160 bulletin: museum of comparative zoology. 



The Coral Reefs and Banks of the "West Coast of the 



Caribbean Sea.^ 



It is to be noted that on the western Florida Bank, as well as on the 

 Yucatan Bank, where the conditions of depth would cseem to be most 

 favorable for the growth of corals, in the one case the coral reefs are 

 limited to a few isolated patches like Arenas Cays (Hydrographic Charts 

 Nos. 403, 1233, Admiralty Chart No. 1209), Sisal Reef (Hydrographic 

 Charts Nos. 403, 1235, Admiralty Chart No. 1206), Madagascar Eeef 

 (Hydrographic Chai-t No. 1235), the Triangles (Hydrographic Charts 

 Nos. 403, 1239), Obispo Shoals (Hydrographic Charts Nos. 403, 1239, 

 Admiralty Chart No. 1830), the Areas Cays (Hydrographic Charts 

 Nos. 403, 1234, Admiralty Chart No. 1829), and the Alacran atoll (Hy- 

 drographic Charts Nos. 403, 966, 1234, 1235, 1240, Admiralty Chart 

 No. 1203) ; while in the other case they form a narrow thread parallel 

 with the course of the Gulf Stream outside of the Florida Keys from 

 north of Key Biscayne to the Tortugas.^ 



Along the west coast of the Gulf of Mexico (see Coast Survey Chart 

 of Gulf of Mexico, ^j-2Woijb) the corals are wanting, with the exception of 

 a few isolated patches of coral reefs off Vera Cruz coming np from six- 

 teen fathoms of water (Hydrographic Chart No. 967, Admiralty Chart 

 No. 523), which, although noted in the A.dmiralty West Indian Pilot, 



1 Tlie reefs of Cuba liave been described in a separate chapter. 



- Since nij' explorations of the Bahamas and Bermudas I am convinced that a 

 more detailed examination is needed to ascertain how far south the older niiocene 

 rocks of Florida extend, and to what depth they are covered by the recent coral 

 growths from Key Biscayne to the Tortugas. An exploration of the inner line of 

 keys may show perhaps how far the configuration of the western part of the Florida 

 Bank to the south of Cape Sable may be due to a slight subsidence, and how far 

 this has been concealed by the growth of corals to form the outer reef, and by the 

 deposition upon these older rocks of coral material which has formed the inner line 

 of cays, or how far erosion has been the main factor in shaping the topography of 

 the submerged southern part of Florida and of the adjacent keys. Borings alone 

 can determine this question, owing to the quantity of coral silt which Iws been de- 

 posited upon the mud flats north of the keys, unless we may succeed in finding 

 somewhere among the inner keys an outcrop of the older miocene or perhaps later 

 tertiary rocks. 



For an account of the Florida Reefs see L. Agassiz, Ann. Rep. U. S. Coast Survey, 

 1851, Mem. Mus. Comp. Zo51., Vol. VIL No. 1, 1880; A. Agassiz, The Tortugas 

 and Florida Reefs, Mem. Am. Acad., Vol. XI., 1882 ; Three Cruises of the " Blake," 

 Bull. Mus. Comp. Zool., Vol. XIV., 1888; and Coast Survey Charts, Nos. 166, 167, 

 168, 169. 



