212 Nezv York State Museum 



The Paleozoic is the oldest of the three main groups 

 (Paleozoic, Mesozoic, Cenozoic) into which the normal 

 fossiliferous strata have been divided, and in time was 

 of vast extent, exceeding in length the combined Meso- 

 zoic and Cenozoic, according to most recent reckonings 

 twice as long. There were widespread crustal disturb- 

 ances before the beginning of the Paleozoic and there 

 were pronounced changes again at the end of the era, so 

 that almost universal unconformities have been produced 

 with the Precambrian beds below and the Mesozoic 

 strata above. Due to the abundance of fossils which fur- 

 nish a reliable means of correlating formations from 

 place to place, even between continents, the post-Protero- 

 zoic strata have been classified in much greater detail. 

 There is no complete record of Paleozoic formations, 

 even by piecing together all the sections studied, but it 

 is believed with reason that the gaps left do not as a rule 

 represent long intervals of time. 



The Paleozoic group of strata has in general been 

 divided into seven periods of time or systems of rocks : 

 Cambrian, Ordovician, Silurian, Devonian, Mississippian, 

 Pennsylvanian and Permian, to which are now added two 

 others, Ozarkian and Canadian (Ulrich '11), which rep- 

 resent respectively the uppermost Cambrian and lower 



PALEOZOIC ERA 



Neopaleozoic 



or Younger Paleozoic (char- 

 acterized by the presence of 

 vertebrates, both fishes and 

 amphibians) 



, [ Permian* Lair 

 •g (Age of Amphibians and 

 o g \ Pennsylvanian Ancient Floras) 



(j<Js, 1 Mississippian Middle 



Devonian (Age of Fishes) 





Silurian 



Ordovician 



Canadian 



Ozarkian 



Cambrian 





Eopaleozoic 



or Older Paleozoic (character- 

 ized by absence of verte- 

 brates) 



Early 

 (Age of Invertebrates) 



• Lower Permian in North America is regarded by some as the top of the Penn- 

 sylvanian; the Upper Permian as Mesozoic. 



