海膽目
Echinoidea \Ech`i*noi"de*a\, n. pl. [NL. See {Echinus}, and {-oid}.] (Zo["o]l.) 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}. [Written also {Echinidea}, and {Echinoida}.]