Iceland & Barents Sea to Canarias, Azores to Mediterranean. Groenland, N. Labrador to N. Carolina. Bering Sea to California.
Intertidal (rare) to continental shelf and slope, in mud and muddy sands. Chemosymbiotic (bacterial dependence), but occasionally suspension feeder. Original taxon: Tellina flexuosa. Synonyms: angulatus, sinuata, unicarinatus…

« Cryptodon flexuosus: Shell subtriangular, subglobose, thin, pellucid, fragile, white; umbones small, slightly inflected, and unequal, that of the right valve smallest, the other resting on the cavity above the primary tooth of the opposite valve; beneath them a large cordate lunule, with an elongated lunule on the cartilage side, pointed at both ends; a sulcus emanates from the umbones in both valves, running nearly parallel with the cartilage, terminating at one side, where it forms a pretty large sinus, or flexure, at the edge; whole surface moderately glossy, remotely and rather irregularly striated concentrically; hinge with a single, erect, triangular tooth in one valve, and a flat, nearly obsolete one in the other; inside smooth, glossy, white, exhibiting slightly nacred reflections, and some indications of longitudinal radii; margins plain, and very acute. » – T. Brown: Illustrations of the recent conchology of Great Britain and Ireland, London 1844, via BHL.