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Family Hemidonacidae - hemidonax clam
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Bivalvia |
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Environment |
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Fresh : No |
Brackish : No |
Marine : Yes |
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Remark |
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Authority from Ref. 3477. Shell equivalve, subtrigonal to wedge-shaped and transversely elongate in outline, usually solid; more or less inequilateral, with the anterior side equal to, or longer than posterior side. Outer surface with weak to strong, smooth radial ribs, often reduced to absent on the anterior part of shell. Ligament external, lying behind the umbones, well within the dorsal part of the hinge plate. Hinge solid, with 2 unequal cardinal teeth and elongate lateral teeth in each valve; left valve with a single anterior and posterior lateral tooth; right valve with 2 anterior and 2 posterior lateral teeth; the upper lateral teeth often fused to dorsal shell margin. Interior of valves porcelaneous. Two subequal adductor muscle scars. Pallial line without a sinus. Internal margins crenulated. Gills of eulamellibranchiate type, with folded branchial sheets; outer demibranch smaller than inner demibranch and extended above the ctenidal axis. Foot wide, rather compressed, devoid of byssus and byssal groove. Siphons absent; posterodorsal exhalant aperture with short, simple tentacles, posteroventral inhalant aperture surrounded by complex, branched tentacles. Mantle widely open ventrally and fringed with small marginal tentacles, fused in its posterior third. Suspension filter-feeding animals, occurring in clean sand bottoms of shallow subtidal areas. Probably moving just below the surface with the posterior apertures flush with the surface, and capable of quick burrowing. Locally collected in the Philippines (Ref. 348). |
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