Superclass Spirotricha Bütschli, 1889 see Class Spirotrichea Bütschli, 1889 Class Oligotrichea Bütschli, 1889 see Subclass Oligotrichia Bütschli, 1889 Subclass Oligotrichia Bütschli, 1889 Order Oligotrichida Bütschli, 1889 see Subclass Oligotrichia Bütschli, 1889 Family Pelagostrombidiidae Agatha, 2004 Genus Pelagostrombidium Krainer, 1991