IN THE MUD OF THE LEVANT. 73 



to my friend Dr. Mantell, is exceedingly rich 

 in analogous forms, only the finer portions are 

 more obviously the direct result of the breaking 

 up of the larger Polythalamia. We also find 

 numerous calcareous shell prisms (looking very 

 like sponge spicula), fragments of larger shells, 

 especially Terebratulse and Inocerami, with some 

 portions of Echinodermata, readily distinguished 

 by those whose eye is familiar with recent exam- 

 ples of the same structures. 



Chalk from the midland counties presents us 

 with similar results, varying, at different localities, 

 as to the distinctness of the organisms, the amount 

 of amorphous matter, and the abundance of shell 

 prisms. The Yorkshire Chalk, which is more 

 compact, exhibits similar structures, though they 

 are less easily separated from their amorphous 

 cement, and in some specimens so broken up as to 

 present few perfect organisms ; — as if the newly 

 forming stratum had been acted upon by gentle 

 aqueous currents, which had transported the 

 more minute atoms to another locality, where 

 some local interruption to the current allowed 

 this sediment to be re-deposited, giving rise 

 to layers of denser structure and finer grain. 

 The Red Chalk, which is of a bright red colour, 



L 



