OF THE ADULT ANTRUM. 



35 



or is divided into compartments by thin plates 

 or thick ridges of bone (Figs. 8, 9, 10). 



Fjg. 8. 



Antnnn divided by a thin plate of bone, with a deep fossa on each side {posterior view). 



Fig. 9. 



Antrum divided by a thick ridge of bone {anterior view). 



Fig. 10. 



Antrum divided hini -ntn'hj . with cells exten^ng beneatlt the orbital plate (jtosterior view.) 



D 2 



