Lamarck's Genera of Shells. 253 



The sepiaria are marine animals, none of them have any true 

 shell, they always live in the sea, some crawling at the bottom, as 

 the octopus, others, as the sepia and loligo, swimming freely in 

 mid water, by means of the membranes or fins with which their 

 sac is furnished. 



The body of these animals is fleshy, half enclosed in a muscular 

 sac, from which the head and anterior part of the body project. 

 The head is crowned with tentacular arms, disposed like radii 

 round the mouth, with suckers on the inner side. The branchiae 

 are enclosed in, and concealed by, the sac, on the outside of the 

 peritoneum which contains the viscera. They are two in number, 

 of a pyramidal form, and are situated one on each side of the pe- 

 ritoneum. The containing cavity has an external communication 

 by the funnel under the neck, at the mouth of the sac, and which 

 conveys the water to and from the branchiae. 



1. Octopus*. 



2. Loligopsis. 



The second of these genera is wholly unprovided with any solid 

 cretaceous or horny substance in the interior of its body, but the 

 octopus has two cartilages inserted in the substance of the purse, 

 or elongated sac, which partly contains the body. Cuvier de- 

 scribes these cartilages as having the form of a dagger, (stilets,) 

 and says that they occupy the lower half of each side of the back, 

 and are the only appearance of any thing resembling the sword of 

 the calmar, {Loligo,) or the bone of the sepia. Hist, et Anutom. 

 des Mollusques, p. 12. 



The general form of the octopus is very analogous to that of the 

 sepia and loligo ; it has eight long, nearly equal arms, surrounding 

 the mouth ; no membranes for swimming attached to the sac, and 

 the suckers are simply fleshy, and not provided with the horny in- 

 dented ring, which constitutes the claw of the latter animals. 

 They are the largest of the sepiaria. The loligopsis has eight 

 sessile and equal arms, round the mouth ; two fins, or membranes, 

 for swimming, attached to the lower part of the sac, and is of 



* From oxIa>, eight, ami -ro-uj, a loot. 



