When describing fossil reef facies, one often speaks of coral communities when several species are found in the same layer. The term "organism community" is of a very general nature and embraces co-incidental or necessary, permanent or temporary associations of organisms. Lately it is being linked to paleoecological statements more often (Paporte 1977), which gives it a sociological and ecological meaning. This is theoretically justified, because only differentiated ecological factors lead to typical coral communities being formed. However, such coral communities are not co-incidental, but regulated by certain laws of environmental conditions, they are not temporary, but permanent phenomena; particularly when environmental conditions are reconstructable and used for a description of the habitats, does it appear advisable to use the well-defined term "association".