GENERAL CLASSIFICATION OF POISONOUS SNAKES 5 
sea, near the shore, with the exception of the genus Distira, which 
is met with in the fresh water of a lake in the Island of Luzon, 
in the Philippines. They are frequently found in very large 
numbers in the Indian seas and throughout the tropical zone of 
the Pacific Ocean, from the Persian Gulf to the west coast of the 
American Continent, but they are entirely absent from the West 
Coast of Africa. 
B. The EHlapine (land-snakes), with a cylindrical tail, and 
covered with smooth or carinate scales. These serpents are fre- 
quently adorned with brilliant colours. Some of them (belonging 
to the genus Naja) have the faculty of expanding the neck in the 
shape of a parachute, by spreading out the first pairs of ribs when 
they are alarmed or excited: the breadth of the neck then greatly 
exceeds that of the head. They are distributed throughout Africa, 
Asia, and North and South America, and are also found in Australia, 
where almost all the snakes that are known belong to this sub- 
family. 
The Family ViPERIDÆ is characterised by a triangular head, 
which is widened posteriorly, and by the general aspect of the 
body, which is usually thick-set and terminated by a short tail. 
The bones of the face are movable. The prefrontal bone is not 
in contact with the nasal; the maxillary is greatly shortened and 
may be articulated perpendicularly to the ectopterygoid; it bears 
a pair of large poison-fangs, one on each side, and these are always 
accompanied by several teeth to replace them, folded back in the 
eum; these latter teeth come in succession to take the place of 
the principal tooth, when this is broken or falls out of itself when 
the snake sheds its skin. 
The poison-fangs are not grooved, as in the Proteroglyphous 
Colubride ; they are pierced by a perfectly formed canal, the upper 
end of which inosculates with the efferent duct of the corresponding 
poison-gland, while its lower extremity opens to the exterior a little 
above and in front of the tip. The latter is always very sharp. 
