They are invariably tubular, sometimes solitary, but more frequently in clusters spirally entwined, adhering to marine substances. In colour they are brown, purple, yellow, tawny, pink or white, and sometimes tinged with green.
Tube solid, calcareous, irregularly twisted, fixed to other substances.
Serpula vermicularis.
S. fascicularis.
S. intestinum.
S. contortuplicata.
S. plicaria.
S. glomerata.
S. decussata.
S. protensa.