From May, 1922, onwards the sq. metre bottom-sampler has been used to collect samples of the bottom-deposits with their animals, in the waters off Plymouth. The animals have been removed as soon as possible after capture by passing the samples through a series of sieves, and have been preserved in alcohol, to be identified and counted ashore. The present report deals with the distribution of the species represented, in the light of Petersen's Community investigations in Danish waters.

I express my thanks to Dr. Allen, Dr. Orton, Mr. Hunt, and Mr. Smith, of the Plymouth Laboratory, for their kind help in the identification of the material. I am particularly indebted to my friend, Mr. R. Winckworth, a late member of the staff, who has not only gone over with me the bulk of my collection of lamellibranchs, but has provided me with an excellent type series as complete as the material would allow.

The extensive use of his bottom-sampler in Danish waters and elsewhere has enabled Dr. C. G. Joh. Petersen to advance an opinion that “as a rule it is best to regard the animals living on the sea-bottom as communities, just as botanists group together the vegetation of the land into plant communities, even though in the present state of our knowledge it is impossible to show how intimate the mutual relations are between the animals of the sea in the single cases.”

It will probably assist the reader if I commence with a short summary recalling the more important points, concerning the recognition of communities, which have been advanced by Peterson, and in doing so I shall adhere closely to his own words.