74 AMPHIBIA. 



The Amj)hiuma and Menopoma have not as yet been ob- 

 served to possess branchiae at any period of their existence, 

 though further observations are necessary to warrant the con- 

 clusion of the absolute non-existence of a metamorphosis in 

 those genera."* 



As it appeared to me that no one an-angement hitherto 

 given had sufficiently distinguished the different forms, I 

 proposed, in the article just quoted, the following modifica- 

 tions as more consistent with the diversities of structure in 

 the different groups. 



Class AMPHIBIA. 

 Order I. anoura. 



Body short and broad. Feet during the tadpole state 

 wanting ; afterwards four, the hinder ones long, and formed 

 for leaping. Tail before the metamorphosis long, com- 

 pressed ; afterwards totally wanting. Ribs wanting. Ver- 

 tebrae few and anchylosed. Tympanum open. Respiration 

 at first aquatic by branchiae, afterwards atmospheric by lungs. 

 Branchiae at first external, but withdrawn within the chest 

 before the metamorphosis. Impregnation effected externally 

 during the passage of the ova. 



Genera. Rcma, Hi/la, Bufo, Sec 



Order II. urodela. 



Body long, slender. Feet always four. Tail long, per- 

 sistent. Ribs very short. Vertebrae numerous and move- 

 able. Respiration at first aquatic by external branchiae, which 

 are never concealed within the chest ; afterwards atmospheric 



* See the article " Amphibia," by the autlior of the present woik in Dr. 

 Todd's Cyclopaedia of Anatomy and Pliysiology. 



