The Serpulidae are a family of sessile, tube-building annelid worms in the class Polychaeta. The members of this family differ from other sabellid tube worms in that they have a specialized operculum
Spirobranchus giganteus
Pecten sp. with serpulid worm encrusters; Duck Harbor Beach on Cape Cod Bay, Wellfleet, Massachusetts.
Spirobranchus is the second largest genus of tube-building annelid fanworms in the family Serpulidae. Members of Spirobranchus are known as Christmas tree worms.