What is "sipuncula"

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. Sipuncula signifies "little tube or siphon." Traditionally considered a phylum, they might be a subgroup of phylum Annelida based on recent molecular work.