The word "valve" can mean "shell;" this is a rare and unfamiliar meaning, but that it what it means here. The word "bivalve," then, means having two shells. The two bivalve shells are hinged together at one place and can be closed tightly by a powerful muscle, the ''adductor.'' | The word "valve" can mean "shell;" this is a rare and unfamiliar meaning, but that it what it means here. The word "bivalve," then, means having two shells. The two bivalve shells are hinged together at one place and can be closed tightly by a powerful muscle, the ''adductor.'' |