MOLLUSKS 311 
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 
The shore waters from the southern peninsula of Alaska down 
to about Vancouver comprise the Aleutian province. Within 
this area occur some arctic species, notably the soft-shell clam, 
Mya arenaria, which the fishermen gather in such large quan- 
tities for bait along the Maine coast. An increasing number of 
species common to this west-coast faunal region and to the 
boreal province of the east coast are being recorded. Some of 
