HERPETOLOGY OF PORTO RICO. 563 



The snakes of the genus Alsopkis, though forming an almost exclu- 

 sively Antillean group, nevertheless betray* South American relation- 

 ship, and those of the genus Leimadophis in a still higher degree. 



The great majority of the Porto Rican species, however, are of 

 decidedly western affinities. Thus the Bufo, the various species of 

 hi, utherodactylus, the Mabuya, the Celestus, the two boas and the 

 fresh-water turtle are obviously related to species in the Great Antilles 

 to the west of Porto Rico. The Anoles and the Sphaerodactylus are 

 also allied more intimately to western species. As a matter of fact 

 the most characteristic species of Anolzs, for instance, A. cuvieri, 

 A. cristatellus, and the little group represented by A. pulchellus, are 

 utterly foreign to the Caribbean islands, and it is quite apparent that 

 the Anoles have developed in a secondary evolutional center located 

 somewhere in what is now known as the Greater Antilles. 



Compared with the other Greater Antilles the herpetology of Porto 

 Rico is negatively defined by the absence of a great many character- 

 istic forms. This poverty is easil} T understood, however, when we 

 reflect that Porto Rico is located at the extreme eastern and northern 

 point of the two series of islands, the Greater and the Lesser Antilles, 

 and that at the maximum distance from both the Central American 

 and South American mainland Porto Rico has obtained its fauna by 

 immigration from both directions, and being at the farthest end has 

 received the fewest number of colonists. 



The herpetological fauna as here understood, for obvious reasons, 

 embraces onty the main island and those of the adjacent islands with 

 which it passed into American possession by the treaty of Paris. 



As has been demonstrated, Porto Rico shows great affinity herpeto- 

 logicallv to the Virgin Islands, and the two islands belonging to the 

 former, but situated intermediate, Culebra and Vieques, are also inter- 

 mediate in their fauna to a certain extent. The coronelline snakes, 

 however, and one of the tree-toads occurring in Vieques or Culebra or 

 both are identical with those of the Virgin Islands, dilfering decidedly 

 from the corresponding species inhabiting Porto Rico proper. This 

 is the more interesting as we know of only one species which occurs 

 both in Porto Rico and Vieques or Culebra and does not also inhabit 

 one or more of the Virgin Islands, viz, Spha&rodactylus grand isquamis. 



The little island of Mona, on the other hand, is situated between 

 Porto Rico and Haiti. Thus far not less than nine species are known 

 to occur there, namely: 



1. J$eutherodactylus monensis. 



2. Sphserodactylns monensis. 



3. Mabuya sloanii. 



•i. Ameiva alboguttata. 



5. Anolis monensis. 



6. Cyclura corttata. 



