secretes and lives in a membranous, cylindrical tube, and occur in either boring or encrusting forms. Individuals are 0.3-1.5 mm in diameter and can grow up to 10 cm in height, although more commonly attain 4 cm. The body is cylindrical and elongate with a slender trunk (metasome) and a bulbous posterior (ampulla). Tentacles (terminal lophophore) occur entirely on the 'head' region, numbering 50-150. The tentacles are 2-3 mm in length and are arranged in a 'horse-shoe' shape. Individuals are translucent white greenish grey, yellowish or fleshy in colour.Phoronis hippocrepia
can occur in densities of more than 20,000 individuals/m². Identification on this species may require microscopic work and dissection (see Emig, 1979). The only other known genus in this phylum is Phoronopsis
. The genus Phoronis
can be distinguished from Phoronopsis
by the absence of a collar-fold below the lophophore (see Emig, 1979).