supraoccipital [7] and opisthotic [8]. Posteriorly it is 

 excavated to form the prootic vestibular recess [1], with 

 which the anterior semicircular [2] canal communicates 

 above and the horizontal laterally. The medial wall of the 

 horizontal canal being formed entirely by the opisthotic, 

 the canal is here represented by a sinus only (sinus canal is 

 inferior) [3]. The medial wall of the recess is perforated 

 by the anterior cribrose foramen [4] which transmits the 

 vestibular branch of the auditory nerve. Viewed from the 

 medial aspect [fig. 49], this foramen [55, fig. 19] is found in 

 the bottom of a fossa whose posterior wall is rendered 

 imperfect by a small sharp notch, [9] (54, fig. 49) this latter 

 is completed by cartilage, forming the posterior cribrose 

 foramen which transmits the cochlea branch of the nerve. 

 The fossa is the internal auditory meatus and is perforated 

 also by the facial canal [5] (3G, fig. 49). Immediately 

 below the auditory meatus the bone articulates with the 

 basisphenoid. Lateral to the basisphenoid surface [6] the 

 bone is grooved by the issuing facial nerve, and presents a 

 fairly wide sulcus, whose outer boundary is the ridge which 

 articulates with the prootic process of the pterygoid, this 

 sulcus forms the roof of the jugular canal. There are two 

 areas for articulation with the quadrate, of which the 

 posterior is very much the smaller, between them the bone 

 forms the medial wall of the temporal sinus and foramen. 

 Behind the regiou of the jugular canal the inferior surface 

 of the bone forms the roof of the jugular sinus. 



The Quadrate (Os quadratum) [Figs. 31-35], a very 

 massive bone, is most conveniently described as consisting 

 of two stout rami united together along the anterior half 

 of their length, and diverging from one another at an acute 

 angle posteriorly. The upper limb [A] (ramus oticus) bears 

 on the medial aspect an oval area [1], which extends along 

 the length of the dorsal margin, for articulation with the 



