PRIMEVAL SALAMANDERS. 71 



orbits, is covered by a complete bony roof, extending 

 continuously from the bone marked P, which immedi- 

 ately covers the brain-case, to the sides of the hinder 

 part of the jaws. If we compare the skull of a 

 crocodile with this figure, we shall find, in place of this 

 continuous roof, a long open channel cut from behind 

 each orbit in the direction of the bone marked S. 

 Temp, to the back of the skull, while there is also a 

 pair of oval vacuities in the region of the bones 

 marked Sq. A Lizard has the hinder part of the skull 

 still more completely opened out. The completely 

 roofed skull of the Primeval Salamanders appears, 

 indeed, to show signs of affinity with some of the 

 earlier fishes ; and there seems to have been a gradual 

 tendency among Eeptiles to emancipate themselves 

 from this type of skull as time went on. For instance, 

 the Fish-Lizards (Ichthyosaurs), which show signs of 

 direct connection with the Primeval Salamanders in 

 the somewhat folded internal structure of their teeth, 

 and in their simply cupped vertebrae, are also those 

 reptiles which exhibit the nearest approximation to 

 this roofed type of skull ; while the modern and highly 

 specialised Lizards are those which depart most 

 widely from it. It may be worth mention that some 

 of those naturalists who are never satisfied with a 

 name, unless it be one for which they are personally 

 sponsors, have proposed to replace the well-established 

 name of Labyrinthodonts by that of Stegocephalians, or 

 Roof-skulled Saurians a term sufficiently appropriate 

 if no earlier one had barred the way to its adoption. 



