18 U.S. NATIONAL MUSEUM BULLETIN 292 



Of the 14 families represented in the West Indies, 11 occur on all 

 of the adjacent continental masses; 2, the Pseudothelphusidae and 

 Trichodactylidae, are also in Mexico, Central America, and South 

 America; and 1, the Astacidae, in North America, Mexico, and 

 Central America. 



Only two families occurring in the Western Hemisphere and having 

 freshwater and terrestrial members are absent from the West Indies. 

 The Parastacidae are found in South America, Australia, New Zealand, 

 Tasmania, New Guinea, and Madagascar, and the Aeglidae are 

 endemic to South America, but neither of these famiUes occurs in 

 the northern part of the South American continent. 



Only 1 of the 14 famihes, the Astacidae, can be adjudged con- 

 clusively as having reached the Antilles from North America, and 

 that via the Central American-Mexican region. Likewise, only one 

 family, the TrichodactyHdae, is unquestionably a South American 

 one, invading the Antilles only to Trinidad. A third family, the 

 Pseudothelphusidae, has apparently reached the Antilles from two 

 sources. South America and the Central American-Mexican region. 



The West Indian genera. — Twenty-two of the 38 genera having 

 freshwater and terrestrial representatives are also found in North 

 and South America and in the Central American-Mexican region. 

 Six ( Typhlatya, Xiphocaris, Troglocuhanus , Barbouria, Epilobocera, 

 and Metopaulias) are endemic in the West Indies, three ( Guinotia, 

 Trichodactylus, and Metasesarma) are found elsewhere only in South 

 America, and three (Jonga, Micratya, and Glyptograpsus) elsewhere 

 only in the Central American-Mexican region. Three genera {Atya, 

 Potimirim, and Pseudothelphusa) occur also both in South America 

 and in the Central American-Mexican region, but only one {Pro- 

 cambarus) inhabits both North America and the latter. None of the 

 genera are confined to the West Indies and North America. 



Only one genus, Procambarus, is believed to have had a North 

 American origin, and it has reached the Antilles from the Central 

 American-Mexican region. 



As to the origins of the stocks from which the West Indian genera 

 probably arose, Barbouria is the only one that has possibly been 

 derived from a marine ancestor in situ, on the Island of Cuba. The 

 ancestors of the endemic Epilobocera almost certainly came from the 

 Central American-Mexican region as have those of the West Indian 

 representatives of Jonga, Micratya, Typhlatya, Pseudothelphusa, and 

 Glyptograpsus. The West Indian representatives of the genera Guinotia, 

 Trichodactylus, and Metasesarma seem unquestionably to have had a 

 South American ancestry, while there is evidence that Potimirim has 

 reached the Antilles from both South American and Central American- 

 Mexican regions. The origins of the ancestors of the endemic Xipho- 



