Africa; the beautifully colored ilysiids, found only in tropical South Amer¬ 
ica and the Indo-Malayan region; the worm-eating, forest-living uropeltids 
of Ceylon and southern India, forty in number; and the three-foot-long 
xenopeltid of southeastern Asia. Only a single species of the last family is 
known. 
Constrictors range in size from the sand boas measuring less than a 
yard in length to the monster anacondas which have been known to attain 
thirty feet. Pythons and boas are subdivisions of the family Boidae. The 
pythons differ from the boas chiefly in that they possess an extra skull 
bone, the supraorbital, and that they are confined with but one exception 
to the Old World while for the most part the boas are situated in tropical 
America. One very rare python is found in Mexico. In all about seventy 
species are known. 
Harmless Snakes include the great majority of typical colubrid snakes. 
They inhabit almost all parts of the globe and may be found in terrains 
as diverse as arid deserts, dense jungles and high mountains. Some of 
these snakes burrow beneath the humus of forests and are small-headed and 
shorttailed; others that dwell in deserts are rough-scaled and colored in 
die pallid tones of their habitat; typical ground-dwellers are cylindrical, 
having in addition distinct heads and fairly long tails; aquatic species are 
provided with nostril valves which can be closed during periods of sub¬ 
mergence; tree snakes tend to be greatly elongated and whiplike. 
Many of the species included in this grouping are beneficial to farmers 
as destroyers of rodents and insects. A bull snake has been known to eat 
as many as thirty-five field mice in one day. Some farmers catch bull 
snakes, place them at the entrance of gopher rat holes, and applaud the 
usefully destructive work of the snakes. 
Sea Snakes are elapids adapted to aquatic life. Like some other water 
snakes their nostrils are provided with valves. The tails of these front-fanged 
snakes are flattened vertically and serve as sculling or sweep oars. About 
fifty species have been described from the Indian and Pacific Oceans. 
Sea snakes range in size from four to twelve feet. All are poisonous al¬ 
though the majority of individuals are rather good-natured and seem not 
to mind being handled. 
Rear-fanged Poisonous Snakes include aquatic species which inhabit 
the fresh waters and estuaries of the Indo-Australian region. They include 
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