Characters: Colonies consist of prostrate, tapered branches which have many branchlets and incipient axial corallites. Corallites are immersed to long and tubular, giving branches a rough, irregular appearance. Tentacles are not extended during the day. Colour: Deep blue (which may photograph mauve) or brown. Similar species: Acropora horrida, which has smaller, more compact corallites and has tentacles extended during the day. Habitat: Lagoons. Abundance: Common at Elizabeth and Middleton Reefs of south-east Australia, rare elsewhere