Phylum Priapula (Penis Worms)
Approximate Number of Species: 16
Largest: Halicryptus higginsi at a length of 15.75 inches (400 mm)
Smallest: Tubiluchus sp. at a length of 0.0787 inches (2 mm)
References:
Shirley TC & Storch V (1999) Halicryptus higginsi sp. nov. (Priapulida). A giant new species from Point Barrow, Alaska. Invertebrate Biology 118:404-413
Brusca RC & Brusca GJ (2003) Invertebrates (Sinauer Associates, Inc., Publishers, Sunderland, MA) 2nd Ed.