126 LUNG-FISHES 
looked upon as furnishing clearly the ancestral history of 
Dipnoans. 
The two remaining forms of recent lung-fishes, Lepz- 
Fig. 129 A. — The African lung-fish, Protopterus annectans. X 4. (After MIALL.) 
dostren 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. 129 A), has 
long been the “ Lepido- 
