Time and the Geological Record 299 



posed shell substance. A consideration of this sequence 

 drives the unprejudiced observer to the conclusion, that the 

 reason the later forms, such as the quadruped skeletons, are 

 not found in the old debris which has preserved crustaceous 

 shells and worm molds, must be that there were none there to 

 be preserved. No other theory is presentable. If there had 

 been any such forms they must have endured in some places, 

 among the many which reveal more fragile things. Yet 

 there are no such examples. It cannot be that we are mis- 

 taken as to their possible contemporary existence, or their 

 comparative durability among the crustaceans and worms. 

 These early types persisted, with some modifications, which 

 do not affect their geological durability, and we find them 

 later along with mammalian relics. We find that after 

 lizards appear, lizards of one kind or another continue, and 

 lead up to the lizards we now see alive; which are not in 

 detail the same, but are clearly descendants, modified as 

 we have seen living forms can be modified. And so we see 

 each form persist for some time, and merge in others nearly 

 resembling it. A reference to bird forms as the most strik- 

 ing example may close this discussion. The birds are, in 

 fossil records, traceable backward until their ancestors ap- 

 pear with only the beginning of bird form as we know it. 

 They are seen as lizardlike creatures whose feathers are al- 

 most as scales and whose wings are but aids to leaping. 

 Such forms are only remotely like our birds, but when these 

 things are found coincident with the disappearance of birds 

 which approximated to these lizards, we may suppose that 

 they are the progenitors of the birds. Let us examine the 

 possible alternatives. If the birds, which appear at a certain 



