(Haeckel, 1887)
All spicules very long, 5-10 times longer than diameter of cell body; sometimes 1-2 (less often 4) equatorial spicules 2 times as long as others. Spicules 4-winged, at base 2 opposing edges serrated (serrations small, distally directed), other 2 smooth. Each spicule with 6-8 long, thread-like myonemes. Shell diameter: 0.6-1 mm; cell body: 0.06 mm; spicule length: 0.03 mm (main equatorial spicules may reach 0.6 mm).