Phylum Mollusca Linnaeus, 1758 - molluscs Conchifera Gegenbaur, 1878 see Subphylum Conchifera Gegenbauer, 1878 Cyrtosoma Class Gastropoda Cuvier, 1795 - snails and slugs Subclass †Archaeobranchia Parkhaev, 2001 Order †Helcionelliformes Golikov & Starobogatov, 1975 Superfamily †Yohelcionelloidea nom. null. see Superfamily Yochelcionelloidea Runnegar & Jell, 1976 Family †Trenellidae Parkhaev, 2001 Genus †Trenella Parkhaev, 2001