Most reef fungiids are free-living . The polyps are among the largest of all corals. These solitary forms have a long fossil history extending back to the early origins of the Scleractinia. It is therefore likely that the colonial genera have evolved from the solitary ones, rather than the reverse. This theory is supported by the fact that the structure of the septa of each colonial genus has an equivalent in one of the subgenera of Fungia. As a general rule, corals with one mouth are called solitary and those with many mouths are called colonial, but clearly this distinction is not always well defined, nor is it basic to the structural organisation of several species. Little is known about many very important aspects of the biology of free-living fungiids, especially their population dynamics, food sources and growth rates. One distinct aspect of the daily existence of all but the heaviest fungiids is that they are at least partially mobile. The genera are solitary or colonial, free-living or attached, mostly hermatypic and extant. Colonial genera are derived from solitary genera and each has septo-costal structures corresponding to those of a solitary genus. These septo-costae radiate from the mouth on the upper surface (as septa) and from the centre of the undersurface (as costae). No similar families. (Veron, 1986 <57>).