Segregates of the Arion hortensis complex (Pulmonata: Arionidae) with the description of a new species, Arion owenii

The name Arion hortensis has been used for three different British species of slug, called A, R and B by Davies (1977).Arton (Kobeltia) hortensis Férussac s. s. is defined as having the anatomy and spermatophore of form R. A. (K.) distinctus Mabille is identified as form A, and is thus given an anatomical definition.External features are discussed with reference to original descriptions and identification.Form B becomes A. (K.) owenii sp.nov.The subgenus KAobeliza is distinguished from the rest of Arion by the short spermatophore, which, instead of entering a longer spermatheca duct, is at first held in the atrium by means ofa collar attached at or within the entrance to a very short spermatheca duct.Details of the spermatophore, and the structures associated with its attachment, may be used to define the three species hitherto known as the A. hortensis complex.A. intermedius Normand, although its spermatophore is not known, may also be placed in Kobeltza because of its general similarity, and in particular, the very short spermatheca duct and the termination of the epiphallus.The oviduct, which is short and undifferentiated in A. intermedius, is long and developed for protrusion in coitus in the other species, in different proportions, and with two alternative forms in one species.The following account attaches names to the three species already described and figured (Davies, 1977), adding some further observations on external features and identification.