Circumscription: A group of marine radiolaria (protists with axopodia, skeletons, and no flagella in the trophic state). Most have a skeleton of amorphous silica with associated organic matter, cytoplasm separated into an inner area by a thick capsule, and an inner layer that is further divided by a cape of vesicles-the cape having three openings: an apical astropyle that seems to be associated with the formation of feeding pseudopodia and two parapyles from which axonemal microtubules arise. Contain aggregates of waste material: the phaeodium. Life cycle may be complex, and flagellated distributive stages are produced. Ultrastructural identity: Little studied, mitochondria probably tubulocristate. Synapomorphy: Radiolaria with central capsule with three openings: an apical astropyle and two parapyles.