OP CREATION. 139 



a kind of internal framework ; but the latter is unpro- 

 vided with any external defence, and only has an 

 imperfect skeleton, known Fig. 53 



in the common cuttle- 

 fish as the bone. Of these 

 two groups the former was 

 abundantly present in the 

 ancient seas, as we know 

 by the fragments that 

 remain of its solid stony NAUTILUS. 



habitation. The latter may or may not have been 

 equally abundant, since from the nature of the case 

 its remains could not be so frequently or so well 

 preserved ; but we know that various species referri- 

 ble to it existed throughout the secondary period, and 

 that one genus at least, now extinct, was then ex- 

 tremely common. 



The nautilus is a remarkable and a very interest- 

 ing genus, belonging to the most highly organized, 

 not only of shell-bearing animals, but of all Inverte- 

 brata, and even exceeding some of the fishes in this 

 respect. 



It is one of the group of Cephalopoda,* or ani- 

 mals whose organs of locomotion are attached im- 

 mediately around and upon the rim of the mouth or 

 head. The fore part of the body forms a strong and 

 wide sheath, each side of which produces a group of 

 conical processes pierced with openings, through which 

 prehensile organs or feelers are, at the will of the 

 animal, projected or retracted. The sheath forming 

 the base of these organs, which are used both for 

 locomotion and prehension, is also a pouch, in which is 



* See ante, p. 42, and p. 95. 



