Amphisbetia operculata (Linnaeus, 1758)

Colonies tall, to 25 cm high, usually comprising many thin, wiry, irregularly arranged branches without obvious main stem. Perisarc thick and tough, hydrothecae tubular, situated in opposite pairs on the branches, one pair per internode, the internodes separated by distinct joints.

Hydrothecae facing upward and outward, margin with two long, opposite, upwardly pointed cusps.

Gonotheca elongate-oval, widest at the top, flattened, perisarc smooth, the distal aperture surmounted by a low collar and closed by an operculum. Reproduction is by release of planula larvae.

Colour: colonies greenish-yellow to honey brown but are often overgrown by a film of pink coralline algae.