Penrose] PHOSPHATES OF ENGLAND. 93 
Most of the fossils in theso Lower Greensand phosphate bods have 
been derived from older formations. They are rolled and worn to such 
an extent that it is frequently impossible to identify them. Keeping, 
in speaking of the piles of phosphatic material at the mines, says, 
that " the coprolite heap looks like one mass of Ammonites biplejc, mostly 
worn and fragmentary." The fossils are mostly worn species of mol- 
lusca of Oxfordian, Kimmeridgean, or Portlandian species of the Upper 
Jurassic (W. Keeping). Many of the derived species are of the Neo- 
comian age, such as Ammonites Deshayesii, Ancyloceras sp., Hamites 
sp., Thetis minor Sowerby, Terebratula ovoides Sowerby, and other 
forms. 
Thus it will be seen that these latter fossils have been derived from 
a bed but very little older than the nodule bed, as this latter deposit 
belongs, according to J. F. Walker, 1 to the Upper Neocomian forma- 
tion. Mr. Walker 2 also thinks that a large number of the derived 
fossils came from the underlying Kimmeridge Clay. Many of the 
fossils of the Upware nodule bed are preserved in amorphous or crys- 
talline calcite, others in ferruginous sandstone and phosphate of lime. 
The fossil wood is silicifled. According to W. Keeping, all the shell 
casts and fossils that have been mineralized by phosphate or limonite 
are derived fossils and belong mostly to Jurassic species. They are 
easily recognized by their rolled and water-worn condition. Walker 
divides the fossils into (a) indigenous fauna, preserved in oxide of iron, 
and (b) derived fossils, preserved in phosphate of lime. H. G. Seeley, 
on the other hand, thinks that all these fossils are natives of the beds 
in which they are found. 
As regards the mode of phosphatization of these beds, Walker, Keep- 
ing, Teall, and others agree in the theory that it is the result of the 
soaking of calcareous substances in decomposed animal and vegetable 
matter. The Coral Eag fragments in the bed are not at all phosphatized. 
In this particular the deposit resembles those of Alabama and the Car- 
olinas, where shells perfectly free from phosphatic matter are associated 
with beds of highly phosphatic nodules and fossils. This would seem 
to show that the non-phosphatic substances were deposited after the 
nodules had been phosphatized. But Dr. C. U. Shepard, jr., 3 and W. 
Keeping explain the phenomenon by supposing that the purer forms of 
carbonate of lime are not so susceptible to phosphatization as the im- 
pure forms. 
A very distinctive feature between the Upper and Lower Greensand 
phosphate deposits is the nature of the matrix of the nodules in the 
two formations. As has been already said, the matrix of the Upper 
Greensand is a calcareous Greensand containing 2 to 10 per cent, of 
phosphoric acid, while the matrix of the Lower Greensand nodule beds 
1 Mon. Fossil TrigonitB, Pubs. PalaBontographical Soc, vol. 29, 1875, p. 14f>, 
2 Annals Mag. Nat. Hist., 1866. 
3 South Carolina Phosphates. 
(.-,07) 
