NATURAL HISTORY. 
41 
Rooai x.] 
generally, at the same time, twisting the end of the 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 respect to 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 
(Coluber javanicus), and the Tiger Boa ( Coluber boce- 
formis). The Eryx differs from the other Boas in having 
a cylindrical body, a very short tail, and the head covered 
with scales similar to those of the back. Cuvier says that 
this genus has no spurs, but the specimen in the British 
Museum shews them distinctly. 
The Sea-Snakes ( Hydras ) 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, dispersed amongst 
the true teeth. Some have a small head, and the body 
covered with scales, as the larger Sea-Snake ( Hydras 
major) ; the others have a large head and broad neck, and 
the body covered with embedded square plates, placed in 
longitudinal series; as the Banded Sea-Snake ( Pelamis fas- 
ciatus), and the Two-coloured Sea-Snake ( Pelamis bicolor). 
The Achrochordus has the habits and many of the cha¬ 
racters 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 com¬ 
pressed, as in the other Sea-Snakes. 
The Cases 14 and 15, between the windows, contain 
dry specimens of Reptiles. 
On the upper Shelves are specimens of the Indian and 
African Crocodiles, and the Gavial, or Long-beaked Croco¬ 
dile of the Ganges. 
On the lower Shelves are a series of Tortoises, arranged 
after the same order as the specimens in spirits in Case No. 1. 
Among them are the Serpentine Tortoises ( Testudo serpen¬ 
tina), which unite with the form of the Tortoises, several 
of the characters of the Crocodiles, as the large head, and 
the long tail with elevated ridges; also species of Land 
