494 MANUAL OF ZOOLOGY SECT. 



another pair, the frontah (fr.). Between the supraoccipital 

 and the parietals is a median ossification, the inter-parietal 

 (int. pa.). Below the parietal and frontal is a broad bone (sq.), 

 the superior margin of which is bevelled off. This is the 

 squamosal. It gives off in front a strong zygomatic process, 

 which curves outwards, then downwards, and finally forwards, 

 to unite with the jugal in the formation of the zygomatic 

 arch. Below the root of the process is a hollow, the 

 glenoid fossa. 



Between the occipital and parietal bones, below and 

 behind the squamosal, are the tympanic and periotic bones. 

 The tympanic forms the bony part of the wall of the 

 external auditory meatus (aud. me.) ; below it is dilated to 

 form a process projecting on the under surface of the skull 

 the bulla tympani (ty. but.). The periotic (peri.) is a bone 

 of irregular shape enclosing the parts of the membranous 

 labyrinth of the internal ear ; externally it presents two 

 small openings the fenestra ovalis and fenestra rotunda, 

 visible only when the tympanic is removed. The periotic 

 and tympanic are not ankylosed together, but are loosely 

 connected with the surrounding bones. 



Roofing over the olfactory cavities are two flat bones 

 the nasals (nas.). In front of the nasals are \.}\Q pre-maxillce 

 large bones which form the anterior part of the snout, 

 bear the upper incisor teeth, and give off three processes. 

 The maxilla (max.), which form the greater part of the 

 upper jaw, and bear the premolar and molar teeth, are large, 

 irregularly-shaped bones, the outer surfaces of which are 

 spongy. Internally they give off horizontal processes the 

 palatine processes (pal. max.) which unite to form the anterior 

 part of the bony palate. A strong process which is given off 

 from the outer face of each maxilla and turns outwards and 

 then backwards to unite with the zygomatic process of the 



