Ordo Mytiloida

de FĂ©russac, 1822

Shell equivalve, inequilateral, beaks in the front half, sometimes at or close to the anterior end. Triangular, rhomboidal or oval in outline. Periostracum prominent, often thick and spiny. Ligament internal or external. Hinge line without teeth but sometimes with tooth-like crenulations. In Crenella these crenulations are gathered onto a process under the beaks which is continuous anteriorly with the crenulate shell margin; this condition has been called pseudo-taxodont. Adductor muscle scars are normally markedly unequal, the anterior being much the smaller. Exceptionally, as in Idas , the muscle scars are almost equal. No pallial sinus.

Source: Tebble, 1966.

The following subtaxa of this order occur in the region:

Family Pinnidae
Genus Atrina
Atrina pectinata
Family Mytilidae
Genus Crenella
Crenella decussata
Genus Idas
Idas simpsoni
Genus Modiolarca
Modiolarca subpicta
Genus Modiolula
Modiolula phaseolina
Genus Modiolus
Modiolus barbatus
Modiolus modiolus
Genus Musculus
Musculus costulatus
Musculus discors
Musculus niger
Genus Mytilus
Mytilus edulis
Mytilus galloprovincialis