CHAPTER? ¥- 
DIVISION OPISTHOGLYPHA. 
(The Back-fanged Snakes.) 
SUB-FAMILY III. D1IPSADOMORPHINAE. 
Tuis 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 paralyze prey preparatory to swallowing it. Owing to the more 
or less rudimentary appearance of these glands, and the absence 
of ducts, etc., 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 (Dispholidus typus) and Schaapsteker (Trimerorhinus rhom- 
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. 
