i6 



PRINCIPLES OF PALAEONTOLOGY. 



For all practical purposes, we may consider that the Aque- 

 ous Rocks are the natural cemetery of the animals and plants 

 of bygone ages ; and it is therefore essential that the palseonto- 





Fisr. 4. Sketch of Carboniferous strata at Kinghorn. in Fife, showing stratified beds 

 (limestone and shales) surmounted by an unstratified mass of trap. (Original). 



logical student should be acquainted with some of the principal 

 facts as to their physical characters, their minute structure 

 and mode of origin, their chief varieties, and their historical 

 succession. 



The Sedimentary or Fossiliferous Rocks form the greater 

 portion of that part of the earth's crust which is open to our 

 examination, and are distinguished by the fact that they are 

 regularly " stratified " or arranged in distinct and definite layers 

 or " strata." These layers may consist of a single material, as 

 in a block of sandstone, or they may consist of different ma- 

 terials. When examined on a large scale, they are always found 

 to consist of alternations of layers of different mineral com- 

 position. We may examine any given area, and find in it noth- 

 ing but one kind of rock sandstone, perhaps, or limestone. 



