(Haeckel)
Diagnosis: Radial tubes club-shaped to cylindrical, straight, gradually thickened toward the distal end, which bears a broad, circular, convex bulge. Margin of bulge bears 2 alternating verticils of radially divergent, straight terminal branches, which are 2 to 3 times as long as the tube is wide. Each branch with 2 opposite lateral rows of numerous small denticles, and bearing a terminal spathilla with 6 to 8 recurved radial teeth.
Length of tubes: 2.0-2.4 mm.