Polycera quadrilineata (Müller, 1776)

22 July, 2009.
Sgarbhstac, Boreray, St. Kilda on the west coast. 
A feeding congregation at 12 metres.
Water temperature 13° C.
Fuji E900 camera in Ikelite housing 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