Page:Popular Science Monthly Volume 12.djvu/709

Rh allied genus is Dinictis, and several smaller cats are known from about the same horizon. The Canidæ are represented by Amphicyon, a European genus, and by several species of Canis, or a very nearly allied form. The peculiar genus Hyænodon, found also in Europe, and the type of a distinct family, is abundant in the Miocene east of the Rocky Mountains, but has not yet been found on the Pacific coast. In the Pliocene of both regions the Canidæ are numerous, and all apparently belong to the existing genus Canis. The genus Machairodus is still the dominant form of the cats, which are abundant, and for the most part belong to the genus Felis. The extinct Leptarctus is supposed to belong to the Ursidæ, and, if so, is the oldest American representative of this family. In the Post-Pliocene, the extinct Felidæ include species nearly as large as a lion, and smaller forms very similar to those still living. Bears, raccoons, and weasels, have also been found.

In the Pliocene of South America, Machairodus represents the Felidæ, while the genera Arctotherium and Hyænarctus belong to the Bear family. Species of. Mustela and Canis have also been found. In the caves of Brazil, the fauna of which is regarded as Post-Pliocene, one species of Machairodus is known, and one of ''Synælurus. Canis and Icticyon, still living in Brazil, and the extinct genus Speothos, represent the Canidæ. Mephitis and Galictis, among the weasels, were also present, and with them species of Nasua and Arctotherium.''

We come now to the highest group of Mammals, the Primates, which includes the Lemurs, the Apes, and Man. This order has a great antiquity, and even at the base of the Eocene we find it represented by several genera belonging to the lower forms of the group. In considering these interesting fossils, it is important to have in mind that the Lemurs, which are usually regarded as Primates, although at the bottom of the scale, are found at the present day only in Madagascar and the adjacent regions of the globe. All the American monkeys, moreover, belong to one group, much above the Lemurs, while the Old World apes are higher still, and most nearly approach man.

In the lower Eocene of New Mexico we find a few representatives of the earliest known Primates, and among them are the genera Lemuravus and Limnotherium, each the type of a distinct family. These genera became very abundant in the middle Eocene of the West, and with them are found many others—all, however, included in the two families Lemuravidæ and ''Limnotheridæ. Lemuravus'' appears to have been most nearly allied to the Lemurs, and is the most generalized form of the Primates yet discovered. It had forty-four teeth, forming a continuous series above and below. The brain