Of reptiles there are many kinds: one snake (a Trigonocephalus, or
Cophias, subsequently called by M. Bibron T. crepitans), from the
size of the poison channel in its fangs, must be very deadly.
Cuvier, in opposition to some other naturalists, makes this a
sub-genus of the rattlesnake, and intermediate between it and the
viper. In confirmation of this opinion, I observed a fact, which
appears to me very curious and instructive, as showing how every
character, even though it may be in some degree independent of
structure, has a tendency to vary by slow degrees. The extremity of
the tail of this snake is terminated by a point, which is very
slightly enlarged; and as the animal glides along, it constantly
vibrates the last inch; and this part striking against the dry
grass and brushwood, produces a rattling noise, which can be
distinctly heard at the distance of six feet. As often as the
animal was irritated or surprised, its tail was shaken; and the
vibrations were extremely rapid. Even as long as the body retained
its irritability, a tendency to this habitual movement was evident.
This Trigonocephalus has, therefore, in some respects the structure
of a viper, with the habits of a rattlesnake: the noise, however,
being produced by a simpler device.
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