The genus Monacha in the Western Caucasus (Gastropoda: Hygromiidae)

Seven Monacha species have been found in the Western Caucasus region. Six of these species are endemic there. They all belong to the subgenera Paratheba and Metatheba. Three species are new to science. M. (Paratheba) claussi, sp. n. and M. (Metatheba) subcarthusiana (Lindholm) are the only Monacha species, in which the right ommatophoral retractor sometimes crosses with the penis. This might be due to an ancestral polymorphism, atavism or a basal position of the two species within Monacha, which would mean that Paratheba is paraphyletic and Metatheba is polyphyletic. Monacha (Monacha) cartusiana (O. F. Muller), the only Monacha sensu stricto species in the Caucasus region, has probably been introduced by man. The shell and the genitalia of every species are described and illustrated. The synonyms and all Caucasian locality records are listed. The distributions of the species are illustrated on UTM-grid maps.