268 



ISLAND LIFE. 



[part II. 



horses, asses, goats, pigs, dogs, and cats, which now run wild 

 in some of the islands. 



Absence of indigenous Mammalia and Amphibia. — As in all 

 other oceanic islands, we find here no truly indigenous mam- 

 malia, for though there is a mouse of the American genus 

 Hesperomys, which differs somewhat from any known species, we 

 can hardly consider this to be indigenous ; first, because these 

 creatures have been little studied in South America, and there 

 may yet be many undescribed species, and in the second place 

 because even had it been introduced by some European or 

 native vessel, there is ample time in tvfo or three hundred years 

 for the very different conditions to have established a marked 

 diversity in the characters of the species. This is the more 

 probable because there is also a true rat of the Old World 

 genus Mus, which is said to differ slightly from any known 

 species ; and as this genus is not a native of the American 

 continents we are sure that it must have been recently intro- 

 duced into the Galapagos. There can be little doubt therefore 

 that the islands are completely destitute of truly indigenous 

 mammalia ; and frogs and toads, the only tropical representatives 

 of the Amphibia, are equally unknown. 



Beptiles. — Kep tiles, however, which at first sight appear as 

 unsuited as mammals to pass over a wide expanse of ocean, 

 abound in the Galapagos, though the species are not very 

 numerous. They consist of land-tortoises, lizards and snakes. 

 The tortoises consist of two peculiar species, Testudo micropliyes, 

 found in most of the islands, and T. abingdonii recently dis- 

 covered on Abingdon Island, as well as one extinct species, 

 T. epJiippium, found on Indefatigable Island. These are all 

 of very large size, like the gigantic tortoises of the Mascarene 

 Islands, from which, however, they differ in structural characters ; 

 and Dr. Giinther believes that they have been originally derived 

 from the American continent.^ Considering the well known 

 tenacity of life of these animals, and the large number of 

 allied forms which have aquatic or sub-aquatic habits, it is not 

 a very extravagant supposition that some ancestral form, carried 



1 Gigantic Land Tortoises Living and Extinct in the collection of the 

 British Museum. By A. C. L. G. Giinther, F.K.S. 1877. 



