10 



the same geological formation in the North of Ireland. These 

 paramoudras are more frequently hollow than the ordinary 

 nodular flints though they do not uniformly contain the fine 

 powdery material which was present in the specimen I met 

 with, but occasionally, as noted by Sir Charles Lyell, they 

 have an internal cylindrical nucleus of pure chalk much harder 

 than the ordinary surrounding chalk and not crumbling to 

 pieces like it when exposed to the winters frost. In com- 

 mon with the other chalk flints of this district the exterior 

 surface of the paramoudras is white and rough, while the 

 interior is of a dark tint. 



The particular specimen which yielded me the fossiliferous 

 powder was about a foot in diameter and more spheroidal than 

 the generality of the potstones. The manner in which the 

 interior cavity became inclosed may be understood by supposing 

 that the process of the deposition of the silica , by which 

 the ordinary cup-shaped paramoudras were formed , was con- 

 tinued further, until the cup was arched over with a solid 

 layer of flint, and thus the soft incoherent ooze included within 

 was preserved safely from the effects of all further mechanical 

 influence. Without entering here into the vexed question 

 about the formation of the flints in the chalk, it may be as 

 well to notice that the beautifully perfect state of preservation 

 of the various delicate fossil organisms in the interior of this 

 flint , when compared with the nearly complete obliteration of 

 their structures in the enveloping chalk points to the conclusion, 

 that the period in which the flints were formed must have been 

 previous to that consolidation of the mass of the chalk by which 

 the smaller fossils were mostly destroyed. The flint powder 

 or flint meal which was preserved in the cavity of this flint, 

 like the ashes of the dead in a funereal urn , had the appear- 

 ance of a very fine flour of a creamy yellow tint, thus differing 

 but slightly from the soft earthy white chalk in which the 

 flints are here imbedded. The finest portions of the flint- 

 meal, under high powers of the microscope were seen to be 



