AGASSIZ: BERMUDAS. 2^7 



abode of Porites in Florida, where it is usually most abuudant on flats 

 more or less sheltered. 



The corals at the Bermudas as well as at the Bahamas do not gener- 

 ally reach the surface. They form a more or less connected belt of coral 

 growth in from five to six fatlioms on the inner edge of the flats to the 

 outer limits, the beginning of the broken ground, the co^-als extending to 

 eight or ten fathoms on the southern sea faces of the flats. 



LEDGE FLATS AND PATCHES. 



Plates II., XV., and XVII. to XXVI. 



The ledge flats, patches, or coral heads, are names given to different 

 parts of the reef, wliich has universally been considered to owe its exist- 

 ence to the growth of corals, and much of the confusion existing regard- 

 ing the structure of both the Bahamas and Bermudas is due to the 

 fact that corals have been assigned a part in the building up of these 

 islands which they have never performed. 



The flats consist, not of coral heads, though they are often so called 

 both here and at the Bahamas, but of ledges of ^olian rock rising from 

 a depth of five to six fathoms or more (Plate XVIII.). These ledges, 

 with their nearly vertical sides and their slopes deeply honeycombed, 

 drop rather abruptly into the coralline bank bottom, which forms more 

 or less extensive irregularly shaped patches separating the ledges. The 

 surHice and sides of the ledges are veneered by corals,^ Gorgonians, 

 and Millepores ; the sharper edges of the ledges are covered by incrust- 

 ing masses of Millepores, and calcareous and other Algse grow in great 

 profusion between the corals and Gorgonians. The Millepores, Gorgo- 

 nians, NuUipores, and calcareous and other Algee, are by far the most 

 abundant growth on the inner patches. On these we find only compara- 

 tively few of the larger Mseandrinas and Astreas. The massive corals 

 increase greatly in number as we approach the outer edge of the reef, 

 and the finest and most numerous specimens appear to grow on the 

 outer sea face in from five to seven fathoms of water. Beyond that, or 

 even at lesser depths, in five to six fathoms, the broken ground begins. 

 This consists mainlv, as far as 1 could ascertain from the observations 

 of others and gather from my own notes and dredgings, of Gorgonians, 



1 Thomson thinks that the patches have been built up by the corals. Atlantic, 

 I. .304. 



