Page:Popular Science Monthly Volume 12.djvu/708

688 nearly the same. The Caviidæ were especially numerous. Cercolabes, Myopotamus, and Lagostomus, are also found; and two extinct genera, Phyllomys and Lonchophorus.

The Cheiroptera, or bats, have not been found in this country below the middle Eocene, where two extinct genera, Nyctilestes and Nyctitherium, are each represented by numerous remains. These fossils all belong to small animals, and, so far as they have been investigated, show no characters of more than generic importance to distinguish them from the bats of to-day. No other members of this group are known from our Tertiary. In the Post-Tertiary, no extinct species of bats have been found in North America, but from the caves of Brazil quite a number have been reported. These all belong to genera still living in South America, and most of them to the family Phyllostomidæ.

The Insectivores date back, in this country, at least to the middle Eocene. Here numerous remains occur, which have been described as belonging to this order, although it is possible that some of them were insect-eating Marsupials. The best-known genera are—Hemiacodon, Centetodon, Talpavus, and Entomacodon; all represented by animals of small size. In the Miocene, the bones of Insectivores are comparatively abundant, and the genera best determined are Ictops and Leptictis. A few specimens only have been found in the Pliocene and Post-Pliocene, most of them related to the moles. No extinct Insectivores are known from South America, and no member of the group exists there at present.

The Carnivora, or true flesh-eating animals, are an old type, well represented in the Eocene, and, as might be expected, these early forms are much less specialized than the living species. In the Coryphodon beds, the genus Limnocyon, allied to the Pterodon of the European Eocene, is abundant. Another genus, apparently distinct, is Prototomus, and several others have been named from fragmentary fossils. In the middle Eocene, Carnivores were still more numerous, and many genera have been discovered. One of these, Limnofelis, was nearly as large as a lion, and apparently allied to the cats, although the typical Felidæ seem not yet to have been differentiated. Another Carnivore, of nearly equal size, was Orocyon, which had short, massive jaws and broad teeth. Dromocyon and Mesonyx were large animals, allied to Hyœnodon. The teeth were narrow, and the jaws long and slender. Among the smaller Carnivores were—Vulpavus, Viverravus, Sinopa, Thinocyon, and Ziphacodon.

In our Western Miocene, Carnivores are abundant, and make an approach to modern types. The Felidæ are well represented, the most interesting genus being Machairodus, which is not uncommon in the Oreodon beds on both sides of the Rocky Mountains. An