1:50 



spine, and which, as has been already mentioned, were of the palisadoe 

 kind, the substance of which they were composed was found very much 

 to resemble cork in its general appearance, and even in its structure, 

 being so light and porous as not to allow them to sink in water. This, 

 it will at once be seen, would be the kind of substance which would be 

 particularly 'well calculated to perform those offices which we may pre- 

 sume would belong to the supposed corresponding substance in the 

 belemnite. Hence I feel little hesitation in concluding, that the spa- 

 those part of the belemnite was originally a light pithy substance, by 

 which the animal and its appendage were so poised in the water, as to 

 be readily susceptible of those occasional changes in situation which 

 the organization of the siphunculus seems to have been capable of 

 producing. 



It is in favour of this opinion respecting the original structure of the 

 belemnite, that on immersing a belemnite in a very weak mixture of mu- 

 riatic acid and water, in the proportion of about twelve drops to a pint, 

 several exceedingly delicate membranous^oa-w/* became evident, hang- 

 ing from the mass, and waving with the fluctuations of the fluid. The 

 notion, then, which we seem to be authorized in forming, respecting 

 the previous state of the belemnite, is, that it was a conical conca- 

 merated shell, imbedded in a light porous body : a siphunculus passing 

 through the septa, and perhaps terminating in the cellular part : the 

 ascent or descent of the animal, with its dwelling, depending on 

 the admission of air or of water into the siphunculus, arid perhaps into 

 the cellular part of the light body itself. This connection of the siphuncle 

 with the light porous body is however assumed, on the existence of the 

 tube passing through this body, as described by M. Walch, and which is- 

 discoverable in the specimen represented Plate VIII. Fig. 10. 



It is hardly necessary to observe, in favour of the marine origin of 

 the belemnites, that they .sometimes have other marine bodies, such as 

 oysters, serpulae, 8cc. attached to their surface. This circumstance is r 



