_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. {279} abingdonii_ recently discovered 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. Guenther believes that they have been originally derived from the American continent.[60] 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 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, _Phyllodactylus galapagensis_, and four species of the American family Iguanidae. Two of these are distinct species of the genus Tropidurus, 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 last were originally described as _Amblyrhynchus cristatus_ by Mr. Bell, and _A. subcristatus_ by Gray; they were afterwards placed in two other genera Trachycephalus and Oreocephalus (_see_ Brit. Mus. Catalogue of Lizards), while in a recent paper by Dr. Steindachner, the marine species is again classed as Amblyrhynchus, while the terrestrial form is placed in another genus Conolophus, both genera being peculiar to the Galapagos. 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, {280} since they are found in a considerable number of islands which possess no mammals nor any other land reptiles; but what those means are has not yet been positively ascertained.