Arion Ferussac, 1819
The genus Arion contains about 30 species, most of which inhabit the Iberian Peninsula (Wiktor 1996) and others which are widespread.
Geomalacus.
External: Single color body or with banding on the sides; thick skin (Wiktor 1983).
Internal: Internal calcareous granules rather than an internal shell; long, twisted epiphallus; spermatheca connected to atrium, with a distinct stalk; epiphallus, oviduct, and spermatheca duct have separate origins in atrium; short atrium (Wiktor 1983; Wiktor et al. 2000).
Arion are distinct from the genus Geomalacus in terms of: reproductive opening posterior to the pneumostome; short genital retractor; internal shell only remaining as granules (Quick 1960).
Native to Europe, N Africa, and to a lesser extent Asia. Arion's major speciation center is the Iberian Peninsula (Wiktor et al. 2000).
Forest-dwelling (Wiktor 1983).
Omivores that usually consume plant material but may opportunistically eat carrion (Wiktor 1983; Barker 2004). Fungus and algae may also be consumed.