and the greater part of a radius and ulna belonging to one individual, and most portions of the hind-limbs in other specimens. The one species, P. petersoni, was about the size of a "jack rabbit," and is late Eocene (Uinta formation) and American in range. The teeth of this mammal are the typical forty-four, and the canines are not pronounced, being incisiform in shape. In the skull the nasals overhang, as in the genus Poebrotherium. The orbit is not closed by bone. There is in this ancient Camel a trace of the supra-orbital notch so characteristic of the Camel tribe. "The vertebrae resemble those of the modern Lamas closely in their general proportions." The lumbars have the usually Cameloid formula of 7. This genus has but two functional toes on the hind-feet, the second and fifth being reduced to vestiges. It is interesting to note that the radius and ulna appear to remain distinct, except in very old animals, in which they come to be co-ossified in the middle only, thus foreshadowing their complete union in the next genus, Poebrotherium. The present genus, moreover, as well as Poebrotherium, was distinctly unguligrade; it has not acquired the characteristic phalangigrade mode of progression of the modern types of Camels.
Fig. 150.—Skull of Poebrotherium wilsoni. i1, i2, i3, Incisors 1-3. × ½. (After Wortman.)
The American and Oligocene Poebrotherium has been recently and exhaustively studied by Professor Scott.[1] It was considerably smaller than a Lama. Its neck was long as compared with other Artiodactyles, but still shorter than that of the Lama. It was a lightly-built, graceful creature, with apparently some external likeness to a Lama. It is an important fact to notice that at this
- ↑ "Osteology of Poebrotherium," Journ. Morph. v. 1891, p. 1.
