(Haeckel)
Diagnosis: Radial tubes club-shaped, straight, tapered proximally, each with 9-12 stout conical terminal branches which are studded with thorns. Foreign siliceous detrital bodies aligned axially within radial tubes (a generic character). As many as 5 varieties or subspecies, possibly distinct warm- and cold-water forms are discussed by some authors.
Length of tubes: 1.2-1.8 mm.