Great Salamanders and tlieir Associates 



above, but if viewed from the back it will be 

 seen that its solidity is superficial, and due to 

 wings of bone running from the brain-case 

 down to the side, over the space in which the 

 jaw muscles lie. Curiously enough, there is 

 one mammal that mimics the turtle in its skull, 

 an extremely rare African rodent called Lophi- 

 omys, one of the many instances wherein Na- 

 ture repeats a character, just as she has done 

 in the matter of mngs. The limbs, so far as 

 known, show no trace of having been modified 

 from the fins of fishes, but resemble in their 

 structure those of other quadrupeds. Some 

 of the small species were legless, and these, 

 like serpents, were slender, long-bodied ani- 

 mals. These Stegocephala were, as indicated 

 by the arrangement of the nostrils, the first 

 vertebrates to breathe by means of lungs ; 

 at least they so breathed when mature, for 

 they are believed to have undergone a change 

 somewhat like that a tadpole undergoes when 

 it is transformed to a frog ; and some are cer- 

 tainly laiown to have had gills when young. 

 This transformation may not have been so 



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