unconformably contouring around the spur-ends of embayed coasts—witness Palawan, the south-westernmost member of the Philippines, and many other embayed islands in that group—well represented in recent charts of the United States Coast and Geodetic Survey; also the Andaman Islands, in the Bay of Bengal; for in all these examples the coast is elaborately embayed; and hence their fringing reefs must be unconformable, and their submergence must have taken place at a faster rate than reef-upgrowth. Many other examples of the same kind might be cited. Fringing Reefs and Submarine Platforms.—Fringing reefs thus assume a much greater interest than is generally allowed to them: their relations to the features of the coasts they border deserve close attention. The breadth of the reefs should be noted as a means of estimating the time that has elapsed since the last movement of submergence took place. The off-shore soundings of reef-fringed coasts of submergence are also of importance, for they frequently reveal a submarine platform that in all probability represents a drowned barrier reef and its lagoon. Such submarine platforms, several miles in width, are found in association with Palawan and the Andamans, although the sea-level fringing reefs of these islands are narrow. A well-developed submarine platform surrounds the greatly denuded “volcanic wreck” of Fauro, a small island with, narrow fringing reefs in the Solomon Group. A similar platform is shown by the latest surveys of the United States Hydrographic Office to surround the Samoan island of Tutuila; but the fact that the spur-ends of this island are rather strongly cliffed behind their fringing reefs distinguishes it from the other examples named. Submarine platforms occur around the Marquesas Islands also; but here, although the spur-ends are cliffed, as in Tutuila, they are not fronted by fringing reefs. The depth of the submarine platforms off reef-fringed shores is not constant: along the west coast of Palawan the platform varies in depth from 25 or 30 fathoms near its southern end to 60 fathoms near its mid-length; the Fauro platform has depths of 70 or more fathoms; the Andaman platform is 30 or 40 fathoms in depth. On the other hand, part of the coast of Samar, in the Philippines, facing the open Pacific, has fringing reefs around its headlands, but its submarine slope descends rapidly to great depths. Now, let it be noted, first, that the three chief elements of the fringing-reef problem as here considered—duration of the pre-submergence period of subaerial erosion, rate and amount of submergence, and duration of post-submergence period of fringing-reef growth—have unlike values on different islands; secondly, that many other islands have well-developed barrier reefs which suggest slow submergence, and that some barrier reefs are broad and others are narrow, thus suggesting that the rate and date of their submergence are unlike; and, thirdly, that many elevated reefs occur at different altitudes and in different stages of erosion. It thus becomes evident that the history of various reef-encircled islands must consist of unlike sequences of movements and pauses. Hence local movements of the reef - formations themselves, which may vary greatly, explain the varied facts much better than changes of ocean-level, which must everywhere be of the same rate, date, and amount. In order to learn how greatly the values of the various elements differ from place to place, their value for every coast should be determined independently. One of the most important of these elements is the