206 — W. M. DAVIS 
Reef A, formed when the island has subsided so that sea-level 
is S., is a barrier of moderate thickness; the cliffs, F, previously 
cut, are not yet wholly submerged and the embayments are small. 
Tahiti, the largest of the Society Islands, is clift and encircled by 
reefs which are, I believe, of this kind; the submergence that 
prompted their formation might at first thought be ascribed to a 
rise of sea-level due to climatic change or to an upheaval of the 
ocean bottom elsewhere while Tahiti stood still; but in that case 
neighboring islands should show similar features, and as they do 
not the submergence of Tahiti as well as of its neighbors is reason- 
ably ascribed chiefly to subsidence. 
Reef B’ is an unconformable fringe formed after greater sub- 
sidence rapidly accomplished; it surrounds the eroded and embayed 
coast of a well-dissected, but not clift, island; and it surmounts the 
previously formed reef, which is now a submarine bank; such a 
fringe should therefore be taken to represent a young reef of a new 
generation formed after a rapid subsidence had drowned a pre- 
viously formed barrier reef in the manner suggested by Darwin. 
Palawan, the southwesternmost of the Philippines, has a strongly 
embayed western coast fronted by a broad, submerged bank, but 
practically without fringing reefs even around its tapering, non- 
clift, spur ends; thus it seems to have recently and rapidly sub- 
merged. Fauro, a small and greatly eroded volcanic island in the 
Solomon group, seems to have an unconformable fringing reef 
like B’; the submarine bank has depths of from 50 to 70 fathoms, 
and has a width of several miles; discontinuous reefs rise on parts 
of its margin, but seldom reach the surface of the sea. The 
granitic islands of the Seychelles have similar fringing reefs of a 
second generation. As the depth of the Fauro bank is greater than 
the climatic changes of level during the glacial period, as the amount 
of erosion that the volcanic mass has suffered below present sea- 
level appears to be much greater than could have been accomplished 
during the lower stands of the ocean in the glacial period, and as 
neighboring islands do not present similar features, the opportunity , 
for the formation of the Fauro fringe above the submerged bank 
must be ascribed chiefly to local subsidence. 
