Genus Mya Linnaeus, 1758

Mya Linnaeus, 1758: 670.

Hiatula Modeer, 1793: 178 (fide Keen, 1969: 691). Myarius Duméril, 1806: 168 (fide Keen, 1969: 691). Arenomya Winckworth, 1930: 15.

Diagnosis. Shell thick, gaping both anteriorly and posteriorly; sculpture of commarginal growth lines. Type species. Mya truncata Linnaeus, 1758 (by subsequent designation of Children, 1822) (ICZN Op. 94, Dir. 72; see ICZN 2011).

Remarks. Some authors recognize two subgenera, Arenomya and Mya (Bernard 1979; Habe 1977; Keen 1969; MacNeil 1965). However, Winckworth (1930) erected Arenomya without diagnosis only because “The marked conchological differences between adult Arenomya and Mya (type truncata L.) seem sufficient reason for giving this name” (Winckworth 1930: 15). Coan et al. (2000) argued that any character chosen for a subgeneric distinction would leave one or more species in a doubtful position. This view is followed here.