X SKULL 473 



bounding the foramen magnum above ; it has a pitted surface 

 and is marked externally by a shield-shaped prominence. ,-4 

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

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

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

 end of the basisphenoid is connected with the basiocci- 



mjc.ti 



_p.majc-m 



Fig. 1Z3. — Skull of Rabbit in longitudinal vertical section. The cartilaginous nasal 

 septum is removed. 

 a. spk. alisphenoid ; e. ac. exoccipital ; e. tb. ethmo-turbinal ; eth, ethmoid ; Jl, fossa 

 for flocculus of brain ; z. incisors ; m, molars ; mx. tb. maxillary turbinals ; «. ib. 

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

 the bony palate ; p. m. premolars ; p. spk. presphenoid ; I. point at which the 

 olfactory nerves leave the skull ; II. optic foramen ; spk.f. sphenoidal fissure 

 (compare Fig. 122 A, just below opt.fo.) ; V vtn. 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 the 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 unittid with the basisphenoid : each 

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



