The distribution of this family of slugs includes Nearctic, Palearctic and Oriental regions.

[1] Cephalic retractors tend to divide into separate branches attached independently to the posterior part of pallial complex.

[1] The shell is strongly reduced in places, most often completely buried in the mantle, usually of loose crystals or plate-like.

[1] Male copulatory organs are generally reduced, their role being taken over by a well-developed atrium and the epiphallus that produces spermatophores.

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