Arcopagia crassa (Pennant, 1777)Tellinoidea : Tellinidae
Inequivalve, RV more convex than LV.
Almost equilateral, beaks just behind midline.
Broadly ovate with a slight flex in the posterior from the umbonal region. Lunule chestnut-brown depression with radial grooves. Escutcheon absent.
Sculpture: Evenly spaced concentric lines/grooves. Margin: Smooth. Ligament: Prominent dark brown band extending halfway to posterior margin. Hinge: 2 cardinals in each valve; in LV anterior bifid, in RV posterior bifid. Anterior and posterior lateral in both valves. Pallial Musculature: Pallial sinus deep, extending past the midline and angled towards the top of the anterior adductor.
Cruciform muscles sometimes visible towards posterior ventral margin near the end of the pallial line. Periostracum: Thin, matt, yellow-brown. Colour: White/cream with orange/red-brown colouration at the umbones and extending as rays to the ventral margin. Internal white, with orange colouration in umbonal area and extending ventrally.
Distribution & Ecology
A deep burrower mostly in clean, coarse sand and shell gravel. Widely distributed on all coasts from the low intertidal and across the shelf but generally uncommon beyond 100m depth.
Continental Shelf (to 200m)
Juveniles & Similar Species
Juveniles are distinctly expanded anteriorly, more ovate than circular.
Key Features & Similar Species
Arcopella balustina is the only other subcircular tellin here and differs in having a thin shell and the co-marginal sculpture of thin slightly crispate lamellae; the pallial sinus is discrepant being much larger in the left valve.
Listed are literature citing Arcopagia crassa (Pennant, 1777). Reference containing the species Type Description is highlighted.
Pennant T 1777. British Zoology vol.IV. Crustacea, Mollusca, Testacea London, B. White. 154pp, 93pls.
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