10 THE REPTILES OF EGYPT. 
Crocodilus niloticus. (Plate I.) 
1 juv. Wadi Haifa. Surgeon-Captain E. H. Penton, D.S.O. 
Snout variable, broader in both sexes in the adult than in semi-adults, narrower in 
females than in males, short and broad in the young. Upper surface of the head more 
or less rugose, most so in adults, but devoid of ridges. Two to six anterior nuchal 
plates arranged singly or in pairs on each side of the mesial line, symmetrically or 
asymmetrically, thus : 1 + 1 = 2; 2 + 2 = 4; 3+2=5; 3 + 3 = 6. Generally six posterior 
4 
nuchals, four anterior and two posterior; but occasionally |, |, or 5=8. These shields 
have generally a few small scales around them. Fifteen to seventeen transverse bands 
of plates along the back to the base of the tail, thirteen or fifteen of them being dorsal 
and two pelvic in position. Generally six juxtaposed plates in each transverse row on 
the bach, with smaller separate plates external to them on the sides, but only four 
plates in transverse series on the pelvic region. The dorsal plates are strongly keeled, 
and constitute six ridges on the back and four on the pelvis. Fifty-one to sixty-one 
rows of scales from the first dorsal to the tip of the tail, and thirty-two to thirty-seven 
from the first dorsal to the commencement of the azygos caudal ridge. Sixty-seven to 
seventy-nine rows of scales from the largest pectoral scale to the tip of the tail. Scales 
on the limbs smooth or carinated ; the hind limb with a broad serrated fringe along its 
posterior border. Hind foot broadly palmate ; fore foot webbed at the base of the 
digits. 
General colour greenish or bronze-green, more or less banded or spotted with black, 
more profusely in some than in others, so that the prevailing colour is brownish black, 
but with the green colour still distinct in the interspaces 1 . Under surface greenish 
yellow. 
The premaxillo-maxillary suture W-shaped, but the degree of openness of the W 
and the length of its limbs variable. 18 or 19 teeth in the upper, and 15 teeth in the 
lower jaw. 
There is considerable variation in the number and size of the nuchals generally. 
The lowest number of the anterior nuchals is 1+1, and the highest 3 + 3 = 6, but 
2 + 2 = 4 appears to be the prevailing arrangement. Occasionally, however, there may 
be 2+3 and 3 + 2. The posterior nuchals are juxtaposed and are generally arranged 
in two lines, thus |±|=6, the most extreme variation being i±_J = 4. However, the 
following formulae also occur, viz. |±?=5, or ^=6. In the formula |, a small plate 
occurs external to each side of the scales of the anterior row. They are doubtless 
plates that have become removed away externally. In the asymmetrical formula \ 
1 It is not known whether the sexes are distinguished by differences of colour. 
