Vol. II, Pt. I] VAN DENB URGH—SLEVIN—GALAPAGOAN LIZARDS 141 



The Tropidiiri of Abingdon, Bindloe, Duncan, and Chat- 

 ham islands show the greatest differentiation. Accordingly, 

 we may believe that these islands early became separated from 

 each other and from the remaining portions of the group, and 

 have maintained independent existence ever since. 



The next lizard, in point of distinctness, is that of Hood 

 Island. Hence it would seem probable that this southern 

 island was the one next separated. The closest relationship 

 of this Tropidiirus seems to be with that of Charles Island. 

 This relationship is not nearly so striking as in the case of 

 the snakes and geckos of these two islands, but it nevertheless 

 may be interpreted as indicating some connection between 

 these islands in the past, probably subsequent to their separa- 

 tion from the rest of the archipelago. 



The Tropidurus of Gardner-near-Hood appears to be 

 identical with that of the main island, so that the separation 

 of this islet from Hood doubtless is of recent date. 



The Charles Island lizard is, in a sense, intermediate be- 

 tween those of Hood and Barrington islands. This apparent 

 relationship with the Barrington form inclines one to believe 

 that the former connection of the Hood-Charles island with 

 the remainder of the archipelago may have been by way of 

 Barrington. 



The lizards of Enderby, Champion, and Gardner-near- 

 Charles do not differ from those of the larger island. The 

 separation of these islets from Charles Island, therefore, may 

 be regarded as having occurred much later than the separation 

 of Charles from Hood. 



Barrington Island probably was the next to assume an in- 

 dependent existence. 



The lizards of the remaining islands — Indefatigable, the 

 Seymours, Daphne, James, Jervis, Cowley, Brattle, Albemarle 

 and Narborough — show so little differentiation that we are 

 led to the conclusion that all of these islands were connected, 

 and formed a single large island for some time after the sep- 

 aration of Barrington. It is probable that a large bay ex- 

 tended from the south toward the center of this island, com- 

 pletely surrounding Duncan Island with water. 



The history of this large central island cannot be clearly 

 traced farther from evidence afforded by the Tropiduri. 



