OF ISLAND FAUNAS 149 
have stout heavy bodies. They are very partial to 
cactuses, but also climb the acacia trees to feed upon 
the foliage. 
Closely related to Conolophus, and therefore like it 
one of the iguana family, is the marine lizard Ambly- 
rhynchus cristatus. It also is entirely peculiar to the 
islands, and is the only lizard known which is marine 
in habitat. It inhabits the shores of most of the islands, 
and feeds upon seaweeds which grow below tide mark, 
and, as Darwin proved, it can tolerate prolonged im- 
mersion without any ill effects. It will be recollected 
(cf. p. 116) that the typical iguanas are forest animals. 
The exceptional conditions to which the forms in the 
Galapagos Islands are exposed has made it necessary 
for these to adopt modified habits. 
The family Iguanidae is further represented in the 
islands by various peculiar species of the genus Tropi- 
durus, other members of which occur on the continent 
of South America. Various species of geckoes belong- 
ing to the widely distributed genus Phyllodactylus also 
occur, most of these being peculiar to the islands. 
There are also two snakes, both being nearly allied to 
South American forms. 
Amphibians are entirely absent. Of the inverte- 
brates the insects are few in number, but show the same 
characters as the other kinds of animals. In other 
words, most of the species and many genera are peculiar, 
and the forms tend to have a limited distribution 
among the islands, very few being found in all the 
islands. Further, there are many wingless forms, 
a common feature in island insects. 
It is not necessary to describe the fauna of other 
islands of the same type as the Galapagos archipelago 
in detail, for the general characters are the same in 
