24 THE SKELETON OF THE CAT. 



Laterad of each condyle the bone is elevated into a blunt 

 triangular projection, the jugular process (/), which covers the 

 caudal end of the tympanic bulla. Between the jugular process 

 and the condyle is a deep depression. 



The internal surface (Fig. 18) is concave dorsoventrally, 

 following the outline of the foramen magnum. It is convex 

 from side to side. It is smooth except at its outer margin, 

 which is rough for articulation with the mastoid portion of the 

 temporal bone. The cranial face of the jugular process (/) 

 shows a rough concavity for the reception of the bulla tympani. 

 Mediad of the jugular process is a notch (jugular notch) (g) 

 which \vhen the bones are articulated forms part of the bound- 

 ary of the jugular foramen. Mediad of this notch is a foramen 

 which forms one end of the hypoglossal canal. It passes dorso- 

 caudad into the cranial cavity and transmits the hypoglossal 

 nerve. Dorsad of the hypoglossal canal is the cranial opening 

 of the condyloid canal, which passes caudad and opens just 

 craniad of the dorsal end of the condyle. It transmits a vein. 

 The outer border of this portion is rough for articulation with 

 the petrous and mastoid portions of the temporal. 



The squamous portion (c) has the form of a sector of a 

 circle whose arc is a little more than ninety degrees. The 

 central angle of the sector is truncated and bounds the foramen 

 magnum dorsally. The arc of the sector forms the dorsal 

 margin of the bone, while along the radii it passes into the 

 lateral portions. Its dorsal portion is thick and porous; its 

 ventral portion near the foramen magnum is thin and compact. 



The external surface (Fig. 17) is marked by a prominent 

 ridge, the lambdoidal ridge (//), parallel with the dorsal border 

 and near to it. The narrow portion of the outer surface that 

 lies dorsad of the ridge forms an angle of about ninety degrees 

 with the remainder of the surface. 



A median crest (/) extends ventrad from the middle of the 

 lambdoidal ridge toward the foramen magnum ; this is the 

 external occipital crest. At its junction with the lambdoidal 

 ridge it is elevated into a tubercle, the external occipital 

 protuberance (/). 



