That shore ecology is a relatively undeveloped branch of zoology is not surprising in view of the number and variety of intertidal animals, and the number of environmental situations that present themselves to them. Each species of animal has its own particular habitat, and its own particular range, and neither the habitat nor the range of any two are alike. The result then is that each individual species presents its own ecological problem. Studies on the intertidal fauna of the Scottish coasts have been few, and it was felt that studies similar to those first begun by Stephen in 1928, but approached more from the angle of a local survey, would be of use in the search for correlations between the distribution of the animals and the major physical characters on different beaches. Such studies immediately suggested other possible lines of investigation. Were there any significant animal migrations between the different levels of the beach Did animals undergo seasonal fluctuations in their numbers Could the deposit, which appears to be of importance in the settling of larval forms, be as important a source of food to some animals as it had been thought Is there something more than the physical and biotic factors influencing the faunal distribution in beaches - These are only some of the questions which present themselves. The studies of which the following is a record, are concerned with the ecology of sandy beaches on the northern coasts of Scotland, In Section I, the faunal, distribution on certain beaches is investigated, and a general pattern of zonation on British beaches is outlined. Near the mouth of the River Ythan there are fairly extensive sand flats whose faunal density is remarkably rich. It was felt that in such a location as attempt could be made to answer some of the problems mentioned above. In Section II the results of a study of these estuarine sand flats are presented. These flats present a fine example of a Macoma balthioa community, and changes both in the numbers of animals and in their distributions have been the subject of some investigation over a period of twelve months. These last provided an opportunity of estimating the total animal production occurring in the community, and of assessing the factors affecting the biomass. One of the fundamental aspects of production is food, and the presence of Arenicola marina in the deposit suggested a suitable method whereby the food requirements of a typical member of the Macoma community could be investigated. The results obtained from this study are presented in Section III. Notes relating to the subject matter of Sections I and II are presented along with the majority of the tables in an Appendix.