Characters: Colonies consist of whorls of delicate, unifacial, undivided or bifurcating fronds. Valleys are shallow and parallel to frond margins. There is almost no development of columellae. Colour: Pale brown or purple. Similar species: Pachyseris involuta. Pachyseris speciosa in turbid water has similar skeletal detail. Habitat: Lagoons and protected reef slopes. Abundance: Uncommon.