The cranial margin is produced dorsally in the form of a blunt triangular spine. Mediad of this spine the bone articulates with the lachrymal bone. The ventral border articulates by its cranial one-third with the orbital plate of the palatine, and by its caudal two-thirds with the body and wing of the presphenoid. =Maxillary Bone.= =Maxilla= (Figs. 27 and 28).--The maxillary bone forms the cranial and lateral portions of the roof of the mouth. The bones of opposite sides meet craniad, but diverge caudad to enclose the palatal plates of the palatine bones. Each consists of a thick prismatic ventral portion or body (_a_) and a thin flat plate, the =frontal process= (_b_), extending dorsad from the cranial part of the bone. [Illustration: FIG. 27.--MAXILLARY BONE, LATERAL SURFACE. FIG. 28.--MAXILLARY BONE, MEDIAL SURFACE. _a_, body; _b_, frontal process; _c_, infraorbital foramen; _d_, elevation for root of canine tooth; _e_, canine tooth; _f_, first premolar; _g_, second premolar; _h_, third premolar; _i_, molar tooth; _j_, zygomatic process; _k_, beginning of lachrymal canal; _l_, ridge to which the ventral nasal concha is attached; _m_, nasal crest of palatine process.] The body (_a_) has the form of a triangular prism whose broader dorsal face looks into the nasal cavity and orbit, while the ventral face looks into the mouth, and the lateral face toward the cheek. From the junction of the dorsal and lateral surfaces at the cranial end the large flat curved frontal process (_b_) passes dorsad, while the teeth are implanted along the border, =alveolar border= or process, formed by the junction of the ventral and lateral surfaces. The lateral surface is continuous with the lateral surface of the frontal process and shows at the base of the frontal process on its caudal border the large =infraorbital= foramen (Fig. 27, _c_), for the vessels and nerves of the same name. Near the medial end of the surface is a cylindrical elevation (_d_) for the root of the canine tooth (_e_). The ventral surface is smooth and looks into the roof of the mouth.