xi SKULL 493 



with the organ of hearing ; the posterior aperture 

 is called the fenestm rotunda. On the internal or 

 cranial surface of the periotic is a large depression 

 (ft) which lodges the flocculus of the cerebellum (Fig. 

 141). 



The olfactory capsules are roofed in by two long and 

 narrow nasal bones* (nas), which meet together in the 

 middle line and unite by suture with the frontals pos- 

 teriorly. Their side walls are formed by the bones 

 which bear the teeth of the upper jaw the premaxilla* 

 (p. max) and maxillee* (max), and in the median line 

 below is a single long and slender bone, deeply grooved 

 on its upper surface, and formed by the fusion of the 

 two vomers* (vo) . The two nasal chambers are separated 

 from one another in the middle line by a median vertical 

 plate of cartilage, the nasal septum (Fig. 135, n. s), 

 embraced below by the vomer. This cartilage, together 

 with the cribriform plate and a median vertical plate of 

 bone (eth) extending forwards from the latter into the 

 septum, constitutes the mesethmoid. Within the nasal 

 chambers certain scroll-like folds of the mucous mem- 

 brane (Fig. 135) are present in order to increase the 

 surface, and in these cartilages are developed. The 

 cartilages become ossified, and the resulting turbinal 

 bones unite with certain of the bones enclosing the 

 olfactory organs, and are named accordingly. The 

 ethmoid turbinals (Fig. 133, e. tb), or true olfactory 

 scrolls, are two complicated, folded bones united to the 

 cribriform plate of the ethmoid, and are covered in the 

 fresh condition by the olfactory epithelium ; the maxillo- 

 turbinals (mx. tb) are similar but more complex bones in 

 the antero-ventral part of the nasal cavities ; and the 

 naso-turbinals (n. tb) are thin, folded bones, much less 

 complex, and fused with the inferior surface of the 

 nasals. 



