Look up an image:
Explore by theme
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.
