THE SKULL. 39 
which is for articulation with the cribriform plate of the ethmoid. 
Craniad of this the surface is marked by ridges and looks into 
the nasal cavity. 
The cranial margin is produced dorsally in the form of a 
blunt triangular spine. Mediad of this spine the bone articu- 
lates 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 
Fic. 27,—MAXILLARY BONE, Fic. 28.—MAXILLARY BONE, 
LATERAL SURFACE. MEDIAL SURFACE. 
a, body: 4, frontal process; c¢, infraorbital foramen; d, elevation for root of 
canine tooth; ¢, canine tooth; /, first premolar; g, second premolar; 4, third pre- 
molar; z, molar tooth; 7, zygomatic process; &, beginning of lachrymal canal; /, 
ridge to which the ventral nasal concha is attached; m, nasal crest of palatine 
process. 
body (a) and a thin flat plate, the frontal process (4), extending 
dorsad from the cranial part of the bone. 
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 
(6) passes dorsad, while the teeth are implanted along the 
border, alveolar border or process, formed by the junction of 
the ventral and lateral surfaces. 
