116 THREE CRUISES OF THE " BLAKE." 



the Vir^n Islands, are somewhat poorer, and as we come to the 

 Windward Islands the West Indian types disappear and are re- 

 placed by continental forms. In the Bahamas we find no con- 

 tinental types, the species being most clearly allied to those of 

 Cuba, with which geologically and physically they are in closer 

 connection. 



While the flora of Florida undoubtedly has many of the char- 

 acteristic features of that of the Southern States, it has also a 

 decided West Indian tinge. Its mangroves, limes, and pal- 

 mettos connect it with the vegetation found on the other side 

 of the Straits of Florida, and along its southern extremity are 

 found West Indian, Mexican, and Central American birds, 

 which rarely find their way farther north than the Everglades. 



Our imperfect knowledge of the geology of Central America 

 tends to show that South America must have remained isolated 

 from North America before the tertiary period ; that during 

 palaeozoic times it formed a huge archipelago, and that its con- 

 nection with North America was never a very close one. Hence 

 the migration during tertiary times of many of the American 

 forms has produced in the West Indies and the Central Amer- 

 ican districts a strange mixture of ancient and recent types. 

 Many of these are now extinct both in North and South America. 

 This want of close connection between the Americas has prob- 

 ably affected the fauna of South America much as it has that 

 of the West Indies, and produced conditions highly favorable to 

 the extraordinary development of specific forms, which charac- 

 terizes the fauna of tropical America beyond all other faunal 

 districts. 



The deep soundings (over three thousand fathoms) developed 

 by the " Blake " south of Cuba, between that island and Yuca- 

 tan and Jamaica, do not lend much support to the theory of an 

 Antillean continent as mapped out by Wallace, nor is it prob- 

 able that this continent had a much greater extension in former 

 times than now, judging from the depths found on both sides of 

 the West India Islands. This would all tend to prove the want 

 of close connection between the West India Islands and the ad- 

 joining continent. It leads us to look, for the origin of the 

 fauna and flora of those islands, to causes similar to those which 



