^6 ELEMENTS OF MAMMALIAN ANATOMY 



the condition found in the sheep, horse, and ox. On the other 

 hand, the orbit is less widely open in the cat than in the dog 

 and rabbit. 



The posterior or caudal boundary of the dorsal surface is 

 sharply elevated into the lamhdoidal crest. The edge of the 

 lambdoidal crest becomes broadened at its central point into 

 a triangular or diamond-shaped area, the external occipital pro- 

 tuberance, which is continued forward on the interparietal bone 

 as the sagittal crest. 



Viewed from the posterior aspect the general outline of the 

 skull, neglecting the zygomatic arches, is dome-shaped. The 

 posterior or nuchal surface, is somewhat triangular in shape 

 and is placed at right angles to the axial line of the cervical 

 vertebrae. The surface is roughened below the lambdoidal 

 crest for the attachment of several important muscles of the 

 head and neck. The lower portion is perforated by a large 

 opening, the foramen magnum occipitale, for the exit of the 

 central nervous system. On either side of the foramen mag- 

 num there is a smooth cylindrical projection, the occipital 

 condyle, for articulation with the atlas of the vertebral column. 

 Laterad and separated from the condyle by the deep jugular 

 fossa is the jugular process. Still laterad from this and sepa- 

 rated by a V-shaped notch is the mastoid process of the tem- 

 poral bone. The two processes cover most of the caudal and 

 caudo-lateral portions of the tympanic bulla. They also fur- 

 nish attachment for the digastric (depressor mandibular), stylo- 

 glossus, and stylomastoid muscles. The dorsal alanto -occipital 

 membrane is attached to the dorsal border of the foramen 

 magnum, between the condyles. The ventral alanto-occipital 

 membrane is attached to the ventral border of the foramen 

 magnum. These together with the articular capsules form the 

 capsular ligament between the occipital bone and the vertebral 

 column. 



Viewed from the ventral aspect (Fig. i8) the skull presents a 

 somewhat oval outline. Its surface is flattened and is divided 



