An attempt has been made to subdivide the intertidal (littoral) zone based on the influence of tidal factors especially the diurnal inequality. On the Pacific coast of Japan, four zones (Subsprash zone→Upper littoral zone→Lower littoral zone→Superior sublittoral zone) are divided. On the coast of the Japan Sea, there is no proper littoral zone and only two zones (Subsprash zone-Superior sublittoral zone) are recognized. The attempt seems to be very suggestive for the consideration of the habitat for seaweeds, because the real zonation of the littoral vegtation in the above mentioned localities corresponds with the above mentioned subdivision in number.
