(Haeckel, 1887)
Six main spicules of unequal size, two equatorial about as long as diameter of shell and nearly twice as large as four polar; all of same form, quadrangular prismatic, with prominent edges and pointed distal ends. Sheaths six-sided prismatic, with strong prominent edges and thinner parallel ribs between them; distal mouth with six strong denticulated teeth. Sheaths envelop two-thirds of spicules, as broad as radius of shell. Sutural pits round, surrounded by somewhat knob-like accessory spines. Diameter of shell: 0.13 mm; length of equatorial spicules: 0.12 mm, of sheaths: 0.08 mm; breadth of latter: 0.06 mm.