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Side and top view of a Cryptella canariensis from the Canary Islands
An unidentified semi-slug from Uganda

Semi-slugs, also spelled semislugs, are land gastropods whose shells are too small for them to retract into, but not quite vestigial.[1] The shell of some semi-slugs may not be easily visible on casual inspection, because the shell may be covered over with the mantle.

This is a type of gastropod that is intermediate between a slug (without an external shell) and a land snail (with a large enough shell to retract completely into).

There exist a number of gastropod families that have semi-slugs species.[2] There exist about 1,000 species of semi-slugs in comparison to about only 500 species of slugs.[1]


Semi-slugs have a worldwide distribution and have evolved in several families; genera include:

See also[edit]


  1. ^ a b Burton D. W. (1982). "How to be sluggish". Tuatara 25(2): 48-63. HTM.
  2. ^ a b c d e Breure A. S. H. (2010). "The rediscovery of a semi-slug: Coloniconcha prima Pilsbry, 1933 (Gastropoda, Pleurodontidae) from Hispaniola". Basteria 74(4-6): 78-86.