STRATIGRAPHIC AND TIME SCALES 1105 



pjyg^i. Local name of series. 



Eastern United States. Western Europe. 



Neodevonic ( Chautauquan 1 f Famennien 



[ benecan J [ Frasnien 



Mesodevonic i tt, ^ ■ f I -r^-r,,- 



Ulstenan I Eifelien 



f Oriskanian \ [ Coblentzien 



i aunusiei 

 Gedinien 



Eodevonic <[ Helderbergian > < Taunusien 



The values of these local series are not always uniform nor 

 equivalent. In practice it is often more convenient to speak of 

 Lotver, Middle and Upper Siluric, Devonie, etc., series (German: 

 Unterdevon, Mitteldevon, Oberdevon, etc. ; French Devonien in- 

 fcrieur, Devonien moyen, Devonien supcrieiir, etc.). These terms 

 are commonly employed in a general discussion of the strata of a 

 series. 



Ages and their corresponding stages receive local names. 

 Stages are relatively restricted in areal distribution and dif- 

 ferent countries have different stages corresponding to the same 

 age. 



Stages end in ian {iefi, Fr. ; ian, Germ.*; iano, Spanish, Italian, 

 Portuguese, Roumanian). Thus we have Bartonian, Bartonien, etc. ; 

 Portlandian, Portlandien, etc., stages. 



The stratigraphic division of the fifth order, the zone, is often 

 needed, and this division is named wherever possible after a par- 

 ticular species of organism which characterizes it. Thus we have 

 in the Lias of England the following 17 zones characterized by 

 particular species of ammonites. (Geikie-4:7/55.) 



1r 1 7 zone of Lytoceras jurense 

 16 zone of Dactylioceras commune 

 15 zone 01 Harpoceras serpentinus, etc. 

 14 zone of Dactylioceras annulatum 



Middle Lias or Liassian \ '^ "°"^ °J Paltopleuroceras spinatum 

 j 12 zone 01 Amattheus margaritalus 



* The German terms are often contracted, instead of Astian Stufe, Astistufe 

 is used. 



