Siruciure of the Bdemnitc. 393 



remains, rests upon the flint, which is impressed with the ra- 

 diated structure of the fossil, and the upper part is broken oft" 

 at right angles, showing not only that it must have been a frag- 

 ment of the belemnite, but also that it was then possessed of 

 the same radiated structure as it now presents. Hence, if it 

 be a petrifaction in place of an original formation, as I have 

 been led to consider it, it must have been transformed previous 

 to its inclosure in the flint. Upon the surface small branches 

 of arborescent flint may also be observed, as if the original had 

 been covered with some delicate conferva, now converted into 

 silex. There are also some of those cylindrical bi'anches veiy 

 short, as if they had occupied only the commencement of the 

 perforation, which have proceeded from the surface inwards, 

 without the appearance of fracture at the extremities, which 

 are rounded off. These are very like the perforations of a 

 worm, and have induced me to believe that many of them are 

 merely casts of flint, in cavities formed in that manner. 



" Nos. 7, 8 and 9. In these experiments the flint which has 

 been displayed by the dissolution of the calcareous spar, pre- 

 sents a new appearance, which may perhaps be best com- 

 pared to the ovarium of some animal. Small roundish masses 

 are connected and entangled with each other by thin and very 



delicate threads In specimens of this kind, I have noticed 



that the connection between these globular masses is main- 

 tained, more particularly, by two fibres larger than the others, 



and more uniform in their position I should observe, that 



the flint in most of these fossils approaches to calcedony, and 

 is lighter in its colour than the general mass. It sometimes 

 presents an opake chalky-looking asp3Ct, wliich, I presume, 

 arises from an admixture of calcareous matter ; for 1 have 

 found this variety very liable to crumble into dust, after the 

 operation of the acid." 



" No. 1 1 is the same fossil found in the limestone, and by 

 being broken longitudinally, there appear in the section of it 

 cavities filled with chalk, as they would have been filled with 

 flint in the specimens I have described. I have a great many 

 more of the same kind, particularly of the fluits, and some of 

 them presenting the most beautiful arborisations I ever saw ; 

 quite similar to the most delicate sea-weed, which had appa- 

 rently been attached to the outer surface of the belemnite." ^ 



" I am possessed," observes Mr. Allan in the sequel, " of a 

 specimen from Oxfordshire, of a belemnite which is covered 

 with seqiuhe, and penetrated with numerous worm-holes ; and 

 supposing these to have lieen filled with flint, and laid open by 

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

 expect a preparation exactly similar to those 1 have been de- 



Vol, 61. No. .'}01. Mmj I'y'iy. ?> 1) scribing. 



