The great importance of changes in the distribution of land and sea has in a general way long been recognized. Of late years interest in the question has been increased by the studies of geologic climate which have been undertaken, as well as by the extension of our knowledge concerning the movements of faunas and floras over the submerged and emerged portions of the earth’s crust. From the time of Strabo down to the present day all those who have looked intelligently on shoreline phenomena have recognized the inconstancy in the relations of sea and land. Almost all the students of such phenomena have, in their thinking, made the assumption that the changes in the positions of the shoreline were due to the simple process of up or down movement of the crust where the changes in elevation have occurred. Strabo saw, and briefly indicated in his writings, that . . .