Bathyarca pectunculoides Scacchi, 1835

Phylum:Mollusca Linnaeus, 1758
Class:Bivalvia Linnaeus, 1758
Synonyms:Arca crenulata Verrill, 1882; Arca koreni Danielssen, 1859; Arca pectunculiformis Locard, 1886; Arca pectunculoides Scacchi, 1835; Arca verrilli Lamy, 1907; Arca pectunculoides var. major Friele, 1878; Arca pectunculoides var. septentrionalis G.O. Sars

To size: To 7mm.

Shell Structure: Thin but not fragile, opaque. Equivalve: Inequivalve, left valve noticeably larger, right valve sitting inside left valve. Equilateral: Almost equilateral, beaks just in front of midline. Tumidity: Somewhat inflated. Outline: Roundly wedge-shaped (length only slightly greater than height), umbos prominent. Dorsal margin long, straight ; posterior broadly rounded, some obliquely subtruncate merging into obliquely sloping almost straight ventral margin invariable with a distinct byssus indentation; anterior narrowly rounded. Contour: Dorsal area narrow, edge of hinge plate raised; posterior angle indistinct, rounded.

Sculpture: Weakly reticulate, numerous radial raised lines dominant over numerous comarginal ridges; sculpture more prominent on the smaller right valve. Margin: Inner margin of larger left valve weakly crenulate adjacent to a submarginal groove; right valve smooth. Ligament: Duplivincular, chevrons developing from the posterior of the dorsal area. Hinge: Taxodont, teeth in two series set on a gently curved hinge plate, anterior set with up to 5 teeth, posterior set up to 5; posterior teeth subparallel to dorsal margin anterior teeth oblique. Pallial Musculature: Anterior adductor scar slightly smaller than posterior. Periostracum: Of fragile, pale straw coloured, very short bristles. Colour: Yellow. 

Attached by a narrow, stalked byssus to small stones and gravel. Mostly found at the shelf edge and upper slope but also on the outer shelf. Along the entire western seaboard and outer shelf areas off Shetland and the Hebrides.

Depth: 100 - 2000 m.

Author: Manushin Igor E. / 18.09.2015
Last edit: Zakharov Denis V. / 19.02.2017

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