Some or all of dorsal scales keeled, although only faintly so in some genera
1. Anal plate single .................................................................................. 2
1. Anal plate divided ................................................................................ 4
2. Lateral stripes confined to scale rows 2 and 3 (fig. 18 illustrates counting scale, rows); tail less than one-fourth total length ........................................................................... 3
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Garter Snakes |
Ribbon Snakes |
2. Lateral stripes on scale rows 3 and 4; dark ventrolateral stripe involving two lowermost scale rows and outer edge of belly; tail is more than one-fourth of total length
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Thamnophis sauritus Eastern Ribbon Snake |
3. Scale rows at mid-body 17; head small, nearly as narrow as neck
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Thamnophis brachystoma Short-headed Garter Snake |
3. Scale rows at mid-body 19; head larger and definitely enlarged from neck
4. Snout normal .........................................................................................5
4. Snout upturned and keeled above ..... Heterodon platyrhinos Eastern Hognose Snake
5. Loreal scale present (fig. 19) ................................................................. 7
5. Loreal scale absent (fig. 19); small dull-colored snakes ............................ 6
6. Scale rows 15; belly usually reddish; light spots on nape
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Storeria occipitomaculata Red-bellied Snake |
6. Scale rows 17; dark downward streak on side of head
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Storeria dekayi Northern Brown Snake |
7. Two nasal scales (snake head scales are illustrated in fig. 20) 22
7. One nasal scale, the nostril in its center; uniform light green in color above (bluish in preserved specimens) ..................................... Opheodrys aestivus Rough Green Snake
8. First 3 to 7 rows of scales smooth, the rest weakly keeled; ventral scales more than 200 (see fig. 20 for location of ventrals); color above, uniform black or with obscure blotches; juveniles conspicuously spotted ............................... Elaphe obsoleta Black Rat Snake
8. Scales strongly keeled except occasionally the first row; ventral scales less than 180 ....9
9. Scale rows at mid-body 17-19 .......................................................................... 10
9. More than 19 rows of scales at mid-body; dark crossbands on neck and forepart of body, but alternating dorsal and lateral blotches on rest of body; black or reddish half-moons on belly (color pattern of entire body extremely variable) ......... Natrix sipedon Northern Water Snake
10. Light lateral stripes on the first and second rows of scales; no dorsal blotches; belly yellow but boldly marked with 4 brown stripes, tend to be most prominent toward neck Natrix septemvittata Queen Snake
10. No light lateral stripes; dorsal blotches present; reddish belly with a row of round black spots down each side Natrix kirtlandi Kirtland's Water Snake
