Spirorbis is a diverse genus of small, tube-building serpulid polychaetes. All members build and inhabit coiled tubes that attach to submerged vegatation, rocks, dock pilings, or other substrata. The tubes may be either dextrally or sinestrally coiled, depending on the species (Fauchald 1978). Anatomical details of the animals themselves differ by species, but all are soft-bodied worms occupying coiled shell tubes. A short abdominal segment connects to a somewhat broadened thorax topped with (typically ten) stiff tentacles modified as feeding appendages. One of the tentacles is modified into a saucer-shaped operculum used to seal off the tube and protect the animal from predators and desiccation.Tube formation in Spirorbis is accomplished through calcium secreting glands in the peristomium of the animal (Hedley 1956).