Siphonariidae Gray, 1827
Williamia eximia (Nevill in G. & H. Nevill, 1869)
Williamia gussoni (Costa O.G., 1829)
Williamia gussonii (Costa O.G., 1829)
Williamia krebsii (Morch, 1877)
Williamia magellanica Dall, 1927
Williamia parva
Williamia peltoides (Carpenter, 1864)
Williamia radiata (Pease, 1861)
Williamia subspiralis (Carpenter, 1864)
