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The various Zoophytic bodies, passing under the names Cho- 

 anites, Polypothecia, Ventriculites, &c., usually owe their pre- 

 servation to their more or less intimate connection with flint. 

 The siliceous material sometimes permeates the whole sub- 

 stance of the organic body, filling up the pores and larger 

 cavities, and accumulating in excess on the exterior, forms a 

 nodule of flint which presents only a rude outline of the 

 contained nucleus. More frequently, however, the Zoophyte 

 is mineralised with opaque silex, associated with pulverulent 

 Carbonate of Lime, but in these cases a deposit of black flint, 

 external to the whole, is invariably present, not confluent 

 however with the included fossil, the two being readily separa- 

 ble, and sometimes removed from actual contact by a consider- 

 able intervening space. The process of mineralization is rarely 

 found to have extended throughout the entire mass of any one 

 individual specimen. Sometimes the expanded cup-shaped por- 

 tion is preserved, at other times part of the stem, but the base of 

 the stem with the commencement of the roots is the part most 

 frequently met with. As the excess of flint in the portions 

 thus preserved would, in the majority of instances, have amply 

 sufiiced for the mineralisation of the entire organic body, it 

 would seem that the original tissues of the Zoophytes of the 

 Chalk had no special afiinity for silex, beyond that of forming, 

 in common with other organic bodies, nuclei for its aggregation. 

 In the examination of the Bridlington Zoophytes, considered 

 in relation to their mineral condition, the attention of the 

 observer is at once arrested by the total absence of flint, either 

 as an external casing or as a material solidifying their mass. 

 In the absence of any chemical test, their appearance conveys 

 the idea that they have been rendered stony, simply by the in- 

 terstitial deposition of calcareous matter. Lime taking the part 

 usually assigned in the laboratory of nature to Silex, in bringing 

 about the mineralization of the Zoophytes which flourished on the 

 bed of the Cretaceous ocean. This phenomenon seeming to call 

 for more special consideration than had yet been given to it, 

 I tried the effect of subjecting various specimens of the Bridling- 

 ton fossils to the action of dilute muriatic acid. The experiment 



