Serpula is a genus of sessile, marine annelid tube worms that belongs to the family Serpulidae. Wikipedia

Genus of annelids Wikidata

Any of numerous species of tubicolous annelids of the genus Serpula and allied genera of the family Serpulidae that secrete a calcareous tube, usually irregularly contorted, but sometimes spirally coiled, with a wreath of plumelike and often bright-colored gills around its head, and usually an operculum to close the aperture of its tube when it retracts. Wiktionary