MOLLUSCA CEPHALOPODA. 231 



Mollusca of this description are found in great 

 abundance in the colder regions of the ocean sur- 

 ,„Q rounding both the north and south 



poles ; and other species are also 

 met with, though in smaller num- 

 bers, in the tropical seas. The 

 Clio boiealis, of which Fig. 120 is 

 a representation, is the most per- 

 fect specimen of this form of con- 

 struction. It swarms in the Arctic 

 seas, and constitutes the principal 

 food of the whale. The position of its gills, which 

 perform the office of oars or feet, at the same time 

 that they resemble in their shape and action the 

 wings of an insect, are characters which have sug- 

 gested the title of Pteropoda, given by Cuvier to 

 this order of Mollusca. The Cymbulia, which also 

 belongs to this order, is found on the coast of Pro- 

 vence, where it is called " le papillon de mer," 

 from the resemblance of its large lateral oars to a 

 butterfly's wings. 



§ 6. Cephalopoda. 



Following the progress of organic developement, 

 we now arrive at a highly interesting family of 

 Mollusca, denominated the Cephalopoda, and dis- 

 tinguished above all the preceding orders by being 

 endowed with a much more elaborate organization, 

 and a far wider range of faculties. The Cephalo- 

 poda have been so named from the position of cer- 

 tain organs of progressive motion, which are situated 

 on the head^' and like the tentacula of the Polypus, 



