Characters: Colonies are massive and cerioid or have several centres in a short series. Columellae are rudimentary. Septa are thin, with pointed fine teeth.
Colour: Usually mottled grey-green with valleys and walls of contrasting colours.
Similar Species: Isophyllia sinuosa.
Habitat: Most reef environments, but especially surge channels.
Abundance: Usually uncommon.
Taxonomic References: Matthai (1928) as Isophyllastrea rigida; Cairns (1982) as Isophyllastrea rigida; Fenner (1993) as Isophyllastrea rigida; Veron (2000a);
Identification Guides: Humann (2002) as Isophyllastrea rigida;