Atractus major Big Ground Snake
Some other names for this species:
Brown Ground Snake
Madre Selva Biological Station, Loreto, PeruJanuary 16, 2014
Big Ground Snake (Atractus major) Big Ground Snake (Atractus major)
The first photo shows this small leaf-litter snake as seen on the trail at night. The second photo is the same individual on the forest floor the next day, where it was released.

Here is a complete list of the herps I saw in the wild on my 2014 MT Amazon Expeditions trip.

Online references: