At the outset we consider it desirable to point out that this book was planned, to bring at one place, all the available data on the studies made on Recent sediments in order to provide a workable tool to the field geologist for reconstructing the ancient environment. Further, we do not hesitate to state that while the readers would go through the book, they would meet with a number of debatable points, and out of such points at least the following two would strike everyone: (1) Have we modern analogues or sedimentation models to all ancient environments? (2) Is it always possible to recognize an ancient anvironment in the light of Recent analogues? Though the questions are logical, they are difficult to answer, and if we are asked to answer the questions catagorically in “Yes” or “No”, under the present state of knowledge we would select “No”. This does not mean that we wish to dishearten those engaged in the environmental reconstruction but we wish to emphasize that at times the Nature is not yet properly understood.