332 THE WONDERS OF GEOLOGY. Lect. IV. 



25. Cephalopoda of the chalk. — The most striking 

 feature in the marine fauna of the chalk, as contrasted with 

 that of the tertiary and modern formations, is the great 

 preponderance of multilocular cephalopoda.* In the ter- 

 tiary, and existing tropical seas, one genus (the Nautilus) 

 occurs abundantly. The beauty, elegant form, and re- 

 markable internal structure of the recent shell, have 

 rendered it in all ages an object of admiration ; yet an 

 accurate knowledge of the organization of the animal to 

 which it belongs, has but recently been obtained. The 

 Nautilus, and the allied fossil genera, may be regarded as 

 Sepiae or Cuttle-fish inhabiting chambered shells, which 

 are furnished with an apparatus to impart buoyancy, and 

 enable the animals to swim on the surface, or sink to the 

 depths of the ocean at pleasure. 



A few remarks on the recent types will serve to render 

 the subject intelligible. The Sepia, or Cuttle-fish of our 

 seas is of an oblong form, composed of a jelly-like substance, 

 covered with a tough skin ; the mouth, which is central, is 

 furnished with horny mandibles, much resembling the 

 beaks of a parrot. The animal has two large eyes, and 

 eight arms studded with rows of little cups, or suckers, 

 which are powerful instruments both of locomotion and pre- 

 hension. The soft body of the sepia is supported by a ske- 

 leton, formed of a single bone or osselet of a very curious 

 structure ; when dried and reduced to powder it is the 

 substance called pounce. The Cuttle-fish has a mem- 

 branous sac, which secretes and retains a dark-coloured 

 fluid, resembling ink ; this the animal can eject when 

 pursued, and by thus rendering the water turbid, escape 

 from its enemies. This fluid, properly prepared, forms 

 the colour termed sepia, which is so much employed in the 

 arts. 



* Sec Medals of Creation, vol. ii. p. 456, for an account of the 

 Cephalopoda. 



