Mr. H. Seeley on the Fossils of the Carstone Formation. Ill 



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 Gryphaa 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 bufl^etting on:sa 

 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- 



