THE MORPHOLOGY OF THE SKULL 



123 



The tympanic bone or annulus is a delicate, horseshoe-shaped ossicle, attached bj' its ante- 

 rior and posterior extremities to the inferior border of the squamosal 



The ear -bones are chiefly of interest from their size, for they are as large at birth as in the 

 adult. The anterior process (P'oHan process) may be 2 cm. in length. 



Fig 148. — The Temporal Bone at Birth. 



Fig. 149. — Tempor.^l Bone at Birth. 



(Medial view.j 



Squamosal 



Tympanic 



Petrosal 



Hiatus canalis facialis 



"Floccular fossa 

 Aquaeductus vestibuli 

 Internal auditory 

 meatus 



Fig. 150. — The Tempor.\l Bone at Birth. (Lateral view.) 



SQUAMOSAL 



Post-glenoid tubercle 



Petro-tympanic fissure 



Tympanic annulus 



^ri-,j3- Petro-squamous suture 

 -^ Petrosal 



Stylo-mastoid foramen 

 Tympano-hyal 



Carotid canal 



The frontal consists of two bones separated by a median vertical (metopic) suture. The 

 frontal eminence is very pronounced, but the superciliary arches and frontal sinuses are wanting. 

 The frontal spine, which later becomes one of the most conspicuous features of this bone, is 

 absent. There is no temporal line. 



Fig. 151. — The Frontal Bone at Birth. 



The parietal is simply a quadrilateral lamina of bone, concave on its inner and convex on 

 the outer surface. The parietal eminence, which indicates the spot in which the ossification of 

 the bone commenced, is large and prominent. The grooves for blood-sinuses, as in other cranial 



