ORDER I. DIBRANCHIATA. 



958. The species of the Dibranchiate Order are extremely 

 numerous ; and they frequent every part of the ocean, from the 

 arctic to the equatorial regions, some preferring the neighbour- 

 hood of the shores, whilst others are found only in the open sea. 

 None of them possess more than ten arms, and a part have only 

 eight ; the latter are considered as forming the highest group, 

 being the most removed from the Tetrabranchiate Order. In 

 only one genus, the Argonauta, do we find the body inclosed in 

 an external shell ; in all the rest, the shell, or that which repre- 

 sents it, is internal, or rather is included between two folds of 

 the mantle ; and it serves rather as an organ of support, than as 

 a protection to the animal. 



959. The Octopod, or eight-footed section of the Order, includes 

 two families, the OCTOPODID^E, or Poulps, and the ARGONAUTI- 

 IXE, or Argonauts. In the former the body is naked, the internal 

 shell is rudimentary, and none of the arms are expanded at 

 the apex into broad webs. To this family belongs the com- 



Fio. 645. OCTOPUS OB POULP. 



mon Octopus or Poulp (Fig. 645), which is abundant on 

 the southern coasts of Europe, and is occasionally met with 

 on our own shores. This animal is the Polypus of ancient 



