AMPHIBIOUS VERTEBRATES. 



197 



blind * Batrachian found in the subterranean caves of 

 Adelsberg in Carniola, Austria. 



FlG. 239. Proteus of Carniola caverns, showing the external gills. 



NOTE. They are pure white, have ^bristling gills and gill-openings, 

 and small teeth. The limbs are four in number, the fore pair having 

 three toes and the hinder pair two. They breathe under water by the 

 gills and above by lungs, while experiment has shown that the former 

 can be removed without injuring them. The mud-puppy (Necturus) 

 of the United States is a familiar form in the Mississippi country and 

 upper New York. The body is broad and flat ; each foot has four 

 toes ; they attain a length of two feet. They are extremely sluggish, 

 living in muddy water. The eggs are about the size of peas. 



Order III. Tailed Amphibians (Urodela). In this 

 order the gills are generally only present in the early 

 stages ; the body is slender and eel-like. The Congo 

 snake (Fig. 240) has extremely delicate limbs, and inhabits 

 the muddy waters of the Southern States. The hell- 

 bender, or Menotoma, found in the Mississippi Valley, pos- 

 sesses permanent gills, is flat, with weak limbs and a prom- 



* The eyes of the Proteus are destitute of a crystalline lens, although 

 they have a retina. 



