131. THE SKULL [CHAP. 



internal angle, through which the Eustachian tube connecting 

 the tympanum with the pharynx passes. 



The inner side of the bulla is perforated lengthwise by a 

 canal, which commences posteriorly within the margin of 

 the foramen lacerum posterius (between the auditory bulla 

 and the exoccipital), and transmits the internal carotid artery. 

 This vessel appears again on the surface, at the anterior 

 extremity of the bulla, close to the Eustachian orifice ; then 

 runs upwards and inwards and enters the cranium through 

 the foramen lacerum medium. 



This completes the enumeration of the bones of the 

 cranium. Before proceeding further, it will be desirable to 

 take a general survey of this part as a whole, pointing out 

 the most prominent features of its various surfaces. 



The posterior surface is, in a general sense, a vertical wall 

 somewhat triangular in form, broad below and pointed above. 

 In the middle line, at its lowest border, is the nearly round 

 foramen magnum, bounded by the supraoccipital above, the 

 exoccipitals on each side and the basioccipital below. On 

 the sides of the foramen magnum, and approaching each 

 other in the middle line below, but diverging above, are 

 smooth eminences, the occipital condyles. Further outwards, 

 and separated from these by a deep valley, are the par- 

 occipital processes, projecting backwards and downwards. 

 Outside of the upper part or origin of these processes, the 



" Beitrage zur Entwicklung. cler knorpeligen gehorknochelchen." 

 Morphol. Jahrb. VI. 1880. Eraser, "On the Development of the 

 Ossicula Auditus of the higher Mammalia," Philosoph. Transact, vol. 

 173, 1883, p. 901. P. Albrecht, " Sur la valeur morphologique de 

 1'articulation mandibulaire, &c.," Bruxelles, 1883. M. L. Dollo, "On 

 the malleus of the Lacertilia, and the malar and quadrate bones of 

 Mammalia," Quart. Journ. Microsc. Science, vol. xxiii. N. S. p. 579, 

 1883. The last contains a complete list of the literature on the subject 

 ar.cl a tabular arrangement of the views held by previous authors. 



