| Actually, I might be wrong now that I reread your description..
It had spikes on the front and it moved from the rock to the sandbed? Did it look anything like that picture? Peanut worms usually just feed by using their mouth, keeping their body in the rock and so it wouldn't think it would move from rock to sandbed...
Hmm... you might really have a mystery worm if it is not a bristle worm |