Some groups of snails have shells that coil to the left (left-handed), while others have shells coiling to the right (right-handed). In some groups both right- and left-handed members are present. The shell affords protection from predators and the rigors of the environment. When threatened, the snail pulls its entire body inside. A small, circular structure called the operculum closes securely behind the snail to form a tight seal that keeps out predators and keeps in moisture.
