The bones of the upper jaw are closely connected with those of the cranium proper and olfactory capsules. The most posterior of them is the _pterygoid_ (fig. 75, 15), a thin vertically placed plate of bone, which articulates above with the basisphenoid, the presphenoid, and the strong pterygoid process of the alisphenoid. The ventral end of the pterygoid is drawn out into a small backwardly-projecting =hamular process=. In front the pterygoid articulates with the _palatine_, a much larger bone, consisting of (1) a vertical portion, which passes up to meet the orbitosphenoid and frontal, and sends inwards a plate which meets the presphenoid and vomer, forming much of the roof of the posterior part of the narial passage; and (2) a strong horizontal portion, the =palatal process= (fig. 75, 16), which passes inwards and meets its fellow in the middle line, forming the posterior part of the bridge of bone supporting the hard palate. The palatal process is continuous in front, with a large bone, the _maxillae_, which, like the palatine, consists of vertical and horizontal portions. The vertical, or =facial portion= (fig. 73, 5), is the largest, and constitutes the main part of the side of the face in front of the orbit, forming also the chief part of the outer wall of the nasal cavity. It is continuous in front with the premaxillae, above with the nasal and frontal, and behind with the lachrymal, jugal, and palatine. The horizontal, or =palatal portion= (fig. 75, 17), forms the anterior part of the bony plate supporting the hard palate, and meets its fellow in a long straight symphysis. The junction line between the palatal and facial portions is called the =alveolar border=, and along it are attached the canine, premolar, and molar teeth. The anterior part of the upper jaw on each side is formed by a small bone, the _premaxillae_, which bears the incisor teeth. It, like the maxillae, has a palatal portion (fig. 75, 20), which meets its fellow in the middle line, and an ascending portion, which passes backwards as the =nasal process=, tapering regularly and lying between the nasal and the maxillae. The two premaxillae form the outer and lower borders of the anterior nares. The last bone to be mentioned in connection with the upper jaw and face is the _jugal_ or _malar_ (figs. 73, 8, and 75, 14), a strong bone which forms the anterior half of the zygomatic arch. It is firmly united in front to the maxillae, and behind meets the zygomatic process of the squamosal, being drawn out dorsally into a short =postorbital process= at the point of meeting. This process lies immediately below the postorbital process of the frontal, and if the two met, as they do in some mammals, they would partially shut off the orbit from a larger posterior cavity, the =temporal fossa=. In the living animal a ligament unites the two postorbital processes. (_b_) THE LOWER JAW OR MANDIBLE.