Arca (Tetrarca) tetragona Poli, 1795
Arcoidea : Arcidae
Strong but not thick, opaque.
Inequilateral, beaks about 1/4 of dorsal margin length from anterior.
Becoming greatly expanded.
Trapezoidal, dorsal margin very long straight, posterior margin oblique straight, ventral margin straight or sinuate with a prominent byssal gape, anterior margin rounded.
Dorsal area flat, becoming very wide. Posterior carina sharp, median area flattened or depressed.
Sculpture: Primary sculpture of closely spaced radial riblets these interrupted by growth stops and overall nodulose; posterior area with a few broad ribs these also nodulose. Margin: Inner margin weakly crenulated in correspondence to riblets. Ligament: Duplivincular, initially between beaks but extending over the whole of the dorsal. Hinge: Taxodont: Of numerous small teeth in two series, set on a narrow straight hinge plate; anterior teeth mostly vertical small up to 30 in number; posterior teeth larger, mostly oblique up to 15 in number although those closest to the centre may be eroded or lost. Pallial Musculature: Anterior adductor slightly smaller than posterior, both with a weak myophoric flange. Periostracum: Of simple dark brown, short bristles, those on the posterior carina longer. Colour: White to dull pale brown.
Distribution & Ecology
Continental Shelf (to 200m)
Additional Information & Related Species
Key Features & Similar Species
Arcoidea : Arcidae
Listed are literature citing Arca (Tetrarca) tetragona Poli, 1795. Reference containing the species Type Description is highlighted.
Poli J X 1795. Testacea Utriusque Siciliae eorumque historia et anatome. vol. 2 Parma, Regio Typographeio. i-lxxvi. 75-264, pls 19-39.
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