THE SKULL, 59 
squamous portions of the temporals (4), frontals (8), the 
sphenoid (5), and presphenoid (6). A slight rounded ridge 
on its lateral wall at about the position of the suture between 
the frontals and parietals separates a smaller cranial portion 
sometimes called the anterior fossa, from a larger caudal por- 
tion sometimes known as the middle fossa of the cranial cavity. 
The walls of the cerebral cavity are marked with numerous 
ridges and shallow furrows for the cerebral convolutions. 
The floor of the cerebral cavity is bounded caudad by the 
prominent dorsum selle (Fig. 42, 7; Fig. 43, g), just craniad 
of which is the rounded depression known as the sella turcica 
(Fig. 42, ¢; Fig. 43, 4), for lodgment of the hypophysis. A 
number of foramina pierce the floor of the cavity in this region. 
Just ventrad of the cranial tip of the petrous portion of the 
temporal is the small foramen lacerum (medius). Craniad 
and laterad of this is a row of four foramina: the caudal one is 
the foramen ovale (Fig. 42, 7); then come in order the foramen 
rotundum (7), the orbital fissure (4), and the optic foramen 
(Fig. 42, 2; Fig. 43, &). The two optic foramina are connected 
by the shallow transverse chiasmatic groove (Fig. 42, ), for 
the optic chiasma. Another small foramen continues caudad 
from a groove on the floor of the orbital fissure; this opens on 
the ventral surface of the sphenoid, between the wing and the 
body of the bone. The groove and foramen constitute the 
pterygoid canal, which transmits a nerve,—the nerve of the 
pterygoid canal, or Vidian nerve. 
The cranial cavity narrows at its cranial end to form the 
small olfactory fossa (Fig. 43, //7) which lodges the olfactory 
bulbs. This is bounded by the frontals and the lamina cribrosa 
(Fig. 42, 0) of the ethmoid; caudad it opens directly into the 
cerebral fossa. Numerous openings through the lamina 
cribrosa for the olfactory fibres connect the olfactory fossa with 
the nasal cavity. The roof of the fossa is marked by a promi- 
nent median crest from the united edges of the frontals. 
The nasal cavity is almest completely filled by the ethmoid 
and vomer and the conche nasales. Its roof is formed by the 
nasal bones and portions of the frontals; its sides by the 
frontals, lachrymals, maxillaries, premaxillaries, and palatine 
