(n.pl.) The class Echinodermata which includes the sea urchins. They have a calcareous, usually more or less spheroidal or disk-shaped, composed of many united plates, and covered with movable spines. See Spatangoid, Clypeastroid.
Webster's Revised Unabridged Dictionary
| APA | Webster's. (2011). echinoidea. Retrieved September 23, 2026, from http://smartdefine.org/echinoidea/definitions/2001473 |
| Chicago | Webster's. 2011. "echinoidea" http://smartdefine.org/echinoidea/definitions/2001473 (accessed September 23, 2026). |
| Harvard | Webster's 2011, echinoidea, Smart Define, viewed 23 September, 2026, <http://smartdefine.org/echinoidea/definitions/2001473>. |
| MLA | Webster's. "echinoidea" 27 May 2011. Web. 23 September 2026. <http://smartdefine.org/echinoidea/definitions/2001473> |