ferent flints, I have reason to believe that the cup-like form is the 

 most frequent which a longitudinal fracture of these bodies offers to 

 our view. 



That this, however, was not the only form with which these bodies 

 were endued, I obtained a very pleasing proof, immediately on my 

 return to town from the excursion, in which these fossils had so much 

 engaged my attention. The late Mr. Jacob Forster, on leaving this 

 country for Russia and Siberia, nearly about twenty years since, had 

 carefully packed up his private collection of minerals and fossils, not 

 to be opened until his return or death. The latter circumstance hav- 

 ing taken place, I availed myself of the opportunity offered me by 

 Mrs. Forster, of purchasing some of the more interesting specimens 

 which that collection contained. Among these was that extraordina- 

 rily illustrative specimen which is represented, Plate XI. Fig. 8. 



The most ample proof is afforded by this specimen, of the kind of 

 bodies to which this immense number of flints, spread over such avast 

 tract, owe some of their peculiar appearances. Here the alcyonium, of 

 a similar species with those which are represented, Plate IX. Fig. 4 and 

 8, with its surrounding cortical part, is seen, permeated with silicious 

 earth, and inclosed in a mass of grey flint. On immersing the specimen 

 in water for a small space of time, the flint, which is hydrophanous in a 

 considerable degree, acquires transparency, and shews the alcyonium 

 itself of a bright red colour, and penetrated by white fibres or tu- 

 bules ; whilst the whole of the surrounding flint is, by the same means, 

 discovered to be very closely filled with a white substance, which is 

 apparently similar to the cartilaginous or cortical part, which immedi- 

 ately invests the alcyonium itself. 



I however here experienced some difficulty, since the fossil alcyo- 

 nium, which I had thus fortunately discovered, did not bear the cup- 

 like form, which appears to be so very prevalent in the flints which 

 had engaged our attention. This difficulty, however, disappeared, on 

 considering, that the cavity, in the superior part of the ficoicl fossil 



