Onchidoris bilamellata (Linnaeus, 1767)

August 2000.
Dunbar on the east coast.
One of several of these 5mm juveniles found on rocks at 9-10 metres at the Johnstone's Hole dive site.

for more information about this species go to one of the links below
OPK - Opistobranquis

 nudibranchs of the british isles sea slug forum