CREATION BY EVOLUTION 



these strong-jawed, pike-like fishes each of the stout paired 

 fins (corresponding to our arms and legs) was supported 

 by an internal skeleton consisting of bony rods converging 

 toward a single bone, corresponding respectively to our 

 single upper arm bone (the humerus) or to our thigh bone 

 (the femur) . The fore paddles were supported by a complex 

 shoulder girdle, parts of which correspond to our collar and 

 shoulder bones ; the hind paddles were supported on a bony 

 plate corresponding to the lower bars of our pelvis. 



The skull of these lobe-finned ganoids, like the human 

 skull, was a complex of two very distinct sets of elements. 

 The inner skull, or braincase, consisted of the bony trough 

 surrounding the brain and of the bony shells or capsules 

 surrounding the organs of smell, sight, and balance. The 

 outer skull consisted of a shell of bones, derived, like the 

 scales on the body, from the skin. In the earlier crossopts 

 (such as Osfeolep/s) the outermost layer of the bony skull 

 and scales consisted of a hard, shiny, porcelain-like substance 

 called ganoin, but in many of the later crossopts this outer 

 layer was lost, leaving a sculptured bony surface. 



Among living fishes only the famous Polypterus, the bichir 

 of the Nile, and a nearly related genus have any claim to be 

 considered the modified descendants of these lobe-finned or 

 crossopt fishes of the Devonian period. These interesting 

 relics still retain vestiges of former air-breathing arrange- 

 ments in their lungs or swim-bladders, but they now rely 

 chiefly on their gills for aeration. 



Origin of the Amphibia 



The connecting links between the lobe-finned fishes and 

 the amphibians of the coal forests are not yet discovered, 

 but all the known earlier land-living forms agree in so many 

 points of structure with the lobe-finned fishes that there can 



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