THE GEOLOGICAL TIME-SCALE. 



193 



II. Tertiary Period 



Professor Le Conte has proposed Psychozoic, on the same 

 principle for the latest geological period, in which man has 

 appeared. (See Le Conte, Elements of Geology, New York). 

 Lyell proposed to make, on this basis, a geological time-scale 

 and applied the term Period to each of the several divisions of 

 the scale. Thus we find in his Geology, second edition, pub- 

 lished in 1 84 1, a recognition of the time element in classification, 

 without as yet the adoption of the biological nomenclature. He 

 gives a table " Showing the order of superposition, or chrono- 

 logical succession, of the principal European groups of fossilifer- 

 ous rocks. Under the heading " Periods and Groups " we find 

 the following: 



T D ^- or v> ■ aS ^- Recent. 



I. Post-Pliocene Period \ 



{ B. Post Pliocene. 



C. Newer Pliocene. 



D. Older Pliocene. 

 1 E. Miocene. 

 L F. Eocene. 



G. Cretaceous group. 

 H. Wealden group. 

 I. Oolite, or Jura limestone group. 

 K. Lias group. 



L. Trias, or New Red sandstone group. 

 M. Magnesian limestone group. 

 N. Carboniferous group. 

 O. Old Red Sandstone, or Devonian 

 group. 



IV. Primary fossiliferous Period — P. Silurian group. 



? O. Cambrian group. 



(Lyell, Elements of Geology, second edition, London, 1841. 

 Vol. ii, p. 178). 



Later Lyell adopted the biological nomenclature, and was 

 prominent among geologists in developing and elaborating the 

 idea of the successive appearance of new types of organisms 

 coordinate with the progress of geological time. 



III. Secondary Period 



