Green Sea Urchin Psammechinus miliaris

The Green Sea Urchin, also called the Shore Sea Urchin, is native to rocky shores of northwestern European coasts, particularly of the North Sea. It is olive green or brown with red-purple tips on its spines (and also called Purple-tipped Urchin). It grows to some 5cm across and often decorates itself with shells and debris for camouflage.

An omnivore eating small marine animals, seaweed and detritus, its mouth is on the underside. The one shown above seems to be attempting to dine on one of the arms of a living sea star.