192 ANIMAL FORMS” 
Both pairs of limbs are absent, but by wriggling movements 
of the body this lizard is able to force its way through light 
soil with considerable rapidity. It is a matter of some 
difficulty to secure entire specimens, for with other than 
the gentlest handling the tail severs its connection with 
the body, as the vertebre in this portion are extremely 
brittle. This peculiarity, together with its shape, has given 
it the popular name of glass-snake. Many species of liz- 
ards will thus detach the tail, a habit which is a means of 
protection, enabling the animal to scamper away into a 
place of safety while its enemy is concerning itself with 
the detached member. Later on a new tail develops, 
though usually of a less symmetrical form. 
181. Horned toads.—The horned toads ( Phrynosoma) are 
lizards peculiar to the hot, sandy deserts and plains of 
Fie. 115.—Gila monster (Heloderma suspectum). One-third natural size. 
Mexico and the western United States. The body is com- 
paratively broad and flat, almost toad-like, and is covered 
with scales and spines of brownish and dusky tint, so like 
dried sticks and cactus spines in form and color as to ren- 
der them difficult of detection. In captivity they readily 
