Species Account

Bathyarca pectunculoides (Scacchi, 1835)

Arcoidea : Arcidae

Tebble name: Arca pectunculoides Scacchi
Smith & Heppell name: Bathyarca grenophia Risso, 1826

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: White.

Distribution & Ecology

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 Range
Continental Shelf (to 200m)
Continental Margin Zone (200 - 500m)
Bathyal (500 - 2000m)

Additional Information & Related Species

Key Features & Similar Species

Most similar in shape to Bathyarca frielei but that species has an almost smooth and hyaline shell. B. philippiana has a coarser sculpture and is proportionately more elongate with a stronger byssal sulcus.

Additional Comments

ICZN Opinion 1887

Related Species


Listed are literature citing Bathyarca pectunculoides (Scacchi, 1835). Reference containing the species Type Description is highlighted.

Oliver G & Allen J A 1980. The Functional and Adaptive Morphology of the Deep-Sea Species of the Arcacea (Mollusca: Bivalvia) from the Atlantic. Philosophical Transactions of the Royal Society of London Series B. 291: 45-76.
Scacchi A 1835. Notizie intorno alle conchiglie ed a’zoofiti fossili che si trouvano nelle vicinanze Gravina in Puglia. Annali Civili del Regno delle Due Sicilie. 6: 75-84.


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Record last modified: 17/05/2016