Phoronis psammophila constructs and lives in a rigid, chitinous tube about 10 cm long, incorporating sand grains and detritus.

The mesosome bears the lophophore, a specialist feeding structure which consists of a ring of up to 190 translucent tentacles arranged in a horseshoe-shape encircling the crescent-shaped mouth.

It favours a substrate of fine sand with a moderate silt content and sometimes occurs at densities of up to 20,000 individuals per square metre.

The diet consists of diatoms, microalgae, flagellates, invertebrate larvae and detritus and these are caught and transported to the mouth by the cilia.

When dispersed, they become amoeboid and make their way through the body wall of an adult worm before fertilising eggs in the metacoel.

[3] The actinotroch larva is transparent and has a ring of ciliated tentacles just behind the mouth, a straight gut and an anus at the posterior end.

[4] Asexual reproduction also takes place, usually by transverse fission, and may result in groups of individuals clustered in close proximity to each other, sometimes tangled together.