TYMPANIC BULLA IX HY.EXAS. 



Text-figure 2. 



305 



hK ' 



tr. 



earn. 



earn. 





earn. 



D 



A. Base of the skull of the Striped Hysna {Hycena liycena) with the left tympanic 



bulla opened. _ h., right tympanic bulla ; c, carotid canal, its course shown by 

 an arrow ; e., inner orifice of eustachian tube, the course of which is shown 

 by an arrow; earn., external auditory meatus ; s., partition or septum between 

 the two chambers ; tr., tympanic ring; st., stylomastoid foramen ; po., par- 

 occipital process ; in., mastoid ; ov., foramen ovale. 



B. Anterior portion of left bulla enlarged and viewed obliquely from the inner side 



to show that the crest mistaken bj' Mivart for a low septum is the tympanic 

 ring {tr.), with the internal auditory meatus {tarn.) ; ijer., periotic ; /;«., fora- 

 men lacerum medium, exaggerated in size. 



Proc. Zool. Soc— 1916, ^o. XX. 20 



