Haeckel, 1887, emend. Schewiakoff, 1926
Family characterized by four spicules longer and thicker than others, with flat, triangular, latticed plates on apical third of length. Each plate of one to five lateral apophyses cross-linked by three to five orthogonal bars delineating square-based lattice. Two species of this family flattened in plane of largest spicules. Endoplasm with numerous zooxanthellae and small nuclei, limited by thick fibrillar meshwork through which axopodia pass. Traffic of tiny kinetocysts active along axopodia. Myonemes short, cylindrical, not very mobile.
One genus Lithoptera with two species:
Lithoptera fenestrata
Lithoptera muelleri