Pecora. (Camel, Giraffe, Stag, Goat, Sheep, Ox, &c.)
Belluæ. (Horse, Hippopotamus, Tapir, Sow, &c.)
In the place of these, Cuvier, as I have stated in the Philosophy (On the Language of Sciences, Aphorism xvi.), introduced the following orders: Bimanes, Quadrumanes, Carnassiers, Rongeurs, Edentés, Pachyderms, Ruminans. Of these, the Carnassiers correspond to the Feræ of Linnæus; the Rongeurs to his Glires; the Edentés are a new order, taking the Sloths, Ant-eaters, &c., from the Bruta of Linnæus, the Megatherium from extinct animals, and the Ornithorhynchus, &c., from the new animals of Australia; the Ruminans agree with the [635] Pecora; the Pachyderms include some of the Bruta and the Belluæ, comprehending also extinct animals, as Anoplotherium and Palæotherium.
But the two orders of Hoofed Animals, the Pachyderms and the Ruminants, form a group which is held by Mr. Owen to admit of a better separation, on the ground of a character already pointed out by Cuvier; namely, as to whether they are two-toed or three-toed. According to this view, the Horse is connected with the Tapir, the Palæotherium, and the Rhinoceros, not only by his teeth, but by his feet, for he has really three digits. And Cuvier notices that in the two-toed or even-toed Pachyderms, the astragalus bone has its face divided into two equal parts by a ridge; while in the uneven-toed pachyderms it has a narrow cuboid face. Mr. Owen has adopted this division of Pachyderms and Ruminants, giving the names artiodactyla and perissodactyla to the two groups; the former including the Ox, Hog, Peccary, Hippopotamus, &c.; the latter comprehending the Horse, Tapir, Rhinoceros, Hyrax, &c. And thus the Ruminants take their place as a subordinate group of the great natural even-toed Division of the Hoofed Section of Mammals; and the Horse is widely separated from them, inasmuch as he belongs to the odd-toed division.[42]
[42] Owen, Odontography.
As we have seen, these modern classifications are so constructed as to include extinct as well as living species of animals; and indeed the species which have been discovered in a fossil state have tended to fill up the gaps in the series of zoological forms which had marred the systems of modern zoologists. This has been the case with the division of which we are speaking.
Mr. Owen had established two genera of extinct Herbivorous Animals, on the strength of fossil remains brought from South America:—Toxodon, and Nesodon. In a recent communication to the Royal Society[43] he has considered the bearing of these genera upon the divisions of odd-toed and even-toed animals. He had already been led to the opinion that the three sections, Proboscidea, Perissodactyla, and Artiodactyla, formed a natural division of Ungulata; and he is now led to think that this division implies another group, “a distinct division of the Ungulata, of equal value, if not with the Perissodactyla and Artiodactyla at least with the Proboscidea. This group he proposes to call Toxodonta.
[43] Phil. Trans., 1853.