28 
NATURAL HISTORY. [UPPER FLOOR. 
and the Shielded Reptiles, according to the structure of the 
scales, and the formation of their skull. 
I. The Scaly Reptiles (Squamata) have their bodies co¬ 
vered with imbricated scales, the skull formed of separate 
bones, and the tympanic bones external, and only arti¬ 
culated to the rest; their vent is a cross slit, and the ge¬ 
nerative organs are bifid. They consist of the Saurian 
Reptiles or Lizards, and Ophidian Reptiles or Snakes. 
The Saurian Reptiles ( Sauna) are generally provided 
with four limbs, but in some the limbs are in such a rudi¬ 
mentary state, as to be hidden under the skin. The jaw 
bones are united together in front, for as these animals 
live on insects, fruits, &c., which they reduce by chewing, 
they are not required to dilate their mouths for the swallow¬ 
ing of large masses, as is the case in the snakes. 
The family of Monitors ( Monitoridoe , Case 3,) have a 
long deeply forked tongue, which, like that of the snakes, 
is retractile into a sheath placed at its base, and the head, 
body and limbs are covered with small scales. They are 
only found in the vrarmer parts of the Old World, living 
near the water’s edge, and are venerated by the natives, 
who assert that they give notice of the approach of the Cro¬ 
codiles, by hissing when they perceive one of those ani¬ 
mals. Whether this be fact or fiction, the name, Monitor, 
is probably to be traced to that origin. 
The family of Heloderms {JTelodermidcE) are peculiar 
for their body and head being covered with large convex 
scales. Unlike other lizards, their teeth have a groove 
behind, like the fangs of serpents ; they are said to be 
poisonous, but this may be a mistake, for ignorant per¬ 
sons are inclined to believe that all reptiles are dangerous. 
They come from Mexico, and having been seen in a dried 
state only, the form of their tongue is not known. 
The following lizards have an equally elongated and 
deeply bifid tongue, but it is only contractile into the 
mouth, and not furnished with any sheath. 
The family of Safeguards, ( Teidce , Case 3,) which 
have the head covered with large shields, and the back and 
limbs with small scales, are confined to the warmer part 
of the New World, as the genera Telus, Ameiva, and Cen - 
tropyoc , differing from each other in the shape of the ab¬ 
dominal plates; the latter are remarkable for their being 
