Phoronis hippocrepia 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).