Genus Thyasira Leach ms in Lamarck, 1818

Type species. Tellina flexuosa Montagu, 1803

Generic Definition. Fragile shells, subcircular, ovate to ovate-polygonal in outline with a posterior sulcus; escutcheon variably expressed, absent to deep, with or without an auricle producing a submarginal sulcus. Hinge teeth lacking or as a single “cardinal” tubercle, ligament sunken. Anterior adductor scar elongate, posterior adductor scar ovate, pallial line entire. Ctenidium with two demibranchs, lateral body pouches large and multilobed, foot vermiform, heel obsolete, toe developed.