Pretty cool stuff, Kevin. I wish I could say that I know without a doubt what it is, but that simply isn't the case.
My first thought was Vermetid - the "tube" looks exactly like one, however, with an obviously different head.
me to think more along the lines of a Serpulid worm (calcareous tube worm) - the "feather dusters" in general. But, these almost always have a 'divided' head, and the "feathers" just aren't quite right.
Which leaves me with 2 choices.
Either a strange type of zoanthid (Epizoanthus or Parazoanthus)
OR, a Cerianthid, or tube anemone. If I had to put my money on one, this would be it. Where the zoanthus tenticles seem to be an extension of the "stem", the Cerianthid anemones have a very distinct "tube", and the animal appears more to be living "within" it. This of course, would also be the case with the Serpulidae.
Here is a Cerianthid: