538 GEOLOGY. 



and pitted by rain-drops, implying a freshly emerged mud-flat again 

 covered before the impressions were lost. 1 This solitary record prob- 

 ably stands for many amphibians that had already attained a dis- 

 tinctive development, a suggestion that is supported by the rather 

 wide differentiation which the amphibians presented when first they 

 were well preserved in the next (Coal Measures) period. The European 

 record is better, nearly complete specimens referred to the labyrintho- 

 donts having been found in the Edinburgh (Lower Carboniferous) 

 coal field of Scotland. 2 



Probably the insects and their allies found in the preceding period 

 were represented, but their fossils are not known to have been found. 



1 Dana's Manual, p. 644. 



2 Described by Huxley, under the name Pholidog aster, Vol. XVIII, Q. J. G. S. 



