50 
ROOM X, 
Nat. Hist. 
plates on the abdomen, and a short conical tail, fur¬ 
nished with two short crooked spurs at its base. These 
spurs have lately been shewn to be analogous to the 
hinder legs of other reptiles. The Boas are not venom¬ 
ous ; they kill their prey by crushing it between the 
folds of their body, generally at the same time twisting 
the end of their tail round a tree, in order to increase 
their power. 
The American species ( Boa) have only a single row 
of plates beneath the tail; they vary greatly in the 
structure of the scales on the head and lips. 
Some of the Indian species, as the Netted Boa (Boa 
regia), have a single series of plates, whilst most of the 
other species have two rows (Python); as the Javan 
Boa (Col.javanicus), and the Tiger Boa (Col . hocefor- 
mis). The Eryx differs from the other Boas in hav¬ 
ing a cylindrical body, a very short tail, and the head 
covered with scales similar to those of the back. 
Cuvier, by some oversight, says that this genus has no 
spurs, but the specimen in the British Museum shews 
them distinctly. 
The Sea-Snakes (Hydrus) are easily known by their 
compressed form, narrow ventral shields, and vertically 
flattened tail. These reptiles, which are peculiar to the 
seas of Asia and New Holland, are in some degree 
poisonous, many of the species having small fangs, dis¬ 
persed amongst the true teeth. Some have a small 
head and the body covered with scales (Hydrophis), 
as the larger Sea-Snake (Hydrus major) ; the others 
have a large head and broad neck, and the body 
covered with embedded square plates, placed in longi¬ 
tudinal series ; as the Banded Sea-Snake (Pelamis fas- 
ciatus), and the two-coloured Sea-Snake (P. bicolor). 
The Achrochordus has the habits and many of the 
characters of the Sea-Snakes; but its body and head 
are covered with rough granular scales, and its tail is 
conical. It is found in the rice-fields of India. The 
Chersydrus has the scales of the Achrochordus, but the 
tail is compressed, as in the other Sea-Snakes. 
The 
