Thamnophus atratus, Taricha granulosa.
The gartersnake held the newt motionless for over a minute, then took over three minutes to swallow it. The slow pace of the predation may be attributable to the toxicity of the newt.
Note: The caption on the photo is out of date, made before atratus was raised to species rank; should be Thamnophis atratus atratus.