32 U.S. NATIONAL JVIUSEUM BULLETIN 29 2 



Indian islands are as follows (numbers in parentheses indicate, in 

 addition, genera or species that are probably there but have not been 

 reported) : 



I a -a S fe -3 2 -s 



Families » 697 745 78 



Genera 2 L8 22 14(4) 18 6 9(1) 17 11(3) 



Species' 32 41 20(4) 28 6 13(1) 28 15(3) 



* Excluding Ponaeidae, Hippolytldae (except Barbouria), PorcoUauidae, Portunidae, and Xanthidae. 

 'Excluding families Indicated by "1," and Aratus, Cydograpnus, Orapaus, Metasesarma, Pachygrapsus , 



and Plagusia. 



* Excluding families and genera indicated by "1" and "2" and Setsanna hanseni and S. rkordi. 



* Excluding Trinidad. 



The numbers of freshwater taxa of West Indian decapods are dis- 

 tributed as follows (numbers in parentheses indicate, in addition, 

 genera or species that are probably there but have not been reported) : 



a 



Families 354 40245 



Genera 10 13 7(4) 10 2 9 6 



Species 20 27 12(4) 16 3 15 9 



» Excluding Trinidad. 



Ecological Discussion 



The majority of the West Indian freshwater and terrestrial decapod 

 crustaceans are known to be tolerant of salinities approaching that 

 of sea water, many actually invading the ocean or having larval 

 stages that typically occur in the sea. In sharp contrast are a number 

 of freshwater forms that are endemic on one or more of the islands. 

 While perhaps no broad classification can adequately depict the 

 ecological distribution of this assemblage of crustaceans, that pre- 

 sented herein represents an attempt to group those species living in 

 broadly similar habitats and requhing, insofar as known, similar 

 ecological conditions for their larval and juvenile development. 



In spite of the fact that some of the distinctions suggested are not 

 respected by all of the species listed, the assignments are made with 

 some degree of confidence, particularly for those species occurring 

 on Dominica; that is, that the animals do indeed exist in the habitats 



