414 ON THE FORMATION OF THE CHALK STRATA, 



This curious arborescent, and most delicate arrangement of 

 the siliceous matter, naturally gave rise to conjectures on the 

 probable mode of its introduction into the fossil. From the 

 specimen designed in Fig. 6. it is quite evident, that a frag- 

 ment only was there inclosed, and the enveloping material 

 being continuous with the cone as well as the little branches 

 formed in the perforations, by which it had been penetrated, 

 it is 'certain that these cavities must have been made in the 

 calcareous mass of the belemnite. I am possessed of a speci- 

 men from Oxfordshire of a belemnite which is covered with 

 serpujae, and penetrated with numerous worm-holes ; and sup- 

 posing these to have been filled with flint, and laid open by 

 the removal of the calcareous portion of the fossil, we might 

 expect a preparation exactly similar to those I have been de- 

 scribing. The great dissimilarity among the specimens, seems 

 to preclude the possibility of attributing their structure to orga- 

 nization, however strongly some of them may resemble it; and, 

 after all, it may be, that this arrangement is due to more than 

 one cause. One thing like uniformity in the interior structure, 

 which may certainly be laid hold of, is the projection of the 

 delicate fibre, from the apex of the concamerated cone, along the 

 centre of the radiated cylinder, to the extreme point of the be- 

 lemnite. This is partly distinguishable in the drawings, Nos. 

 3. and 9. ; and, as I have observed it in many others, I think 

 it may, with propriety, be attributed to an organic connection 

 between the siphunculus and the apex of the fossil, which Par- 

 kinson says, vol. iii. p. 130., has already been described by 

 Walch. 



With respect to the singular arrangement displayed in Figs. 

 7. 8. and 9. ', on a minute examination of these, and several 

 other specimens, it is very difficult to come to any conclusion. 

 The first idea that suggested itself, was the striking similarity 



to 



