Characters: Colonies are free-living, irregular and dome- or bell-shaped or flat. They are usually attached to the substrate. They are thin and fragile. Septa have distinctive knob-shaped teeth. They are mostly perpendicular to the colony margin, but are sometimes in two or more groups, one group being perpendicular to the colony margin. Colour: Brown with pale margins. Corallite centres may be white. Similar species: Halomitra meierae. See also H. pileus, which is less fragile and does not have club-shaped septal teeth, and Zoopilus echinatus, which has a similar superficial appearance but dissimilar septa. Habitat: Sheltered habitats. Abundance: Rare.