GEOLOGY AND PALEONTOLOGY OF THE CANAL ZONE. 301 



The shore-line phenomena of Panama and Costa Rica have been 

 carefully described by D. F. MacDonald in his forthcoming report 

 on the physiography and geology of the Canal Zone and adjacent 

 areas. His conclusions in general accord with those I have expressed 

 for other areas. 



SOME OTHER WEST INDIAN ISLANDS. 



R. T. Hill in 1899 ^ pointed out "that Jamaica was once a more 

 extensive land than now, with benched and terraced margins which 

 were submerged by subsidence," and that "similar submerged 

 plains are now occupied by the growing reefs around the island." 

 Hill appears to hold the view that the reefs were formed during 

 uplift, after submergence, and as regards the elevated fringing reefs 

 I beheve he is correct. In fact, Mr. Meinzer and I make a similar 

 interpretation of the conditions under which the coral-reef terraces 

 of Cuba were formed. But, it seems to me that the barrier reef off 

 Morant Point, Jamaica, has been formed after an episode of sub- 

 mergence. The pouch-shaped harbors of Jamaica suggest that 

 considerable stretches of the Jamaica shore hne have undergone 

 recent submergence. 



I have compiled information on the shore Hnes of other West 

 Indian islands, but to present more seems unnecessary. Possibly 

 except a reef off the southeast side of Barbados, all the off-shore 

 West Indian reefs on which I have obtained information have 

 formed on preexisting flats or plateaus during or after an episode of 

 submergence. 



BEAZIL AND ARGENTINA. 



Herbert M. Smith,^ it seems, was the first to recognize evidence of 

 submergence on the east coast of South America, and Rich ^ has 

 made a pertinent apphcation of Smith's observations and deductions 

 to the coral-reef problem. Smith says: 



Such an estuary as I have described could only have been formed by the subsidence 

 of the land over a great area, and the encroachment of the sea on some former Amazons 

 and its tributaries. 



During late geologic time there is in the region of the Amazon 

 evidence of a higher followed by a lower stand on the land. 



Branner has made the most careful study of the shore Hne of 

 Brazil, and summarizes his conclusions as f oUows : * 



8. Although no changes of level are known to have taken place within the historic 

 period, there are eAddences of both elevation and depression of the Brazilian coast in 

 late Geologic times. 



» Mus. Comp. Zool. Bull., vol. 36, pp. 99, 100. 



2 Smith, Herbert M., Notes on the physical geography of the Amazon Valley, Amer. Naturalist, vol. 

 19, pp. 27-37, 1885. 



8 Rich, John L., The physiography of the lower Amazon Valley as evidence bearing on the coral-reef 

 problem. Science, new ser., vol. 45, pp. 589-590, June 8, 1917. 



* Branner, John Casper, The stone reefs of Brazil, their geological and geographical relations, with a 

 chapter on the coral reefs, Mus. Comp. Zool. Bull., vol. 44, pp. 168, 169, 1904. 



