There were literally hundreds, if not thousands, of these on the beach. They created small mounds, many of which had one end of the sea cucumber partially exposed.
Another family found these recently and dug one up. They're definitely peanut worms. The picture of the one in the hand is apparently only a part of the organism.
For the full write-up on this trip, visit: http://keepontrekkin.ryanmarquis.com/2013/06/03/a-may-day-at-bishops-beach/
Morphology of the introvert hooks unknown. We only have this picture the picture to go by.
C. Piotrowski, C. Dixon, S. Ellsworth, N. West, M.E. Hannibal
Kind of sad I didn't get better pics, as this species isn't well-represented on the net. Upper left is Serpulorbis and lower right is a sabellid worm.
Saw more peanut worms than I think I ever have before.
Not sure what kind. About 5 cm long in the recoiled state shown here. Never really got it to relax and extend itself.
I was thoroughly convinced this was a sea cucumber, until I was completely failing to find anything like it in Light's, decided to flip through the worms, and saw it under the Sipunculans. I mean, spiny skin! Feeding tentacles! Still so much to learn.
Does anyone know if these things are known to brood? If you look you'll see a smaller one with yellow tentacles to the lower left of the big one.
The Sipuncula or Sipunculida (common names sipunculid worms or peanut worms) is a group containing 144-320 species (estimates vary) of bilaterally symmetrical, unsegmented marine worms. Traditionally considered a phylum, they might be a subgroup of phylum Annelida based on recent molecular work.