32 
NATURAL HISTORY. [UPPER FLOOR. 
with scales, different from those of the rest of the tail. If 
the tail be cracked only on one side, and not thrown off, a 
new tail often springs out of the crack, so that the mem¬ 
ber becomes forked. A specimen of a Lizard with such a 
tail, may be seen in this Case. 
It also contains those Saurian Reptiles which have short 
contractile tongues, slightly notched at the end. 
The first of these are the Guanas, which have their teeth 
attached to the inner edge of the jaw-bone, and most fre¬ 
quently lobed and indented. They are all found in America. 
Some of the Guanas have a compressed dewlap under 
the throat, and the back crested; among which are the 
common Guana ( Iguana tuberculata), which is used both 
for food and medicine in the West Indies, and the banded 
Guana (Iguana fasciata). 
Other species of this genus have only a fold across the 
throat, as the Spiny-tailed Guana ( Iguana acanthnra ), 
Clouded Guana (Iguana nubila ), Sword-tailed Ophyessa 
(Ophyessa super ciliosa), Umber Ophyessa (0. plica), 
Collared Tropidurus (Tropidurus torquatus), Keeled Leio- 
cephalus (Leiocephalus carinalus ), Northern Tropidolepis 
(Tropidolepis undulatus ), Collared Tropidolepis (T. tor qua* 
tus ), Douglass’s Toad-Lizard (Phrynosoma Douglassii), 
and Blainville’s Toad-Lizard (P. Blainvillii). These ani¬ 
mals are very quarrelsome, and fight with great ardour 
when they meet. 
In other species of Guanas, the false ribs, or those which 
are not united to the sternum, meet underneath, so as to 
inclose the abdomen in a complete circle, like those of the 
Chameleon, and, like that animal, these have the faculty of 
changing their colour with great rapidity. Three of the 
genera belonging to this division of the Guanas are marked 
with very striking characters; the first, the Basilisk ( Basi - 
liscus ), has a compressed hood on the back of the head, and 
a fin-shaped crest down the back; the second, ( Cha - 
mceleopsis ,) 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 flat head, 
but the penultimate joint 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 
