SKULL OF THE OX AS A WHOLE 143 
than the rest of the floor. The ethmoidal fossze are smaller, and the hypophyseal 
fossa or sella turcica is much deeper than in the horse. A deep groove leads from 
the petrous temporal forward over the foramen ovale to the foramen rotundum. 
Behind the sella there is often a distinct prominence (Dorsum sell). The internal 
parietal crest is prominent anteriorly, but subsides further back. A faintly marked 
elevation represents the internal occipital protuberance. The petrous temporal 
bone projects into the cavity laterally. The ridges and digital impressions are very 
pronounced. The temporal canal is formed entirely in the temporal bone, and 
opens internally at the apex of the petrous, where it is joined by the condyloid 
canal. The foramen lacerum is divided into two parts (For. lacerum orale et ab- 
orale). 
The nasal cavity is incompletely divided by the septum, which does not reach 
Dorsal meatus Nasal bone 
Dorsal turbinate Lacrimal bone 
Di ee canal 
M Mazilla 
Middle meatus 
Fic. 141.—Cross-SEcTION OF Nasat ReEGIon oF SkuLt oF Ox. SectTion 1s CuT BETWEEN FotrtH anD FirrH CHEEK 
Toor 
1, Cartilage of septum nasi; 2, vomer; 3, ventral meatus; 4, 4’, maxillary sinuses; 5, 5’, palatine sinuses; 6, infra- 
orbital canal and nerve; 7, horizontal part of palatine bone; 8, communication between maxillary and palatine sinuses. 
Dotted lines indicate mucous membrane which closes gap in bony floor of nasal cavity. 
the floor posteriorly. The floor is relatively long, and is more concave from side to 
side than in the horse. Inthe dryskull it has a large oval opening (Hiatus maxillaris) 
into the palatine sinus, which is closed during life by mucous membrane. The 
middle meatus is divided behind into upper and lower branches by the great eth- 
moturbinate. The choanz or posterior nares are narrow and oblique. 
The frontal sinus is very large. It involves almost all of the frontal bone and 
a large part of the posterior wall of the cranium. It also extends for a variable dis- 
tance into the horn processes when these are present. A complete median septum 
separates the right and left smuses. The anterior limit is indicated by a transverse 
plane through the middle of the orbits. It extends laterally to the crest, which 
limits the temporal fossa above, and into the root of the supraorbital process. At 
the highest part of the cranial cavity and at the external occipital protuberance 
