22 GEOLOGICAL BIOLOGY. 



In the nomenclature here proposed Eocene is derived from 

 the Greek //Gl>?, dawn, and Kaivo'S, recent; Miocene from 

 jueiov Kaivos, less recent; Pliocene from nXeiov Kalvos, more 

 recent ; and the definite meaning of the nomenclature and the 

 classification is to signify that the strata called Eocene contain 

 the first traces of the fauna now living, the Miocene strata 

 a small proportion of the living species, the Pliocene and 

 Post-Pliocene more and still more of the living types, and 

 that the whole of the Tertiary is distinguished from the 

 Secondary and all older beds by containing some representa- 

 tives of the faunas now living. 



In this earliest attempt to estimate time-relations by bio- 

 logical data, Lyell, like his contemporaries, considered species 

 to be sharply defined natural groups, and therefore it was 

 that the relations between a fossil fauna and its recent repre- 

 sentatives could be expressed in mathematical terms, indicat- 

 ing the number of identical species. The principle underly- 

 ing the classification, however, was of a deeper nature, and 

 concerned the orderly succession of faunas and floras in time. 

 Extension of the Lyellian System by Forbes, Sedgwick, and 

 Murchison. — From the application of this method of time- 

 analysis to the Tertiary beds, it was extended to an analysis 

 of the whole series of geological formations on the basis of 

 their organic remains, and the Lyellian classification took the 

 place of the older Lehmann classification as follows: 



In place of Tertiary we have Cainozoic. 



" " " Secondary " Mesozoic. 



" " " Transition " Palaeozoic. 



" " " Primitive " Azoic. 



This latter classification and nomenclature was gradually 

 built up, and mainly by English geologists, as the Lehmann 

 and Wernerian classification was largely elaborated by 

 German and French geologists. 



Edward Forbes proposed to divide the known faunas and 

 floras into two great groups. Neozoic (modern) and Palaeozoic 

 (ancient). The two terms Palaeozoic and Protozoic were pro- 

 posed about the same time. Palaeozoic by Sedgwick, for the 

 formations known to be fossiliferous, extending from his 

 lower Cambrian upwards to include Murchison's Silurian sys- 



