Source : Webster's Revised Unabridged Dictionary (1913)

Spatangoidea \Spat`an*goi"de*a\, n. pl. [NL. See {Spatangus},
   and {-oid}.] (Zo["o]l.)
   An order of irregular sea urchins, usually having a more or
   less heart-shaped shell with four or five petal-like
   ambulacra above. The mouth is edentulous and situated
   anteriorly, on the under side.