These "third eyelids" help protect the eyes and hold in moisture. In addition, the markings on the membranes may help camouflage the eyes to make them less obvious to predators when these nocturnal frogs are resting during the day (Peruvian Amazon).
These snakes are arboreal and nocturnal. They are rear-fanged with a mild venom but not dangerous to humans. This one was around thirty inches long and no thicker than a pencil. In cross-section its body is almost triangular - I wonder if the body shape helps the snake maintain rigidity when it needs to lean well away from a branch when stalking a frog or lizard (Peruvian Amazon).
