CETOTOLITES. 531 



characters are sufficiently marked in the specimens of the 

 fossil tympanic bones, to justify their being regarded as 

 belonging to a species distinct from the known existing 

 Baleenee, but nearest allied to the Bal. antarctica, and 

 which I propose to call Baleena affinis. 



Fig. 222. 



Tympanic bone of Balcena definita, nat. size. Felixstow. 



A second species is characterised by the distinct defini- 

 tion of the involuted convexity (a); and the extent of the 

 slightly concave surface extending from it to the commence- 

 ment of the overarching wall (5) ; the anterior extremity of 

 the involuted convexity is equally well defined, and a wide 

 concavity divides it from the anterior extremity of the 

 Eustachian outlet (o). The thickest part of the involuted 

 convexity is not very prominent. The under and outer 

 surfaces of the bone meet at a right angle. 



The species indicated by the tympanic bones of this form 

 I have termed Balana definita. 



M M 2 



