48 ELEMENTS OF MAMMALIAN ANATOMY. 



supraoccipital near its parietal margin is the lambdoidal 

 ridge, to which the cephalohumeral muscle is attached 

 (Fig. 48). 



The exoccipitols bound the cerebellum laterally and 

 support the occipital condyles, which articulate with the 

 atlas or first vertebra. Immediately caudad of the bulla 

 is the paroccipital process. There are two foramina, 

 one of which, the anterior condyloid, opens ventrally 

 with the jugular foramen adjacent to the bulla, while 

 the other, the posterior condyloid, opens more dorsally 

 at the side of the condyle. The former transmits the 

 twelfth (hypoglossal) cranial nerve, supplying the larynx, 

 hyoid bone, and tongue. The jugular foramen, or 

 foramen lacerum posterius, is at the juncture of the 

 bulla, exoccipital, and basioccipital. The internal jugular 

 vein and the ninth, tenth, and eleventh nerves pass 

 through it. The basioccipital portion of this bone lies 

 entirely on the ventral aspect of the skull. It articu- 

 lates cephalad with the basisphenoid by a suture which 

 is generally obliterated in cats three or four years old. 



The sphenoid bone lies in the center of the base of the 

 skull. It is composed of eight parts, corresponding to 

 eight distinct bones in the lower vertebrates : the basi- 

 sphenoid, articulating caudad with the basioccipital; 

 two alisphenoids, extending dorsad from the basisphenoid 

 and articulating caudad with the temporals (Figs. 17 

 and 1 8); two pterygoids, projecting ventrally from the 

 basisphenoid and terminating in sharp processes; a 

 presphenoid in the midventral line cephalad of the 

 basisphenoid ; two orbito sphenoids, extending dorso-later- 

 ally from the presphenoid and articulating cephalad with 

 the frontals. In an old cat, the sutures between these 

 eight parts become more or less obliterated. The basi- 

 sphenoid together with the alisphenoids is sometimes 



