CETOTOLITES. 



Fig. 224. 



533 



Tympanic bone of Balaena emarginata, nat. size, Felixstow. 



There is a fourth form (fig. 224), which differs from the 

 last in the less degree of convexity of the involuted part, 

 but more particularly in its outer border being notched or 

 indented, as in Baltena mysticetus, by a vertical angular 

 impression deeper and wider than the smaller vertical 

 fissures. 



The comparative shortness of the involuted convexity 

 distinguishes this species from the existing Balana and the 

 Bal. affinis, the notched and less convex involution from 

 Bal. gibbosa, and the immediate rising of the overarching 



Fig. 225. 



Tympanic bone of the recent Cachalot, nat. size. 



