60 



STORY OP THE AMPHIBIANS 



According to Professor Le Conte the first traces 

 of an amphibian ever found were some tracks in an 

 ancient mud-flat near Pottsville, Pa. It was the foot- 

 prints of one of the giant labyrinthodonts, breaking, 



Fig. ' 26. — Jaw of Dendrerpetoii acadeanum, and section of tooth, 

 enlarged. (After Dawson.) 



r 

 into the records as a creature with fully developed 

 limbs, whose ancestry had lived long enough to lose 

 one finger, as you may see_by the cut (Fig. 25). 

 Then the next was found in a stump which was set, 

 petrified also, into a great table of rock (Fig. 27). 

 This one was quite reptilian in structure. Above is a 

 •cut of its jaw (Fig. 26). Figure 28 shows the Orche- 

 gosawrus which is quite fishlike. It was three 



and one-half feet long. It 

 was Oammd in scales and 

 had both lungs and gills as 

 some Ganoid fishes yet have ; 

 and it is about the best 

 known connecting link be- 

 tween the old monsters, the 

 sturgeonlike fishes and the living amphibians. Re- 

 cently hosts of little labyrinthodonts have been found 

 in Ohio. They had sharp noses and snakelike, limb- 

 less bodies (Fig. 29). There were some of these old 



Fig. 27. — Section of hollow 

 SigUlaria stump filled with 

 sandstone. (After Dawson.) 



