78 AMPHIBIA. 



lungs, and in undergoing consequently a total change in 

 the medium of their respiration ; whilst the Proteus and 

 the Siren retain their branchiae with lungs, (rudimentary, 

 at least,) and probably throughout life possess synchro- 

 nously the two-fold function of aquatic and atmospheric 

 respiration. The Ampkiuma and Menopoma have not as 

 yet been observed to possess branchiae at any period of 

 their existence, though further observations are necessary 

 to warrant the conclusion of the absolute non-existence 

 of a metamorphosis in those genera."* 



As it appeared to me that no one arrangement 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, 

 compressed ; afterwards totally wanting. Ribs wanting. 

 Vertebrae few and anchylosed. Tympanum open. Respi- 

 ration at first aquatic by branchiae, afterwards atmospheric 

 by lungs. Branchiae at first external, but withdrawn with- 

 in the chest before the metamorphosis. Impregnation ef- 

 fected externally during the passage of the ova. 



Genera. Rana, Hyla, Bufo, &c. 



* See the article " Amphibia," by the author of the present work in Dr. 

 Todd's Cyclopaedia of Anatomy and Physiology. 



