(Table 2). 2) The density of bristles on the plates— sei whales 

 have from 35 to 60 baleen fringes per centimeter; all other 

 rorquals have far fewer (less than 35). 3) The relative lengths 

 of the ventral grooves— the grooves of sei whales end well 

 before the navel; those of blue, fin, and Bryde's whales 



extend at least to the navel. 4) The relatively small numbers 

 of ventral grooves (38-56)— both blue and fin whales have 

 more; Bryde's whales have approximately the same number. 

 If the animal is not in an advanced state of decomposition, 

 the region of white coloration of the belly may also be visible. 



Figure 24.— The head of a sei whale is intermediate in shape between that of the blue whale and that of the fin whale. When 

 viewed from the side it is slightly arched. Note the single central head ridge, from just in front of the blowholes to near the tip of 

 the snout. Bryde's whales, with which sei whales are most likely to be confused in the tropical and subtropical portions of their 

 range, have two auxiliary ridges, one on each side of the top of the head, in addition to this main central ridge. (Photo from the 

 North Pacific by Japanese Whalei Research Institute, courtesy of H. Omura.) 



Figure 25. — Sei whales are dark gray on the right lower lip. They can be distinguished from fin whales, 

 which have a white right lower Up, by approaching them from the right side. {Photo from the North 

 Pacific by Japanese Whales Research Institute, courtesy of H. Omuro.) 



33 



