74 Dr. G. A. Mantell on the Animalculites of the 



been laid before this Society. My friend the Rev. J. B. Reade 

 (of Stone^ Bucks), a gentleman well-known as an eminent observer, 

 was the first to investigate the flints of the English chalk in 

 search of those curious bodies termed Xanthidia ; several species 

 of which were discovered by him, and are figured and described in 

 the ninth number of the ' Annals of Natural History.' Mr. H. 

 Hopley White subsequently pursued the inquiry, and contributed 

 a notice on flint Xanthidia to the first vol. of the ' Microscopical 

 Journal,' illustrated with figures of several new forms. 



Many interesting remarks on the microscopical examination of 

 flint and chalk by Mr. Reade are inserted in the fourth edition 

 of my ' Wonders of Geology,' as well as in my recent work, ' The 

 Medals of Creation' ; which also contains an account of some dis- 

 coveries by my assistant Mr. Hamlin Lee, and by my son*. 



I propose on the present occasion, to lay before the Society the 

 general results of a microscopical examination of numerous spe- 

 cimens of chalk and flint, from the south-east of England, with 

 the hope of exciting those who have more leisure and greater 

 ability than myself, to pursue the inquiry, and not from an undue 

 estimate of the importance of the facts embodied in this commu- 

 nication. 



With a view to conciseness, it will be convenient to arrange 

 my observations under three heads, viz. — 



I. On the organic composition of the white chalk. 



II. On the organic structure and minute fossil bodies of chalk 

 flints. 



III. On the animalcuHtes of the tertiary strata of England; 

 and on the occurrence in the British seas of living genera and 

 species of infusoria, identical with many that occur fossil in the 

 miocene deposits of Virginia. 



I. On the White Chalk. — Mr. Lonsdale long since demon- 

 strated that the white chalk of England was largely constituted 

 of minute shells, corals, and foraminifera, which bodies might be 

 readily detected by brushing the chalk in water and collecting 

 the sediment ; but it was not at that time suspected that almost 

 the whole of the residue of the detritus was composed of distinct 

 organisms, so minute as to require the highest magnifying powers, 

 and a peculiar mode of manipulation, to develope and define. 

 Ehrenberg, who has determined several hundi'ed species of ani- 

 malculites from the chalk, states that some layers of that lime- 

 stone are so rich in fossil remains, that a cubic inch is made up 

 of at least one million of recognizable forms. In his memoir 

 " On numerous Animals in the Chalk Formation which are 

 still to be found in a living state," are particularized all the 



* See * Medals of Creation,' vol. i. chap. vii. 



