Phylum: Echinodermata

Echinoderms exhibit radial symmetry (their organs are arranged in a circle, or like the spokes of the wheel), have an endoskeleton (an internal support), and typically have many tube feet and a water vascular system (instead of muscles). Echinoderms always live in salt water. Some of the members of this phylum include sea stars, sea urchins, sand dollars, and sea cucumbers.

NOAA

National Aquarium in Baltimore