Cuthona genovae (O'Donoghue 1926), an aeolid nudibranch new to the fauna of the British Isles

Cuthona genovae, a common Mediterranean nudibranch, is recorded for the first time outside the Mediterranean from Lough Hyne, Co. Cork, Ireland. It is described and figured and compared with its close relative Cuthona foliata (Forbes & Goodsir 1839). The previously known distributions of these two species suggested that C. genovae replaced C.foliata in the Mediterranean. The records given here show that they are in fact sympatric over a considerable part of their ranges, and confirm their distinct specific status.