310 Dr Fleming on the Neptunian Formation 



tortion of these strata, crystals of quartz, calcareous spar, 

 and magnetic iron ore, occur. 



Vegetable remains occur in this bed. Several trunks of 

 trees, with their branches, could be distinctly traced, enclosed 

 by the flinty and calcareous matter, as in the specimens ex- 

 hibited. In some cases the woody matter was removed, and 

 petrifaction had taken place so completely, as to leave only 

 the traces of the original in the fibrous structure of the cast. 

 In other cases the texture of the wood seemed to be but 

 little altered, as the concentric zones were visible, the per- 

 pendicular fibres separable, and even sectile. These re- 

 mains were sometimes of a brown colour, crossed with veins 

 of calcareous spar. In the petrified matter, both flint and 

 limestone abounded. The casts, except in one instance, pre- 

 sented no marks by which the species or genus could be de- 

 termined. This example seems to be identical with the 

 Phytolithus Plantites verrucosus of Martin, " Petrificala Der- 

 biensia,' n Tab. XI. fig. 1, and which I have found to be a 

 common production of the sandstone, clay-ironstone, and ve- 

 getable limestone of the Lothian coal-field. 



The same objections present themselves against the igneous 

 origin of the flint in this case, as in th« chalk-rocks. I may 

 add, that I have observed calcedony in a similar position to 

 the flint in the present specimens, in the compact limestone 

 at Inverugie, near Duffus, Morayshire. Are we, therefore, 

 to consider that this peculiar botryoidal structure in limestone 

 is produced by the irifluence of siliceous matter with the ten- 

 dencies of calcedony ? We should feel inclined to adopt this 

 opinion, were we not aware of a similar structure prevailing 

 in limestone, destitute of any notable quantity of siliceous 

 matter, as at Inchkeith. 



In the cavities of the chambered univalve shells, which oc- 

 cur in a petrified state in our limestone rocks, no earthy sub- 

 stances are observed, unless in the pipe which opens external- 

 ly, or in those chambers which have broken walls. In those 

 which are closed on all sides, crystalline minerals are observed 

 to have exclusive possession, and these are usually calcareous 

 spar and quartz, or rock crystal. That the former, in solu- 

 tion, percolated the walls of the chamber, and crystallised in 



