TERRESTRIAL VERTEBRATES 369 



the same Devonian period have been discovered in Greenland. Previous 

 to these no remains were known earUer than the Carboniferous period. 

 As to the manner in which feet developed out of fins, it has been suggested 

 that the fin rays might have been reduced in size and number and the 

 basal bones of the fin rearranged (Fig. 259.) Thus an appendage was 

 formed which came to possess five digits, the typical number in the 

 amphibian limb. 



