566 POPULAR SCIENCE MONTHLY 



here in older rocks than in Europe. Among the many forms known 

 may be mentioned some with a peculiar type of vertebra in several 

 allied genera found in Ireland, western Europe and North America ; 

 some with, fish-like scales over the whole body found in Ireland and 

 Ohio; the presence of the snake-like forms in Ireland, England, western 

 Europe and Ohio and the presence on the continents of Europe and 

 North America of the Branchiosauria already referred to. All of the 

 types of amphibians possess the peculiar ventral armature which was 

 arranged in a chevron pattern over the belly, breast, throat, and even 

 extended, in some cases, out on the limbs. 



The earliest quadrupeds, as we know them, form highly specialize 1 

 groups of organisms which had become differentiated into five distinct 

 lines by the close of the Carboniferous. We must await the progress 

 of discovery to unfold for us the nature of the most primitive quad- 

 rupeds from which the earliest known forms have sprung. 



