Differences in mitochondrial DNA and minor anatomical differences exist between populations of "A. rufus" found in the British Isles and the commonest form found on the European continent. These have been given the status of species or subspecies. Because of the designation of the lectotype, the name "rufus" now refers to the British form, which may be called "Arion rufus", "Arion rufus rufus" or "Arion ater rufus" depending on which taxa are considered as species or subspecies. Garsault (1764) appears to have been the first to describe the Continental form under a name other than "rufus", so its name should be "Arion ruber", "Arion rufus ruber" or "Arion ater ruber". Quite possibly there are further forms of similar status from elsewhere in France and Spain.