OF PETRIFACTIONS. 233 



From the short account now given, it appears, that the 

 floetz trap-rocks, in whatever situation they occur, con- 

 lain very few organic remains.* 



IX. Newest Flcetz Formations. 



Over the chalk rests a series of calcarious and siliceous 

 formations, which, in general, abound in petrifactions. 

 They appear to have been deposited from the water of 

 lakes or inland seas, some of which are conjectured to 

 have been alternately filled with fresh and salt water ; and 

 hence, in a general view, are of a more local nature than 

 those which have been deposited from the waters of the 

 ocean. The newest members of the series are of so 

 loose a texture, the fossil organic remains they contain 

 so nearly resemble those that now inhabit the earth, and 

 they are so nearly related to the alluvial formations which 

 are daily forming, that it is often extremely difficult, nay 

 even sometimes impossible, to determine whether they 

 belong to the alluvial or newest floetz formation. There 

 appears to be a gradation or transition from the one into 

 the other. The petrifactions they contain are of zoo- 

 phytes, shells, fishes, and amphibious animals ; and fossil 

 remains of birds and quadrupeds here for the first time 

 appear enclosed in strata. The country around Paris, 

 that of the Isle of Wight, and other districts in the south 

 of England, as particularly described in Note K (B), be- 

 long to these newer formations. 



X. diluvial Formations. 



The mineral substances included under this class are 

 considered to be of newer formation than any of the 

 iloctz rocks ; and the following are the most frequent and 



* This is the formation considered by many geologists as entirely of 

 volcanic origin. 



30 



