Phylum Mollusca Linnaeus, 1758 - molluscs
Count: -
   Conchifera Gegenbaur, 1878 see Subphylum Conchifera Gegenbauer, 1878
  Count: -
     Cyrtosoma
    Count: -
       Class Gastropoda Cuvier, 1795 - snails and slugs
      Count: -
         Subclass †Archaeobranchia Parkhaev, 2001
        Count: [†g] †2o;8f;67g
           Order †Helcionelliformes Golikov & Starobogatov, 1975
          Count: [†g] †6f;62g
             Superfamily †Helcionelloidea Wenz, 1938 see Superfamily Scenelloidea Miller, 1889
            Count: [†g] †3f;41g
               Family †Helcionellidae Wenz, 1938 see Family Scenellidae Miller, 1889
              Count: [†g] †31g
                 Genus †Helcionella Grabau & Shimer, 1909
                Count: -