228 BARBOUR: ZOOGEOGRAPHY. 



most of them in Porto Rico, while not a single one occurs in Jamaica. On the 

 other hand, Aristelliger and Mabuya are found in Jamaica and Haiti, and the 

 latter in Porto Rico, and neither in Cuba. These remarks refer to entire genera. 

 The distribution of certain species may be traced out in the same way. 

 Thus Cuba has but one species of Celestus, while Jamaica has three and Haiti 

 four, these four being the representatives of both the Cuban and Jamaican spe- 

 cies. Broadly speaking, then, the Haitian species which have obviously been 

 derived from the Central American mainland have come by two routes, the one 

 the Cuba bridge, which undoubtedly endured for a considerable length of time, 

 and which existed after and perhaps even came into existence after the disap- 

 pearance of the connection between Jamaica and Haiti, since a number of Cuban 

 genera and groups of species are found in Haiti and Cuba, but not in Jamaica; 

 while a very small number of species derived from Haiti have representatives 

 that passed to Cuba. Alsophis and Leimadophis occur on all three islands, 

 but all the genera previously mentioned are confined to either pair of Islands, 

 always including Haiti, and not upon the third. The fauna is a large one, and 

 embraces at least fifty-five species, for this number takes no account of any of 

 the possible records for several species which are not absolutely authenticated. 

 Forty-seven species certainly, and possibly others, are peculiar to the island. It 

 will be seen from this, that, although a number of the continental genera occurring 

 upon Cuba are not represented in Haiti, the total number of species found on 

 the island is almost as great as that found upon Cuba, the difference being made 

 up by those which have been derived through direct connection with Jamaica. 



Porto Rico. 



Omitting special mention of Mona Island, which is not of great importance 

 in the present connection, we may pass directly to a brief study regarding the 

 fauna of Porto Rico. This has been very fully discussed by Stejneger in his 

 Herpetology of Porto Rico (Rept. U. S. nat. mus. for 1902, 1904, p., 549-724). 



Stejneger says (p. 562): — 



" The herpetological fauna of Porto Rico falls into two groups, namely, the species which 

 have in all probability originally extended their range from northeastern South America 

 and those whose ancestors came from the west, primarily from the present mainland of 

 Central America, and secondarily from the other Great Antilles." 



The fauna of Porto Rico is less in number than that of either Cuba or Haiti ; 

 and is almost exactly comparable to that of Jamaica, there being twenty-six 



