PLATE 51, 52. 
A SEED-VESSEL, together with minute shells. 
IRONSTONE, 
FIp. 1, 2. 
PHYTOLITHUS pericarpii * oblongi, ad basin tri- 
quetri, apicem versus compressi, longitudinaliter 
costati : costis aequalibus pluribus. S. t. 
A petrified vegetable. The original a Pericarp or seed- 
vessel ; oblong, smaller at each end, towards the apex 
compressed, triquetrous or three-sided at the base. The 
surface longitudinally ribbed ; the ribs equal, numerous, 
slender, rounded, and somewhat distant, the intermediate 
spaces even and flat. 
Very rare. Found near Chesterfield in argillaceous iron- 
stone. 
I have only met with a single specimen of this curious 
and interesting fossil. Another petrifaction with a some- 
what similar form, and which at first I concluded to be the 
same species, has already been figured in plate 26, fig. 3. 
I believe, however, these fossils must be considered as per- 
fectly distinct ; for, exclusive of the difference of size, which 
is considerably greater than is usual in seed-vessels pro- 
duced by any one species of plant, they do not appear to 
* Capsuls ? 
