The two halves of the =mandible= do not fuse completely even in advanced age. The symphyseal surfaces are extremely rough and are marked by reciprocal projections and cavities. The body is shorter, wider, and flatter than in the horse, and has eight round and relatively shallow alveoli for the lower incisors. The interalveolar border is long, curved, thin and sharp. There are no alveoli for the canine teeth, which are absent. The anterior part of the ramus constitutes a long narrow neck. The mental foramen is further forward than in the horse, and is in the posterior end of a fossa. The rami diverge more, so that the submaxillary space is wider than in the horse. They are also more strongly curved, and the angle is more pronounced. The molar part is not so high, especially in its anterior part. Its lower border is convex in its length. Its upper border bears six alveoli for the lower cheek teeth; the first is quite small, and they increase in size from before backward. The vertical part is much smaller than in the horse and its posterior border is relatively thin below, concave and wider above. The mandibular foramen is about in the middle of its inner surface, and a groove for the lingual nerve curves downward and forward from it. The condyle projects inward further than in the horse, and is concave from side to side. The coronoid process is extensive and curves backward. The =hyoid bone= has a short tuberous lingual process. The middle cornua are almost, as large as the small cornua. The great cornua are narrow, except at the ends. The upper end divides into two branches, which correspond to the two angles of that of the horse. The thyroid cornua do not fuse with the body. SKULL OF THE OX AS A WHOLE The skull of the ox is more clearly pyramidal than that of the horse, and is shorter and relatively wider. The cranium is quadrangular and larger externally than in the horse; its large size is due mainly to the great extent of the frontal sinus, and does not affect the cranial cavity, which is smaller than in the horse. The =superior= or =frontal surface= is formed by the frontals, nasals, and premaxillæ. The frontal part is quadrilateral and very extensive, the greatest width being at the orbits. It presents a central depression on its anterior part, and on either side are the supraorbital grooves and foramina. Behind is the median frontal eminence, and at the lateral angles the “horn-cores” project in horned cattle. The nasal part is very short. The osseous nasal aperture is wide. The premaxillæ do not bend downward as in the horse; they are relatively thin and weak, and are separated by an interval which has a wide anterior part in place of the foramen incisivum.