350 



LOLIGO, SPIRULA, BELEMNITE. 



development of a chambered shell, of which we find some traces 

 in most of the different forms included in it. To this group 

 belong the Loligo, or Calamary (Fig. 540), already several 

 times noticed ; the common Sepia, or Cuttle-fish, whose body 

 is more bulky in proportion to its length ; the Loligopsis, so 

 remarkable for the length of its additional pair of arms (Fig. 543); 

 and several others having the same general form. In all these, 

 the only rudiment of a shell is a straight flat body, sometimes 

 broad and firm, as in the Cuttle-fish (forming the pounce-bone, 

 which may be picked up on every coast), sometimes slender and 

 horny, as in the Loligo. There is an existing genus, however, 

 in which a chambered shell exists, very 

 strongly resembling those of the Ammo- 

 nite (Fig. 549) in general form, but com- 

 pletely inclosed by the animal, so as to 

 become altogether internal ; this is the 

 Spirula, an inhabitant of tropical seas, 

 whose delicate little shell may be picked 

 up on almost any sandy shore in warm 

 latitudes. The animal has not yet been 

 very carefully examined ; but it is known 

 to possess no more than ten arms ; whence 

 its position is fixed as belonging to this 

 group, rather than to the succeeding 

 Order. 



893. With this family we are to asso- 

 ciate an extremely interesting genus, the 

 Belemnite, whose remains abound in 

 several of the older rocks, especially the 

 Lias and Oolite. The shell consists of a 

 conical chambered portion, implanted (as 

 it were) into a corresponding hollow of a 

 long solid sheath, tapering to a point at 

 its lower extremity (Fig. 547). The 

 conical chambered portion extends con- 

 siderably beyond the hollow of the stony 

 sheath ; but the border of the latter seems to have been prolonged 



FIG. 547 BELEMNITES; 



a, large extremity, showing 

 the insertion of the cham- 

 bered cone into the sheath. 



