OF THE CETACEA. 75 



too, is by much the most numerous and varied, 

 being in fact one of the largest tribes which exists 

 in nature. 



Some further division, therefore, becomes indis- 

 pensable. The first and most important group has, 

 by Cuvier and others, been distinguished by a very 

 striking peculiarity, viz. the enormous size of the 

 head, which, according to common apprehension, 

 appears disproportionate, extending to a fourth, and 

 even a third, of the dimensions of the whole frame. 

 Under this first subdivision we class the Common 

 or Greenland Whale, the Rorquals, and the Sper- 

 maceti Whales. The two former of these have no 

 teeth whatever, but whalebone or baleen only ; and 

 the Sperm Whale has no baleen, and has teeth in 

 the lower jaw only. 



