In regularly Norway Post issued a stamp set features the marine life species of Norway. On March 29, 2006, they has been issue one stamp as the third series depicted the Naked snail or Polycera quadrilineata which have been observed from the Mediterranean to the North of Norway. The stamp picture base on a photo by Erling Svensen.
Polycera Quadrilineata
Polycera quadrilineata grows to about 40 mm in length. Its body is white with blotches of yellow or orange. Sometimes black spots or speckling can be present. The orange marks usually from a line down the dorsal midline, with others in the sides and dorsal part of the posterior foot. The rhinophores, gills and tentacles are tipped with orange, and in some cases the gills are edged in orange. There usually four pointed papillae around the anterior (head end) of the mantle. It feeds on ectoproct bryozoans, especially Membranipora membranacea.
These sea slugs can often found on kelp or red algae where they graze on moss animals. They often congregate in large number. This is one of the sea slugs that is most often observed by divers.This species have distribution range from Iceland and Greenland South to the Mediterranean (Western Europe Region).