Phoronida (Horseshoe Worms)

Phylum Phoronida (Horseshoe Worms)

Wikipedia Entry
Approximate Number of Species: 20

Largest: Phoronopsis californica at a length of 17.71 inches and a width of 0.2 (450 x 5 mm)

Smallest: Phoronis ovalis at a length of  5.9 inches (150 mm)

Phoronis muelleri (closely related to ovalis) photo by Peter Grobe via Flikr

References:

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

Abele LG, Gilmour T, & Gilchrist S (1983) Size and shape in the phylum Phoronida. Journal of the Zoological Society of London 200:317-323.