60 THE SKELETON OF THE CAT. 



bones ; its floor by the horizontal plates of the palatines, 

 maxillaries, and premaxillaries. 



The nasal cavity opens craniad by the large nares (Fig. 

 39, /; Fig. 42, r), which are bounded by the premaxillary and 



FIG. 43. SKULL, MEDIAN LONGITUDINAL SECTION, SHOWING THE CAVITIES. 



7, cerebellar fossa; //, cerebral fossa; ///, olfactory fossa. I, occipital bone; 2, 

 interparietal; 3, 3', parietal; 4, temporal (4, squamous portion; 4', petrous portion; 

 4", tympanic portion); 5, sphenoid; 6, presphenoid; 7. palatine; 8, frontal; 9, max- 

 illary; 10, premaxillary; II, ethmoid; 12, nasal; 13, incisor teeth; 14, canine; 

 15, 16, 17, premolars; 18, molar, a, condyloid canal; b, hypoglossal canal; f. 

 jugular foramen; d, internal auditory meatus; e, appendicular fossa; f, tentorium; g, 

 dorsum sellse; k, sella turcica; i, hamular process; j, pterygoid process of sphenoid; 

 k, optic foramen; /, presphenoid sinus; m. m' , frontal sinus; n, lamina perpendicu- 

 laris of the ethmoid (broken at cranial edge). 



nasal bones. In the natural condition this opening is divided 

 by a median cartilage which is continuous with the lamina per- 

 pendicularis (Fig. 43, n) of the ethmoid, thus forming a parti- 

 tion which divides the nasal cavity into two separate halves. 

 From the floor of the cranial part of the cavity rises a ridge 

 formed of the nasal crests of the maxillaries and premaxillaries, 

 and the cranial portion of the vomer. Farther caudad the 

 vomer spreads out in a horizontal plane and separates from the 

 floor of the cavity, so that the nasal cavity is thereby divided 

 by a horizontal partition into dorsal and ventral portions. The 

 ventral portion is small, forming the inferior meatus of the 

 nose; it ends caudally at the choanae (posterior nares, Fig. 

 41, <?) which lead into the nasopharynx. That portion 

 of the nasal cavity lying dorsad of the vomer is almost com- 



