EVOLUTION OF THE AMPHIBIANS 



i»i 



have been only local. The last of the great Palaeozoic seas dis- 

 appeared from the surface of the continents, while the border 

 seas give evidence of the rise of the ammonite cephalopods. 

 Toward the close of Permian time the continent was com- 

 pletely drained. Along the eastern seaboard the Appalachian 



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PALEOGEOGRAPHY. EARLIEST PERMIAN (LOWER ARTCNSKIAN-ROTLIEGENDE-AUTUNIAN). A GLACIAL TIME 

 AFTER SCMUCHERT, APRIL, 1916 



E FIELDS t 



Fig. 62. Theoretic World En\tronment in Earliest Permian Time. 

 A period of marked glacial conditions in the Antarctic region. Vanishing of the coal 

 floras and rise of the cycad-conifer floras, along with the rise of more modern insects and 

 the beginning of the dominance of reptiles. Modified after Schuchert, 1916. 



revolution occurred, and the mountains rose to heights esti- 

 mated at from three to five miles. 



An opposite extreme, of slender body structure, is found 

 in the active predaceous types of water-loving amphibians such 

 as Cricotus, of rapid movements, propelled by a long tail fin, 

 and with sharp teeth adapted to seizing an actively moving 

 prey. This type retrogresses into the eel-like, bottom-loving 

 Lysorophus with its slender skull, elongate body propelled by 



