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An echinoderm of the class Echinoidea, which includes the sand dollars and sea urchins.
(Animals) any of the echinoderms constituting the class Echinoidea, typically having a rigid ovoid body. The class includes the sea urchins and sand dollars
(Animals) of or belonging to this class
e•chi•noid(ɪˈkaɪ nɔɪd, ˈɛk əˌnɔɪd)
1. any echinoderm of the class Echinoidea, comprising sea urchins and sand dollars, characterized by a rounded, armless body and a rigid endoskeleton with movable spines.adj.
2. of, belonging to, or resembling the echinoids.