Arion (Mesarion) sibiricus Simroth, 1901
A. sibiricus is morphologically very similar to A. subfuscus, from which it probably split during the Ice Ages (WIktor et al. 2000).
Arion subfuscus.
External: Brown-black body, with dark stripes and lighter upper edge along sides, and orange-yellow sides below stripes; strong winkles; striations along foot fringe; pale sole (Wiktor et al. 2000).
Internal: Very similar internally and externally to A. subfuscus, although genitalia are shorter and thicker (Wiktor et al. 2000).
To 30 mm contracted/preserved (Sysoev & Schileyko 2009); 20-30 mm long, 7-9 mm wide, mantle 8-11 mm long (Wiktor et al. 2000).
Far E Russia: Central and E Siberia, central and S Amur River Basin, Primorye Territory, Sakhalin, Kunashir Id (Likharev & Schileyko, MS; Sysoev & Schileyko 2009); probably N China (Wiktor et al. 2000).