36 
NATURAL HISTORY. £uPPER FLOOR. 
with large regular shields. These species are, in general, 
innocent; a few have some of the upper lateral teeth 
rather larger than the rest, and grooved on the hinder 
edge, the groove communicating with a gland placed on 
the side of the face, but their bite is seldom so danger¬ 
ous as that of the eminently poisonous snakes. They are 
divided into three families. 
The family of Colubridce , (Cases 7—12,) which contains 
more than half of the species of snakes, are characterized by 
having the belly covered with broad cross plates like the 
Poisonous Serpents. Their tail is elongated and conical. 
Such of them as live on the ground and take to the water 
for protection, or to catch their food, have generally a 
cylindrical form, and a tail scarcely as long as the body; 
sometimes the head is large, and the scales are placed in 
longitudinal series, as in Coronella, Lycodon, Tropidonotus, 
&c. Others differ in having a smaller head, smooth 
scales, and a small frontal plate, as Calamaria , Bnngarus , 
and the Coral Snakes ( Elaps ) ; the latter are often 
marked with alternate black and bright coloured bands, 
as in Elaps corallinus; and the Flat-tailed Coral Snake 
(Platurus) found in the Indian Seas, differs from the 
others by its tail being flattened like the Sea-Snakes. Some 
of these, as the Spectacle Snake or Naja, and Sepedon , 
have a small head, and the scales placed iu cross bands ; 
the former have the faculty of dilating the skin of the 
neck, so as to form a kind of hood over the head. The 
Indian species have usually a yellow spot on the back 
of the neck, somewhat resembling a pair of spectacles. 
These snakes are used by the native jugglers in their ex¬ 
hibitions. Those which live the greater part of their life 
on trees, and are thence called Tree-Snakes, ( Dendrophis ,) 
are long and slender, and generally have the scales on the 
sides of the back narrow, and longer than those on the 
dorsal line : in some of these the end of the muzzle is 
lengthened out into an acute appendage ( Passerila ). The 
Bull-headed Snakes ( Dipsas) resemble the Tree-Snakes 
in form, but the head is short and broad, the body com- 
f ressed, and have a series of larger scales down the back. 
n the two last groups the fangs are most commonly 
found intermingled with the teeth. 
The family of Boas ( Boidce, Case 13) have usually a short 
