Well, "luna" is Latin for "moon", and Luna was the Roman goddess of the
moon.  A few shells come to mind whose scientific names incorporate that
word, in a variety of ways.  The genus Lunatia (family Naticidae), one of
the "moon snail" genera, is a group of smooth, globular shells, presumably
named for their resemblance to a full moon.  The genus Lunella (Turbinidae),
meaning "little moon", is a group of small, round, mostly smooth turban
shells.  In Australia there is a marine mussel (family Mytilidae) called
Ciboticola lunata.  This is a crescent-shaped shell, resembling the crescent
moon or "new moon".  Interestingly, the inner (concave) curve of its shell
precisely matches the convex curvature of the ark shell Anadara (Scapharca)
pilula, which is its usual place of attachment.  In the little columbellid
snail Mitrella lunata, the name refers to the markings rather than the shape
of the shell.  It is a dark shell with light crescent-shaped markings.  Of
course, we have english words derived from that Latin word too, including
lunar, and lunatic, meaning one who is "moon-struck".
Paul M.