This superbly patterned Sea Urchin is a night time grazer feeding mostly on fine algae and detritus which adheres to coral rock.  It has hard grinding teeth on its underside and often you'll find the tiny scrapes where they have been feeding.  During the day they hide in crevices in the coral and are quite hard to see. 

20 x 25cm Acrylic Block

Includes free delivery within Australia.