20 THE AMERICAN MIDLAND NATURALIST 



8. Anal plate single. — Garter Snakes, Thamnophis 9. 



Anal plate divided ll- 



9. Lateral stripes normally not involving the second row of scales. Tail 28% 



or more of total length. — RiBBON Snake, Thamnophis saurilus sauritus. 

 Lateral stripes normally involving all or part of the second row of scales. 



Tail less than 28% of total length 10. 



10. Lateral stripes normally on the second and third rows of scales. Labials 



usually 7 upper and 10 lower. — CoMMON Garter Snake, Thamnophis 

 sirlalis sirtalis. 

 Lateral stripes on the third and adjacent halves of the second and fourth 

 rows of scales. Labials usually 6 upper and 8 lower. — Butler's GarteR 

 Snake, Thamnophis bulleri. 



11. Rostral turned up in front and keeled above. — HoG-NoSED Snake, Helero- 



don conlortrix. 

 Rostral normal 12. 



12. Loreal present 14. 



Loreal absent. — Brown Snakes, Storeria 13. 



13. Scale rows 15; belly red. rarely black. — Storer's 5nake, Storeria occipilo- 



maculata. 

 Scale rows 17; belly white or pinkish. — Dekay's Snake, Storeria del(a\)i. 



14. Loreal separated from the eye by one or more preoculars 15. 



Loreal in contact with the eye. — GROUND Snake, Virginia valeriae valeriae. 



15. Two nasals . 16. 



One nasal; the nostril in its center; uniform light green in color above. — 



Keeled Green Snake, Opheodr^s aestivus. 



16. First three to seven rows of scales smooth, the rest weakly keeled. — Rat 



Snakes, Elaphe 17. 



Scales strongly keeled except occasionally the first row. — Water Snakes, 



Nairix 18. 



17. Color above, uniform black or with obscure blotches; ventrals 228 to 242; 



juveniles conspicuously spotted. — PlLOT Black Snake, Elaphe ohsoleia 

 obsoleta. 

 Color above, yellowish to light brown with prominent dark brown or black 

 blotches; ventrals 195 to 212; juveniles similar to adults. — Fox Snake, 

 Elaphe vulpina. 



18. Scale rows 19-17 19. 



Scale rows 21 or more 20. 



19. Light lateral stripes on the first and second rows of scales; no dorsal blotches. 



— Queen Snake, Natrix septemvittata. 

 No light lateral stripes ; dorsal blotches present — Kirtland's Water Snake, 

 Nairix }(irtlandii. 



20. A pattern of dorsal and lateral blotches more or less evident throughout the 



length of the body and tail 21. 



Pattern of dorsal and lateral blotches obsolete or lacking 22. 



21. Lateral blotches alternatino with dorsal blotches to or almost forward to the 



head. Belly uniform red or orange. — Red-Bellied Water Snake, 

 Natrix er\)throgaster er^throgaster (juvenile). 



Lateral blotches fused with dorsal blotches to form dark cross bands anteriorly. 

 Belly mottled. — Common Water Snake, Natrix sipedon sipedon. 



