SKULL 



473 



bounding the foramen magnum above ; it has a pitted surface 

 and is marked externally by a shield-shaped prominence, r? 

 The middle, or parietal segment, consists of five bones, — a 

 basisphenoid ( b.spK) below, an alisphenoid (a.sph.a.s) on either 

 side, and two parietals * {pa) above. The broad posterior 

 end of the basisphenoid is connected with the basiocci- 



mjT.ii 



jy-mojc- 



■^'' JZ c.sph P^ 



^/ majc p.'m m 



psph 



Ir/.liu/ par-, 



Fig. 123. — Skull of Rabbit in longitudinal vertical section. The cartilaginous nasal 

 septum is removed. 

 a. spk. alisphenoid ; e. oc. exoccipital ; e. tb. ethmo-turbinal ; €th. ethmoid ; //. fossa 

 for flocculus of brain ; /. incisors ; Jit. molars ; iiix. tb, ma-xiUary turbinais ; n. tb. 

 naso-turbinals ; oc. c. occipital condyle ; pal. palatine ; pal' . palatine portion of 

 the bony palate ; /. nt. premolars ; /. sph. presphenoid ; I. point at which the 

 olfactory nerves leave the skull ; II. optic foramen ; sph./. sphenoidal fissure 

 (compare Fig. 122 A, just below opt./o.') ; V uul. foramen for mandibular division 

 of trigeminal ; VII. for facial nerve; VIII. for auditory nerve; IX, X, XI, for 

 glossopharyngeal, vagus, and spinal accessory ; XII. for hypoglossal. Other 

 letters as in Fig. 122 : the unlettered line above b. sph points to the sella turcica, 

 or depression in which tire pituitary body lies. 



pital by a thin plate of cartilage, and tapers in front to a 

 blunt point ; it is perforated at about its middle by an oval 

 pituitary foramen, and on its upper surface is hollowed out 

 to form a depression in which the pituitary body lies. 

 The alisphenoids are wing-like bones, directed upwards 

 and outwards, and firmly united with the basisphenoid : each 

 is produced ventrally into a pterygoid process {as), consist- 



