Mr. H. Seeley on the Fossils of the Carstone Formation. 111 
XX.—On the Fossils of the Carstone Formation. 
To the Editors of the Annals of Natural History. 
GENTLEMEN, 
In April the ‘ Geological Magazine’ contained a short paper 
on the phosphatic nodules of Bedfordshire, which I first observed 
in company with my friend Mr. Knowles, of Emmanuel College, 
several years ago, when the cuttings for the Bedford Railway 
were being made. Both before and ever since then I have been 
gathering material for a memoir on the Carstone and its southern 
extension, in which this phosphate-bed is found; but I should 
not have been tempted to refer to the bed yet, had not the 
paper in the ‘Geological Magazine’ called forth another, from 
an old friend, which you have inserted in the last Number of 
your Journal. 
The author of the former paper asserts that “every organism 
of this phosphatic bed is evidently extraneous, and probably 
was derived from the destruction of the Oxford and Kimmeridge 
Clays and intervening Coral Rag, from which the phosphatic 
matter must have been obtained, while the Lower Greensand 
was in process of formation.” 
To any one who knew the fauna of the bed in question (the 
Carstone) this would seem remarkable; for, instead of every 
fossil being extraneous (and I have dozens of genera), I have 
never obtained one that is extraneous: they all appear to me 
denizens of the old sea-bed where they abound. The multitudes 
of Saurians are chiefly Cretaceous species ; and among the shells 
I seek in vain for fossils from the Oxford or Kimmeridge Clay, 
or for blocks of Coral Rag. The Gryphea dilatata is perversely 
wanting ; the Ostrea deltoidea cannot be found ; the Ammonites 
will not answer to any of their Oolitic names, or show a trace 
of iron pyrites. And yet when fossils endurable like these, and 
abundant, are wanting, it is imagined that the fragile and very 
rare argillaceous casts of shells—no firmer than the clay they 
rest in—have withstood with impunity ages of buffetting on a 
gravelly beach. 
The truth is, the “Sandy nodule bed,” as this bed in the 
Carstone may be called, reproduces, earlier in time, the conditions 
of the Cambridge Greensand. There are specimens in it of other 
rocks in hundreds; but they are old rocks, like those the Carstone 
was derived from. 
And if the fossils had been extraneous specimens from a clay, 
it would have been no more astonishing to have found that the 
alumina, magnesia, and fluorine in the nodules only make up 
4 per cent. together than to have discovered Oxford or Kim- 
