The preceding sketch of the wonderful cave fauna of Central Brazil, is sufficient to show that it represents, in the main, a period of great antiquity. Not only are almost the whole of the species extinct, but there are twenty extinct genera, and three others not now inhabitants of South America. The fact that so few remains of the living animals of the country are found in these caves, indicates that some change of physical conditions has occurred since they were the receptacles of so many of the larger animals; and the presence of many extinct genera of {146}large size, especially among the Edentata and American families of Rodents, are additional proofs of a very high antiquity. Yet many of these cave animals are closely allied to those which are found in North America in the Post-Pliocene deposits only, so that we have no reason to suppose the cave-fauna to be of much earlier date. But the great amount of organic change it implies, must give us an enlarged idea of the vast periods of time, as measured by years, which are included in this, the most recent of all geological epochs. _Pliocene Period of Temperate South America._--We have now to consider the numerous remains of extinct animals found in various deposits in the Pampas, and in Patagonia, and a few in Bolivia. The age of these is uncertain; but as they are very similar to the cave-fauna, though containing a somewhat larger proportion of extinct genera and some very remarkable new forms, they cannot be _very_ much older, and are perhaps best referred at present to the newer portion of the Pliocene formation. _Carnivora._--The genus _Machairodus_ or sabre-toothed tigers, represents the Felidæ. There are several species of wolves (_Canis_); a weasel (_Mustela_); two bears of the Brazilian cave-genus _Arctotherium_; and the extinct European genus _Hyænarctos_. _Ungulata._--There are two species of _Equus_, found in the Pampas, Chili, and Bolivia; two of _Macrauchenia_, an extraordinary extinct group allied to the tapir and _Palæotherium_, but with the long neck, and general size of a camel. A second species found on the highlands of Bolivia is much smaller. A more recent discovery, in Patagonia, is the almost perfect series of teeth of a large animal named _Homalodontotherium_; and which is believed by Professor Flower, who has described it, to have been allied to _Rhinoceros_, and still more to the Miocene _Hyracodon_ from North America; and also to present some resemblances to _Macrauchenia_, and though much more remotely, to the curious genus _Nesodon_ mentioned further on.