Schewiakoff, 1926, emend. Reshetnjak, 1979
Ten diametral spicules simply crossing in cell center, long, equal, cylindrical, straight and very thin. Endoplasm with brown or yellowish inclusions and numerous nuclei, clearer towards periphery. Capsular wall very thin, consisting of thin network. Ectoplasm limited by periplasmic cortex, consisting of hexagonal elastic lattice. Two large flat triangular myonemes anchored on each spicule, completely covered by periplasmic cortex. Large spherical granules scattered around each spicule just under periplasmic cortex (these spheres were confused with zooxanthellae by Schewiakoff, 1926), so ectoplasm seems to bear small umbrellas around the 20 spicules. As in other members of Holacanthida, gametogenesis takes place in an oval cyst after complete remodeling of cell.
One genus Acanthoplegma.
Only one species:
Acanthoplegma krohni