104 PICTURESQUE SKETCHES 



With regard to our own country, the principal 

 deposits subsequent to the carboniferous rocks fringe 

 these rocks both on the western and eastern sides. 

 They pass in some cases by regular transition from 

 the coal-measures, occasionally containing similar fossil 

 vegetable and animal remains, and rarely indicating 

 the lapse of any long period corresponding to a con- 

 siderable break in the continuity of the successive 

 strata. 



Overlying the coarse sandy beds which rest upon 

 the coal-measures, there is next met with a limestone, 

 (the magnesian limestone,) which differs considerably 

 from most of the ordinary limestones in its general 

 appearance, and which, in the possession of a variable 

 proportion of carbonate of magnesia, mixed with its 

 carbonate of lime, seems to have required either a 

 totally different condition of deposition from any with 

 which we are acquainted, or a subsequent change only 

 seen at present in recent volcanic districts, and then 

 on a small scale. This limestone, however, contains 

 fossils, and among them a few corals and shells ; and 

 there are also found in it fragments and sometimes 

 complete skeletons of fishes, which seem to have been 

 tolerably abundant in the seas, since whole beds are 

 charged with animal bitumen, probably derived from 

 their decomposition, and in these beds the skeletons 

 and other indications of the fishes are more than usu- 

 ally plentiful. But the most remarkable phenomenon 

 of the magnesian limestone and contemporaneous 

 strata is the presence in them of distinct reptilian 

 remains, at least five species of which have already 

 been made out. 



Over various parts of the continent of Europe, as 



