Phylum Porifera Grant, 1836 - sponges Class Demospongea Sollas, 1875 see Class Demospongiae Sollas, 1885 Subclass Clavaxinellida Lévi, 1956 Order Protomonaxonida Finks & Rigby, 2004 Family †Halichondritidae Rigby, 1986 Genus †Halichondrites Dawson & Hinde, 1889