Radially symmetrical marine invertebrates of the phylum Echinodermata (which includes starfish, sea urchins, and sea cucumbers) having an internal calcareous skeleton and often covered with spines
US Department of Commerce, National Oceanic and Atmospheric Administration, Glossary - NOAA's State of the Coast (SOTC), Washington, DC, USA 2013. http://stateofthecoast.noaa.gov/glossary.html, (CoaStormEmr - Amer) {881}