96 - ZOOLOGY. 
recognised by naturalists: Ophidians! or Serpents; Saurians,? including 
lizards, crocodiles, and all species of lizard-like form; and Chelonians,? 
containing tortoises, turtles, &c. 
SERPENTS have no limbs, and in general the body is very much 
elongated. The body and tail are covered with scales, the head very 
often with plates. The vertebre and ribs are extremely numerous, 
some serpents having more than three hundred pair of ribs, <A serpent 
moves by means of its ribs and the scales of the abdomen, which are 
joined to the ribs by slender cartilages, and take hold of the surface 
,over which the animal passes. Many serpents not only glide over 
the ground with great rapidity, but climb trees with comparative ease. 
The vertebrae are so formed and jointed together as to give great 
pliancy to the body. Serpents abound chiefly in the warm parts of the 
world, to which also the largest species belong, and those of which the 
venom is most deadly. Venomous serpents depend on their poison- 
fangs for the capture of their prey. The fangs are a pair of tubes 
firmly fixed into a movable bone in the front of the upper jaw. 
When not in use, they are laid back on the roof of the mouth; but 
when the animal is irritated, and about to assail its enemy or its prey, 
they stand out like two lancets. Above them, towards the back of the 
head, is a large gland for the production of the poison, which passes 
down the fangs into the wounds which they make. Many serpents, 
however, are not venomous, but depend on other means for catching 
their prey, some feeding chiefly on insects or very small animals; and 
some, the largest and most powerful of all—as the Boa-constrictor and 
the Pythons of the East Indies—killing even large quadrupeds by mere 
muscular effort when they have laid hold of and coiled themselves 
around them. 
LizARDS may be regarded as exhibiting the perfection of the Saurian 
type. In them, and in chameleons, iguanas, &c., the body is covered with 
scales ; but in crocodiles and alligators it is covered with bony plates, 
and these animals have therefore been separated from Saurians by some 
naturalists, and constituted a distinct order under the name of Loricata.* 
They are all large reptiles, much larger than any of the scale-covered 
Saurians, and formidable from their strength and voracity. - They 
inhabit the lakes and rivers of warm countries. The scale-covered or 
true Saurians are also chiefly inhabitants of warm countries, and most 
of them love dry situations and sunshine. Some climb trees, and gener- 
ally live in them, pursuing there their insect prey. A few of them, as the 
Iguana or Guana of the West Indies, feed on leaves and fruits. The 
1 From Greek ophis, a serpent. . 3 From Greek cheloné, a tortoise. 
2 From Greek sauros, a lizard. 4 That is, mailed, from Latin lorica, a coat of mail. 
