298 THE EEPT1LES OP EGYPT. 
In P. sibilans the first three lateral rows of body-scales are larger than the other 
dorsal scales, while the fourth row is about one-half as broad as the first row ; but in 
P. schokari there is not the same marked difference between the first and fourth row, 
and the scales generally are of more equal size as compared with those of P. sibilans. 
In the latter also the oblique arrangement of the scales is more defined than in 
P. schokari, in which the scales are slightly more elongate. The uniformly rufous 
specimens from the island of Shadwan, Assuan, Khargeh, and Khartum, which at first 
sight look so remarkably distinct from the striped form, are undoubtedly most nearly 
allied to it, not only in the character of their scales, but also in the extent to which 
the rostral appears on the upper surface of the head. In P. sibilans the rostral becomes 
more visible, as it is higher than in P. schokari. The rufous snakes, such as those from 
Khargeh and Khartum, conform to the latter shape of rostral and are unquestionably 
only a variety of this species. With the exception of the individuals from the island 
of Shadwan and from Khartum, they have 17 rows of scales, but in these two there 
are 19 scales round the body. In view, however, of the similarity of these snakes 
to this species in the characters already indicated, much importance cannot be attached 
to a trifling variation of this kind. There is another point also in which the 
Khargeh snake differs from the other three rufous examples of P. schokari mentioned 
in the accompanying table, viz., in possessing 10 upper labials, i. e., one labial 
more than usually occurs in this species, and two more than the normal number of 
P. sibilans. The additional labial is due to the division of one of the front labials 
and not to the addition of a labial posteriorly ; consequently in this specimen the 
sixth and seventh labials enter the eye, a condition of the orbital margin found on 
one side of the head in the Khartum individual, which has only 9 upper labials 
and is unquestionably inseparable from the Khargeh specimen. In P. sibilans, with 
8 upper labials, the fourth and fifth generally enter the orbit ; but I have met with a 
snake (see table) presenting these features, but at the same time distinctly referable to 
P. schokari. In the specimen from Jerusalem figured by Jan (livr. 34, pi. iii. fig. 2) 
as P. sibilans, var. hierosolimitana, the fourth and fifth labials enter the orbital rim on 
the left side ; but it will be noticed that the second labial is abnormally broad, probably 
due to the amalgamation of two shields, and, if so, fully accounting for the abnormality 
of the presence of the fourth and fifth labials below the eye. On the right side of the 
same figure another abnormal condition exists, brought about by the third labial 
having so encroached on the fourth, which, although present in the labial margin, 
is shut out from the orbital rim by the third labial being projected backwards into 
contact with the fifth. 
In 47 examples of this species there is only the afore-mentioned specimen from Gizeh 
in which the fourth and fifth labials enter the orbit on both sides of the head ; whereas 
in one from Dizak, Baluchistan, the fifth and sixth enter it on one side and the fourth 
