476 
NATURAL HISTORY OF AFRICA. 
11. Pbaethon. Two species, neither of which 
are pecuhar to Africa. 
12. Plotus. Two species, which are pecuhar 
to Africa. 
13. Colymbus. One species, which occurs 
also in other countries. 
14. Aptenodytes, penguin. One species, which 
is^ pecuhar to Africa,. 
III. — Amphibious Animals, 
Reptiles. 
Of the tortoise tribe, the most frequent species 
is that named Tyrse (Trionyx Mgyptiacus^ Geoff, ) 
w^hich is about three feet long, green spotted with 
white, and is singularly useful in Egypt by devour- 
ing the young crocodiles the moment they are 
hatched. 
The common crocodile, or the crocodile of the 
Nile, has been long celebrated. It was formerly 
abundant in Lower Egypt, but at present it is 
principally met with in Upper Egypt. It is very 
abundant in all the rivers of Guinea, and also in 
the Senegal. The monitor of the Nile or Oua-^ 
ran, the Lacerta Nilotica of Linnaeus, a species 
of lizard three feet long, was much venerated by 
the ancient Egyptians, because it devours the eggs 
of the crocodile. In Congo, there is another mo^ 
pitor lizard, six feet long, and which is useful to 
