ROOM X.] NATURAL HISTORY. 35 
Some of the Guanas have a compressed dewlap under 
the throat, and the back crested; among which are the 
common Guana ( Iguana tuberculatd), which is used both 
for food and medicine in the West Indies, and the banded 
Guana (Iguana fcisciata ). 
Other species of this genus have only a fold across the 
throat, as the Spiny-tailed Guana ( Iguana acanthura ), 
Clouded Guana ( Iguana nubild), Sword-tailed Ophyessa 
( Ophyessa super ciliosa ), Umber Ophyessa (0. plied), 
Collared Tropidurus (Tropidurus torquatus), Keeled Leio- 
cephalus (. Leiocephalus carinatus), Northern Tropidolepis 
(Tropidolepis undulatus ), Collared Tropidolepis (T. torqua¬ 
tus), Douglass’s Toad-Lizard ( Phrynosoma JDGuglassii ), 
and JBlainville’s Toad-Lizard (P. Blainvillii). These ani¬ 
mals are very quarrelsome, and light with great ardour 
when they meet. 
In other species of Guanas, the ribs surround the body 
like those of the Chameleon, and like them, these animals 
have the faculty of changing their colour with great ra¬ 
pidity. Three of the genera belonging to this division of 
the Guanas are each 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, ( 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 simple fiat head, but the last joint but 
one of the toes is dilated on the sides into a pear-shaped 
disc, 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 the ribs surrounding the abdomen, like the Anolis, 
but their toes are not dilated, and they have no dorsal 
crest. 
In the lower part of this Case (No. 3) are the Geckos; 
nocturnal Lizards, of a dull, lurid appearance, with 
depressed heads, and large round eyes. Their body 
is usually covered with small scales, amongst which are 
frequently larger tubercles; and the under side of their 
toes is generally furnished with variously shaped, imbri¬ 
cated scales, or folds of the skin, which enable the animal 
to crawl up glass, and even to run with facility, the back 
