NATURAL HISTORY. 
ROOM II.] 
108 
of India, and some even assert that they infect every substance which 
they walk over, but this is, at least, extremely doubtful; some of them 
hold so fast by their short, sharp, hidden claws as to produce small cuts 
on the skin of the person over whom they walk, which in w^arm climates 
are painful and difficult to heal. 
Other Geckos have the scales under the toes divided by a central 
groove, into w r hich the claws are withdrawn ( Thecadactyli). One of 
these, the Smooth Sheath-claw ( Gecko Icevis) has many scales under 
the toes, and on being caught, the animal, in its exertion to escape, 
often casts off its tail. It does the same if thrown alive into spirits, in 
which case the separated tail contracts, and assumes an almost globular 
shape, and is most usually found in this state in collections, whence this 
species has been generally called the Turnip-tail Gecko ( Gecko rapi*~ 
cauda ). The Phyllodactylus has only two or three cross scales on each 
side of the claws, so that the ends of the toes very nearly resemble the 
tips of the feet of the common fly. In the Ptyodactylus , the scales 
under the toes spread out from a centre, like the sticks of a fan ; and 
the Ur opiates, from Madagascar, has the scales under the toes very like 
the former, but the edges of its body and tail are spread out into flns 
like lobes. Those Geckos which have these fringes, have been com¬ 
monly regarded as aquatic animals; they are now known to live on 
trees, using the fins as parachutes to assist them in leaping. 
Another group ( Hemidactylus ) has only the base of the toes swollen 
out, the ends being narrow and free. These are common about 
dwellings in warm countries, and are therefore usually called House 
Lizards. Their food consists principally of insects, especially flies, for 
destroying which they are protected by the inhabitants. The last 
group ( Cyrtodactylus ) has the form and habits of the Geckos, but 
differs in the toes being very thin, slender, versatile, and peculiarly 
arched, so as to give them the power of grasping very strongly; most of 
these have the tail slender and round, while the Phyllurus of New 
Holland has a heart-shaped, broad, flat tail. 
The family of Guanas (Iguanidje, Case 6) have their teeth at¬ 
tached to the inner edge of the jaw-bone, and most frequently lobed 
and indented. They are Day Lizards, covered with variously formed 
overlapping scales, and are only found in America. Some have a 
compressed dewlap under the throat, and the back crested; as the 
common Guana ( Iguana tuberculata), which is used both for food and 
medicine in the West Indies. Other kinds of this family have only a 
fold across the throat, as the genera Cyclura , Ophyessa , Tropidurus, 
Leiocephalus , Tropidolepis, Phrynosoma. These animals are very 
quarrelsome, and often fight with great ardour when they meet. In 
other species, the false ribs, or those which are not united to the sternum, 
meet underneath, so as to inclose the belly in a complete circle, like 
those of the Chameleon, and, like that animal, these have the faculty 
of changing their colour with great quickness. The genera belong¬ 
ing to this division are marked with very striking characters; the 
first, the Basilisk ( Basiliscus ), has a compressed hood on the back 
of the head, and a fin-shaped crest down the back; the second, ( Chamce - 
leopsis ,) from Mexico, has a compressed ridge on the back of the 
head, but only a slight dorsal crest; both these have simple toes: the 
third ( Anolis ) has a flat head, but the last joint but one of the toes is 
