univalve

adjective Also u·ni·valved, u·ni·val·vu·lar [yoo-nuh–val-vyuh-ler] /ˌyu nəˈvæl vyə lər/.

1. having one valve.
2. (of a shell) composed of a single valve or piece.

noun

3. a univalve mollusk or its shell.

adjective

1. relating to, designating, or possessing a mollusc shell that consists of a single piece (valve)

noun

2. a gastropod mollusc or its shell

1660s (noun and adjective), from uni- + valve.

1. A gastropod, especially one with a single shell, such as a snail, cone, whelk, abalone, or limpet. Univalves belong to the subclass Prosobranchia. Their shells are usually spiral and can hold the whole animal inside. Compare bivalve.