238 
SNAKES. 
as well as by the absence of horns. The upper surface of the head is covered with 
scales, and the keeled scales of the body form from twenty-five to thirty-five rows. 
The common desert saw-viper, or, as it is called in Egypt, eja (Echis carinata), 
attains a length of about 2 feet; and has the keels on the lateral scales of the body 
strongly serrated. In colour it varies from pale buff to greyish, reddish, or pale 
brown on the upper-parts, with three series of whitish spots edged with dark 
brown, in addition to which there may be a dark brown zigzag band along each 
side, while the head is ornamented with a cross or arrowhead mark; and the 
under-parts are whitish, either with or without brown dots. This species inhabits 
the desert regions of Northern Africa, South-Western Asia, and India, being 
replaced in Arabia and Palestine by E. colorata. 
The most remarkable peculiarity of this viper (which, however, it may possess 
in common with the horned vipers, since the scales of the latter have a similar 
structure) is its power of making a curious, prolonged, almost hissing sound, 
produced by rubbing the folds of the sides of the body one against another, when 
the serrated lateral scales grate together. That this is the true cause of the 
sound may be proved by twisting the body of a dead specimen, and thus causing 
friction between the scales. Sir J. Eayrer writes that this species is a very fierce 
and vicious viper; it throws itself into an attitude of defence and offence, coiled 
up like a spring, rustling its carinated scales as it moves one fold of the body 
against another. It is aggressive, and does not wait to be attacked before darting 
its head and body at its enemy, the mouth wide open, and the long fangs 
vibrating, thus presenting a most menacing appearance. It is very poisonous, 
and there can be little doubt that it destroys many human lives, as men are 
much more exposed to contact with this species than with Russell’s viper. 
The dreaded rattle-snakes of the New World are our first repre¬ 
sentatives of the subfamily of pit-vipers ( Crotalince ), which, are 
common to Asia and America, and are characterised by the presence between 
the nostril and the eye of a deep pit in each loreal shield, the physiological 
significance of which is still unknown. All have triangular broad heads, and 
short thick bodies. The Asiatic representatives of the group are less deadly 
serpents than their American relatives; while the only vestige of the rattle of 
the latter to be found in the former is a small horny spine at the end of the tail 
of one species. Many of the Indian species are arboreal in their habits; their 
coloration assimilating to that of the foliage and boughs among which they 
dwell. As regards their geographical distribution, pit-vipers present a curious 
similarity to bears and deer; and since they are most abundant in the Oriental 
region, and also more numerous in North than in South America, Mr. Wallace is 
of opinion that the group originated in the Indo-Chinese countries, and thence 
spread north-eastwards to North America, and so onward to the southern half of 
the New World, which area, having been the last to receive the group, has not 
had time, in spite of its extreme fitness for reptilian life, to allow it to attain its 
full development. 
The rattle-snakes are sufficiently distinguished from their allies by the 
jointed horny appendage at the end of the tail from which they derive their name. 
In the young rattle-snake the tail terminates in a somewhat nail-like “ button,” 
Rattle-Snakes. 
