The Conchological Society of Great Britain and Ireland

Two species which were confused by Quick under the name Arion lusitanicus are distinguished from each other and from the other British species. Some of their external features, their eggs, the functional morphology of their genitalia, and their mating behaviour, all point to the inclusion of A.flagellus in Mesarion, and of A. lusitanicus in Arion s.s.