"the hind end of a chaetopterid polychaete, probably Chaetopterus. People thought that one species in particular, C. variopedatus, was a cosmopolitan species, meaning it lived everywhere around the world. Lately some researchers have been taking a closer look at the worms & realizing that you could easily tell the difference between regional populations, even between habitat populations in an area, and that these are all valid species. Chaetopterids are especially nifty even for polychaetes. They have 3 distinct body regions none of which look as if they belong together. Some of them create mucus nets to filter food particles out of the water as it flows through their tubes."
General information here: http://www.seafriends.org.nz/indepth/nd002.htm
and more specific information here http://www.mbl.edu/marine_org/marine_org.php?func=detail&myID=ITA-67097
