The genus madrepora is probably the most widely distributed and abundant of all reef-building corals of the world. This species represents one of the most characteristic forms assumed by these corals. There is usually a long, thick, erect, main stem from which large, irregular, lateral branches are given off, which subdivide, but rarely anastamose. This form is popularly known as the stag horn coral from its resemblance to the branching horn of the stag. Montipora is another important reef building coral, widely distributed in the tropical seas of the old world, but absent in the Atlantic Ocean and the West Indian waters. The specimens vary a great deal in appearance and often attain a very great size. They may be rounded and massive or encrusting, branching or foliate. All parts of the colony are profusely perforated