Cnemodesmus riparius, n. sp., the southernmost species of Cnemodesmus and the first generic record from Namibia, occurs in silt banks along the upper and middle Kuiseb River in the Namib Desert. A conspicuous part of the assemblage of flood-activated detritivores and carnivores. its aggregations are evident within days of brief surging flows ("floods") down the normally dry bed of the Kuiseb, and can remain for at least a month in sheltered bank habitats after such events. Keywords: Namibia, Gobabeb, Kuiseb River, Diplopoda, life history, ecology, classification, taxonomy.