PLATE 51, 52. 
agree in their internal structure : — the specimen first noticed 
is furrowed on the inside, and seems to have had its cavity 
divided by longitudinal dissepiments : — in the present fossil 
the surface of the cavity is dotted with hollow points, and, 
as far as may be judged by a single specimen, the cavity 
itself is simple or one-celled. It will be difficult to deter- 
mine with certainty, the kind of plant from which either 
of these petiifactions has originated. The larger one, from 
its oblong angular form, has some resemblance to the cap- 
sule of the Iris; but its internal structure does not accord 
with that genus. 
Tig. 1 lepiesents the only specimen of P. costatus yet 
found in Derbyshire, formerly in Mr. Watson’s collection at 
Bakewell. It consists of a somewhat conical nodule of iron- 
stone; on breaking which, one side of the lower part of the 
seed-vessel was laid bare, as exhibited in the drawing. On 
a further endeavour to detach the petrifaction from its ma- 
trix, the nodule was again broken, as shown in the next 
figure. 
2. In this state the compressed form of the upper part of 
the petrifaction became evident; together with the inter- 
nal structure of the lower part ; the outside of the capsule 
being there broken away. The seeds were probably shed 
before any change of substance had taken place, as no 
vestige ot them remains. On a close examination, however, 
a considerable number of minute shells are discoverable in 
