Page:Popular Science Monthly Volume 12.djvu/705

Rh that the Cameloid type of ruminant had already become partially specialized, although there is a complete series of incisor teeth, and the metapodial bones are distinct. In the Pliocene, the camel tribe was, next to the horses, the most abundant of the larger mammals. The line is continued through the genus Procamelus, and perhaps others, and in this formation the incisors first begin to diminish, and the metapodials to unite. In the Post-Tertiary we have a true Auchenia, represented by several species, and others in South America, where the alpacas and llamas still survive. From the Eocene almost to the present time, North America has been the home of vast numbers of the Camelidæ, and there can be little doubt that they originated here, and migrated to the Old World.

Returning once more to the upper Eocene, we find another line of descent starting from Oromeryx, which, as we have seen, had apparently then just become differentiated from the older Bunodont type. Throughout the middle and upper Miocene, this line is carried forward by the genus Leptomeryx and its near allies, which resemble so strongly the Pliocene Cervidæ that they may fairly be regarded as their probable progenitors. Possibly some of these forms may be related to the Tragulidæ, but at present the evidence is against it.

The deer family has representatives in the upper Miocene of Europe, which contains fossils strongly resembling the fauna of our lower Pliocene, a fact always to be borne in mind in comparing the horizon of any group in the two continents. Several species of Cervidæ, belonging to the genus Cosoryx, are known from the lower Pliocene of the West, and all have very small antlers, divided into a single pair of tynes. The statement recently published, that most of these antlers had been broken during the life of the animals, is unsupported by any evidence, and is erroneous. These primitive deer do not have the orbit closed behind, and they have all the four metapodial bones entire, although the second and fifth are very slender. In the upper Pliocene, a true Cervus of large size has been discovered. In the Post-Tertiary, Cervus, Alces, and Tarandus, have been met with, the latter far south of its present range. In the caves of South America, remains of Cervus have been found, and also two species of antelopes, one referred to a new genus, Leptotherium.

The hollow-horned ruminants, in this country, appear to date back no further than to the lower Pliocene, and here only two species of Bison have as yet been discovered. In the Post-Tertiary this genus was represented by numerous individuals and several species, some of large size. The musk-ox (Ovibos) was not uncommon during some parts of this epoch, and its remains are widely distributed.

No authentic fossil remains of true sheep, goats, or giraffes, have as yet been found on this continent.

The Proboscidians, which are now separated from the typical