﻿16 



BRITISH BELEMNITES. 



as many as eighty in the section of the thinner guard over the alveolar cavity. 1 The 

 thickness of the laminae is about ^th of an inch on the average, sometimes not more than 

 Tireoth of an inch. 



DIAGRAM 4. 



V I d 



v Is the ventral or lower aspect, I, the lateral, and d the dorsal, of Belemn. canaliculatus, Oxford Clay. 



In some Belemnites in the calcareous nodules of the Lias, and in others which 

 occur in the hard Chalk of Antrim, it is difficult to see the lamina? of growth in the clear, 

 horny, yellow, spathose mass of the guard. On the other hand, specimens which occur in 

 clay, shale, or open-grained limestone, show these laminae very clearly and in great 

 plenty. 



DIAGRAM 5. 



Longitudinal section of Transverse section of lamina; 



lamina; of guard. of guard. 



1 Owen, 'Phil. Trans.,' 1844. 



