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COLLEGE ZOOLOGY 



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PIALIA | 



MALI A ! 



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.'MODERN BIRDS S , 



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\ MONOTREMATA /SERPENTES ,' TOOTHkp BIRDS 



salientiAn'.testudinataX \ l " w | fc<i > 



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Fig. 551. — Phylogenetic tree of vertebrates. Double underscoring in- 

 dicates an extinct group; single underscoring, those that have but a few 

 living representatives. The boundaries of the classes are represented by 

 dotted lines. (Modified after Wilder.) 



