Of the seven species of giant tortoises known to science (although at the discovery of the islands there were probably fifteen) all are indigenous, and each is confined to its own islet.
The land tortoises chiefly belong to the genus Cynyxis.
No remains, and of course no living species, of these tortoises are known to exist or have existed on the mainland.
Past elevations of land, however (and doubtless equally great subsidences) have taken place in South America since the Eocene, and the conclusion that extensive areas of land have subsided in the Indian Ocean has long been based on a somewhat similar distribution of giant tortoises in the Mascarene region.
As for reptiles, Australia has a few tortoises, all of one family, and not of great size.
The reptiles (tortoises) are also nearly allied to the Mascarenes and Madagascar species which once existed.
AMPHIBIA, a zoological term originally employed by Linnaeus to denote a class of the Animal Kingdom comprising crocodiles, lizards and salamanders, snakes and Caeciliae, tortoises and turtles and frogs; to which, in the later editions of the Systema N aturae he added some groups of fishes.
In addition Cuvier accepts the Linnaean subdivisions of Amphibia-Reptilia for the tortoises, lizards (including crocodiles), salamanders and frogs; and Amphibia-Serpentes for the snakes, apodal lizards and Caeciliae.
Some nine or ten other species of snakes are present, together with an abundance of lizards, including the Varanus, and most species of Mediterranean tortoises are represented.
Both these groups seem to have reached their climax but recently, while the tortoises, crocodiles and sphenodon are on the descending scale, mere remnants of formerly much more numerous and cosmopolitan development.
Turtles and tortoises are plentiful on the coast.
Ceratochelys insculpta of the Fly river, a chelonian peculiar to New Guinea, is remarkable in having its nearest affinities (as have the Papuan tortoises) with South American species.
Among the reptiles are various species of serpents, tortoises, turtles, lizards, &c. Locusts are common and sometimes do great damage.
Lizards are reptiles which have a transverse external anal opening (instead of a longitudinal slit as in Crocodilians and tortoises) and which have the right and left halves of the mandibles connected by a sutural symphysis.
He has applied the theory with especial ingenuity to the interpretation of the circular bony plates in the carapace of the aberrant leather-back sea-turtles (Sphargidae) by prefacing an initial land phase, in which the typical armature of land tortoises was acquired, a first marine or pelagic phase, in which this armature was lost, a third littoral or seashore phase, in which a new polygonal armature was acquired, and a fourth resumed or secondary marine phase, in which this polygonal armature began to degenerate.
On its shores are tortoises, mud-turtles, crayfish and innumerable sand-hoppers; and at varying depths in the lake several species of Melania, Melanopsis, Neritina, Corbicula and Unio have been found.
Several species of large fossil tortoises have also been discovered; they are quite different from the living ones of Aldabra, in the same zoological region.
The hippopotamus, manatee, crocodile and beaver are found in the rivers, and both land and fresh-water tortoises are common.
Land tortoises have also disappeared,' but one freshwater species (Sternothaerus sinuatus) is still found; and the adjacent seas contain many turtles.
Reptiles are infested as well as mammals, and it is no uncommon thing to find specimens of Ixodidae of various kinds adherent to tortoises, snakes and lizards.
Edible frogs, tree-frogs, lizards, snakes, tortoises and scorpions are found in all parts.
There are several peculiar tortoises, but the gigantic species are now found alive only on the little island of Aldabra, to the north.
There are also a clean race of frogs and tortoises, and a few mussels in it; muskrats and minks leave their traces about it, and occasionally a travelling mud-turtle visits it.
Many tortoises are notable.