Habitat: Usually found at depths greater the 20 m. Can be one of the most abundant species on outer coral reef slopes. Distribution: Known throughout the Caribbean. Characteristics: Corallum unbranched, 1 m or more in height; lower part of stem straight or curved, upper part spiral (in large colonies). Spines covered with small knob-like or coneshaped tubercles. Polyps densely arranged in a single series. Living colonies yellow-green.