THE OCCIPITAL BONE. 17 



articulate with the temporal bones ; the upper half with 

 the mastoid portion, the lower half with the petrous part 

 of the temporal bone. The upper half merely abuts 

 against the mastoid portion; the lower half has project- 

 ing a well-marked process of bone the jugular process 

 which articulates with the jugular surface of the 

 petrous portion of the temporal. Anterior to the jugular 

 process is the jugular notch, which, with the jugular 

 fossa on the petrous portion of the temporal, forms the 



FIG. 6. OCCIPITAL BONE, OUTER SURFACE. 



jugular foramen for the transmission of the lateral sinus 

 down the neck. The inferior lateral borders are sepa- 

 rated anteriorly by a thick quadrilateral process of bone, 

 the basilar process, which, in the developing skeleton, 

 articulates with the sphenoid, but after the twenty-fifth 

 year the layer of cartilage between them ossifies and the 

 occipital and sphenoid form one bone. The outer sur- 

 face is convex, and midway between the apex and fora- 

 men magnum presents the external tuberosity for the 

 attachment of the ligamentum nuchae; branching out 



