408 CALIFORNIA ACADEMY OF SCIENCES [Proc. 4th Ser. 



There may be some difference of opinion as to whether 

 Phyllodactylus bauri or Phyllodactylus barrmgtonensis is the 

 more differentiated form. P. barringtonensis is intermediate 

 between P. leei and P. galapagoensis. It agrees with P. gala- 

 pagoensis in the number and arrangement of the postmental 

 plates, but has tubercles only on that portion of the back which 

 lies between the insertions of the hind limbs. Phyllodactylus 

 bauri, on the other hand, has quite a different arrangement of 

 the postmentals, which are reduced in number to two, and its 

 dorsal tubercles have a distinctive distribution. On cursory 

 examination, P. bauri resembles P. galapagoensis much more 

 than P. barringtonensis does. Nevertheless, I believe that the 

 differences found in P. bauri, involving as they do changes 

 in arrangement as well as in number, are of greater import 

 than the mere reduction in dorsal tubercles which characterizes 

 P. barringtonensis. This view of the case leads to the con- 

 clusion that the islands occupied by P. bauri — namely. Hood 

 and Charles — probably were the next to become separated in 

 the breaking up of the original large island, and that the 

 isolation of Barrington occured soon after. 



Phyllodactylus bauri inhabits both Charles and Hood 

 islands, with their outlying islets. Since we cannot believe 

 that this species has been independently evolved in two separate 

 islands, and do not think that it has been carried across the 

 water from one island to the other, we are forced to conclude 

 that Charles and Hood islands were connected, and formed 

 parts of a single large southern island, for a considerable 

 time after their separation from the rest of the land area which 

 later became the present archipelago. 



The relationship which exists between Phyllodactylus barr- 

 ingtonensis and P. leei perhaps may indicate that the last con- 

 nection of Chatham with the central island was by way of 

 Barrington Island. 



The geckos of the remaining islands have undergone much 

 less differentiation than those which we have thus far consid- 

 ered. For the present, we must refer them all to one species, 

 Phyllodactylus galapagoensis, although it is quite possible that 

 more abundant material might enable us to recognize differ- 

 ences which now are hidden. We have only the following 

 specimens : 



