AQUATIC MAMMALS 



Other external features, such as position of the narial openings, length 

 of neck, tail, and form of appendages will be discussed in detail in other 

 chapters. Suffice it to say here that in the highly modified aquatic mam- 

 mal the tendency always has been for the elimination of any unevenness 

 of body contour that could offer resistance during progression through 

 the water. The pinna of the ear disappears, the scrotum is eliminated, 

 and the appendages that are not used definitely either for propulsion or 

 in equilibration will first atrophy and then sink beneath the surface of 

 the body. 



[60] 



