200 HISTORICAL GEOLOGY 



northern Siberia (Ordovician) ; New York (Salina epoch of the 

 Silurian); Michigan, Montana, Nova Scotia, and Australia 

 (Mississippian) ; and southwestern United States, western and 

 central Europe, and other parts of the world (Permian). 



Organic History 



Viewed in a broad way, the life of the Paleozoic is distinctly 

 different from that of the succeeding Mesozoic or Cenozoic. Very 

 few species and not many genera passed from the Paleozoic to the 

 Mesozoic, and even the larger groups of organisms which did con- 

 tinue usually underwent important structural changes. Paleozoic 

 organisms were the more primitive in structure, and it has been 

 aptly said that they bear somewhat the same relation to the suc- 

 ceeding forms that the embryo does to the adult. 



Of plants in the early Paleozoic only the simplest Cryptogams 

 are known, while in the later Paleozoic periods there are abundant 

 records of the higher Cryptogams such as Lycopods, Equisetae, 

 and Ferns, as well as of the Gymnosperms. Angiosperms (typical 

 flowering plants) are wholly unknown from the Paleozoic, and even 

 the later forests and foliage of the era must have presented a gloomy 

 appearance because of the lack of true flowering plants as com- 

 pared with today. 



The animals of the Paleozoic were predominantly inverte- 

 brates, though Fishes were common in the Devonian and later 

 periods, and Amphibians and Reptiles appeared in the later periods. 

 Among the most common and characteristic types of invertebrates 

 were Graptolites, Corals, stemmed Echinoderms (Pelmatozoans), 

 Bryozoans, Brachiopods, Tetrabranch Cephalopods (Nautiloids 

 especially), Trilobites, and Eurypterids. Certain of the higher 

 Arthropods such as Spiders, Myriapods (Centepedes) , and Insects 

 did not appear till the era was pretty well advanced. 



The accompanying chart has been devised by the writer for the 

 purpose of bringing together the salient facts in the organic history 

 of the Paleozoic era. Period b} r period the principal evolutionary 

 changes in the subkingdoms and classes of plants and animals are 

 graphically represented. 



