DECAPOD CRUSTACEANS OF THE WEST INDIES 17 



It may be noted that the number of species shared by the Lesser 

 Antilles \vith South America alone is only six, and those with Central 

 and South America, only two. No species are limited to the Central 

 American-Mexican region and the Lesser Antilles. 



Four species are common exclusively to the Greater Antilles and 

 the Central American-Mexican region. A single species occiu's only 

 in the Greater Antilles, the Central American-Mexican region, and 

 in North America. 



As for the species shared in common by the Lesser and Greater 

 Antilles, 12 occur also in South America and in the Central American- 

 Mexican region, two in only the Central American-Mexican region, 

 three in South America and North America, and one each in South 

 America and in the combination of the Central American-Mexican 

 region and North America. 



Perhaps surprising is the fact that none of the Antillean species 

 are shared with North America alone (as used in this discussion, 

 exclusive of Mexico) ; fm*thermore, none of the endemic species occur- 

 ring on the islands seem to have been derived from ancestors moving 

 directly to them from North America. The ancestors of a majority 

 of the endemic fauna seem to have reached the Greater Antilles from 

 the Central American-Mexican region, and a few have undoubtedly 

 been derived from stocks from South America. Evidence for a West 

 Indian origin du-ectly from salt water ancestors exists for only one 

 species, Barbouria cubensis, which occm-s in brackish pools in Cuba. 



The West Indian families. — The following is a summary of the 

 distribution of the West Indian decapod families having freshwater 

 or terrestrial members: 



> Marine families, some members of which occur In the supralittoral or in estuarine habitats, occasionally 

 Invading freshwater. 



