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ABRANCHIA. 



ORDER IV. ABRANCHIA. 



{AmpMhia without gills.) 



North America, wliicli presents us witli all 

 the anomalous forms that we have been consider- 

 ing, with the exception of the Proteus, produces 

 two or three species which are still more eel- 

 like in their appearance than the Sirens. The 

 body is greatly lengthened, flexible, and formed 

 for swimming, terminating in a thin, and verti- 

 cally compressed tail. The skull is sohd. There 

 are four limbs, but in one of the genera, these 

 are so widely removed, so short and slender, 

 and so rudimentary, the toes being almost 

 evanescent, as to convey the idea of tentacula 

 rather than feet. But what is most remarkable 

 in these animals, is the peculiarity on which 

 the name of the Order is founded, the absence 

 of hranchice, or gills. These organs have not 

 been observed at any period of life, but there 

 is an orifice on each side of the neck. Respira- 

 tion is performed exclusively by lungs, the struc- 

 ture of which is reticulated, and puckered into 

 longitudinal folds : hence these animals are air- 

 breathers, though habitual residents in water. 

 It is believed that this is the permanent con- 

 dition of their existence, and that they undergo 

 no metamorphosis. 



