I enjoyed a visit to the Bailey-Matthews National Shell Museum on Sanibel Island, Florida.

It has extensive exhibits of shells from all over the world, which are not only beautiful but also educational. Besides the public displays, the museum has a world-class research collection of mollusks. Learn more about the museum's exhibits here:
http://shellmuseum.org/exhibits.cfm

Among the many exhibits is one with about the growth and development of the Lightning Whelk, Busycon sinistrum (see photo). This species has a left-handed shell (most gastropods are right-handed).

The species is closely related to the Lightning whelk that occurs in Texas, Busycon pulleyi. The two have been considered as either subspecies, synonyms, or separate species. The Biodiversity of the Gulf of Mexico (BioGoMx) database accepts both as separate species. See more at:
http://gulfbase.org/biogomx/biospecies.php?species=Spp-33-0949