408 ON THE FORMATION OF THE CHALK STRATA, 



that occur in chalk and flint are translucent, and of an amber- 

 yellow. 



This curious fossil, of whose nature nothing but the most 

 vague conjectures have hitherto been hazarded, seems to have 

 been the appendage of some animal, handed down to us pro- 

 bably unchanged since its creation. It will be remarked, that 

 its structure is quite different from that of other calcareous 

 fossils, which are formed in general of the common rhom- 

 boidal carbonate, while it is composed of radiated striae, di- 

 verging from a point, which appears to have been dependent 

 on some internal organisation. These striae are interrupted 

 by concentric lines, which are not frequently visible, although 

 they are rendered so by the action of acid, and sometimes 

 are displayed in the longitudinal fracture. This arrangement 

 seems to indicate the growth of the animal, and had the be- 

 lemnite undergone a conversion like other petrified substances, 

 must certainly have been obliterated. 



On this account we may perhaps be allowed to consider the 

 belemnite as unaltered ; but to what species of animal it has 

 belonged, no conjecture can be formed. The thick end of the 

 fossil is always broken, as, in consequence of the conical form 

 of the alveolus, it is reduced to a thin, delicate edge, and may 

 have been attached by cartilaginous matter to the body of the 

 animal it belonged to. 



Although the alveolus be very frequently filled with the ma- 

 terial in which the fossil is imbedded, it likewise happens, oc- 

 casionally, to present an organic structure. When the Antrim 

 fossils, which are formed in flint, have been reduced by acid, 

 the siliceous cone is found to be impressed with rings, set at 

 regular distances ; but this is only superficial, as the flint itself 

 breaks in its usual conchoidal form, without any interruption 

 from the external appearance. It is different, however, in 



1 1 some 



