. II. RELICS. Phenomena. 11 



o. Of petrified shells it has been observed, that 

 some families are most common, which afford the 

 fewest known species in the recent state, f 



p. A petrifaction rarely, if ever, exhibits a com- 

 plete change, or substitution of mineral for organic 

 matter ; more or less of the original animal or vegeta- 

 ble substance being generally present, and discover- 

 able either in the external or internal parts of the 

 fossil, ff 



q. The petrifying process is carried on, in some 

 waters, at this day ; but appears to be confined to 

 the formation of petrified wood, or woodstone. 



ascertained to originate from certain plants and animals peculiar to 

 tropical climates; and a few others, particularly in France and 

 England, have been referred to native species ; but the far greater 

 number remains unknown in the recent state. 



t Anomia, nautilus, &c. shells of the same genera as those 

 most frequent on our shores, the volutte, patellce, and cyprete, for 

 instance, rarely occur petrified. 



ft This remark, we believe, will hold good in almost every in- 

 stance ; even in what are called the most perfect petrifactions, if they 

 be properly submitted to examination. In shells and corals petri- 

 fied, the original calcareous matter is frequently seen covering the 

 surface, or remaining in small portions in the internal parts (a sin- 

 gular example of this occurs in a specimen of petrified coral de- 

 scribed in " Derby shire Petrifactions" Vide Plate 18. Fig. 2. 3.) 

 and is readily distinguished, although the substituted mineral, form- 

 ing the principal portion of the fossil, be also calcareous. In the 

 common vegetable petrifactions of our coal-strata, some vestige or 

 remains of the original bodies, may almost always be traced ; and in 

 jasperizcd wood, which presents, perhaps, the most complete mi- 

 neral change known, vegetable matter still exists, according to the 

 experiments of Mr. Parkinson. Vide " Organic Remains." p. 344. 



