AGASSIZ: FIJI ISLANDS AND CORAL REEFS. 73 
correct in my interpretation of what I have observed ; information, in 
fact, which may be obtained as one steams along, without the trouble or 
cost of boring. Should I be correct in my inference, I am inclined to 
look upon the boring at Funafuti much in the same light, and to assume 
that that island is also in an area of elevation, as well as others in the 
Ellice group, and that the great thickness of coral obtained was reached 
in the base of an ancient limestone, and that the results obtained by the 
boring there do not assist us in any way in corroborating the theory of 
subsidence as essential to the formation of atolls. 
The evidence which has been brought forward regarding the great 
thickness of modern reefs, as postulated by Darwin, from that of the fos- 
sil coral reefs existing during former geological periods, seems to me to 
be of little valne. Langenbeck? and von Lendenfeld? have both urged 
this point. The former has given an excellent résumé of the subject of 
these ancient reefs, although he has no personal knowledge of recent 
reefs. All that can be said at present is that these so called fossil 
reefs are coralliferous limestones of great thickness, which first occur in 
the Devonian ; they are little developed eitber in the Permian, or Trias, 
or Lias. They are again well developed in the Jurassic period, less so 
in the Cretaceous, and increase in Tertiary times. That parts of some 
of these coralliferous limestone masses represent reefs there can be little 
doubt, yet the observations we made in Fiji regarding the coralliferous 
elevated Tertiary limestones, which have been considered as elevated 
reefs of the present epoch, only show how guarded we should be in an 
expression of opinion as to what constitutes a fossil reef, —I mean a 
fossil fringing or barrier reef, or a fossil atoll, —when we are not able to 
decide that point in the reefs of to-day, and when one set of observers 
claims that the Tertiary elevated limestones represent elevated atolls, 
while the other set clearly shows that these elevated limestones have 
played no part in the formation of the recent atoll, or barrier reef, but 
have merely built up the substratum upon which the moderately thin 
crust of recent reefs has established itself. 
Granting, even, as is very probable, that when these Tertiary lime- 
stones were formed they were formed in great part by subsidence, 
and in part by accretion from the carcasses of the invertebrates living 
upon their surface, this would in no way help us to a satisfactory 
1 Langenbeck, R.: Die Theorien iiber die Entstehung der Koralleninseln und 
Korallenriffe und ihre Bedeutung fiir Physische Fragen. Leipzig, Abschnitt IV. 
2 Nature, May, 1890, p. 29. See also the interesting note by von Fritsch, 
quoted by Kramer, loc. cit., p. 38. 
