Observations on the genus Mastus from Crete (Greece), with descriptions of twelve new species (Gastropoda Pulmonata: Buliminidae)

In challenging the view that only two species of the genus Mastus occur in Crete, it is demonstrated that this genus is very speciose on the island instead. An identification key is presented and 12 new species are described, emphasizing that several more await description. Conchologically these species may be almost indistinguishable, but the structure of the genitalia enables their identification. In several areas more than a single Mastus species is represented.