Haeckel
Diagnosis: Radial tubes cylindrical in the proximal half, prismatic in the distal half, with 3 to 6, usually 4, prominent, thick, parallel edges, which are dentate towards the thicker distal end; their teeth short, conical, directed outwards, scarcely one fourth as long as the thickness of the tube. The edges are separated in the distal third by more or less deep furrows, like a channelled column.
Length of tubes: 1.2-2.5 mm.