Almost all shells open on the right-hand side, with the exception of a few snail species whose shells open on the left. If you find a shell that opens on the left (as long as it’s from a normally right-hand species), you have a rare shell sometimes highly sought by collectors.
Most gastropod shells are spirally coiled. The majority (over 90%) of gastropod species have dextral (right-handed) shells, but a small minority of species and genera are virtually always sinistral (left-handed), and a very few species (for example Amphidromus perversus) show a mixture of dextral and sinistral individuals. There occur also aberrantly sinistral forms of dextral species and some of these are highly sought by shell collectors.
The left-handed turrid (Antiplanes vinosa)
If a coiled gastropod shell is held with the spire pointing upwards and the aperture more or less facing the observer, a dextral shell will have the aperture on the right-hand side, and a sinistral shell will have the aperture on the left-hand side…. Continue Reading (11 minute read)