CHAPTER XLIII: THE VIPERINE SNAKES 

 Family Viperid>€ 



The Thick-bodied Poisonous Snakes of the New World — Serpents 

 Distinguished by Their Long Fangs, which Fold Against the 

 Roof of the Mouth when it is Closed 



Classification and Distribution. — The family Viperidce is of 

 moderate size. It is composed of about one hundred and twenty- 

 five species, representing thirteen genera. The species are scat- 

 tered over the temperate and tropical portions of both the Eastern 

 and the Western Hemispheres. The Viperidce is divided into 

 two sub-families, these technically termed the Viperince (the 

 True Vipers), the species of which are found only in the Old World, 

 and the Crotalince, or "Pit Vipers," occurring in both the Old 

 and the New World, but attaining their greatest size and varia- 

 bility of form in the latter. Thus, in North America, all of the 

 thick-bodied poisonous snakes are "Pit Vipers" or Crotaline ser- 

 pents. The members of both sub-families may be recognised 

 by the flat triangular head, very distinct from the neck and the 

 elliptical (cat-like) pupil of the eye. The top of the head, with 

 the majority of the species, is covered with very small, granular 

 scales. Some show regularly arranged head shields of much the 

 same formation and character as those of the colubrine snakes. 



The Pit Vipers: The sub-family Crotalince, containing 

 the rattlesnakes, the copperhead snake, the moccasin and the 

 "fer-de-lance" has acquired the popular title for its members — 

 the Pit Vipers — owing to a peculiar development seen with all 

 the species. This consists of a deep pit, situated between the 

 eye and the nostril. The orifice is lined with a delicate epidermis 

 and connects with a well-developed nerve extending backward 

 to the brain. That this pit is of some use to the snake, seems very 

 probable, when the attendant nerve development is considered. 

 Many investigations have been attempted, with the result of com- 

 plicated anatomical repetitions in the line of description, but 



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