324 



R. J. Anderson, 



The breadth of the parietal exceeds the antero-posterior diameter 

 in these birds. The interparietal suture does not reach the full length 

 of the Cerebral Cavity in the ostrich (Struthio). The parietal bone is 

 thickish externally and posteriorly. The bone is much thinner 

 anteriorly, the frontal takes a great part in roofing of the Cranial Cavity. 



The transverse diameter of the parietal bones in Grallus (var) 

 is one third greater than antero-post diameter, which is one fourth 



Fig. 13. 

 Turtle. 



Fig. 14. 

 Owl. 



the length of the interfrontal suture. The parietal bones are thick 

 externally, and become thin near the middle line at 2 mm distance. 

 They are thickest at the postero-lateral part. They are somewhat 

 thinner in front of this, along the outer border. The parietals in 

 relation to the C'ranial Cavity are larger in the owl and they are 

 thin. The parietals in parrot are also thin. The question arises 

 whether the thickening is due to comparative retrocession of the brain 



