MOLLUSCA 



HS 



The cuttlefishes^ or Sepias, have ten arms and a pair of highly 

 developed eyes. The body is covered by the mantle. Cuttle- 

 bone comes from the inner shell, which is very porous and light in 

 weight and largely lime. Cuttlefishes furnish sepia ink which is 

 used in art. Ground cuttlebone called " pounce " is used somewhat 

 in medicine as an anti-acid and when powdered fine is used by 

 draftsmen to prevent blotting. Italians esteem the " sepias " a 

 delicacy. India ink is made from the ink bags of fossil cuttlefishes. 



The octopus {Octopus vulgaris) bears eight arms. It may reach 

 a length of fifteen feet and weigh seventy-five pounds. Terrible 

 stories are related (at a few dollars a column) regarding the battles 

 of divers with these horrible " devil fishes." They are used for 

 food by the Chinese and Italians. 



Fig. -jiA. Female Argonauta argo. (Lull, Organic Evolution, after Claus-Sedgwick. 



Courtesy of Macmlllan and Co., Ltd.) 



The squid (Loligo) reaches a length of about one foot. The 

 internal shell, called the " pen " on account of its resemblance to a 

 feather, is relatively thin and chitinous (horny), not calcareous. 



6 The Arctic cuttlefish is said to reach a length of eighteen feet, its size being ap- 

 parently correlated with the greater abundance of diatoms and other food in the 

 plankton of northern waters. 



