236 MOLLUSCA. 



in places, by spots, with a rapidity which greatly surpasses that of the 

 Chameleon. 



These animals are voracious and cruel ; possessed both of agility and 

 numerous modes of seizing their prey, they destroy immense quantities 

 of Fish and Crustacea. Their flesh is eaten ; their ink is employed in 

 painting, and the India, or China ink, is supposed to be made from it. 



The Cephalopoda comprise but a single order, which is divided into 

 genera, according to the nature of the shell. 



Those which have no external shell, according to Linnaeus, formed 

 but the single genus. 



SEPIA, Linnaiis, 



Or the Cvtlle-Jisli, which is now divided into a variety of subgenera, the most 

 interesting of which are the two following : 



ARGONAUTA, Linrueus. 



These Mollusca are always found in a very thin shell, symmetrically fluted 

 and spirally convoluted, the last whorl so large that it 

 bears some resemblance to a galley of which the spine is 

 the poop. The animal makes a consequent use of it, 

 and in calm weather whole fleets of them may be ob- 

 served navigating the surface of the ocean, employing 

 six of their tentacula as oars, , and elevating the two 

 membranous ones by way of a sail. If the sea becomes 

 rough, or they perceive any danger, the Argonaut with- 

 draws all its arms, concentrates itself in its shell, and 

 descends to the bottom. 

 Several species are^known, closely resembling each other both in the 



animal and the shell, which were united by Linnaeus under the name of 



Aryonauta argo, or the Paper Nautilus. 



SEPIA, Lamarck. 



The Sepia:, or Cutlle-Jisli properly so Culled, have two long arms and a 

 fleshy fin extending along the whole length of each side of the sac. The shell 

 is oval, thick, convex, and composed of numerous and parallel calcareous 

 laminae, united by thousands of little hollow columns, running perpendicularly 

 from one to the other. This structure rendering it friable, causes it to be 

 employed for polishing various kinds of work; it is also given to birds in 

 aviaries, for the purpose of whetting their beaks. 



NAUTILUS, Linnceus. 



In tbis genus Linnaeus united all spiral, symmetrical, and chambered shells; 

 that is to say, such as are divided by septa into several cavities ; their inha- 

 bitants he supposed to be Cephalopoda. 



This genus is now divided into Spirula and Nautilus proper. 



