This suborder includes some very aberrant extinct South American ungulates, which have characters recalling the Proboscidea, both groups of Ungulata vera, and the Rodentia. The limbs are subplantigrade or digitigrade, and the digits are three, rarely five, in number, the third being most developed. The carpus resembles that of the Ungulata vera, in that the bones interlock and the magnum articulates with the scaphoid. In the tarsus, however, the bones do not interlock. The astragalus has a pulley-like proximal surface (except in _Astrapotherium_, in which it is flat), and articulates only with the navicular, not meeting the cuboid. The calcaneum has a large facet for articulation with the fibula, as in Artiodactyla. There is no alisphenoid canal, and the orbit is confluent with the temporal fossa. Some of the forms (e.g. _Nesodon_) referred to this group have the typical mammalian series of forty-four teeth, but in others the canines are undeveloped. In _Toxodon_ all the cheek teeth have persistent pulps, while in _Nesodon_ and _Astrapotherium_ they are rooted. A clavicle is sometimes present (_Typotherium_), and the femur sometimes has a third trochanter (_Typotherium_ and _Astrapotherium_), sometimes is without one (_Toxodon_). The remains of these curious Ungulates have been found in beds of late Tertiary age in South America. _Suborder_ (2). CONDYLARTHRA[128]. This group includes some comparatively small extinct ungulates, which are best known from the Lower Eocene of Wyoming, though their remains have also been found in deposits of similar age in France and Switzerland. Their characters are little specialised, and they show relationship on the one hand to the Ungulata vera and on the other to the Hyracoidea. They also have characters allying them to the Carnivora. They generally have the typical mammalian series of forty-four teeth, the molars being brachydont and generally bunodont. The premolars are more simple than the molars. The limbs are plantigrade, and have five digits with rather pointed ungual phalanges. The os magnum, as in living Subungulates, articulates with the lunar, not reaching the scaphoid. The astragalus has an elongated neck, a pulley-like proximal and a convex distal articular surface, and does not articulate with the cuboid. The humerus has an ent-epicondylar foramen, and the femur has a third trochanter. The best known genus is _Phenacodus_; it is perhaps the most primitive ungulate whose skeleton is thoroughly well known, and is of special interest from the fact that it is regarded as the lowest stage in the evolutionary series of the horse. Its remains are found in the Lower Eocene of Wyoming. _Suborder_ (3). HYRACOIDEA[129].