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BRITISH BELEMNITES. 



have been a thin cellular tissue (s') like that of the youngest parts of the conotheca and 

 the smallest septa. 



DIAGRAM 2. 



It is supposed by some writers to have been extended backward into a small canal at 

 the meeting of the fibres along the axis of the guard, and forward into the pipe or 

 siphuncle of the phragmocone, of which more hereafter. On the little spherule a system 

 of pencils of radiating cells grows up, in a lamina which embraces the spherule on all 

 sides except its anterior or part of its anterior face. There the phragmocone is already 

 begun, either by the spherule extending into a short tube representing the siphuncular 

 opening in a septum, or without such entering short tube. Successive laminae of 

 radiating cells, more and more extended backward, but stopped in a forward direction by 

 the growing phragmocone, cover the spherule, meet on the axial line, and constitute a 

 small, rather fusiform Belemnite (middle figure), in which the septa appear, and the 

 siphuncle takes its place. 



In some instances there appear to be traces of more than one such spherule, with its 

 pencils of diverging fibres, enclosed in the guard, as if the phragmocone had aborted, or 

 its earliest chambers were spherical, and united by a short pipe. 



If this description be well considered, it will appear certain that the phragmocone is 

 not a chambered body made to fit into a conical hollow previously formed in the Belemnitic 

 sheath, as some have conjectured, but that both sheath and cone grew together ; or, if any 

 difference there were, the phragmocone must have been of earlier growth, and by its 

 enlargement limited the forward extension of the successively deposited laminae of the guard. 



