24 



GEOLOGICAL BIOLOGY. 



Joseph Le Conte proposed Psychozoic, on the same prin- 

 ciple, for the latest geological period in which man has 

 appeared.* 



Chronological Succession included in Lyell's System. — Lyell 

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

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

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

 lished in 1 84 1, a recognition of the time element in classifi- 

 cation, without, however, the adoption of the biological 

 nomenclature. He gives a table " showing the order of 

 superposition, or chronological succession, of the principal 

 European groups of fossiliferous rocks." Under the heading 

 " Periods and Groups" we find the following: 



A. Recent. 



B. Post-pliocene. 

 ( C. Newer Pliocene. 



D. Older Pliocene. 



E. Miocene. 

 1^ F. Eocene. 

 ' G. Cretaceous group. 



H. Wealden group. 

 I. Oolite, or Jura Limestone 

 group. 

 I K. Lias group. 



-^ L. Trias, or New Red Sandstone 

 group. 

 M. 

 N. 



L Post-pliocene Period : 



IL Tertiary Period : 



in. Secondary Period : 



Magnesian Limestone group. 

 , Carboniferous group. 

 O. Old Red Sandstone, or De- 

 vonian group. 

 Silurian group. 

 Cambrian group. 



IV. Primary Fossiliferous ( P. 

 Period: i Q. 



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 Avith the progress of geological time. 



Dana's Elaboration of a Geological Time-scale. — Dana was 

 the first to classify and teach the facts of geology from a purely 



* See Le Conte, "Elements of Geology," first edition, New York, 1878. 



\ Lyell, " Elements of Geology," second edition, London, 1S41, vol. n. p. 178. 



