Phylum Porifera Grant, 1836 - sponges Class Demospongea Sollas, 1875 see Class Demospongiae Sollas, 1885 Subclass Choristida Sollas, 1880 see Order Tetractinellida Marshall, 1876 Family †Helminthophyllidae Schrammen, 1936 [monotypic] 1 Genus †Helminthophyllum Schrammen, 1936