' THE ATRACTASPIS VIPERS. 245 
fangs. The fangs are abnormally developed, so much so that I 
do not think it possible for the jaws to be opened sufficiently wide 
for the snake to inflict a bite. Most of the solid teeth have dis- 
appeared, or are in a rudimentary condition. There can be little 
doubt but that these Atractaspis vipers once had the general 
appearance and habits of other members of the family, but 
owing to their taking to burrowing habits, their outward form has 
gradually been undergoing a change, and doubtless in course of time 
the fangs will disappear or become considerably smaller. Owing 
to its habit of burrowing, this genus of snake is seldom found. 
The Atractaspis Vipers furnish us with an illustration of what 
Darwin means by the Evolution of species. Here we have a 
Viper which, through changing climate and other conditions, took 
to burrowing habits. The whole anatomy of the creature has 
been slowly modified to suit its new environment. 
Fic. 100.—358. Fangs of an Atractaspis Adder. Its nose is sharp and hard, and suited for digging 
in soft ground, and its body is smooth and formed for gliding through loose earth and sand 
with the minimum amount of resistance and friction. 
