﻿GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 299 



than at present (and has been submerged to a similar amount). Besides the suggested 

 larger swing there have been intermediate stands of sea level and numerous minor 

 oscillations. The last movement of importance was one of submergence, but subse- 

 quent to it there has been a minor uplift of some 10 feet or slightly more in the vicinity 

 of Miami. 



The accompanying figure (fig. 18) shows that the flat that the living 

 barrier-reef margins or above which coral-reef patches rise extends 

 beyond the northern reef limits, near Fowey Rocks. The living bar- 

 rier reef has developed seaward of the Pleistocene barrier near the edge 

 of a previously prepared platform, for the continuity of the platform 

 irrespective of the presence of the reefs shows that its origin is inde- 

 pendent of them. 



CAMPECHE BANK. 



The best known reef on the Campeche Bank is Alacran Reef, which 

 was described by A. Agassiz in considerable detail in 1888.^ (See 

 pi. 73, photograph of model.) Heilprin in 1891^ said regarding 

 Yucatan, "the evidence is aU but conclusive that there has been 

 recent subsidence"; but I am unable to discover in his article the 

 basis of this opinion. Dr. C. W. Hayes orally informed me shortly 

 before his deeply lamented death that there is clear evidence of 

 recent submergence aroimd Terminos Lake at the base of the penin- 

 sula on its west side. The lagoons between Progreso and Holbox 

 Island are strongly suggestive of submergence. There is a steeper 

 slope between about 20 and 28 on the outer edge of the bank, indi- 

 cating change in position of sea level by submergence, similar to the 

 change already recorded for St. Thomas and other West Indian 

 islands. 



In this connection the following quotation from Alexander Agassiz 

 win be introduced :^ 



In fact, what I have seen so far in my exploration of the coral reefs of the^West Indies 

 would show that wherever coral reefs occur, and of whatever shape, they form only a 

 comparatively thin growth upon the underlying base, and are not of great thickness. 

 In Florida they rest upon the limestones which form the basis of the great peninsula. 

 On the Yucatan Bank they are underlain by a marine limestone. In Cuba they abut 

 upon the Tertiary limestones of its shore. Along Honduras, the Mosquito Coast, and 

 the north shore of South America they grow upon extensive banks or shoals, parts of 

 the shore plateau of the adjoining continent, where they find the proper depth. 



I doubt if there is any one bold enough to claim that Campeche 

 Bank has been formed by infilling behind a barrier reef, for it is too 

 obviously due to a large gentle flexm'e of the earth crust or some 

 other kind of broad structural uplift, and that in suitable places 

 coral grows on the surface of the submarine plateau formed in the 

 manner indicated. E. W. Shaw^ collected a few bottom samples 6 to 



* Agassiz, A., Three cruises of the Blake, vol. 1, p. 71, 1888. 



» Heilprin, A., Geological researches in Yucatan, Phila. Acad. Nat. Sci. Proc. for 1891, p. 148. 

 3 Mas. Comp. Zool. Bull., vol. 26, p. 172, 1S94. 



* Shaw, E. W., Oral communication. 



