CLASS REPTILIA. 5 



plates, or shields, formed by the ribs and the ster- 



num 



IT. The Saurians, or Lizards (Sauria), in which 

 the heart has two auricles, and the body supported 

 on four, or on two feet, is covered with scales ; — 



III. The Ophidians, or Serpents (Ophidia), in 

 which the heart has two auricles, and the body is 

 always destitute of limbs; — and 



IV. The Batracians (Batrachia), in which the 

 heart has but one auricle, the body is naked, and 

 the majority of them pass, with age, from the form 

 of a fish respiring by gills, to that of a quadruped 

 respiring by lungs. Some, however, never lose their 

 gills, and some have never more than two feet.* 



* Other writers, as Merrem, make a different arrangement of the 

 Sauria and Ophidia. They make a separate order of the crocodiles, and 

 unite, to the rest of the Sauria, the first family of the Ophidians {Anguis), 

 a distribution founded on some peculiarities of organization in the croco- 

 diles, and on a certain resemblance between the angues and the lizards. 

 We have thought it sufficient merely to hint at these relations, which are 

 all internal, while we preserve a division more easy of application. 



