HORNED TOADS. 503 
the shoulder-girdle invariably remains, the pelvic-girdle in 
such cases disappearing; the pelvis being complete, how- 
ever, when there are hind limbs. The feet are usually five- 
toed. The internal anatomy of lizards has already been de- : 
scribed and illustrated on p. 493. In the snake-like lizards — 
{Anguis) the left lung is the smaller, and in Acontias 
and Typhline it is almost wanting. A urinary bladder, 
wanting in the snakes, is present in lizards. 
The lizard lays eggs in the sand or soil; those of the iguana 
are deposited in the hollows of trees. Certain lizards are 
viviparous. 
There are between seven hundred and eight hundred species 
of existing lizards, most of which inhabit tropical or subtrop- 
ical countries ; eighty-two species of lizards inhabit America 
north of Mexico. The earliest lizards date back to the Per- 
mian formation in Texas,and in Europe to the Jurassic 
rocks. 
Reviewing some of the more interesting lizards in the as- 
cending order, we may, passing over the snake-like, limbless 
Amphisbena, and the limbless glass snake (Opheosaurus), 
first consider the chameleon of the Mediterranean shores, in 
which the eyes are movable with a circular eyelid, and with 
the five toes in two opposable gronps adapted for grasping 
twigs of trees. It is remarkable for its power of changing 
its colors. The tongue of the chameleon (Fig. 448) is 
capable of extending five or six inches, and is covered with 
a sticky secretion for the capture of insects, as the crea- 
ture itself is very sluggish. The chameleon of our country 
is the Anolis of the Southern States, and is a long smooth- 
bodied lizard, which can change its color from a bright pea- 
green to a deep bronze-brown. 
The horned toads (Phrynosoma) are characteristic of the 
dry western plains ; the body is broad, flattened, and armed 
with spines ; its coloration depends on that of the soil it in- 
habits. It will stand long fasts. When Phrynosoma Dou- 
giassti of the Northwestern Territories and States is about to 
moult, small dry vesicles appear on the back and sides, run- 
ning along the horizontal rows of pyramidal scales forming 
the margin of the abdomen. In a day or two the vesicles 
break and desquamation begins, which continues for eight or 
