In colour and appearance they greatly vary, some being smooth and beautifully variegated with delicate colours, or radiated with purple and white; some are coarsely ribbed or granulated, and have only one colour, as black, blue, yellow, brown, or green; all are covered with an epidermis, to which oftentimes the colour is confined.
Shell of a close texture, elongated, more or less oval, sometimes sub-triangular, equivalve, summits anterior, more or less curved, a little sloping inferiorly; hinge generally without teeth, or with two very small rudimentary teeth; ligament dorsal, linear, sub-interior, inserted in a long and narrow furrow; two muscular impressions, of which the anterior is very small, with or without longitudinal grooves or furrows.
Mytilus Magellanicus.
M. erosus.
M. crenatus.
M. decussatus.
M. hirsutus.
M. elongatus.
M. latus.
M. zonarius.