REPTILES 85 
were defended by three bony plates. They varied 
in size from an inch or two in length to about eight 
feet. One or two kinds managed to flourish without 
limbs. There were many species in Carboniferous 
times ; new species are found in Permian strata, 
and the Triassic rocks yield remains of some of them, 
as well as their footprints. These creatures have, 
indeed, left “ footprints in the sands of time ”’ in the 
most literal fashion. 
Fig. 32.—FootTrrints, HEAD AND TOOTH OF Ligvreenont 
(LABYRINTHODON GIGANTEUM) FROM TRIASSIC ROCKS. 
3. Reptiles * (Latin, repere = to creep). — Cold- 
blooded animals which breathe entirely by lungs, 
and crawl on their bellies or by short,legs. They 
have their bodies covered with scales or ‘bony plates. 
Examples : Crocodiles, Snakes, Lizards, and Alli- 
gators. The Mesozoic Era is well called “The Age 
of Reptiles,” for they flourished then as they have 
never done since. Remains of the earliest known 
reptiles have been found in Permian rocks, but the 
