Kingdom Animalia Linnaeus, 1758 - animals
   Phylum Echinodermata Bruguière, 1789 - echinoderms
     Subphylum Eleutherozoa Bell, 1891
       Class Echinoidea (Leske, 1778) - sea urchins and sand dollars
         Subclass Euechinoidea Bronn, 1860
           Superorder Gnathostomata Zittel, 1879
             Order Clypeasteroida A. Agassiz, 1872 - true sand dollars
               Genus Clypeaster Lamarck, 1801
               Genus Dendraster Agassiz, 1847
               Genus Echinarachnius Gray, 1825
               Genus Echinocardium Gray, 1825
               Genus Echinocyamus van Phelsum, 1774
               Genus Echinodiscus Leske, 1778
               Genus Fibularia Lamarck, 1816
               Genus Mellita Agassiz, 1841