III.] GALAPAGOS ISLANDS. 14! 



coast of Ecuador. Entirely volcanic in structure, they are sur- 

 rounded by a sea of great depth ; and according to the view both 

 of Wallace and Darwin, they have never been connected with the 

 mainland, while the latter observer is also of opinion that for 

 countless ages they have been separated from one another. The 

 known mammals include a bat (Atalapha], a rat (Afus), doubtless 

 introduced, and a peculiar species of white-footed mouse (Sitomys 

 bauri). Of reptiles the islands contain two peculiar genera of 

 iguanoid reptiles, and no less than five species of giant tortoises 

 belonging to the genus Testudo. The iguanoids are nearly related 

 to South American types ; but there are no tortoises now living 

 on the mainland, although a large species flourished in Argentina 

 during the Pampean epoch, while, as already stated, others are 

 now found living in the Mascarene islands, and extinct species 

 occur in the middle and later Tertiary deposits of the United 

 States, Europe, and Northern India. It may accordingly be 

 taken for granted that both the iguanoid lizards and the giant 

 tortoises reached the island from the South American mainland ; 

 but the question is how did they arrive ? Dr Wallace is of opinion 

 that both were transported across the sea, although by what means 

 is unknown. This view is, however, disputed by Dr G. Baur 1 , 

 who believes that the Galapagos islands were formerly connected 

 not only with one another, but likewise with the mainland. He 

 observes that if the Galapagos be oceanic islands, their inhabitants 

 could only have been introduced by accident from other regions ; 

 " but on such a supposition we are absolutely unable to explain 

 the harmonious distribution, we cannot explain why every, or 

 nearly every, island has its peculiar race or species, not repre- 

 sented on any other island. If some animals could be carried 

 over hundreds of miles to the islands, why are they not carried 

 from one island to the other? But besides that, how could we 

 make plain the presence of such peculiar forms as the gigantic 

 land-tortoises? According to the elevation theory, we can only 

 think of an accidental importation of these tortoises by some 

 current, because they are unable to swim. After the islands had 

 been elevated out of the sea, it happened once, by a peculiar 



1 Proceedings American Antiquarian Society, Oct. 1891. 



