TEIONYX TEIUNGLIS. 33 
specimens, but obscure or obsolete in adults ; margin of fleshy disk yellowish ; under 
surface white, but the posterior margin of the fleshy disk marked with dusky. 
It attains to a metre in length 1 . 
Common in the Nile in Lower and Upper Egypt, and, according to James Burton 2 , 
present in the lakes in the Wadi Natrun. 
In the month of April it deposits from 50 to 60 eggs on the sandbanks, where they 
are hatched by the heat of the sun. 
The Arabs say that the Nile turtle searches for the eggs of the crocodile, and that it 
scratches them out of the sand and devours them. Maillet 3 , however, who was an 
excellent observer, did not credit the existence of this habit. Sonnini 4 , on the other 
hand, not only believed in it, but has stated that the turtle devoured the newly 
hatched young of the crocodile ; and James Burton 5 has recorded that it is not so much 
the ichneumon as the Nile turtle that destroys the young of the crocodile. This may 
be possible, but that so thoroughly an aquatic animal as a Trionyx should leave the 
water in search of food is highly improbable. 
Fish and shell-fish appear to be its staple food, which it procures and devours under 
water. 
Dr. J. E. Gray considered that the turtle of the Nile found in the reaches of the 
river at Khartoum was not only specifically, but generically distinct from the turtle of 
Lower Egypt, and he described it under the name of Fordia africana. His reasons for 
regarding it as generically distinct from Trionyx must unquestionably be rejected ; but 
at first sight the marked differences between the forms of the two skulls would seem to 
favour the supposition of their specific distinctness, whereas on the other hand the two 
animals, in external characters, are alike. Agassiz 6 , writing in 1857, held, however, 
that it was impossible to distinguish the species of Trionychidw by their external 
characters, and that nothing short of a careful examination of their jaws, and especially 
of the skull, would reveal the generic characters. 
The alveolar surfaces of the Khartoum turtle are characterized by great breadth, 
associated with a short, truncated, broad snout, whilst the same surfaces of the turtle 
of the Lower Nile are narrow and the snout is sharp and pointed. 
Mr. Boulenger, who was the first to direct, special attention to these extreme forms of 
jaws, points out that no young specimens of Trionyx have been met with in which the 
alveolar surfaces are broad and molar in their character, and that all young specimens 
have sharp and edged jaws. He holds that the two forms of alveolar surface are found 
1 Prospero Alpini (1553-1617) says, Eerum -^gypt. lib. iv. cap. 2 (1735), p. 203, that it attains to 
such a size that the carapace was used for making shields, which is still the case in Nubia. 
2 Add. MSS. B.M. 25,623. 
3 Descr. de l'Egypte, 1735, p. 33*. 
4 L. c. i. pp. 334, 335. s L- e. 
Contrib. to Nat. Hist, of U.S.A. 1857, 2 pis. 4to, p. 396. 
F 
