Vol. 1] VAN DEN BURGH— GECKOS OF GALAPAGOS ARCHIPELAGO 407 



Hood, Charles, Gardner-near-Charles, Enderby, Champion, 

 Barrington, Duncan, Indefatigable, Daphne, James, Cowley, 

 Albemarle, and Brattle islands. 



Chatham is the only island upon which there occurs more 

 than one species of Phyllodactylus. Here, two very distinct 

 species have been found. One of these has been regarded as 

 identical with Phyllodactylus tuberculosus of the North and 

 South American continents. It has no close relatives on any 

 of the other islands of the archipelago, and may have been 

 introduced on Chatham since the plantation was established 

 there. 



The other Galapagoan geckos are all closely related. There 

 can be little doubt that all are directly descended from a single 

 species which formerly occupied this entire area. We must 

 believe that the isolation resulting from the separation of an 

 original large island into the various small islands which 

 now exist, has made possible the differentiation which we now 

 find in these geckos. 



If this be true, we should expect to find that the greatest 

 differentiation exists where isolation has been longest main- 

 tained, and, conversely, that separation has existed longest 

 where the greatest differentiation is found. Thus we may 

 proceed to sketch the history of the Galapagos Islands as 

 indicated by the geckos of the genus Phyllodactylus. 



Origin and History of the Galapagos Islands 



Phyllodactylus gilberti has been found only on Wenman 

 Island. It is the most distinct of all the Galapagoan geckos.^ 

 Hence, we may infer that Wenman Island has had an indi- 

 vidual existence longer than any of the other gecko-bearing 

 islands of the archipelago. 



No geckos have ever been found on Culpepper, Abington, 

 Bindloe or Tower Islands. 



The next gecko in point of distinctness is Phyllodactylus 

 leei of Chatham Island. This leads us to believe that Chatham 

 became a separate island at a time when the other central 

 and southern islands still were connected. 



' Except P. tuberculosus, which we shall not consider farther. 



