Perna viridis

BéarlaShell elongate, roughly trigonal-ovate in outline, swollen and pointed anteriorly, rounded and compressed posteriorly. Umbones terminal and sharply tapering, rather incurved. Anterior margin reduced. Ventral margin long and often somewhat concave. Outer surface nearly smooth apart from concentric growth marks and faint radial lines. Periostracum rather thick and smooth, adherent. Ligamental ridge finely pitted. Hinge with 1 small tooth in right valve and 2 in the left. Anterior adductor scar absent in adult specimens. Posterior retractor scars large, confluent with the posterior adductor scar. Anterior retractor scar separated, elongate-ovate in shape, situated a short way to posterior end of ligament. Internal margins smooth. Colour: outside of shell whitish under a bright periostracum which is dark brownish green anteriorly and olive-green to bright green posteriorly. Interior an iredescent pale bluish green, with a vivid green margin on periostracum.

• Mytilus viridis Linnaeus, 1758
• Mytilus smaragdinus Chemnitz, 1785