Rhexenor (Rafinesque 1820)[1][2] Narceus is a genus of large cylindrical millipedes of the family Spirobolidae native to eastern North America.

The species of Narceus include some of the largest and most recognizable millipedes in eastern North America.

Narceus individuals range from 4 to 12 cm (1.6 to 4.7 in) long, with 45 to 59 segments as adults.

Their body color is various shades of brown with reddish to yellow stripes on each segment.

[3] The species N. americanus and N. annularis are widely distributed in North America, and may represent an intergradation of forms rather than two distinct species, a group known as the "N. americanus/annularis complex".