SERPULA

noun any one of numerous species of tubicolous annelids of the genus serpula and allied genera of the family serpulidae. they secrete a calcareous tube, which is usually irregularly contorted, but is sometimes spirally coiled. the worm has 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.