Characters: Colonies are flat or hemispherical and mostly phaceloid with one to three centres per branch. They seldom exceed 0.5 metres across except in the Red Sea where they commonly exceed 2 metres. Calices are deep, with well defined walls. Septa are thick near the walls and thin within the calice. Septal teeth are tall and blunt, decreasing in size towards the columella. Colour: Greenish brown, grey or mustard, usually with pale centres. Similar species: Lobophyllia dentatus, which is distinguished from phaceloid L. corymbosa by the shape of the calices and septa. Lobophyllia pachysepta has thickened primary septa with large lobed dentations. These species are distinct underwater. Habitat: Upper reef slopes. Abundance: Sometimes common.