A review of the data on the Atlantic Ocean has already been presented in Chapters 6, 8 and 9. It was decided not to choose an arbitrary depth to separate off the data on the continental margins from those of the deep sea because it would have been artificial and would have obscured the progressive changes in the faunas. The aim of this chapter is to summarise some of the impor­ tant features and to draw comparisons. Where neces­ sary, reference is made to the seas adjacent to the Atlantic, especially the Gulf of Mexico-Caribbean (Ch. 7) and the Mediterranean (Ch. 11).