This group includes land snails and land slugs. Loss of the shell has taken place many times in different groups that are not evolutionarily closely related, and land snails and slugs are most often treated together as a single group in specialized malacological literature.Barker G. M. (ed.) The biology of terrestrial molluscs. CABI Publishing, 2001, 558 pp. .Barker G. M. (ed.) Natural enemies of terrestrial molluscs. CABI Publishing, 2004, 644 pp. .
