Marine invertebrates at various trophic levels point at an important role in many ecosystems. Echinoderms (Greek for "spiny skin") is a phylum which contains only marine invertebrates. The adults are recognizable by their radial symmetry (usually five-point) and include starfish, sea urchins, sand dollars, and sea cucumbers, as well as the sea lilies. Echinoderms are found at every ocean depth, from the intertidal zone to the abyssal zone. The phylum contains about 7000 living species, making it the second-largest grouping of deuterostomes (a superphylum), after the chordates (which include the vertebrates, such as birds, fishes, mammals, and reptiles). Echinoderms are unique among
Starfish site and Sheffield. The new "Special Fire" decoys were set up to simulate the bomb drops of German pathfinder squadrons. By 23 January 1941 the programme had been increased to 43 sites protecting 13 town and cities and by March operational sites numbered over 100. By the end of the war there were 237 Starfish sites protecting 81 locations. One of the first decoy sites was constructed on Black Down on the Mendip Hills; it was code-named "Starfish", derived from Turner's original SF code, and built to protect the nearby city of Bristol. The Starfish name was eventually adopted to describe