48 THE ORIGIN OF MAN 



the Middle Devonian. The Reptilia, however, 

 appeared first in the Upper Pennsylvanian. The 

 evolution of the air-breathing vertebrate life of 

 the Carboniferous is the most important phase of 

 the whole progress of evolution, for at the close 

 of this period forms foreshadowing the chief 

 groups of modern times are found. The Am- 

 phibia, for the most part, were small creatures 

 related to the living salamanders and known as 

 branchiosaurs and microsaurs. They were rather 

 sluggish animals living about or in the water and 

 were more or less protected against their enemies 

 by an external bodily armor. Some of the micro- 

 saurs, however, lost the dermal armor completely 

 and became fleet of movement, which is best seen 

 in the structure of the limbs. 



As to the invertebrate life of the Pennsyl- 

 vanian brachiopods are very common but toward 

 the close of this period their places were being 

 taken by the bivalves. While the brachiopods 

 were vanishing, the shelled cephalopods in the 



