After supplementary notes on the structure of the Red Sea coast, the coral fauna, and decay of corals, the distribution of corals in the neighbourhood of the Biological Station of the Egyptian University is described and charted, showing that extension and recession of reefs go on in the same area. The latter is connected with the breadth of the reef, and consequent cooling and fouling of the water. A series of small reefs showing stages from embryonic to senile is described, and the ecologic puzzle of shoals covered with Galaxea alone, while others in the neighbourhood of these bear mixed corals and alcyonaria. The relationship between coral and alcyonaria is an important problem for reef students.