418 Rev. W. Buckland on the Paramoudra, and 



The organic bodies that afforded nuclei to these nascent flints, 

 appear to have been dispersed pretty uniformly through the ori- 

 ginal compound mass which is now divided into beds of chalk and 

 flints, but it is not easy to determine what cause it was that re- 

 gulated the distances at which the beds of flint have been disposed, 

 or to say why we sometimes find organic bodies preserved in flint, 

 at other times enveloped and filled only by pure chalk. The solu- 

 tion of the latter question may be, that different genera of organic 

 remains afforded centers that attracted the silex with unequal force, 

 and that this will in some degree explain the phenomenon so com- 

 mon in the chalk formation, that bodies allied to the genus spunge 

 and alcyonium, are most frequently preserved in flint and chalce- 

 dony, whilst shells and other bodies, which in their natural state 

 were more calcareous, generally have their form retained by chalk 

 or calcareous spar. 



In cases of many of these silicified spunges and alcyonia (of which 

 there is in the Ashmolean Museum at Oxford, an extensive collec- 

 tion, from Henley and Stokenchurch, in Oxfordshire) the outer 

 crust being composed of flint in its common state, represents 

 rudely the outline of the body inclosed. But the internal structure 

 retains traces of all its tubes and fibres, most delicately preserved in 



fissures are rather rare, and were probably of high antiquity, nearly contemporaneous 

 with the consolidation of the rock they traverse, and before the separation of its siliceous 

 from its calcareous portions had been fully and finally completed. I have given in the 

 drawing (Pi. 24, No. 8) an example of these veins, from a chalk pit on the south side 

 of the London road, at the western extremity of Hurley Bottom, at the first ascent of 

 the hill towards Henley, and about four miles east of that town ; here the lower termi- 

 nation of the veins is covered by rubbish. A similar appearance may be seen near 

 Brighton, at Rottingdean, where both the lower and upper terminations of the sili- 

 ceous veins are distinctly laid open by a vertical section of the cliff. I have not seen the 

 spot, but copy the sectiou in PI. 24, No. 9, from a drawing and description of it that 

 were lately sent to me. The lines represent beds and veins of plated flint ; the dots ex- 

 press siliceous uodulcs. 



