OSSEOUS SEMICIRCULAR CANALS OF BIRDS. 263 



7. Types of bony labyrinths, distinguished according to rela- 

 tive positions of the canals, appear to stand in no relation to 

 mode of locomotion, but to a certain extent are indicative of 

 genetic affinity. 



8. There are two main modes in the position of the pharyngeal 

 aperture of the Eustachian tubes : a common pharyngeal aperture, 

 or two distinct ones. 



