Lithophaga Röding, 1798

(Fig. 1)

Type species. L. mytuloides Röding, 1798, by monotypy, referring to Gmelin’s (1791: 3351) species 6, Mytilus lithophagus Linnaeus, 1758 .

Diagnosis. Shell cylindrical, posteriorly more compressed, with vertical striae antero-ventrally and lacking any self-deposited calcareous incrustation (subgenus Lithophaga) or shell smooth and (partly) covered with own incrustations, particularly on the posterior half (subgenus Leiosolenus Carpenter, 1857). Umbones subterminal, ligament deep-set, along a toothless hinge.

Remarks. Anal and branchial siphons fused as in Adula, but the branchial part lacks papillae on its edge in Lithophaga . In L. lithophaga, there is a tonguelike structure, the valvular membrane, with minute papillae at the base of the branchial sipho (List 1902: pl. 7, fig. 6). Some examples of valvular siphonal membranes with central lappet and lateral digits in three L. ( Leiosolenus) species are figured in Wilson (1985: figs. 5 and 7a, c), those of B. fusca by Wilson & Tait (1984: figs. 4, 5A, B). All seem to be quite variable and, therefore, of no help for species determination.