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 

 (Anyuis} 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 

 Amphtsbana, and the limbless glass snake (Oplieosaurus)* 

 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 groups adapted for grasping 

 twigs of trees. It is remarkable for its power of changing 

 its colors. The tongue of the chameleon (Fig. 443) 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 (PJirynosoma] 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 Don- 

 glassii 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 desquamatioii begins, which continues for eight or 



