396 



General Biology 



or 



changing climatic conditions which give us the terms "ages 

 "periods," such as the carboniferous age and the glacial period. 



If the deposition of the earth's layers has been laid down by water 

 and air, the various strata show such causes by forming a coarse sand- 

 layer, followed by a layer of finer sand or mud. Or, two sandy layers 

 will be found separated by thin layers of muddy shale, the exact forma- 

 tion depending upon the velocity of both sand and water. 



Or, there may be mechanical and chemical changes which produce 

 beds of rock sand or gypsum between beds of marl. Likewise, organic 



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Q. 





E&rliest of true 



Reptiles, 



Amphibions, 



Lung Fishes; 



Fringe Fins; 



First Cray Fishes. 



Insects abundant; 



Spiders; 



Fresh Water Mussels. 



Ferns, 



Cal&mites. 



Lycopods, 



Cycacls, 



Conifers. 



First Amphibians. 

 (FrogliKe Animals) 

 SharKs; 

 Ostracophores. 

 First Long Shells 



(Snails) 

 HollirtKs abundant 



First Crabs 

 Ferns 

 Calamites 

 Lycopods 

 Cycads 

 Conifers 



First truly 

 terrestrial or air- 

 breathing animals; 

 First Insects, 

 Corals abundant , 

 Mailed Fishes 

 Probably some 

 Land Vegetation 



First Known Fishes: 

 Ostracophores; 

 (Fishes having no jaw*. 

 Segmented Backbones or 

 Limbarches & Forepart 

 protected by bony Plates 

 Cartilaginous Skeleton ; 

 Brachiopods , 

 Tribolites;MollusKs.«tt 



Invertebrates only. 

 Probably some 

 Higher Algae 



41 



tx> 



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Permian 



Red Sandstone, etc 

 riagnesian Limestone 



Coal Measures. 

 First Reptiles(?) 



Sub-carboniferous 



Carboniferous Limestone 



Corniferous 



Schoharie Grit 





Sandstones, 

 Shales, 

 Some Limestone 



Slates, Sandstones, 

 Volcanic KocKs, etc. 



Slates Sandstones, etc 



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T 00_e< 



Simple Marine 

 Invertebrates 



Probably very 

 simple Algae 



Slates, Volcanic Rocks, etc 

 No Vertebrates Known 



Fig. 245. 



