Corals in this genus have several different forms but are usually massive, leaf-like or plate-like. Members of the genus are distinguished from other corals by having no walls to thecorallitesbut having clearly delineated septocostae that connect each corallite to its neighbours.
Graham’s sheet coral (Agaricia grahamae) grows in large, thin plates, which are either flat or slightly curved, and often overlap. Graham’s sheet coral is generally yellowish-brown to grey in colour, usually with pale margins,and, like other corals, its coloniesare made up of numerous tiny, anemone-likepolyps, which secrete a hard skeleton.In Graham’s sheet coral, the polypsare widely spaced along the bottom of long, roughly concentric depressions (‘valleys’), which are V-shaped in cross-section and are separated by parallel ridges.The underside of the colonyis smooth, lacking polyps. In this species, the individual coral skeletons, known as ‘corallites’, measure around 2 to 2.9 millimetres in diameter.
Graham’s sheet coral is similar in appearance to the relatedAgaricia lamarcki(Lamarck’s sheet coral), but has smaller corallites, more pointed tops to the colonyridgesand lacks the white polyp‘mouths’ of the latter.It can be distinguished fromAgaricia fragilis(fragile saucer coral) mainly by its longer valleys, larger corallites and the smoother appearance of its colonies.