1902 - 3 .] Sir William Turner on the Sperm Whale. 
433 
delicate furrows, situated behind and somewhat overhanging the 
tympanic bulla. It was so light in weight that it obviously was 
composed of very cancellous tissue. From its position and size 
it was possibly a mastoid, but the absence of the skull prevented 
me from precisely localising it. The long diameter of the bulla 
was 30 mm. and its greatest breadth was 18 mm. It was united 
at its posterior end to the possible mastoid element by a very 
Kight and left Tympanic Bullse and Petrous Bone — Kogia — (natural size). 
constricted neck. The posterior end consisted of two lobes sepa- 
rated by a shallow groove ; the outer was the longer, and projected 
towards but did not reach a depression in the possible mastoid. 
The inferior surface was smooth, and a faint furrow, continuous 
with the groove between the two lobes, passed obliquely across it 
on to the outer surface of the bulla. Kogia did-not have a definite 
ridge on the outer surface similar to Physeter and most other 
Odontocetes, though a scarcely perceptible elevation on one side 
