\Ser"pu*la\, n.; pl. {Serpul[ae]}, E. {Serpulas}. [L., a
little snake. See {Serpent}.] (Zo["o]l.)
Any one of numerous species of tubicolous annelids of the
genus {Serpula} and allied genera of the family
{Serpulid[ae]}. 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.