Redescription of two problematic Alpine Oxychilus: O. adamii (Westerlund, 1886) and O. polygyra (Pollonera, 1885) (Pulmonata, Zonitidae)

The taxonomic and nomenclatural status of Oxychilus adamii (Westerlund, 1886) and O. polygyra (Pollonera, 1885) is revised. These two, very similar species are tentatively assigned to Mediterranean a ‘subgenus’ of Oxychilus characterized by (1) absent or very short flagellum; (2) penial retractor inserted where epiphallus ends and proximal penis begins; (3) internal ornamentation of penis consisting of pleats and rows of papillae, some of which or all with apical thorn; (4) short epiphallus internally with series of transverse crests on one side and a few slender longitudinal pleats on the other; (5) mucous gland forming muff of glandular tissue, denser and yellower around distal portion of free oviduct; (6) and short mesocone on the central tooth. O. adamii is distinguished by a medium-sized shell (diameter 16.1 ± 1.0 mm) and very small papillae without apical thorn covering the initial portion of the proximal penis. O. polygyra is distinguished by a small shell (diameter 10.4 ± 0.5 mm) and large papillae with an evident cuticularized apical thorn covering the initial portion of the proximal penis. The paper concludes with a review of the current status of Oxychilus taxonomy, including the main problems and some tentative solutions to be verified in the context of individual revisions.