Characters: Corals are free-living, with a base that is flat or keeled primarily according to the nature of the substrate. Larvae initially settle on a microgastropod shell which they envelop during subsequent growth. They have an obligate commensal relationship with a sipunculid worm (Aspidosiphon corallicola) and usually have one parasitic mussel (Lithophaga lessepsiana) embedded above the sipunculid. The sipunculid moves the coral about on soft substrates and prevents it from becoming buried. Individual corals are rounded, up to 25 millimetres diameter. They usually have one or two corallites; where there is one it is usually hourglass-shaped. Some populations have colonies with up to 30 corallites. Corallites have well developed septa which follow Pourtalès plan. Columellae are broad, compact, and deep seated. Walls are composed of porous coenosteum. Tentacles are usually fully extended only at night. They are zooxanthellate in tropical localities but are possibly azooxanthellate in temperate locations and in deep water.

Colour: Pale grey, orange-brown or greenish.

Similar Species: Heteropsammia moretonensis is smaller, has solitary corallites and is distinctively coloured. Heteropsammia and the caryophylliid Heterocyathus aequicostatus are structural and ecological equivalents.

Habitat: Almost always found on soft horizontal substrates at depths of 20 metres or more. Usually occurs in association with Heterocyathus aequicostatus and Cycloseris cyclolites.

Abundance: Up to three hundred individuals per square metre have been found on the Great Barrier Reef.