Dendronotus frondosus (Ascanius, 1774)

September 1998.
The Summer Isles on the west coast.
This animal is being used for shelter by a juvenile Lumpsucker. The gills are are either missing or are retracted.

for more information about this species go to one of the links below
scottish nudibranchs

 nudibranchs of the british isles sea slug forum