CHAPTER V. 



Division II. Opisthoglypha. 

 {The Back-fanged Snakes.) 



Sub-family III. Dipsadomorphinae. 



This third sub-family of the Colubrines belongs to a division or 

 series of snakes known as the Opisthoglypha, which means a 

 class of snakes with the posterior (back) maxillary teeth 

 grooved. There are about 300 species of them to be found in 

 the temperate and tropical parts of the world, with the 

 exception of New Zealand. 



This family of snakes possesses one or more pairs of grooved 

 teeth situated in the upper jaws, midway between the front and 

 base of the jaws. They are set in the posterior or back maxil- 

 lary bone, which is more or less movable. Above these grooved 

 teeth there are glands which secrete a venom sufficiently strong 

 to paralyse prey preparatory to swallowing it. Owing to the 

 more or less rudimentary appearance of these glands, and the 

 absence of ducts, as in the typical venomous snakes, it has been 

 assumed by naturalists that all this sub-family of snakes are 

 practically non-venomous as far as man is concerned, the fluid 

 secreted not being thought of sufficient quantity or quality to 

 affect animal life seriously, other than the small creatures on 

 which these snakes prey. 



This belief has recently been shown to be erroneous, — at least, 

 in the case of two of these Back-fanged Snakes, viz., the Boom- 

 slang {Dispholidiis typus) and Schaapsteker {Trimerorhinus rliom- 

 beatus) of South Africa, an account of which is given later on. 



The Back-fanged Snakes should all be regarded as venomous 

 to a greater or lesser degree, and liberties should therefore not 

 be taken with them. 



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