47 
characterized by the want of legs, and having very dila¬ 
table mouths, which enable them to swallow entire very 
large bodies. 
Case 6 contains those serpents that are pre-eminently 
poisonous, whose upper jaws are toothless, but pro¬ 
vided with large moveable fangs on the palate. These 
fangs are furnished with a groove on the convex edge, 
by which the poison, secreted in a bag placed at the 
root of the teeth, is conducted into the wound. The 
poisonous snakes are distinguished by the size of 
their head, which in general is large, and often covered 
with small scales; by the scales of the body being 
usually rough and keeled, and by the tail being very 
short, and in most instances thin in comparison with 
the body. 
The most deadly of these have a large pit like a se¬ 
cond nostril on the cheek, just before the eye. These 
have been divided into several groups according to the 
structure of the tail. Thus, in the True Rattle Snakes 
(<Crotalus ), the tail ends in a rattle formed by a series of 
horny joints, fitting one into the other, which the animal 
can shake and rattle at pleasure. There are in the 
Collection, several species of this genus, and some de¬ 
tached rattles, to shew their structure. 
The Tisiphone ( Tisiphone) is much like the Rattle 
Snake, but the tail ends in a small recurved spine; 
these are all peculiar to America. Most of the Snakes 
of this division have the tail simple at the end, and are 
found both in the Old and New World. Some of these 
(Cophias ), have the head covered with scales like 
those on the back, as the Fer de Lance of the French 
American Colonists ( Cophias lanceolatus ), from the 
West India Islands ; and the Green Cophias ( Cophias 
viridis), the Purple-spotted Cophias (Cophias purpureo- 
maculatus ), and the Beautiful Cophias ( Cophias orna- 
tus ). The last three are the most beautiful, and the 
most poisonous snakes of India. 
Other species, with simple tails, have the head co¬ 
vered with large shield-like plates ( Trigonocephalus ). 
The 
ROOM X. 
Nat. Hist. 
