• Kingdom: Animalia
  • Phylum: Annelida
  • Class: Polychaeta
  • Subclass: Sedentaria
  • Order: Sabellida
  • Family: Serpulidae
  • Subfamily: Spirorbinae
  • Scientific name: Spirorbis spirorbis
  • Norwegian: posthornmark


The greenish body of this small tubeworm rarely exceeds a length of 6mm. It lives in an evenly coiled tube spiraling clockwise, in contrast to C. spirillum. The tube diameter is approximately 3 mm. The outer edge of the smooth tube spreads out on the substrate as a distinct peripheral flange. The crown of tentacles are colorless.


It prefers shallow water, below the tidal zone. It is most frequent on algae.


It is widespread in the North-East Atlantic, including the Arctic, the North Sea and the British Isles.