Polycera quadrilineata (Müller, 1776)

22 July, 2009.
Cul Cleite, Dun, St. Kilda on the west coast. 
A pair of 22 mm animals at 14 metres. Water temperature 13° C.
Fuji E900 camera in Ikelite housing, 2 x Inon CU lenses and 2 x Inon D-2000 flashes.

for more information about this species go to one of the links below
OPK - Opistobranquis nudibranchs of the british isles sea slug forum