118 THE ‘SNAKES OF SOUTH APRICA. 
or 21 rows; ventrals rounded or obtusely angulate laterally. 
Tail long ; sub-caudals in two rows. 
GENUS THELOTORNIS.—Maxillary teeth 16 or 17, gradually increasing 
in length, followed after a short interspace by two or three 
enlarged grooved teeth situated below the posterior border 
of the eye; anterior mandibular teeth strongly enlarged. Head 
distinct from neck. Eye large, with horizontal pupil; nasal 
entire. Body cylindrical, very slender. Scales narrow, very 
oblique, feebly keeled, with apical pits, in 19 rows; ventrals 
rounded. Tail long; sub-caudals in two rows. 
Skull of Dispholidus typus. 
(Brit. Mus. Cat. Snakes.) 
Fic. 51.—Skull of typical Back-fanged Snake. 
1. Side view showing the position of the fangs (B). 
2. Top of head and lower jaw (C). 
3. Roof of the mouth (A). Showing position of the fangs at posterior 
end of outer row of upper teeth. 
The inner row of teeth are the palatines. 
GENUS AMBLYODIPSAS.—Maxillary very short, with 5 teeth gradually 
increasing in size, and followed, after an interspace, by a large 
grooved fang situated below the eye; mandibular teeth decreas- 
ing in size posteriorly. Head small, not distinct from neck ; 
eye minute, with round pupil; nostril in a single very small 
nasal; no internasals; no loreal; no preocular; no anterior 
temporal. Body cylindrical. Scales smooth, without pits, in 
I5 rows; ventrals rounded. Tail very short, obtuse; sub- 
caudals in two rows. 
GENUS CALAMELAPS.—Maxillary very short, with 3 or 4 _ teeth 
gradually increasing in size and followed, after an interspace, 
by a large grooved fang situated below the eye , anterior mandi- 
bular teeth enlarged. Head small, not distinct from neck ; 
