All 10 diametral spicules of equal size and same shape, thin, cylindrical, flexible, with sharp tips. Specimens with 1, 2, or 4 larger equatorial spicules very rare. Spicules linked in cell center by edges of 5- or 6-edged pyramidal bases. Cell body polygonal, with yellow-green endoplasm, with numerous zooxanthellae (usually in groups of 2-3) and nuclei. Endoplasm limited by thin, colorless, transparent capsular wall. Ectoplasm clear, with delicate cytoplasmic strands. Periplasmic cortex of 20 polygonal pieces, fixed to each other by elastic junctions. Each spicule with 24-40 thread-like cylindrical myonemes (juveniles with 8-16). Diameter of cell body: 0.24 mm; spicule length: 0.43-0.56 mm. One of commonest and most abundant acantharians world-wide.