CHAP, xiii.] THE GALAPAGOS ISLANDS. 



269 



out to sea by a flood, ^vas once or twice safely drifted as far 

 as the Galapagos, and thus originated tlie races which now 

 inhabit them. 



The lizards are five in number; a peculiar species of 

 gecko, Pliyllodadylus galapagensis, and four species of the 

 American family Iguanidse. Tv/o 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 Amblyrliynchus cristatiis 

 and A. siibcristatus ; they were afterwards placed in two 

 other genera Trachycephalus and Oreocephalus {see Brit. Mus. 

 Catalogue of Lizards), while in a recent paper by Dr. Glinther, 

 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 



