Natricidae — Harmless Live-bearing Snakes
Species I've seen:
Natrix — Grass Snakes
Nerodia — North American Watersnakes
Nerodia clarkii
Saltmarsh Watersnake
Nerodia erythrogaster
Plain-bellied Watersnake
Nerodia fasciata
Southern Watersnake
Nerodia floridana
Florida Green Watersnake
Nerodia rhombifer
Diamond-backed Watersnake
Nerodia sipedon
Northern Watersnake
Nerodia taxispilota
Brown Watersnake
Regina — Crayfish Snakes
Regina grahamii
Graham’s Crawfish Snake
Storeria — North American Brownsnakes
Storeria dekayi
Dekay’s Brownsnake
Storeria victa
Florida Brownsnake
Thamnophis — North American Gartersnakes
Thamnophis atratus
Aquatic Gartersnake
Thamnophis couchii
Sierra Gartersnake
Thamnophis cyrtopsis
Black-necked Gartersnake
Thamnophis elegans
Terrestrial Gartersnake
Thamnophis gigas
Giant Gartersnake
Thamnophis hammondii
Two-striped Gartersnake
Thamnophis marcianus
Checkered Gartersnake
Thamnophis ordinoides
Northwestern Gartersnake
Thamnophis proximus
Western Ribbonsnake
Thamnophis radix
Plains Gartersnake
Thamnophis saurita
Eastern Ribbonsnake
Thamnophis sirtalis
Common Gartersnake
Thamnophis validus
Mexican West Coast Gartersnake
Xenochrophis — Keelbacks
Xenochrophis maculatus
Large-eyed Water Snake
Xenochrophis trianguligerus
Triangle Keelback