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

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