70 Lamarck's Genera of Shells. 



sessile eyes ; two horny mandibles at the mouth ; three hearts ; 

 sexes separate. 



The cephalopoda, have been so named by M. Cuvier, because the 

 head of each animal is furnished with a kind of inarticulated arms, 

 forming a coronet round the mouth, which is terminal. 



Except of the family of the sepiaria, and of the genus spirilla, 

 we know little of the animals of the families and genera included 

 in this order, most of them inhabiting the great depths of the sea, 

 and, consequently, being beyond the reach of our observations. 

 From those which are known to us, we can ascertain that the 

 cephalopoda are the most perfect of the mollusca ; their organiza- 

 tion is the most complicated, and most developed, and they are 

 in this respect, superior to the other invertebrated animals. 



The body of the cephalopoda is thick and fleshy, and its lower 

 part contained in a muscular sac, formed by the mantle of 

 the animal. This mantle, closed at the posterior part, is only 

 open at the upper, from which the head and a portion of the body 

 projects. The head is free, surrounded by a coronet of tentacular 

 arms, the number and size of which vary in the different genera. 

 Tt has at the sides two large, sessile, immoveable eyes, without 

 eyelids, but very complicated with regard to their humours, mem- 

 branes, vessels, ^c. The mouth of these animals is terminal, ver- 

 tical, and armed with two strong horny mandibles, which are 

 hooked, and resemble a parrot's bill. Lastly, the organ of hearing, 

 although unprovided with any external conduit, as in fishes, is dis- 

 tinguishable in these mollusca. 



The cephalopoda are furnished with three hearts for the circula- 

 tion of the fluids; or, perhaps we should rather say, they have but 

 one heart, and two separate lateral auricles. In fact, the principal 

 trunk of the veins, or that which carries the blood, divides into two 

 branches, which convey the fluid to the lateral auricles ; these send 

 it to the branchia;, whence it is carried to the true heart, situated 

 in the middle, and from thence over the whole body, by means of 

 the arteries. 



These mollusca all live in the sea ; some swimming about freely, 

 and fixing themselves to marine substances at pleasure, the others 



