Phylum Sipuncula (Peanut Worms)
Approximate Number of Species: 320
Largest: Sipunculus indicus at a length of 15.75 inches (400 mm)
Smallest: Phascolion psammophilus at a length of 0.0787 inches (2 mm)
References:
Cutler EB (1994) The Sipuncula, Their Systematics, Biology, and Evolution (Cornell University Press) p 480.
Brusca RC & Brusca GJ (2003) Invertebrates (Sinauer Associates, Inc., Publishers, Sunderland, MA) 2nd Ed.