432 Proceedings of Royal Society of Edinburgh. [suss. 
and formed a well marked convex projection in the transverse 
plane of the bulla, which was continued by one end into the 
inferior surface of the outer lobe of the bulla, and by the other it 
reached its tympanic mouth • a deep fissure separated it from the 
outer limb of the fork of the denticulated process. The inner 
surface of the bulla was continued into the thick rounded border 
of the tympanic mouth, and was divided by a deep depression 
into an anterior and a posterior lobe. The anterior end of the 
bulla opened freely into the cavity, and was bounded by an arched 
border, the piers of which were thickened. 
The petrous bone was 65 mm. long and 39 mm. in greatest 
breadth. It articulated between the limbs of the fork by a pos- 
terior process, having a concavo-convex curve. Its tympanic wall 
had two foramina, one much larger than the other, but none of the 
tympanic ossicles had been preserved. The internal meatus was 
large and its walls were cribriform for the transmission of the 
branches of the auditory nerve. 
In Kogia an irregularly shaped mass of bone formed a well 
marked projection, marked with a reticulated arrangement of 
