224 



THE SKULL. 



[CHAP. 



cerebral fossa of the cranial cavity being formed by the pari- 

 etals (Pa). The upper surface of the skull is very narrow, 

 and flat or slightly arched in the longitudinal direction ; its 



FIG. 68. Section of the skull of an African Manatee (Manatiis senegalensis). \. 

 PMx premaxilla; Vo vomer ; MX maxilla; Fr frontal; ET ethnioturbinal : 

 M E mesethmoid : Fr frontal ; Pa parietal ; Sq squamosal ; SO supraoccipital ; 

 E.rO exoccipital ; Per periotic ; BO basioccipital ; 'J y tympanic ; AS alisphenoid ; 

 US basisphenoid ; /'.9 prcsphenoid ; Pt pterygoid ; PI palatine ; Vl/.r maxilla ; 

 cp coronoid process of mandible ; cd condyle : a angle ; ^ symphysis ; sh stylo- 

 hyal ; bh basihyal ; tk thyrohyal. 



sides, which are parallel for a considerable distance, join 

 at a right angle the vertical inner wall of the great temporal 

 fossa. The squamosal has an extremely massive and long 



