pallial

Their valves are equal in size and very thin, the hinge has no teeth and the pallial line is sinuated.

The ligament is external, the hinge has usually three diverging teeth in each valve, and the pallial line is sinuated.

In these there are neither branchia nor osphradium, and the pallial chamber which retains its large opening serves as a lung.

Patella, pallial branchiae forming a complete circle, no epipodial tentacles, British.

No ctenidia but pallial branchiae in a circle between mantle and foot.