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



full action, with its floods of melted rocks, its opened fissures, 

 and its fountains of boiling waters and jets of heated vapours ?" 

 For a full explanation of these views I refer to the original paper 

 of Mr. Dana in the ' American Journal of Science ^ for January 

 1845. The elaborate work of Dr. Blum on the Pseudomorphous 

 Minerals may also be studied with advantage*. 



I return from this digression to the consideration of the minute 

 fossils which are of most frequent occurrence in our flints. The 

 polythalamian forms are chiefly referable to the genersiRotalia, Ro- 

 talina and Textilaria ; there are also some kinds of the compound 

 foraminifera, but these are comparatively rare, and I have not yet 

 examined them with sufficient attention. In some slices of flint 

 prepared by Mr. Darker from the Paramoudra of Ireland, polytha- 

 lamia are very numerous. The shells or cases invariably appear to 

 be silicified, and the cells of the dead shells to be filled with flint. 

 By dead shells I mean those in which the animal was dead, and its 

 soft parts removed and the shell empty, before its immersion in the 

 silex ; for I can now bring unequivocal evidence to prove, that in 

 many examples the animal itself must have occupied its shell, and 

 all its soft parts been entire, at the moment when it became en- 

 veloped by the siliceous fluid. A specimen figured in the ^ Me- 

 dals of Creation ' first directed my attention to this interesting 

 fact ; and several specimens both of Rotalice and Textilarice have 

 since been discovered, which confirm the opinion I then ventured 

 to suggest. 



In illustration of this highly interesting fact, I select on the 

 present occasion an atom of flint (scarcely larger than a pin^s 

 head) discovered by Mr. Lee, in which are imbedded two Rotative, 

 having the cells filled with a rich amber-coloured substance, that 

 under a high power presents a granular structure analogous to 

 that of the body of the recent Rotalia. In these fossils the soft 

 parts appear to be in the state of molluskite, or they may have 

 undergone silicification ; the mineral being coloured by the ani- 

 mal matter. To persons unaccustomed to the microscopical ex- 

 ploration of objects of this nature, these specimens may seem to 

 be merely casts of the interior of the shell ; but to the eye well- 

 instructed in the character of such remains, they will at once be 

 seen to be entirely dissimilar. I would content myself with re- 

 ferring to the ' Medals of Creation,^ in proof of the above infer- 

 ences, did I not know that many of the Fellows of this learned 



* The experiments of Mr. JefFrys, published in the Report of the British 

 Association for 1840, confirm these opinions, and prove that simply by the 

 agency of heated water and vapour, silex will be dissolved, and be precipi- 

 tated upon the cooling of the liquid or vapour. In one of these experiments 

 several pounds of silica were deposited on substances placed within reach of 

 the current of vapour. 



