62 THE DOCTRINE OF DESCENT. 



6. Triassic formation or New Red Sandstone. 



Keuper or Variegated Marls. 



Muschelkalk. 



Variegated Sandstone. 



7. Permian formation or Dyas 



Zechstein (Magnesian Limestone or Dolomitic Conglomerate). 

 Rothliegendes or Red Conglomerate. 



8. Carboniferous formation. 



Coal Measures. 

 Millstone Grit. 

 Mountain Limestone. 



9. Devonian formation. 

 TO. Silurian formation. 

 it. Cambrian formation. 

 12. Laurentian formation. 



Although we are not writing on geology, a short 

 explanation of these strata will be requisite, as their 

 mutual relations also throw light on the nature and 

 distribution of the contemporaneous organisms. All 

 displacements of earth which we now see occurring by 

 means of rain, rivers, sea and other natural forces 

 which have taken place in historic times, in short, in 

 the so-called Present, such as the great delta deposits, 

 and the moraine formations of our glaciers, are ascribed 

 to the Alluvium. 



It was formerly supposed that its limits might be dis- 

 tinguished from the Diluvium by the appearance of 

 man, but as it is now, and always has been impossible 

 to affirm anything positive respecting that epoch, and 

 as, although a portion of the organisms of which the 

 remains occur in the Diluvial strata is extinct, much 

 more still exists, these" two formations are inseparably 

 intermingled. 



To the Diluvium belong the vast mud deposits of 

 the great rivers, alternating with sand banks, the clay 

 and loess formations caused by the removal of the soil 



