126 



LUNG-FISHES 



looked upon as furnishing clearly the ancestral history of 



Dipnoans. 



The two remaining forms of recent lung-fishes, Lepi- 



dosiren and Protopterus, 

 resemble each other so 

 closely that Ayers has 

 contended that they 

 should be regarded as 

 distinct only specifically. 

 Lepidosiren, the South 

 American form (Fig. 

 129), was discovered by 

 its describer, Natterer, 

 in 1837 in the upper 

 Amazon. It then, for 

 many years, succeeded 

 in eluding the collectors, 

 and was known as one 

 of the rarest specimens 

 of foreign museums. In 

 1887 it was, however, re- 

 discovered in Paraguay, 

 where it appears to have 

 long been known as a 

 food-fish. Its structures 

 are now regarded as en- 

 titling it unquestionably 

 to the rank of a distinct 

 genus. 



Protopterus, common 

 in the White Nile and 

 Congo (Fig. \2()A), has 

 long been the " Lepido- 



