ALBAILLELLARIA: Bilaterally symmetrical radiolarians characterised by an initial skeleton made of three intersecting bars: two curved bars (a, b) and a straight one (i - intersector), lying in the plane of symmetry, or by only some of them. Bar a usually with pairs of curved ribs (caveal ribs) which may be free or connected by a lamella.

LATENTIFISTULARIA: Radiolarians with an initial skeleton made up fundamentally of a small, heteropolar, globular, hollow central shell with an entopically placed spicule. Spicule point-centred with three, four or more spines of which one (apical) is opposed to the others (basal). Medullary shell well perforate to commonly imperforate. In both cases, there is always one special pore at the base of each spine determining the development of a groove along a portion of the spine. Cortical shell with three or four arms developed along the spines of the initial skeleton, or triangular, tetrahedral or globular, and composed of more or less spongy meshwork arranged or not in several layers, or in twisted spirals.