SKELETONS OF PRIMEVAL SALAMANDERS. 

 (Much enlarged.) 



Protriton, A, and Pelosaurus, B. From Credner. 



CHAPTER III 

 THE PRIMEVAL SALAMANDERS ORDER LABYRINTHODONTIA 



THE remaining amphibians are extinct, and form an order mainly characteris- 

 tic of the upper Palaeozoic and Triassic periods, but also lingering into the Juras- 

 sic. They derive their name of L,abyrinthodonts from the complex structure of 

 the teeth of the higher forms; these displaying a peculiar pattern, caused by infold- 

 ings of the outer layer, which penetrate nearly to the centre of the crown in fes- 

 tooned lines. Most of these creatures have the general form of a salamander, with 

 the front limbs shorter than the hinder pair; the latter having always five toes, al- 

 though in the former the number may be reduced to two. Their most characteristic 

 feature is, however, to be found in the structure of the skull, in which the bones 

 are generally covered with a pitted or radiated sculpture, somewhat similar to that 

 of crocodiles. From the following figure of the skull of the mastodonsaur, it 

 will be seen that the whole of the upper surface behind the sockets of the eyes is 

 covered by a complete bony roof, extending continuously from the bone marked P. 

 which immediately covers the brain cavity to the sides of the hinder part of the 

 jaws (QJ}, whereas in all the modern salamanders this region is more or less open. 

 This roofed skull of the primeval salamanders presents an approximation to the 



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