Sea urchin

Sea urchins are small, globular, echinoderms that, with their close kin, such as sand dollars, constitute the class Echinoidea. About 950 species of echinoids inhabit all oceans at various depths. They feed primarily on algae, have five-fold symmetry, and moving on tiny tube feet. Subclass Euechinoidea includes both spiny urchins and the irregular echinoids, such as sand dollars. For more information, visit the Wikipedia entry. Get back to Echinodermata
† Cidaris Urchin	Sand Dollar