50 SQUAMATA 



dd'. — Plates on top of head not larger than those on 

 body; anus bordered in front by a single plate j 

 a small spine at end of tail. 



Leptotyphlopidae. — p. 624. 



cc . — Ventral plates more than twice as broad as dorsal 

 scales, 

 ddd. — No rattle at end of tail; no pit between nostril 

 and eye. 



ee. — A small spur at each side of the anus; tail 

 short and tinincate; or top of head with 

 small scales; pupil vertical. 



Boidae. — p. 630. 



ee'. — No spur at side of anus; tail tapering; top 

 of head with large plates; pupil round or 

 vertical, 

 ff. — No enlarged fangs at front of mouth; 

 coloration, if in rings, not red separated 

 from black by white (yellow). 

 Colubridas. — p. 644. 



f f. — A pair of large, permanently erect fangs 

 near front of upper jaw; coloration, in 

 rings, red separated from black by white 

 (yellow). 



Elapidffi,— p. 887. 



ddd'. — A horny rattle at end of tail; a pit between 

 nostril and eye; a pair of large erectile fangs; 

 pupils vertical. 



Crotalidae.— p. 893. 



bb'. — Tail short, strongly compressed laterally, paddle- 

 shaped. 



Hydridas.— p. 891. 



