IO 



PAPERS FROM THE DEPARTMENT OF MARINE BIOLOGY. 



volcanic and calcareous particles which have evidently been swept along and 

 over the northeastern reef-flat by the current due to the southeast trade wind 

 and the strong incoming tide. 



The mud from Haddon Brook and Hedley Brook prevents a vigorous 

 coral growth along this part of the shore, and the reef-flat is here dead and 

 covered with silt, only its wave-washed outer edge and its precipitous sea- 

 ward slope affording foothold for successful coral growths. Similarly the 

 silt from these brooks is carried around the southwest side of the island, 

 sweeping over the reef-flat and killing most of the corals excepting those near 

 the outer edge of the reef, where the largest coral heads of the island are 

 found. Indeed, where silt is being drifted over a bottom only large coral 

 heads which project above it can thrive. 



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Volcanic ash and lava 



Fragments of old limestone imbedded in ash Recent coral reef 



Horizontal and vertical scale 

 spo isoo 3000 Feet 



Old limestone 



Fig. 3. — Section of Maer Island through the shore end of Line I, and the western corner of the Island. 



The seaward wall of the reef surrounding Maer Island is from 15 to 30 

 fathoms in depth, this being the depth of the submarine plateau above which 

 the modern fringing reefs have arisen. 



R. T. Hill in 1899 1 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." A. Agassiz in 1894 2 sa id: 



" 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 conti- 

 nent, where they find the proper depth." 



Agassiz and others had adduced evidence indicating recent submergence 

 in the Bermudas and the Bahamas. Information regarding other coral 



■Mus. Comp. Zool., Bull., vol. 36, pp. 99, 100, 1899. 'Mus. Comp. Zool., Bull., vol 26, p. 172, 1894. 



