CLASS AMPHIBIA 



365 



the eyes are without lids. These animals live a rather sluggish existence 

 on the muddy beds of lakes and rivers. They are most active at night, 

 when they wander about in search of food. The most primitive of the 

 perennibranchs and perhaps the most primitive salamander is the hell- 

 bender, Cryptobranchus, of the eastern states, which is a large species 

 reaching a length of nearly 2 feet. It has no external gills and the gill 

 clefts are vestigial. The hellbender, like the mud puppy, is a very 



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I I II I II 





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Fig. 247. — Urodeles. A, mud puppy, Nedurus maculosus (Rafinesque), from Ohio. 

 X M- -S, axolotl larva of Amhystoma tigrinum (Green). X ^-3. C, tiger salamander, 

 Amhystoma tigrinum (Green). The axolotl and the salamander from Nebraska. X %• 

 A and B from preserved specimens, C from a living one. 



voracious bottom form. A similar amphibian, found in Japan, is the 

 largest of all living types, exceeding 5 feet in length. 



One of the commonest caducibranchs found in eastern United States 

 is the large tiger salamander, Amhystoma tigrinum (Green). This 

 animal (Fig. 247C) deposits its eggs Singly in ponds in the spring. The 

 young salamander passes through a tadpole stage and metamorphoses 

 into a terrestrial form which lives in damp situations under stones or 

 logs and which frequently finds its way into cellars. The common newt 

 found in eastern United States is a small form, Desmognathus, which 

 lives under logs and stones. The female lays her eggs in a hole in the 



