are invertebrate marine animals distinguished by a hard, spiny covering
or skin hence the name from the Greek echinos spiny and derma skin.
They have been used as food since ancient times particularly by
the Romans. All echinoderms have a five way (pentamerous) symmetry
and a water vascular system. They come in various forms and include
the brittle-stars, sea urchins, starfish and sea cucumbers.