(Haeckel, 1860)
Two (more rarely 3 or 4) equatorial spicules differing markedly from other 18, which are much shorter. Main spicules of equal or almost equal length, but shape usually differing: posterior thicker, with 3 wing-like extensions, anterior with 4. Main spicules with central cylindrical axis from which wing-like extensions protrude. Eighteen secondary spicules thorn- or needle-like, thickened basally, tips sharp. Length of main spicules: 0.05-0.08 mm; secondary: 0.025-0.05 mm.