﻿STRUCTURE. 



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structure is difficult to demonstrate in these fibres, which Owen describes, in specimens 

 from Christian Malford, as of a trihedral prismatic form, and of ^th of an inch in 



DIAGRAM 1. 



Transverse Sections. Longest Section. 



G. Guard, (p. Phragmocone. C. Conotheca. A. Alveolar cavity, s. Sphericle of the guard, a a. Axis of guard. 

 S' S" S'". Transverse sections, d. Dorsal aspect, v. Ventral aspect. 



diameter. In some species they are very much larger. They appear sometimes connected 

 into pencils ; mostly, however, they are ranged perpendicularly to the laminae of growth, 

 which they cross without interruption, to meet on the axial, or, as it is called by Voltz, the 

 apicial, line. The Belemnite is found in nearly the same mineral condition whatever be 

 the containing rock. It is sometimes wholly removed, leaving a hollow, into which the 

 conical mould of the alveolar cavity projects. This happens in the upper beds of the Lias 

 in Yorkshire and in the Marlstone of Rutland. 



The Belemnitic shell begins in a very small spherule, the wall of which has not been 

 very clearly seen ; but, by observation of specimens in Oxford Clay and Lias, it appears to 



