univalve shell

Land or aquatic mollusk having a foot and head, which retract into a spiral shell made of a single piece.

morphology of a univalve shell

spiral rib

Protruding line on the whorl of the shell parallel to the suture line.

whorl

Each of the turns around the apex, except the last; its diameter grows.

siphonal canal

Tubular extension of the opening of the last complete turn allowing water to circulate.

inner lip

Inner wall of the opening made by the last complete turn of the shell, opposite the outer lip.

columella fold

Small protuberance located along the columella.

axial rib

Protruding line on the whorl of the shell parallel to the columella.

outer lip

Outer wall of the opening made by the last complete turn of the shell, opposite the inner lip.

aperture

Orifice of the last complete turn allowing the head and foot of the mollusk to exit; it also withdraws into its shell through this opening.

suture

Line marking off the successive whorls of the shell.

columella

Solid axis of the shell that can be solid or hollow; the whorls turn around it.

nuclear whorl

First complete turn of the shell formed at the larval stage.

apex

Crown from which the shell grows.