Genus:
Williamia >
Family:
Siphonariidae >
Superfamily:
Siphonarioidea >
Order:
Siphonariida >
Superorder:
Siphonarimorpha >
Subterclass:
Tectipleura >
Infraclass:
Euthyneura >
Subclass:
Heterobranchia >
Class:
Gastropoda >
Phylum:
Mollusca >
Kingdom:
Animalia >
Unranked:
Biota >