240 FOSSIL CHAMBERED SHELLS, 



the economy of millions of creatures long since swept from 

 the face of the living world. From the similarity of these 

 mechanisms to those still employed in animals of the exist- 

 ing creation, we see that all such contrivances and adapta- 

 tions, however remotely separated by time or space, indicate 

 a common origin in the will and design of one and the same 

 Intelligence. 



We enter then upon our examination of the structure and 

 uses of fossil Chambered shells, with a prehminary know- 

 ledge of the facts, that the recent shells, both of N. Pompi- 

 lius and Spirula, are formed by existing Cephalopods; and 

 we hope, through them, to be enabled to illustrate the his- 

 tory of the countless myriads of similarly constructed fossil 

 shells whose use and office has never yet been satisfactorily 

 explained. 



We may divide these fossils into two distinct classes; the 

 one comprising external shells, whose inhabitants resided 

 like the inhabitant of the N. Pompilius, in the capacious 

 cavity of their first or external chamber (PI. 31, Fig. 1 ;) the 

 other, comprising shells, that were wholly or partially 

 included within the body of a Cephalopod, like the recent 

 spirula, (PL 44, Figs. 1, 2.) In both these classes, the 

 chambers of the shell appear to have performed the office of 

 air vessels, or floats, by means of which the animal was 

 enabled either to raise itself and float on the surface of the 

 sea, or sink to the bottom. 



It will be seen by reference to PI. 31, Fig. 1,* that in the 

 recent Nautilus Pompilius, the only organ connecting the air 

 chambers, with the body of the animal, is a pipe, or siphun- 

 cle, which descends through an aperture and short project- 

 ing tube (y) in each successive transverse plate, till it ter- 



* The animal is copied from PI. 1, of Mr. Owen's Memoir; the shell 

 from a specimen in the splendid and unique collection of my friend W. 

 J. Broderip, Esq., by whose unreserved communications of his accurate 

 and extensive knowledge in Natural History, I have been long and largely 

 benefited. 



