(Haeckel, 1860)
Spicules of equal length, 4-winged, edges deeply serrated (serrations small, distally directed, deepest distally), 4-5 times longer than cell body, tapering proximally and distally (broadest at middle), tips sharp (usually broken off in adults). Basal ends with 4 pear-shaped thickenings. Spicule length: to 1 mm.