[2] With over 1700 recognized recent and fossil species,[2] this is among the most diverse families of terrestrial gastropods (cf.

Most species of Clausiliidae have an anatomical structure known as a clausilium, which enables the snail to close off the aperture of the shell with a sliding "door".

The clausilium is a calcareous structure, tongue-shaped or spoon-shaped, which can close the aperture of the snail shell to protect the soft parts against predation by animals such as carnivorous beetle larvae.

The narrow end of the clausilium slides in the grooves that are formed by the folds on the inside of the shell.

In this family, the number of haploid chromosomes lies between 21 and 30 (according to the values in this table).