38 CETACEOUS ANIMALS. 



veloped in a tendinous membrane, so as to be effec- 

 tually converted into fins. The posterior extremi- 

 ties or limbs are entirely wanting. 



The brain is large and well developed. The 

 bone containing the organ of hearing, or internal 

 ear, is separated from the rest of the head, being 

 attached thereto by ligament alone. The orifice of 

 the external ear is very small and destitute of exter- 

 nal appendage. The teats, two in number, are either 

 pectoral or abdominal. 



