The term area 24 of Brodmann-1905 (guenon) refers to a cytoarchitecturally defined area of the cerebral cortex in the guenon. It includes portions of the cingulate gyrus and the frontal lobe. The cortex is thin; it lacks the internal granular layer (IV) so that the densely distributed, plump pyramidal cells of sublayer 3b of the external pyramidal layer (III) merge with similar cells of the internal pyramidal layer (V); the multiform layer (VI) is very thin ( Brodmann-1905 ). Note that Brodmann later divided this area into two areas, area 24 of Brodmann-1909 (guenon) and area 25 of Brodmann (guenon) ( Brodmann-1909 ).