of the Bahama Islands. 319 



Virgin Bank, have no special relations with those of the Ba- 

 hamas. Most of the Anegada species occur in otlier of the 

 Virgin Islands and in Porto Rico, none of them in the Ba- 

 hamas. 



In connection with the facts stated as to the distribution 

 of terrestrial shells in the Bahama Islands, and the infer- 

 ences with regard to their former more intimate relations 

 with each other and with adjacent lands, the views of Prof. 

 Dana (Corals and Coral Islands, 1872) are of great value. 

 In the chapter vi (p. 348), entitled "Geological Conclusions," 

 Dana considers at some length "The Oceanic Coral Island 

 Subsidence," and after treating the subject with reference 

 more especially to the Pacific tropics, he says (p. 368) : — 



" The changes which took place cotemporaueously in the Atlantic trop- 

 ics are very imperfectly recorded. The Bahamas show by their form and 

 position that they cover a submerged land of large area, stretching over 

 six hundred miles from northwest to southeast. The long line of reefs 

 and the Florida Keys, trending far away from the land of southern Flor- 

 ida, are evidence that this Florida region participated in the downward 

 movement though to a less extent than the Bahamas. Again, the islands 

 of the West Indies diminish in size to the eastward, being quite small in 

 the long line, that look out upon the blank ocean, just as if the subsidence 

 increased in that direction. Finally, the Atlantic beyond is water only, 

 as if it had been made a blank by the sinking of its lands. 



"Thus the size of the islands as well as the existence of coral banks, 

 and also the blankness of the ocean's surface, all appear to bear evidence 

 to a great subsidence. 



"The peninsula of Florida, Cuba and the Bahamas look, as they lie 

 together, as if all were once part of a greater Florida, or southeastern 

 prolongation of the continent. The northwestern and southwestern 

 trends, characterizing the great features of the American continent, run 

 through the whole like a warp and woof structure binding them together 

 in one system; the former trend, the northwest, existing in Florida and 

 the Bahamas, and the main line of Cuba; and the latter course, the west- 

 southwest, in cross lines of islands in the Bahamas (one at the north ex- 

 tremity, another in the line of Nassau, and others to the southeast), on 

 the high lands of northwestern and southeastern Cuba, and in the Florida 

 line of reefs, and even further, in a submerged ridge between Florida and 

 Cuba. This combination of the two continental trends shows that the 

 lands are one in system, if they were never one in continuous dry land. 



" We can not here infer that there was a regular increase of subsidence 

 from Florida eastward; or that FJoridaand Cuba participated in it equally 

 JUNE, 1873. 22 Ann. Ltc. Nat. msT., Vol. x. 



