Historical. General descriptions of intertidal zonation have been published by many workers for almost all littoral areas, both marine and lacustrine (Doty, 1957; Glynn, 1965; Hedgpeth, 1957; Lewis, 1964; Pennak, 1951). The fact that animal species of the sandy shore are few in number eliminates many complex interspecific reactions, while great numbers of individuals make population studies feasible. In addition to certain general works (Dahl, 1952; Pirrie et al., 1932; Yonge, 1950) a number of papers have discussed causative factors or mechanisms for animal zonation.