Ideally, the world could be divided into 12 geographic regions that could be analyzed for their coralline distributions, if enough data were available. Distributional studies fall into two categories: descriptive and causal. W. H. Adey presented a series of world maps on which he summarized the relative distributional importance of several crustose coralline genera. Adey has made extensive studies of the distribution, ecology, and taxonomy of epilithic crustose coralline algae in the Gulf of Maine. The epilithic crustose coralline algae present on the east coast of North America are dominated by the Melobesioideae. Identification may be made on the basis of reproductive, vegetative, and anatomical characteristics. In Cold Northeastern Atlantic region, extending north of the Straits of Gibraltar, the nonarticulated coralline algae are better known than anywhere else in the world. The relationship between seawater temperature and the distribution of crustose coralline algae in the waters around Hokkaido, the northernmost island of Japan, was studied by Adey et al.