1 104 PRINCIPLES OF STRATIGRAPHY 



1. International Geological Congress. At the first meeting 

 of the Congress in Paris in 1878 a commission was appointed to 

 frame a plan of procedure for the unification of geologic classifi- 

 cation and naming. The recommendations of this Commission, 

 adopted at the Bologna Congress in 1881, as far as they affect 

 the point in question, are as follows. (1) Era — Group; (2) 

 Period — System; (3) Epoch — Series; (4) Age — Stage; '(5) 



. . . — Assize. No time equivalent for (5) (Assize) was 

 designated. 



During succeeding Congresses proposed modifications of this 

 scheme were discussed until in 1900 the 8th Congress, convened 

 in Paris, accepted the following scheme : 



Chronologic. Stratigraphic. 



I, Era (Eres). I. (No stratigraphic term). 



2. Period (Periode). 2. System (Systeme). 



3. Epoch (Ejioque). 3. Series (Series).* 



4. Age (Age). 4- Stage (Etage).t 



5. Phase (Phase). 5. Zone (Zone). 



Periods, and the corresponding systems, have a worldwide value, 

 and are characterized by the development of the organisms during 

 the period, and their entombment in the strata of the system. Pe- 

 lagic faunas, where available, are especially characteristic, owing 

 to their wide distribution and independence of local environments. 

 The termination of the names of periods and systems adopted is ic, 

 ique (French) ; isch (German) ; ico (Spanish, Italian, Portuguese, 

 Roumanian) ; Ex. Cambric (Cambrique, Kambrisch, Cambrico) ; 

 Devonic (Devonique, Devonisch, Devonico) ; also Carbonic (Car- 

 bonique, Karbonisch, Carbonico) ; Cretacic (Cretacique, Kretacisch, 

 Kreide Formation), etc. 



Periods are generally divisible into three epochs each, which are 

 designated by the prefixes Palcco-, Meso-, and Neo-. For Palcco- 

 the term Eo may be used, wherever the name is long and the name 

 itself further abbreviated. (Williams-19.) Thus, while Palseocam- 

 bric, Mesocambric and Neocambric are used, Eodevon, Mesodevon 

 and Neodevon, or, Eocret, Mesocret and Neocret, may be used for 

 these longer terms. Locally, series are commonly given names de- 

 rived from typical locaHties, these ending in ian (ien, Fr., etc.), as 

 the following example will show : 



* German, Abtheilung. t German, Stufe; Italian, pia^io; Spanish, piso. 



