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 two 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. 
Reptiles. — Reptiles, 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 microphyes, 
found in most of the islands, and T. abingdonii recently dis- 
covered on Abingdon Island, as well as one extinct species, 
T. ephippium, 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. Gunther believes that they have been originally derived 
from the American continent . 1 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. Gunther, F.K.S. 1877. 
