have an uneven number of toes—as the horse with one toe, and the rhinoceros with three—and the Artiodactyles, or the ungulates with an even number of toes—as the hippopotamus with four toes, and the hog with its two functional toes. Now, of these fossil ungulates it is remarkable that the expedition has brought home from the Miocene twenty Perissodactyles, and the same number of Artiodactyles; and from the Pliocene nine Perissodactyles, of which four are new, and six Artiodactyles, of which three are new; thus making fifty-three ungulates. Of these there are several horses, and all of them, including Anchitherium and Protohippus, have three toes to each foot. These cloven-footed beasts were some of them strange, comprehensive types, possessing in the same individual structural resemblances to both swine and deer; "like the latter, these had no horns; they were about as large as sheep. Others were about the size of gray squirrels, being the smallest of this class of animals ever discovered" (American Naturalist). Indeed, an important paleontological result has been Prof. Cope's determination of the correct relationship of five species (three new, and one new genus, Hypertragulus) to the musk family. The general reader should perhaps be told that the order Ungulata, or hoofed quadrupeds, really absorbs three of the orders in the older classifications, namely, the Pachydermata, the Solidungula, and the Ruminantia. This mentioned, we would say, with no irreverence, that in the Colorado fauna of Tertiary times Nature seemed to indulge, as respects the animals of this order, in the most eccentric extremes of structure, both as to form and size; for some of these hoof-footed ones are scarcely larger than a squirrel, while some are as large as the elephant; and there is a seeming oddity of structure. Though a fact before every one's eyes, yet many are not aware of its existence, viz., that the ox and cow have no teeth in the front part of the upper jaw. When this animal grazes, the tongue makes a curl, or twist, and pulls in the grass, then the lower front teeth are made to meet the firm pad of the front part of the upper jaw, and the grass is then severed. Such is the mode common to the ruminating animals, that is, those which chew the cud. Now, in the natural group Ruminantia, comes a sub-group, the Camelidœ, which includes the camels and the llamas. The dentition of these animals is very aberrant. The upper incisors are not entirely wanting, "there being two canine-like upper incisors, and upper canines as well." In the Pliocene strata of Colorado are found the remains of two species of camels, of enormous size, and which, strange to say, are furnished with complete upper incisors, or front-teeth. These ancient camels, then, did not graze like the ox, but like the horse.
And, among these hoofed creatures, the Rhinocerotidœ are represented by three genera. Two of them belong to the Miocene, and the third, the last discovered, to the Pliocene. This is the new genus Aphelops, a monster of immense proportions. The other two genera