A new species of Oniscus Linnaeus, 1758 (Crustacea: Isopoda: Oniscidea) from northern Spain, with a revised key to members of the genus

Oniscvs ancarenisis from the Sierra de Ancares in northern Spain is described as new. The genus Oniscus now contains four species: ancarensis sp. nov., asellus Linnaeus, lusitanus Verhoeff and simoni Budde-Lund. The distribution of these species is figured and discussed, and a key is given for their determination.