populations are posteriorly more acute but do not have the posterior depression.
Listed are literature citing Abra alba (W Wood, 1802). Reference containing the species Type Description is highlighted.
Allen J A & Sanders H L 1966. Adaptations to abyssal life as shown by the bivalve Abra profundorum (Smith). Deep Sea Research and Oceanographic Abstracts. 13: 1175-1178.
Wood W 1802. Observations on the hinges of British Bivalve Shells. Transactions of the Linnaean Society. VI: 174.
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