CHAP. XIII.] 
THE GALAPAGOS ISLANDS. 
209 
out to sea by a flood, was once or ' twice safely drifted as far 
as the Galapagos, and thus originated the races which now 
inhabit them. 
The lizards are five in number; a peculiar species of 
gecko, Pliyllodactylus galapagensis, and four species of the 
American family Iguanidae. Two of these are distinct species 
of the genus Liocephalus, the other two being large, and so 
very distinct as to be classed in peculiar genera, One of these 
is aquatic and found in all the islands, swimming in the sea at 
some distance from the shore and feeding on seaweed ; the other 
is terrestrial, and is confined to the four central islands. These 
were originally described by Mr. Bell as Amblyrhynchus cristatus 
and A. subcristatus ; they were afterwards placed in two 
other genera Trachycephalus and Oreocephalus (see Brit. Mus. 
Catalogue of Lizards), while in a recent paper by Dr. Gunther, 
the marine species is again classed as Amblyrhynchus, while 
the terrestrial form is placed in another genus Conolophus. 
How these lizards reached the islands we cannot tell. The 
fact that they all belong to American genera or families indicates 
their derivation from that continent, while their being all 
distinct species is a proof that their arrival took place at a 
remote epoch, under conditions perhaps somewhat different 
from any which now prevail. It is certain that animals of this 
order have some means of crossing the sea not possessed by 
any other land vertebrates, since they are found in a consider- 
able number of islands which possess no mammals nor any 
other land reptiles ; but what those means are has not yet been 
positively ascertained. 
It is unusual for oceanic islands to possess snakes, and it is 
therefore somewhat of an anomaly that two species are found 
in the Galapagos. Both are closely allied to South American 
forms, and one is hardly different from a Chilian snake, so that 
they indicate a more recent origin than in the case of the 
lizards. Snakes it is known can survive a long time at sea, 
since a living boa-constrictor once reached the island of St. 
Vincent from the coast of South America, a distance of two 
hundred miles by the shortest route. Snakes often frequent 
trees, and might thus be conveyed long distances if carried out 
