REVOLUTION VS. EVOLUTION 
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self-same reptiles whose numbers were so great during the age 
which followed; for to me their story is fraught with the greatest 
interest. 
D’Orbigny taught that the reptiles were created immediately 
following the world-wide cataclysm, into which the three 
episodes enumerated above were exaggerated, as a part of the 
process of re-peopling a world from which all life had been 
annihilated. But the researches of Williston and others have 
revealed the fact that the reptiles had been in existence long 
before these staggering events, had indeed progressed far along 
their varied and spectacular career before the close of Paleozoic 
time. Already they had deployed into several distinct orders; 
already more than one strain had risen to the climax of its 
career, tasted the fruits of success in its chosen line, and passed 
away, blotted out of existence in the never-ceasing competition 
of rival races, or failing utterly to withstand new and adverse 
conditions in their environment. 
Take for example the curious fin-backed lizards,’’ known to 
science as Pelycosaurs. From each vertebra of their spinal 
columns a long bony spine grew vertically upward, and, the 
whole series sheathed in leathery integument, formed a ^^fin” 
along the middle of their backs. Successive genera are known 
with increasingly high fins until the climax of this reptilian strain 
was achieved in a creature whose fin was twice as high as his 
back even when his body was lifted as far from the ground as 
was possible for his stubby legs to elevate it. His fin spines 
were more than two feet long and each was decorated by short 
spicules of bone growing horizontally at right angles to the 
long bony column. Just what purpose was served by these 
bizarre appendages is not known; whether for decoration, 
defense or other practical use, it matters not in the present dis- 
cussion. The important fact is that this entire reptilian race 
was swept out of existence at the close of the Paleozoic Era and 
left, so far as now known, no descendants to make their contribu- 
tion to the Age of Reptiles. 
Again, there lived at this time one group, the Mesosaurs, who 
had become entirely adapted to life in the fresh waters of rivers 
