144 CLASSIFICATIOX OF AMPHIBIANS. 



covered in all its parts with small uniform scales^ each 

 of which is slightly raised and marked with three 

 ridges. 



{145.) The family of Crotalid^_, as containing the 

 most terrible serpents of the whole tribe^ is pre-emi- 

 nently typical of the ophidian or serpent reptiles. 

 These terrific beings, from which, but with a solitary 

 exception, the kingdoms of Europe are happily free, 

 infest the warmer regions of America, Asia, and Africa ; 

 and by and from their venomous fangs can inflict almost 

 instant death. They possess, as M. Cuvier well ob- 

 serves, a '' very peculiar structure " in their organs of 

 manducation, abundantly sufficient, indeed, to justify us, 

 did no other reasons exist, in viewing them as a primary 

 division of the whole tribe. 



(146.) The truly venomous serpents have isolated 

 fangs, from which the poison is distilled. '' Their upper 

 maxillary bones are very small, and supported on a long 

 pedicle, analogous to the external pterygoid apophysis 

 of the sphenoid, and are very mobile. There is fixed 

 in them a sharp tooth, pierced by a small canal, -^.'hich 

 gives issue to a liquor secreted by a considerable gland 

 situated under the eye. It is this fluid, flowing into 

 the wound made by the tooth, which carries destruction 

 into the body of animals, and produces effects more or 

 less fatal, according to the species of the serpent from 

 which it comes. This tooth is concealed in a fold of 

 the gum, when the serpent does not choose to make use 

 of it j and there are behind it several germs destined to 

 replace it, if it should be broken in a wound. Natural- 

 ists have named these venomous teeth moveable fangs^ 

 but, properly speaking, it is the maxillary bone which 

 moves : it bears no other teeth whatsoever, so that in 

 these serpents it is only the tv/o ranges of palatine teeth 

 which are visible in the roof of the mouth." * In other 

 respects this family, at least in its external characters, 

 does not diiier very remarkably from the last. Their 



• Cut. 



