390 PRINCIPLES OF STRATIGRAPHY 



in the West Indies, off the coast of Floricln and on tlie coast of 

 Brazil. This is clearly due to the fact tliat the tropical belt is most 

 contracted in the Atlantic. The Bermuda Islands are a remarkable 

 exception to the jjeneral law of distribution of coral reefs, for they 

 are found in the latitude 32° N., and are therefore the farthest re- 

 moved from the equator of any modern coral reefs. Their occur- 

 rence in such a position is favored by the Gulf Stream, which brings 

 the warm waters of the tropics. No coral reefs are known in the 

 eastern part of the Atlantic. 



The eastern part of the Pacific is likewise free from reefs, and 

 this is to be correlated with the fact that the cooler ocean currents 

 from north and south converge here, as in the east Atlantic, to form 

 the equatorial currents. The coral reef area of the Pacific lies west 

 of the I20th meridian (E.), the greatest area lying between 130° E. 

 and 145° W. longitude and between 15° N. and 25° S. latitude. 

 The most extensive eastern group is that of the Low Archipelago 

 with Ducie Island, its eastern outpost. The largest western group 

 is that of the Caroline Archipelago, but many scattered atolls and 

 fringing reefs occur to the west of this, notably in the China Sea, 

 where the Paracelle group forms an extensive cluster of atolls in 

 lat. 112° W., long. 17° N. The fringing reefs of the Sandwich 

 Islands form a large single and isolated group in the mid-Pacific 

 north of the equator. 



The coast of the mainland and the islands of the western Pacific 

 within the coral zone are generally bordered by reefs either fringing 

 or barrier, beginning with the Great Barrier Reef on the south, and 

 extending to the fringing reefs of the Loo Choo group. 



The Indian Ocean is generally lined by fringing reefs, which ex- 

 tend with interruptions from Madagascar north along both sides of 

 the Red Sea, in the Persian Gulf around Ceylon and the Nicobar 

 Islands and south along the coast of Sumatra and Java to Australia. 

 In the western half lies the great group of atolls, the Maldives and 

 Laccadives, extending from the equator north to lat. 13° and the 

 Chagos and Sava de Malha groups. The fringing reefs of the 

 Seychelles and of Mauritius also fall in this half of the Indian 

 Ocean. The eastern half contains only the Cocos-Keeling group 

 and some atolls off the northwest coast of Australia. 



In general, then, reefs of various kinds occur in the three larger 

 oceans, but are mainly confined to the western half of these oceans. 

 The Indian Ocean alone has representatives in the eastern half, but 

 they are far less abundant than in the western. The Atlantic has 

 no typical atolls, though the Bermudas come near to representing 

 them. 



