110 PROCEEDINGS OF THE MALACOLOGICAL SOCIETY. 



The best-studied coastline in the world is, beyond a doubt, that of 

 Eastern North America, from Texas and Florida to Labrador, thanks 

 to the work of Ball, of Verrill, Bush, and many others. Let us for 

 a moment employ some of the material gathered by them,' and fix our 

 attention on the tropical fauna of the extreme south-east States, 

 a fauna wliich is in close alliance with the West Indian. What is the 

 extreme northern range along that coast of such thoroughly tropical 

 genera as Conns, Cyprcea, Trivia, Stroinbus, Oliva, Olivella, Fasciolaria, 

 and the PJiyllojiotus group of Murex'^ 



Of Conus ten species occur, nine of them on Florida Keys ; four 

 reach Cape Hatteras, none further north. 



Of Cyprcea there are three species, all West Indian ; one only 

 ( C. exanthema, L.) reaches Cape Hatteras, and no further. 



Of Trivia there are seven species, all found on Florida Keys, but 

 only one reaches Cape Hatteras, and no further. 



Strombus is represented by five species (four of them West 

 Indian) ; all five occur on Florida Keys ; three only reach East 

 Florida, one reaches Georgia, one {pnrjilis, L.) Cape Hatteras, and 

 no further north. 



Oliva has two species ; one of these reaches Cape Hatteras, and no 

 further. 



Olivella has six species, all West Indian ; three reach Cape Hatteras, 

 but no further north. 



Of Fasciolaria there are three species, all represented on Florida 

 Keys; all reach Cape Hatteras, but no further. 



Finally, of Fhyllonotns there are four species ; two of these reach 

 Cape Hatteras, but no further. 



This list might be considerably extended, and it would not be easy 

 to find a more striking instance of the power of a current of warm 

 surface-water to carry a tropical fauna northward. Cape Hatteras, 

 be it remembered, is in about the latitude of the Straits of Gibraltar. 

 The Gulf Stream, issuing from the Gulf of Mexico, makes a right- 

 angled turn at Cape Sable, the extreme southern point of Florida, 

 and hugs the East American coast more or less closely until it reaches 

 Cape Hatteras, when it parts company with the land and moves 

 north-east and east across mid-Atlantic. A further factor which 

 accentuates the sudden break in the range of the tropical fauna, and 

 makes the northward barrier more effective, is the fact that a cold 

 current, the remains of the Polar and Labrador drift, running 

 a westerly and southerly course from the outer banks of Newfoundland* 

 and the south coast of Nova Scotia, parallel to. but in the reverse 

 direction to, the Gulf Sti'eam, impinges on the North American coast 



' See particularly W. H. Dall, " A preliminary Catalogue of the Shell-bearing 

 Marine MoUusea ... of the south-east coast of the United States " : 

 Bull. U.S. Nat. Mas., vol. xxxvii, pp. 1-221, 1889. 



^ " The Grand Banks of Newfoundland . . . are inhabited by an extremely 

 Arctic fauna, including many species of Mollusca which have not yet been 

 found further south " (A. E. Verrill, Trans. Connect. Acad., vol. v, 

 pp. 447-587, 1878-82). 



