The presence of a clausilium is in fact the reason for the common name "door snails", because all the snails in this family have a sliding "door" or clausilium, which can close the aperture of the shell.
The presence of a clausilium is in fact the reason for the common name "door snails". All the snails in this family have a sliding "door" or clausilium. Clausilium can close the aperture of the shell.