Just south of Cape Hatteras an observer is struck with the sudden change in the appearance of the shells on the beach. /Cardium/, /Cassis/, /Dolium/, /Arca/, and /Cancellaria/ at once suggest the West Indies. About the vicinity of Hatteras the Gulf Stream approaches very near the land, bringing with its warm waters many wanderers from tropical homes. From Beaufort to Florida there is another long stretch of exposed and shifting sand-beach, which offers a scant return to the collector of mollusks. THE CARIBBEAN PROVINCE When Florida is reached a new world is opened to the naturalist, for there a better acquaintance is made with the great Caribbean province, which, extending from Florida to the northern shores of South America, embraces all the Bahamas, the West [pg311] Indies, the Gulf of Mexico, and the coast of Central America. Strangely enough, the mollusks of the west coast of Florida are more nearly related to those of the transatlantic province than are the shells of the east Florida coast. This remarkable fact in geographical distribution can only be explained by assuming that an open waterway once existed across the northern part of the Florida peninsula, connecting the Atlantic and the Gulf, through which a mingling of the shallow-water forms from Georgia, the Carolinas, West Florida, and the Gulf coast took place. Thus it would appear that when Florida was an island the fauna of its east coast, originally largely Antillean, was less disturbed by the southern migration of American species. The Florida Keys are essentially Antillean. The Caribbean or Antillean fauna is an exceedingly rich and varied one. Among the most prominent genera which may be encountered upon the Florida coast are /Strombus/, /Fasciolaria/, /Oliva/, /Marginella/, /Natica/, /Sigaretus/, /Littorina/, /Tectarius/, /Neritina/, /Melongena/, /Cardium/, /Callista/, /Tellina/, /Lucina/, and /Cyrena/. In such an extensive and rich faunal province one must not expect to find in any given locality a representation of all the characteristic genera. For instance, collections made at Havana, at Nassau, and at Vera Cruz would each contain forms more or less peculiar and local, but certain species would be found in each collection. * * * * * On the west coast of America quite the same faunal division into more or less well-marked provinces is to be found. Bering Sea belongs to the arctic province, and contains, with Labrador and Greenland, many identical forms. THE ALEUTIAN PROVINCE