In front of the nasal openings the face is prolonged as a narrow beak or rostrum of varying length, formed by the maxillae and premaxillae surrounding the vomer and large mesethmoid (fig. 93, 11), which sends forwards a long partially cartilaginous process, and is fused behind with the presphenoid (fig. 93, 8). The basi-occipital (fig. 93, 1) too is fused with the basisphenoid. The foramen rotundum is confluent with the sphenoidal fissure, and the foramen ovale with the foramen lacerum medium and the foramen lacerum posterius. The palate is mainly formed by the maxillae; the premaxillae and palatines (fig. 93, 17), though both meet in symphyses, forming very little of it. The pterygoids vary in size in the different genera, sometimes as in _Lagenorhynchus_ and _Delphinus_ meeting in the middle line, sometimes as in _Phocaena_ and _Globicephalus_ (fig. 93, 18) being widely separated. The tympanic and periotic are not fused together, and the periotic has generally no bony union with the rest of the skull. The mandible is rather slightly developed, with the rami straight, compressed and tapering to the anterior end. The condyle is not raised at all above the edge of the ramus; the angle is rounded and the coronoid process is very small. _Platanista_ has a curiously modified skull; the rostrum and mandible are exceedingly long and narrow, and arising from the maxillae are two great plates of bone which nearly meet above. In the Physeteridae the skull is raised into a very prominent crest at the vertex behind the nares. In front of this in _Hyperoödon_ a pair of ridges occur, formed by outgrowths from the maxillae. In the old male these ridges reach an enormous size and almost meet in the middle line. In _Physeter_, the Sperm whale, these ridges are not developed; the maxillae and premaxillae unite with the other bones of the crest enclosing an enormous half basin-shaped cavity, at the base of which are the very asymmetrical anterior narial apertures. In all living Cetacea the hyoid has the same general shape, consisting firstly of a crescentic bone formed by the fusion of the thyro-hyals with the basi-hyal, and secondly of the anterior cornu formed principally by the strong stylo-hyal. UNGULATA. None of the distinctive characters separating the Ungulata from the other groups of mammals are drawn from the skull. But in the Ungulata vera as opposed to the Subungulata a distinguishing feature is found in the fact that the lachrymal and jugal form a considerable part of the side of the face, and that the jugal always forms the anterior part of the zygomatic arch, the maxillae taking no part in it. UNGULATA VERA. _ARTIODACTYLA._ The skull in Artiodactyla differs from that in Perissodactyla in the fact that the posterior end of the nasal is not expanded and there is no alisphenoid canal. The skulls in the different groups of Artiodactyla differ considerably from one another.