What is "sabellaria"

Sabellaria is a genus of marine polychaete worms in the family Sabellariidae. The type species is Sabellaria alveolata (Linnaeus, 1767). These worms are sedentary and build tubes in which to live from sand and shell fragments. Some species are called honeycomb worms and when they occur in great numbers they can form reefs on rocks and other hard substrates. They are filter feeders, extending a plume-like fan of radioles from the end of the tube in order to catch plankton and detritus floating past. They have a distinctive operculum which is used to block the opening of the tube when the radioles are retracted.