Haeckel, 1887
Skeleton of 20 spicules of equal length and generally same shape, with 4 longitudinal wings so that spicule is cruciform in cross section. Wings bear simple or branched apophyses which may link with 4 or more apophyses of neighboring spicules forming latticed shell. Bases of spicules with 4 lateral blade-shaped extensions delineating deep cavities between spicules. Endoplasm spherical to polygonal, surrounded by thick capsular wall. Periplasmic cortex thick, with elastic junctions, linked to spicule by 40-60 myonemes resembling long cylindrical threads.
Four genera:
Genus Phatnacantha
Genus Pristacantha
Genus Stauracantha
Genus Xiphacantha