ROOM X.] 
NATURAL HISTORY. 
33 
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 (. Iguanidce , Case 3) have their 
teeth attached 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 Gu¬ 
ana ( Iguana tuberculato ), 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, Tropidwrus , Leiocephalus , Tropidolepis , Phry - 
nosoma. 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. Three of the genera belonging 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 An-shaped crest down the back; the second, 
(Chamceleopsis,) 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 dilated on the sides 
into a pear-shaped disk, so as to enable these animals to 
walk on smooth and nearly perpendicular surfaces; of this 
genus there are many species. Lastly, the marbled Lizards 
( Polychrus ) have neither dilated toes nor any dorsal crest. 
Other broad-tongued Lizards have their teeth placed on 
the edge of the jaws, and so flrmly Axed to them as to 
appear part of the jaws themselves; as the Chameleons 
and Agamse. Thev are only found in the warm parts of 
the Old World. 
The Agames ( Agamidce , Case 4) present several pe¬ 
culiarities of form, and have therefore been divided into 
inany groups. Some have the head lyre-shaped, and the 
back and tail crested ( Gonyocephalus ); others have the 
c 3 
