Translations:Adventist Youth Honors Answer Book/Nature/Shells - Advanced/27/en

c. Aperture

Semicassis pyrum, which has a large aperture.

The aperture is the main (or only) opening in the shell of a gastropod or snail. It is where the soft parts of the animal emerge. In some prosobranch gastropods, the aperture is able to be closed, and even completely sealed, with a sort of door or operculum.