Mellita Quinquiesperforata- Sand Dollar
Sand dollars, like all members of the order Clypeasteroida, possess a rigid skeleton known as a test. The test consists of calcium carbonate plates arranged in a fivefold radial pattern. In living individuals the test is covered by a skin of velvet-textured spines; these spines are in turn covered with very small hairs (cilia). Coordinated movements of the spines enable sand dollars to move across the seabed. The velvety spines of live sand dollars appear in a variety of colors—green, blue, violet, or purple—depending on the species. The tests of dead individuals are often found on beaches, the textured skin missing and the skeleton bleached white by sunlight.