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THE COLLECTION OF FOSSIL VERTEBRATES 31 
Crocodiles in their palmier days were of world-wide distribu- 
tion and comprised marine as well as fresh-water types. Turtles 
are among the commonest of fossils in the Bad-lands and some 
of them of very large size. Lizards and snakes, the only common 
reptiles of modern times, are very rare and fragmentary as 
fossils, and little is known about them. 
Besides these surviving groups, several extinct groups of rep- 
tiles are shown on the south side of the hall. The BELopontTs, 
of the dawn of the Reptilian Era, were partly intermediate be- 
tween Dinosaurs and Crocodiles. The still older PELYcosAuRS 
were remarkable for an enormous rigid bony fin on the back; 
among the contemporary THERIODONTs there existed perhaps the 
remote ancestors of the Mammals. The PTreropacty ts or Fly- 
ing Reptiles were the most extraordinary of reptiles, tailless, with 
batlike wings, supported on the enormously lengthened little fin- 
ger, and with a spread in the largest species of twenty feet from 
tip to tip. The RHyYNCHOCEPHALIANS are an interesting group 
of very primitive reptiles, of which a single species, the Tuatara, 
still survives in New Zealand. 
Fossit AMPHIBIANS. 
The Age of Reptiles was preceded by an Age of Amphibians, 
when the dominant animals were allied to modern Frogs, Toads 
and Salamanders, but had the skulls covered by ag ovea 
solid bony roof and the bodies by more or less scaly Amphibi- 
armor. These Armored Amphibians have been called ans (Stego- 
Stegocephalia (oréyy, xepadr = deck-head) or Laby- °¢Ph#lia). 
rinthodonts (AafupivO0s, odous = labyrinth-tooth, from the com- 
plicated fluting or infolding of the enamel on the teeth). Some 
of them, like Eryops, were large animals with heads eighteen 
inches long and a foot wide; others resembled colossal tad- 
poles; but the majority of them were quite small animals, either 
proportioned like salamanders or else long and eel-like with 
minute limbs or none at all. 
These fossil Amphibians are the most ancient of fourfooted 
animals, and are not far removed from the central type from 
which all the higher vertebrates are believed to be descended. 
They are exhibited near the middle of the south side of the Hall 
of Fossil Reptiles. 
