Art. II.—The Significant Features of Reef-bordered Coasts. By W. M. Davis, Harvard University, Cambridge, Mass., U.S.A. [Read before the Wellington Philosophical Society, 16th October, 1918; received by Editor 16th October, 1918; issued separately, 14th May, 1919.] In recognition of the honour conferred by the New Zealand Institute in adding me to its list of honorary members, and in return for the kind reception given me at its meetings during my Pacific journey in 1914, I desire to offer the following notes for publication in its Transactions, in the hope that they may aid students of coral reefs in observing certain features of significance in connection with the origin of those extraordinary structures. References are appended to a number of my articles, the product of observation, reading, and reflection during five years past, where certain aspects of the coral-reef problem are treated more fully than they can be here. Sea-level Coral Reefs are silent as to their Origin.—The corals and other organisms of a sea-level reef are truly of marvellous interest, and from a zoological point of view merit all the attention they have received; but when a reef is examined from a geological point of view its organisms are found to be reluctant, not to say incompetent, witnesses as to the manner of its formation. An observer may sail along the front of a reef, wander over its surface, or row about in its lagoon, and discover many facts regarding the varied forms of life there visible, and regarding the processes, organic and inorganic, now in operation; but, apart from such factors as the temperature and the depth of sea-water at which reef-building corals grow, he can learn little, if anything, about the past conditions under which the reef has been developed, so long as his study is directed to the reef alone. On atoll reefs there are, indeed, no facts visible at the surface by which the various theories of the origin of coral reefs can be tested: it is only from borings in sea-level atolls or from natural sections of elevated atolls that competent testimony as to their origin can be gained. In this connection it may be noted that the interpretation of the Funafuti boring recently published by Professor E. W. Skeats, of Melbourne (1918),* For references see p. 30. gives a much better statement of its evidence as to the origin of that atoll than is to be found in the original report published by the Royal Society, which was almost silent as to the meaning of the facts that it set forth so minutely. Fringing and barrier reefs are, on the other hand, associated with the coasts of land-masses, which may yield much information as to the past conditions and processes of reef-formation, if the geological structure and the physiographic development of the coastal slope are examined. For these reasons it is to the coasts of the land-masses which fringing or barrier reefs adjoin that attention is here chiefly directed. Coasts of Emergence and of Submergence. The general features of coasts on which coral reefs occur—either fringing reefs alone, or fringing reefs in the lagoons enclosed by barrier reefs—give helpful indications of the relative changes of level that the coasts have