Vol. I] VAN DENBVRGH— SNAKES OF THE GALAPAGOS ISLANDS 331 



ever, must await the gathering of larger series from all the 

 islands except Hood, and perhaps Charles. 



No snakes ever have been taken on Culpepper, Wenman, 

 Abingdon, Bindloe, Tower, or Chatham islands. One of the 

 residents of Chatham told Mr. Slevin that snakes were not 

 uncommon there, but careful search failed to bring one to 

 light. They must now be quite rare on Charles ; for no mem- 

 ber of our expedition saw one on Charles Island itself, although 

 one was secured on the close-lying islet known as Gardner- 

 near-Charles. 



Origin of the Galapagos Snakes 



The closest relatives of the serpents of the Galapagos Archi- 

 pelago are a number of distinct species native to the Bahamas, 

 Greater and Lesser Antilles, Costa Rica, and all of South 

 America — species which Boulenger includes in the genera 

 Dromicus and Liophis. Whether or not all of these species 

 actually belong in the genus Dromicus cannot be positively 

 stated until the hemipenial structure of each has been exam- 

 ined. The results of such an examination, however, cannot 

 be expected to affect the truth of the statement that the Gala- 

 pagos snakes have very close relatives throughout the West 

 Indies and South America. 



This being true, the snakes of these localities must have had 

 a common origin. Either the West Indian and Galapagos 

 snakes have been derived from South America, or else all 

 must be descendants of species which, in a former geological 

 period, occupied a great central land-mass which has sunk 

 below the level of the sea, leaving mere remnants in Central 

 America, northern South America, the Antilles, and the Gala- 

 pagos. Much may be said in favor of each of these theories. 

 I believe that the data are not yet at hand which will enable 

 us to choose between them. 



Either view implies a former land connection and a conti- 

 nental origin of the Galapagos ophidian fauna. I cannot 

 bring myself to share the opinion of those who believe that 

 the fauna of the Galapagos has reached these islands by the 

 more or less accidental agency of the winds and ocean currents. 

 The various species must have spread slowly over some conti- 



