Haeckel, 1862, emend. Schewiakoff, 1926
Skeleton consisting of 20 spicules of same length and same shape, or with two to four spicules longer than others. Cell body polygonal or oblong. Endoplasm with zooxanthellae, limited by capsular wall. Ectoplasm clear, limited by periplasmic cortex. Cylindrical myonemes.
Three genera:
Genus Acanthometra
Genus Amphilonche
Genus Tetralonche