356 KANSAS UNIVERSITY SCIENCE BULLETIN. 



Order OPHIDIA. 



Body elongated, slender; covered with scales. Limbs want- 

 ing (vestigial hind limbs present in some species). Mandibles 

 loosely articulated, quadrate long and freely movable. Shoul- 

 der girdle absent. No eyelids or external organs of hearing. 



KEY TO FAMILIES. 



No pit between eye and nostril. No erectile fangs. Pupil of eye 



round CoLUBRiD/f:. 



Pit between eye and nostril. Erectile fangs. Pupil of eye elon- 

 gated, vertical CROTALiDiE. 



COLUBRID^. 

 I. — Dorsal scales carinated. 

 a. — Anal entire. 



Scales in 27-33 rows PUyoiihis. 



Scales in 17 23 rows Eutacnia. 



Scales in 19 rows. One nasal Tropidoclonium. 



b. — Anal divided. 



1. — Loreal present. 



Scales in 17 rows. One nasal Cyelojohis. 



Scales in 23-25 rows. Rostral large, recurved. . . . Heterodon , 



Scales in 19-29 rows. Gastrosteges less than 170 Natrix. 



Scales in 27-35 rows. Gastrosteges more than 170. . . Coluber. 



2. — Loreal absent. Scales in 15 17 rows Storeria. 



II. — Dorsal scales smooth. 

 a. — Anal entire. 



Urosteges in two series Ophibolus. 



Urosteges undivided RhinochiJus. 



b. — Anal divided. 



Scales in 13 rows. One nasal. No anteorbital (J arphophi ops . 



Scales in 15-17 rows. A pale ring on the neck Diadophis. 



Scales in 15 rows. Color green LiojieUis. 



Scales in 15-19 rows Zomenis, 



Scales in 15 rows. No loreal Tantilla. 



Scales in 13-17 rows. One nasal. Anteorbital present Contia. 



CROTALID^. 



I. — Rattle present. 



1. — Top of head with plates Sisfrurits. 



2. — Top of head with scales Crotalus. 



II. — No rattle present , , . , Ancistrodon. 



