CEOCODILUS. 7 
mummified skull figured by Owen the suture appears only to have reached the anterior 
margin of the seventh tooth ; and, apropos of this, Huxley asked : " Are there, then, 
two or more species of crocodile in Egypt, as Geoffrey St.-Hilaire supposed ] " In the 
skull of C. siichns figured by the latter author the suture is asymmetrical on either 
side. On the left it passes backwards to the middle of the alveolus of the seventh 
tooth, and then forwards internally to halfway between the alveolus and the com- 
mencement of the suture in the canine groove. It then bends abruptly inwards and 
slightly backwards to join the suture of the right side, but before doing so, it again for 
a very limited space bends abruptly forwards. The last bend represents the inner 
fourth limb of the W, but almost aborted. On the right side, the W form of the 
suture is still more obscured, as it becomes reduced to a zigzag line running backwards 
from the canine groove to the mesial line of the maxilla, as far as on a level with the 
middle of the alveolus of the sixth tooth, and then inwards, as a jagged almost trans- 
verse line, to the middle of the palate, with a short angular forward bend to join its 
fellow of the opposite side. 
In view of the modifications in the form of the premaxillo-maxillary suture that 
occur in the skulls of Egyptian crocodiles undoubtedly referable to C. niloticus, the 
slight differences indicated in the foregoing description of the suture in these two 
skulls, in the extent to which the outer limb of the W is prolonged backwards, 
cannot be regarded as illustrating more than variation, as in all other respects these 
skulls are specifically identical. The W form of the suture is always more or less 
present, but it is more open in some individuals than in others, and the length of the 
limbs of the W varies considerably. 
Geoffroy believed that the proportion in which the length of a crocodile skull stood 
to its base served as a comparative measure that could be usefully applied in the deter- 
mination of the species, but he allowed at the same time that differences were introduced 
depending upon the conditions of age and sex. As he was, however, under a 
misapprehension as to the age of the type of C. suchus, the figures he adduced 
regarding the relative proportions of the length of the skull to its basal breadth do 
not prove it to be distinct from C. niloticus. 
Geoffroy allowed that the coloration, as already stated, was almost the same in the 
two supposed species, but that there was this difference, that C. niloticus was green 
inclining to bronze, with the black arranged in narrow bands, whereas in C. suchus 
the black was in small spots on a clear green ground. It has been impressed on 
me, by the study of a considerable series of crocodiles, that the general tint is subject 
to much variation, and that the black may either be arranged more or less in bands, 
distinct in some, less so in others, and even becoming broken up into small spots. 
The crocodile of the Nile is thus no exception to the colour-variation which prevails to 
so great an extent in many other reptiles, and indeed is trivial compared with what 
is met with in some snakes and lizards. In certain species of the former group the 
