MAN FROM THE FARTHEST PAST 
only 300 remained to represent the Permian. The ratio at 
present would be more favorable to the Permian, but the 
decline is startling. Simpler, hardier forms of vegetation 
took the place of the rich Carboniferous flora. Among 
vertebrate animals arose a new order, the reptiles. Strange 
forms they took. There was, for instance, the fin-back lizard, 
Dimetrodon, found six to seven feet in length. Highly in- 
teresting is the discovery of reptilian forms which, in the 
shape of head and skeleton, begin to suggest the mammals. 
But before the age of mammals, the earth had yet to see 
the long ascendency of the gigantic reptiles which ruled at 
length air, land, and sea. The Triassic period witnessed the 
rise of the reptilian land dinosaurs, which, although they 
did not rival the monstrous forms of the two following 
periods, yet attained a length of fifteen feet. Reptiles of 
marine habit became lords of the sea, preying upon its 
previous rulers, the fishes. But the shell-armored inverte- 
brates also attained a new prominence with the rise of the 
cephalopod ammonites, somewhat similar to the modern 
nautilus. Their beautifully sculptured spiral shells present 
hundreds of varieties. 
From the Triassic we pass to the Jurassic period, in 
which the ammonites attained their maximum of luxuri- 
ance and beauty. Among the fishes, which during their 
earlier dominance in the Devonian had been limited to the 
families related to the lampreys and sharks, the modern 
bony types now first made their appearance. However, 
the Jurassic stands for the grand period of the reptiles, both 
on sea and land. Ichthyosaurs and plesiosaurs reached 
their highest development. The former took on something 
of the lines of a fish, though crocodilian of snout, with pad- 
cles, fins, and sharklike tails suitable to rapid marine loco- 
motion. The plesiosaurs were ungainly reptiles described 
by some one as having “the body of a turtle strung on a 
snake.” Like the ichthyosaurs, they were covered by 
smooth skins unprotected by scales. They ranged from 
eight to forty feet or more in length. 
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