Members of the order Polydesmida are known as "flat-backed millipedes", because each body segment has wide lateral keels. These keels are produced by the posterior half (metazonite) of each body ring behind the collum. Polydemids have no eyes, and vary in length from 3 to 130 mm (0.12 to 5.1 in). Including the telson, adults have 19 or 20 rings, while juveniles may have from 7 to 19 rings.
Found one under a small (liftable) log inside the loop trail towards the NE corner. Dark Gray hue, very slow. I suppose it is a decomposer. Living in close corridors with other insects.
Black, glossy back with yellow coxas.
Millipede on Multnomah Falls trail.