A revision of three Maghrebian hygromiid genera: Numidia Issel, 1885, Xerofalsa Monterosato 1892, and Xeroplana Monterosato, 1892 (Pulmonata: Helicoidea)

The taxonomic status of the following nominal genera of the xerophilous hygromiids is revised: Numidia Issel, 1885, Xerofalsa Monterosato, 1892, and Xeroplana Monterosato, 1892. Numidia and Xerofalsa are objective synonyms, but the senior name is not available because of the existence of two senior homonyms. Examination of the type species of Xerofalsa (Helix idia Issel, 1885) and Xeroplana (Helix doumeti Bourguignat, 1876) shows that they are identical in anatomical organization. Xerofalsa and Xeroplana, therefore, cannot be regarded as distinct taxa, but are synonymous. Since they were published at the same time, according the principle of the first revisor, it is established that Xerofalsa is a junior synonym of Xeroplana. Xeroplana seems close to the group of Cernuella Schutler, 1838 (Cernuella, Xeroamanda Monterosato, 1892, and Xerocincta Monterosato, 1892) with which it shares the following characters: (1) penial nerve from pedal ganglion, (2) right ommatophore retractor independent of genitalia, (3) mantle border with long left lateral lobe, (4) 0 + 2 dart-sac complex, and (5) penial complex joining vaginal complex at level of dart-sac complex. It differs from the group of Cernuella by virtue of: (1) dart-gun open as far as tip, (2) openings of two stylophores very close to each other, and (3) section of dart.