SERPENTES 623 
THEOREP TILES ‘OF 
WESTERN NORTH AMERICA 
Suborder II. SERPENTES (Snakes) 
Synopsis OF FAMILIES 
a.—Tail cylindrical or conical, not oar-shaped. 
b.—Ventral scales less than twice as broad as dorsals. 
Plates on top of head not larger than those on body; 
anus bordered in front by a single plate; a small spine 
at end of tail. 
Leptotyphlopide.—p. 624. 
b’.—Ventral plates more than twice as broad as dorsal 
scales. 
c.—No rattle at end of tail; no pit between nostril and 
eye. 
d.—A small spur at each side of the anus; tail short 
and truncate, or top of head with small scales; 
pupil vertical. 
Boidze.—p. 630. 
d’—No spur at side of anus; tail tapering; top of head 
with large plates; pupil round or vertical. 
e.—No enlarged fangs at front of mouth; coloration, 
if in rings, not red separated from black by 
white (yellow). 
Colubridz.—p. 644. 
e.—A pair of large permanently erect fangs near 
front of upper jaw; coloration, in rings, red 
separated from black by white (yellow). 
Elapidz.—p. 887. 
c.—A horny rattle at end of tail; a pit between nostril 
and eye; a pair of large erectile fangs; pupil vertical. 
Crotalidz.—p. 893. 
