RECENT AND 

 PLEISTOCENE 

 PLEiOCENC 



MIOCENE: 



oligocene: 



EOCENE 



UPPER CRCTACEOl/S 



LOWER CRETACEOUS 



UPPER JURASSIC 

 HIDDIE JURASSIC 



LOWER JUMCctiAssi^ 



RHAETIC 

 KEUPER 



mm TRiAssic 



LOWER TRIASSIC 



(ZECHSTEIN 

 ROTHLIEGENDES 



UPPER PtHNSYLVANMN 



(STEP HANI an) 

 (URALIAN) 



MIUD1EPENN5YMAN 



WESTPH/VLIAN 

 MUS COVI AN 



LOWER PENNiUWN 



NAMURIAN 



MISSISSIPmN 



(kulm; 



UPPER DEVONMN 

 MIDDLE DEVONMN 

 LOWER DEVONIAN 



Fig. 2.— Diagram indicating a conjectural position of the various gymnosperm 

 groups in geological time. The horizons were compiled by Dr. A. C. Nofi from various 

 sources. The comparative amount of space docs not equal the comparative amount of 

 time on account of the lack of space for the illustration. 



