Subphylum Cephalochordata (Lancelets)

Wikipedia Entry

Approximate Number of Species: 25

Largest: unknown species at a length of  3.15 inches (80 mm)

Smallest: unknown species at a length of 1.57 inches (40 mm)

References:

Kristensen RM (2004) An introduction to Loricifera, Cycliophora, and Micrognathozoa. Integrative and Comparative Biology 42:641-651.

Brusca RC & Brusca GJ (2003) Invertebrates (Sinauer Associates, Inc., Publishers, Sunderland, MA) 2nd Ed.