Flat-backed millipedes resemble centipedes. The bodies of the adults are flat, dark brown, with about twenty segments. They measure 0.6 to 1.0 inches (14 to 25 millimeters) in length and are about 0.16 inches (0.4 millimeters) wide. The plate segments covering the back are ridged along their lengths. The antennae and legs are longer than in most other millipedes.