30 
NORTH AMERICAN BATRACHIA. AND RfiPTlLtA. 
y. Anteorbitals present. 
fSuperciliaries small, narrow, width nearly uniform ; 
eye small 7. Contia. 
^Superciliaries quite large, broadest posteriorly; eye 
large 13. Cyclophis. 
. b. Nasals two. 
1. Loral absent 4. Tantilla. 
2. Loral present. 
x. Anteorbitals present. 
fOne anteorbital. 
^Dorsal rows 17 12. Dromicus. 
**Dorsal rows 25 to 29 14. Coluber. 
JTwo anteorbitals. 
*Head depressed; anteorbitals nearly equal in 
size 11. Biadophis. 
**Head deep; upper anteorbital much the largest. 
17. Bascanium. 
y. Anteorbitals absent 2. Virginia. 
B. Dorsal scales smooth ; anal entire. 
a. Loral absent 9. Osceola. 
b. Loral present. 
1. Rostral acute, produced forwards, causing a sharply 
pointed snout 8. Cemophora. 
2. Rostral not produced. 
x. Superciliaries moderate; scales scarcely overlapping; 
head depressed 10. Ophibolus. 
y. Superciliaries broad ; scales imbricate; head deep. 
15. Spilotes. 
C. All or part of dorsal scales carinate; anal entire. 
a. Rostfrontals two pairs 16. Pi.tyophis. 
b. Postfrontals one pair 18. JEutcenia. 
D. All or part of dorsal scales carinate; anal divided. 
a. Nasals two. 
1. Rostral produced, recurved and keeled. 23. Ileterodon. 
2. Rostral ‘not produced. 
x. One prefrontal 3. Haldea. 
y. Two prefrontal s. 
fLoral present. 
' x 'Scales on back slightly carinate; sides smooth; 
G. 200-235 14. Coluber. 
-x-x-All dorsal scales carinate; G. 130-170. 
21. Tropidonotus. 
19. Storeria. 
J Loral absent. 
