36 REPTILES AND BIRDS. 
The class of Reptiles is divided into three orders :—the OPHI- 
DIANS, comprehending the Snakes; the Saurians, the Lizards and 
Crocodiles ; and the CHELONIANS, the Turtles and Tortoises. 
OPHIDIANS. 
In Ophidians, commonly known under the name of Snakes, the 
body is long, round, and straight. They have neither feet, fins, 
nor other locomotive extremities. Their mouths are furnished with 
pointed hooked teeth. In the Boas and Pythons the teeth are 
slender, curved, bending backwards and inwards above their base of 
attachment. In others each maxillary bone has a row of larger 
ones, which gradually decrease in size as they are placed further 
back. These teeth are not contiguous, being separated by consider- 
able intervals. The smaller non-venomous Serpents, such as the 
Colubride, have two rows of teeth in the roof of their mouth. Each 
maxillary and mandibular bone includes from twenty to twenty- 
five teeth. In the Rattlesnakes and some other typical genera of 
poisonous Snakes, the short maxillary bone only supports a single 
perforated fang. Their lower jaw is highly distensible ; the opening 
being longer than the skull. They have no neck; their eyelids are 
immovable ; their skin is coriaceous, highly extensible, and scaly 
or granulous, covered with a thin caducous epidermis, which de- 
taches itself in one entire piece, and is reproduced several times in 
one year. Their movements are supple and varied. In conse- 
quence of the sinuosity of their bodies—for, though scale-clad, 
Snakes are without apparent means of progression—they make 
their way with the utmost facility. ; 
The very numerous species of the genus inhabit either arid or 
moist ground, bushes or trees. Some pass much of their time in 
the water, and one family (that of the Aydrophide) is exclusively 
aquatic, even pelagic in the instance of one very widely diffused 
species, the Pelamis bicolor. In the arboreal Snakes the tail is very 
long, and highly prehensile; in others, as the Vipers, it is short 
and without any prehensility. In the Sea Snakes (4ydrophide), it is 
laterally much compressed. Like other true Reptiles, Snakes abound 
more especially in warm climates, and there are many kinds of them 
in Australia; but the order has not a single representative in New 
Zealand. : 
Most of the Snakes feed on living animals, only a few on birds’ 
eggs. Several kinds of them prey habitually on other Snakes, as. 
the genera Hamadryas, Bungarus, and Elaps, even Psammophis 
