and not climbing or grasping organs; the number of toes becomes reduced, and culminates twice (in the horse and in the Litopterna) in one toe on each foot; at the same time the ulna becomes rudimentary and fuses with the radius, and the fibula in the hind-limb undergoes a like reduction. The clavicle is absent even in some of the oldest types; its presence in Typotherium[1] is highly remarkable. The tail too, an organ which is long in some of the early forms, gets short in their modern derivatives.
Fig. 110.—An early Ungulate. Phenacodus primaevus. × 1⁄12. (After Osborn.)
Coupled with the increasing perfection of the foot as an organ used merely for the support of the body, certain interesting changes have taken place in the arrangement with regard to each other of the several bonelets of the wrist and ankle. It has been held by Cope and others that the truly primitive disposition of these bones was that presented to us by certain early types, such as Meniscotherium or the existing elephant or Hyrax. In these animals there is (see Fig. 112) a serial arrange-
- ↑ This creature is, however, sometimes referred to the neighbourhood of the Rodents.
