This group of animals is very isolated, having no very close allies, either living or extinct. The digits are provided with flat nails, except the second digit of the pes, which is clawed. Canine teeth are absent, and the dental formula is usually given as _i_ 1/2, _c_ 0/0, _pm_ 4/4, _m_ 3/3. The upper incisors are long and curved, and have persistent pulps as in Rodents; their terminations are, however, pointed, not chisel-shaped, as in Rodents. The lower incisors have pectinated edges. The grinding teeth have a pattern much like that in _Rhinoceros_. In the skull (fig. 83) the postorbital processes of the frontal and jugal almost or quite meet. The jugal forms part of the glenoid cavity for articulation with the mandible, and also extends forwards so as to meet the lachrymal. There is an alisphenoid canal. There are as many as twenty-one or twenty-two thoracic vertebrae, and the number of thoraco-lumbar vertebrae reaches twenty-eight or thirty. There are no clavicles, and the scapula has no acromion; the coracoid process is, however, well developed. The ulna is complete. In the manus the second, third and fourth digits are approximately equal in size, the fifth is smaller, and the first is vestigial. The femur has a slight ridge representing the third trochanter. The fibula is complete, but is generally fused with the tibia proximally. There is a complicated articulation between the tibia and astragalus, which has a pulley-like proximal surface. In the pes the three middle digits are well developed, but there is no trace of a hallux, and the fifth digit is represented only by a vestigial metatarsal. The only representatives of the suborder are some small animals belonging to the genus _Procavia_ (_Hyrax_), which is found in Africa and Syria; some of the species are by many authors placed in a distinct genus _Dendrohyrax_. _Suborder_ (4). AMBLYPODA[130]. This suborder includes a number of primitive extinct Ungulates, many of which are of great size. Their most distinguishing characteristics are afforded by the extremities. In the carpus the bones interlock a little more than is the case in most Subungulata, and the corner of the os magnum reaches the scaphoid, while the lunar articulates partially with both magnum and unciform, instead of only with the magnum. In the tarsus the cuboid articulates with both the calcaneum and the astragalus, which is remarkably flat. The manus and pes are short, nearly or quite plantigrade, and have the full number of digits. The cranial cavity is singularly small. Canine teeth are present in both jaws, and the grinding teeth have short crowns, marked by =V=-shaped ridges. The pelvis is large, the ilia are placed vertically, and the ischia do not take part in the ventral symphysis.