PLATE 11, 12, 13, 13^ IL 
sulcus. This, after a certain distance, appears to strike out 
laterally, and form a branch. The trunk is then continued 
for some length, perhaps a foot or more, without the fur- 
row or the internal imbricated body. After which, this 
part is again found, and another branch put out, in an 
opposite direction. 
This fossil is common in those parts of Derbyshire where 
coal and iron-stone abound : it is particularly frequent In 
a hard, light-coloured siliceous grit, which our miners call 
Crou’stone*. The petrifactions lie imbedded in the solid 
parts of the grit; and are generally covered with a thin 
black, or dark brown, ferrugincous crust; which, when 
broken into, is found gradually to pass into the same mat- 
ter as the surrounding matrix. 
The usual size of this Phytolithus is about that of the 
specimen represented in Plate 11. But it is sometimes 
found considerably larger. I have met with it near a yard 
in length, and twelve or thirteen inches in circumference. 
In all the specimens, however, I have yet procured, the 
extremities are imperfect; nor have I been able to ascer- 
tain in what manner they terminate in the original ; though 
individual fossils of this kind have been traced, as I am in- 
formed, several yards through the gritstone before noticed. 
The vegetable which has furnished this curious petrifac- 
tion is not known : it has been considered as a species of 
* Probably from the number of black or dark-coloured petrifactions it 
commonly holds. It is principally used in repairing roads. 
