Check this ID, but I believe it to be accurate.
Couldn't find an ID in the field guide I have. Coordinates taken with GPS at site.
"Striped Sharpnose Snake".
Originally classified under "Xenoxybelis argenteus", via "Peru", D.L. Pearson and L. Beletsky. ISBN 978-1-56656-545-5
Other classification: http://reptile-database.reptarium.cz/species?genus=Xenoxybelis&species=argenteus&search_param=%28%28genus%3D%27Oxybelis%27%29%29