208 



MAMMALIAN ANATOMY 



behind the bulla (Fig. 140). It articulates behind with the exoccipital 

 part of the occipital. It presents an external, an internal, and a 

 posterior surface. 



The external surface (Fig. 141) is a narrow strip, prolonged below 

 into a rounded prominence, the mastoid process proper. The long 

 axis of the external surface is directed downward and forward. The 

 surface is sharply defined, and is separated from the squamous in front 

 by a prominent ridge, the continuation downward of the lambdoidal 

 ridge which meets the posterior end of the posterior root of the 

 zygoma, and is thence continued to the stylomastoid foramen. It 

 affords attachment to the lower parts of the sternomastoid and splenius 



FIG. 141. 



With Parietal. 



Zygomatic Process. 



Glaserian Fissure. 



Posterior Root of Zygoma. 



Roof of Tympanum. 



Fenestra Ovalis. 



With Malar. 



Glenoid Cavity, with Jaw. 



Notch for Canal of Huguier. 

 Postglenoid Process. 



Groove for Eustachian Tube. 



With Basisphenoid. 



Fenestra Rotunda seen through aperture 

 / of communication between Ecto- and 

 Entotympanic Chambers of Bulla. 



Stylo-mastoid Foramen. 



Mastoid Process. 

 With Occipital. 



Pit for Tympano-hyal. 



Entotympanic part of Bulla. 



Ectotympanic part oj Bulla. 



LEFT TEMPORAL BONE, OUTER SURFACE. 



muscles. The posterior edge of the external surface is also directed 

 downward and forward, and consists of an upper and a lower half. 

 The upper half is quite straight and jagged, and forms the outer edge 

 of the posterior surface joining the occipital. The lower half forms 

 an obtuse angle with the upper half; it is directed forward and is 

 sinuate. Its upper part is sharp and applied to the bulla, and gives 

 origin to the styloglossus muscle. The lower part is rounded into the 

 back of the mastoid process, to which the cleidomastoid is attached. 

 The mastoid process is small, convex, and marked by an irregular 

 groove in front of its long axis, from which the trachelomastoid muscle 



