5. Teredina. Two fossil species.

A genus without a living species, given here to preserve the family

entire, having a shell thick, oval, short, very gaping posteriorly,

equivalve, inequilateral; summits well marked; a spoonlike cavity in

each valve.

Tube or sheath testaceous, cylindrical; anterior end open; posterior end

closed, but exhibiting the two valves of the shell.