OUR BEST FEATURES 



or highly specialized modes of attachment found 

 in modern amphibians and reptiles, since it was 

 the starting-point of the conditions found in the 

 higher vertebrates, including man. 



To sum up then, the lobe-finned fishes exhibit a 

 great advance upon the sharks toward the am- 

 phibians and higher vertebrates in the following 

 respects: (1) the primary upper and lower jaws 

 are now covered with tooth-bearing bony plates, 

 only the back part of the primary upper jaw 

 (forming the quadrate bone) and of the primary 

 lower jaw (forming the articular bone) being 

 exposed and forming the articulation between the 

 upper and lower jaws; (2) the secondary upper 

 and lower jaw (premaxilla, maxilla, dentary) for 

 the first time appear as ossified tooth-bearing 

 plates, which may be compared directly with those 

 of amphibians and higher vertebrates; (3) each 

 tooth represents an enlarged denticle with the 

 base infolded into the labyrinthodont pattern. 

 It is fastened to the bone by the infolding of the 

 latter into the labyrinthodont folds; (4) thus the 

 upper and lower jaws as a whole are of complex 

 construction, including a large number of distinct 



bony plates, some of which disappear as we pass 



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