425 
the fossils of this kind mentioned by Dr. Woodward, and others, 
will show that very few indeed of this numerous species can now 
obtain any other denomination than that of fossilia incognita ; bo- 
tanists not having yet been able to discover any existing analogous 
plants. Plate III. Fig. 3, represents a fossil of this description from 
Chepstow, in Monmouthshire. This, as well as most others of this 
kind, is little more than an impression, covered with a bituminous 
film, of a very inconsiderable thickness, its internal part being 
entirely sand-stone. The explanation of this circumstance does not, 
however, appear very difficult. The plant, having been surrounded 
by the soft, or fluid, materials, of which the sand-stone has been 
since formed, its internal succulent part would soon waste away, and 
its place be filled with the soft magma; whilst the more solid and 
ligneous epidermis would remain, and, after a time, would give its 
correct impression to the surrounding lapidifying matter. Then 
passing through the bituminous change, it would fill its own mould 
with its own altered substance, forming such a surface, as the sur- 
rounding stony -matter would adhere to but slightly ; and would 
therefore dispose to that separation, by which its form is displayed. 
This fossil is frequently found, where strata of sand-stone are 
found nigh to the strata of coal, in various parts of England and of 
Wales. Mr. Martin says he has seen single joints of this fossil in 
iron-stone ; and one in particular, of a large size, measuring about 
twelve inches in circumference. Mr. Da Costa relates, that in the 
collieries at Swanwich, in Derbyshire, in 1752, a plant of the cane 
kind was found, fourteen feet long : it ended in a point at one end, 
and at the root in a large knot ; and in the middle measured nine 
inches about*. He also mentions, that Dr. Woodward describes 
two specimens of this kind ; one a yard long, and the other six feet 
and a half in length. Reference to Dr. Woodward’s Catalogue 
VOL. I. 
Philosophical Transactions, Vol. L. Part I. p. 231. 
, 3 I 
