Ctenella

Ctenella is a monotypic genus of stony coral in the family Euphylliidae. It is represented by a single species, Ctenella chagius. These corals are massive in size with meandering valleys between the calyces which have solid, non-porous walls and fine, evenly spaced, solid septae. They are found in the Indian Ocean being endemic to the Chagos Archipelago. It forms solid, smooth hemispherical domes.

==Description== Ctenella chagius is a massive, hemispherical, colonial coral with a fissured surface and brain-like appearance. The individual polyps that secrete the stony skeleton project from stony cups called corallites arranged in rows in long meandering valleys. The width between the solid ridges on either side is about with the valleys being about deep. The fine septa that radiate from the corallites are closely packed and evenly spaced, some continuing upwards and over the ridges. This coral is a pale brown colour and can grow to a metre (yard) in diameter. It is a zooxanthellate coral and has symbiotic unicellular dinoflagellate algae living within its tissues.