AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 81 
where we can begin the study at the very base of the elevated limestone 
reef at its point of contact with the underlying volcanic rock, will teach 
us a great deal regarding the interior structure of a coral reef. This we 
can follow to the surface, or nearly so, by following the faces of exposed 
cliffs or the slopes of the ridges. Ofcourse, the uppermost part of the reef 
rock, that which formed the original surface of the reef, will have been 
denuded and eroded to a considerable depth. But it ought to be possible 
from the study of an extensive area of an elevated reef, both vertical 
and horizontal, to settle the question of the growth of a reef seaward by 
its gradual extension upon a talus formed at a comparatively shallow 
depth (say twenty fathoms) from the fragments and masses which have 
dropped at the foot of the sea slope of the reef, after having been de- 
tached by the action of the breakers from the edge of the reef. It is 
natural to suppose that there must exist at the base of the reef a num- 
ber of coral masses, judging from the multitude which are thrown upon 
the sea face of any modern reef when exposed to violent breakers. 
Dr. William H. Dall? has been kind enough to examine the fossil 
mollusks which I collected from the elevated limestone reefs in the 
Fijis. He confirms the impression I had formed of their late tertiary 
age. Dr. Dall writes: “The fossils comprise Turbo, Cassis, Lithophaga, 
Macha, Tellina, Meretrix, Dosinia, Chama, Pholas, and fragments of 
Pecten. None of the genera are extinct. The rock, however, looks 
decidedly too old for Pleistocene. I should say the fossils were younger 
than Eocene, and might be either Miocene or Pliocene.” 
The boring which I started at Wailangilala Island in the atoll of the 
same name reached at forty feet a limestone similar in all respects to 
that composing the elevated reefs we had observed at Ngele Levu, 
at Vanua Mbalavu, at’ Mango, at Yangasd, at Oneata, at Ongea, at 
Kambara, at Vatu Leile, and at different points along the eastern, 
southern, and western shores of Viti Levu. At some points the elevated ” 
limestones attain a height of over 1,000 feet (Vatu Vara Island 1,030 
feet), and the volcanic rocks underlying the elevated limestone reefs 
were observed at Vanua Mbalavu, at Mango, at Kambara, and at several 
points along the southern and western coast of Viti Levu. A renewed 
examination of the elevated reefs of the Paumotus, of the Friendly 
Islands, of the Gilbert, Ellice, and other groups of atolls in the Pacific 
will be needed to determine their age and correlation to the Fiji ele- 
vated limestones. At any rate, it is evident that the tertiary corallif- 
erous limestones of Fiji have not played any part in the formation of 
1 See Am. Journ. Science, Vol. VI. p. 165, 1898. 
VOL. XXXIII. 6 
