HEEPETOLOGY OF PORTO RICO. 561 



RELATIONS AND ORIGIN OF THE PORTO RICAN HERPETOLOGICAL 



FAUNA. 



In analyzing the composition of the Porto Rican herpetological 

 fauna we find that out of a total of thirty-five species (excluding the 

 marine turtles) no less than twenty-one are peculiar, of which fifteen 

 are peculiar to Porto Rico proper and six to Mona. 



On the other hand Porto Rico has only 2 species in common with 

 the Caribbean Islands, the same 2 species also ranging over the other 

 larger Antilles. Two more species Porto Rico proper shares with the 

 latter. The rest of the species occur in the Virgin Islands. Porto 

 Rico thus forms with the latter a group characterized by an extraor- 

 dinarily great proportion of peculiar species. 



But while the fauna of Porto Rico, both in itself and in combination 

 with the Virgin Islands, shows a high amount of specialization demon- 

 strating a considerable degree of isolation in time, it must not be 

 imagined that the separation is very deep seated. On the contrary, 

 the affinities with the other Antilles, especially the larger ones to the 

 w'est, are very close and can readily be traced. 



Before doing so we must first dispose of those species which, as 

 shown in the table of distribution of the Porto Rican species, have 

 been found outside of the Antillean islands. 



The first of these is the blind snake, Typhlops lumbricalis, of which 

 specimens are said to have come from British Guiana. The range of 

 this species embraces almost all the Antilles, and its presence in 

 northeastern South America presents nothing unusual except, perhaps, 

 the circumstance that it has been able to retain its specific integrity 

 over an area so disconnected. But examples of this kind are not rare. 

 The species is further on referred to the category of forms showing 

 South American affinities. 



The next species is Hermdactylus mabouia. This is one of the most 

 widely distributed geckos and seems to possess an extraordinary 

 capacity for being carried about in cargoes and establishing itself 

 permanently in places where so introduced. It is most likely that 

 this dispersal is effected through the eggs, which are fastened to the 

 objects shipped, rather than by transport of the adult animals them- 

 selves. It is now found in South Africa, Madagascar, various parts 

 of South America, Mexico, and several of the West Indian islands. 

 Its introduction into Porto Rico is probably of very recent date, which 

 accounts for its comparative rarity. 



The status of the frog, Leptodactylus albilabris, is quite different 

 from that of the other species of the fauna. In the Antilles it is 

 restricted to the Virgin Islands, St. Croix, Vieques, and Porto Rico. 

 There is apparently no indigenous species of the genus in the Carib- 

 bean chain, the other two which occur in various islands being evi- 

 NAT mus 1902 36 



