Ammodesmidae are represented in western Africa by two species of a single genus, Ammodesmus Cook, 1896 (= Cenchrodesmus Cook, 1896, syn. n.). The type-species A. granum Cook, 1896 (= Cenchrodesmus volutus Cook, 1896, syn. n.) is redescribed, based on neotype selection, as well as on additional samples, often containing numerous specimens, from Liberia, Guinea and the Ivory Coast. A new species is described from Mount Nimba, Guinea: A. nimba sp. n.