OUR ANCIENT RELATIVES 



On the other hand, many of the bony plates of 

 the skull roof were taken over with little change by 

 these oldest amphibians and the same is true of 

 the derm bones of the lower jaw. On the under 

 side of the skull (Fig. 53) the parasphenoid or keel 

 bone had grown backward so as to cover the base 

 of the braincase. 



The teeth of the oldest amphibians were closely 

 similar to those of the lobe-finned ganoids, both in 

 general appearance and in microscopic structure. 

 The porcelain-like outer layer of the skin bones 

 covering the head of the lobe-finned fish had dis- 

 appeared, leaving a rough surface. Thus the face of 

 the oldest known amphibian, still consisting chiefly 

 of a bony mask, was not as different from that of 

 a lobe-finned fish as one might have expected. 



Truly Nature's ways are not as man's ways. 



After producing a beautiful mask-face of great 



perfection and serviceableness, Nature started in 



to reduce and simplify it and eventually to cover 



up this mask with tender, sensitive flesh. From 



now on, the story of the human skull is the story 



of simplification and sacrifice of numbers, together 



with the refinement and constant differentiation 



of the elements that remained. 



31 



