242 USE OF CHAMBERED SHELLS. 



A similar apparatus is shown to have existed in the beaks 

 of the inhabitants of many species of fossil Nautili, and Am- 

 monites, by the abundance of fossil bodies called Rhyn- 

 cholites, or beak-stones, in many strata that contain these 

 fossil shells, e. g. in the Oolite of Stonesfield, in the Lias at 

 Lyme Regis and Bath, and in the Muschelkalk at Lune- 

 ville. 



As we are warranted in drawing conclusions from the 

 structure of the teeth in quadrupeds, and of the beak in birds, 

 as to the nature of the food on which they are respectively 

 destined to feed, so we may conclude, from the resemblance 

 of the fossil beaks, or Rhyncholites, (PL 31, Fig. 5 — 11,) to 

 the calcareous portions of the beak of the Cephalopod, inha- 

 biting the N. Pompilius, that many of these Rhyncolites 

 were the beaks of the cephalopodous inhabitants of the fossil 

 shells with which they are associated; and that these Cepha- 

 lopods performed the same office in restraining excessive in- 

 crease among the Crustaceous and Testaceous inhabitants 

 of the bottom of the Transition and Secondary seas, that is 

 now discharged by the living Nautih, in conjunction with 

 the carnivorous Trachelipods.* 



Assuming, therefoi'e, on the evidence of these analogies, 

 that the inhabitants of the shells of the fossil NautiU and 

 Ammonites were Cephalopods, of similar habits to those of 

 the animal which constructs the shell of the N. Pompilius, 

 we shall next endeavour to illustrate, by the organization 

 and habits of the living Nautilus, the manner in which these 

 fossil shells were adapted to the use of creatures, that some- 

 same hard calcareous substance at its point; this substance is of the nature 

 of shell. 



These calcarcous'extremities of both mandibles are of sufficient strength to 

 break through the coverings of Crustacea and slielis, and as they are placed 

 at the extremity of a beak composed of thin and tough horn, tlie power of 

 this organ is thereby materially increased. 



In examining the contents of the stomach of the Sepia vulgaris, and Lo- 

 ligo, I have found Ihem to contain numerous shells of small Conchifera. 



* See p. 192. 



