If 5H ZOOLOGY. 



602. We have said above that the mollusca have no 

 solid articulated framework comparable to the skeleton of the 

 vertebrata. Nevertheless, in the cephalopoda we still find 



Fig. 450. Nautilus.* 



vestiges of something analogous ; for there is in the head a 

 cartilage which not only protects the brain, but also spreads 

 out in different directions, furnishing points of insertion to 

 the different muscles of the animal. It is also to be ob- 

 served, that the abdomen of these animals is in general sup- 

 ported by a sort of internal shell, which in theloligo is horny, 

 but in the sepia is of a calcareous nature, and is called the 

 bone of the sepia. 



603. The disposition of the organs of locomotion and 

 prehension, fixed around the mouth, varies in these mollusca. 

 In the dibranchiate cephalopodes there is a corona of large 

 fleshy teutacula, whose internal surface is provided with 



* In this figure the shell is represented open : t, the tentacula; e, the 

 funnel; p, the foot ; m, a portion of the mantle ; o, the eye; t, the syphon. 



