These shells were once home to a sea snail called Turritella terebra, native to the Indo-Pacific.
The shell has a long tower-like shape which resembles a drill, hence its name which translates to towered drill. We’ve included a whole shell as well as a cutaway shell so the interior geometry is visible.
Shells begin at the larva stage with a protoconch, a tiny— sometimes microscopic—version of the shell. At this point the chirality, which way the shell will spiral, is already determined. The mollusk converts minerals in the ocean into calcium carbonate and excrete them to construct the shell as it grows.
More than 90% of mollusk shells are right handed and left-handed shells are sought by collectors. If you hold the shell with the point upward, turn the shell until the opening at the bottom points at you. If the opening is on the right side of the shell, it is right handed.
The Smithsonian currently has the world’s largest mollusk shell collection, consisting of nearly 20 million shells.