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I.—Venomous Serpents, with Isolated Movable Fangs. 
Famiry. CROTALOIDEA. 
These are the most remarkable of the Serpent tribe; their habits and peculiar 
properties have caused them to be regarded with universal abhorrence. 
CHARACTERS. 
1. The head is generally large; the superior maxillary bones are small, and 
attached by ligaments to a long pedicle, analogous to the external pterrigoid 
apophysis. 
2. The upper jaw bones are destitute of teeth, but are armed with sharp-pointed, 
pervious, movable fangs, through which the poisonous fluid flows. These 
fangs are sometimes only grooved—at others there is a complete canal, 
opening near their extremity, but in all instances these channels communicate 
with the excretory ducts of the gland. The fangs, when not erect, are con- 
cealed by a fold in the gum, from which they can be raised at the will of the 
animal. Behind these are the germs or rudiments of several other fangs, 
destined to become developed, and to replace the original, should these be 
destroyed by accident, as not unfrequently happens. 
3. The palate bones are armed with two rows of small, hard, solid, and fixed 
teeth. 
