50 



represent in a general way the fossils we obtain from the Carbon- 

 iferous rocks ; but although there is a general resemblance, very 

 few of the fossils are actually identical in form. Most of them are 

 more or less dwarfed, and the few that look most like the remains 

 from the older formation have more or less of a changed aspect. 

 In this case we seem to have got some kind of evidence that the 

 life groups of the Carboniferous fauna survived at no great distance 

 from their old ground, and that when marine conditions temporarily 

 set in again, a few of their descendants, more or less changed in 

 form, returned for a time, until a relapse of uncongenial environ- 

 ments again caused their banishment. Whether such of their 

 relations as did not return betook themselves elsewhere, and lived 

 on till later times we have no means of knowing. But we do 

 know that at no great distance off, at this same time, a great colony 

 of other animals had been gradually encroaching upon the ground 

 occupied by the older forms of life, and that when marine con- 

 ditions again set in over this area, the advancing colony obtained 

 possession of the ground, and the representatives of the older 

 phases of life appear here no more. The few traces of life that 

 have hitherto been detected in the Penrith Sandstone are almost 

 exclusively those of terrestrial animals, and these traces, as I have 

 before mentioned, are almost exclusively mere footprints of the 

 animals that wandered over the half-consolidated silt on the shores 

 of the old lake. Such vestiges as these do not afford any very 

 satisfactory data for the reconstruction of the forms of animals 

 otherwise quite unknown to us ; but they that have given much 

 attention to the subject — Professor Owen amongst others — tell 

 us that these footprints were probably those of gigantic frog-like, 

 tortoise-like, lizard-like, and it may even be also of bird -like 

 vertebrates. 



In regard to the general nature of the life of the period, not 

 only had man not yet appeared upon the earth, but so far as we 

 know, no representatives of the class that man belongs to had yet 

 appeared, or perhaps I ought rather to say, have yet been found. 

 The oldest known mammal was obtained firom beds of the same 

 age as the Stanwix Marls. We have likewise no certain evidence 



