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THE NATIONAL GEOGRAPHIC MAGAZINE 
SOUTHWESTERN UNITED STATES 
GILA MONSTER (Heloderma suspectum) 
The fangs are grooved and in the lower jaw, and the 
This and another species of the same genus are the only known poisonous lizards. 
Photo by Raymond L, Ditmars 
The bite is not so dangerous as that from a venomous snake. 
iry glands. 
c 
venom is secreted in the saliv 
| provided with such tiny 
and almost useless limbs 
that when frightened they 
fold these members against 
the side of the body and 
literally swim out of sight 
in the yielding sands. 
Unlike the members of 
the other orders of reptiles, 
few lizards have become 
even semi-aquatic. None 
is strictly aquatic—a con- 
dition rendering the order 
of lizards unique among 
reptiles. 
In the southwestern part 
of the United States and 
similar desert regions of 
Mexico are found the only 
known poisonous lizards, 
two in number, forming a 
family by themselves. The 
more northerly species is 
popularly known as the 
Gila monster. It is stout 
of body, with a short, thick 
tail. The venom-conduct- 
ing teeth are in the lower 
jaw, and the poisonous se- 
cretion is much like that of 
the venomous serpents. Its 
chemical properties, how- 
eve., are not so powerful 
as the virus of snakes, al- 
though this lizard must be 
rated as highly dangerous 
to man. Captive examples 
become so tame they may 
be handled without exhibit- 
ing any symptoms of bit- 
ing. The specimens in the 
Zoological Park subsist en- 
tirely upon raw eggs. 
SNAKES 
Snakes are the most 
widely distributed of the 
reptiles. | hey anatase man 
beyond the lizards into 
the temperate regions. In 
North America serpents 
extend well into Canada. 
In the boreal regions of the 
Old World they extend 
northward to the latitude 
