#class_Echinoidea__Echinoidea  sea urchins and sand dollars
  supertype:  class__clas  (biology) a taxonomic group containing one or more orders
  member of:  phylum_Echinodermata
  member:  sea_urchin__seaurchin  shallow-water echinoderms having soft bodies enclosed in thin spiny globular shells
  member:  order_Exocycloida__Exocycloida  flat sea urchins
     member:  sand_dollar  flattened disklike sea urchins that live on sandy bottoms
  member:  order_Spatangoida__Spatangoida  heart-shaped sea urchins
     member:  heart_urchin__hearturchin  sea urchin having a heart-shaped body in a rigid spiny shell

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