Schewiakoff, 1926
Twenty spicules of equal length, same shape, very thin, with or without apophyses or plates. Endoplasm yellow-brownish in center, clearer at periphery, with single large nucleus and lithosomes. Ectoplasm very clear, transparent, with thin cytoplasmic strands forming wide-meshed pseudopodial network. Thin capsular wall limiting endoplasm near cell center. Periplasmic cortex stretching between tips of spicules. Numerous axopodia and 16 flat myonemes per spicule.
Three genera:
Genus Dicranophora
Genus Haliommatidium
Genus Pseudolithium