192 VEETEBRATA. 



Class II. AMPHIBIA. 



PsiLODERMATA. NuDIPELLIFERES. 



Vertebrate animals breathing by gills, mostly external in the 

 earlier stages of life, afterwards by lungs. With or without 

 limbs ; never with fins in the adult. Heart with two auricles 

 and one ventricle. No amnion nor allantois. 



In some Amphibia the gills are retained through life, notwith- 

 standing the presence of lungs ; but much of the respiration is 

 also carried on by the skin. They all undergo a metamor- 

 phosis, the young gradually departing from their fish-like form 

 and developing limbs. 



The lungs are generally long and narrow, sometimes extending 

 nearly to the anus. There is no diaphragm. The kidneys are 

 homogeneous in texture, as in fishes, reptiles, and birds. The 

 tympanitic cavity in the ear first makes its appearance in the 

 Batrachia. There is a single occipital condyle on each side. 

 True ribs are wanting, or they are only rudimentary, or are not 

 supplemented by sternal ribs. The vertebrae vary from 10 to 

 230. Reproduction is by ova. 



None of the Amphibia are poisonous, but several secrete a 

 very acrid fluid in their subcutaneous glands. 



There are four orders : 



Recent. 



Without limbs ; vermiform OPITIOMORPHA. 



With limbs ; never vermiform. 



Body elongated, tailed URODELA. 



Body short, tailless BATRACHIA. 



Extinct .. LABYKINTHODONTA. 



Order I. OPHIOMORPHA. 



APODA. GYMNOPIIIONA. PSEUDOPHIDIA. OPIIIOSOMA. 

 PEROMELA. 



Apodal vermiform amphibians, with small scales imbedded in 

 the soft skin. Anus terminal. Eyes rudimentary or wanting. 

 Young breathing by gills. 



The body is transversely grooved or ringed. The ribs are 

 numerous and very short, and there is no sternum. The teeth 



