The term area 24b of Carmichael refers to a portion of the anterior cingulate gyrus that is defined on the basis of internal structure in the macaque. It is one of three components of area 24 of Carmichael in the medial prefrontal cortex (macaque). The other components are area 24a of Carmichael and area 24c of Carmichael. Features that distinguish area 24b of Carmichael from one or the other adjacent area are: 1) vertical striations revealed by Nissl stain in the external pyramidal layer (III) and internal pyramidal layer (V); and 2) few neurons stained for neurofilament protein by SMI-32 ( Carmichael-1994 ). This description is based on the definition of area 24b as a component of medial prefrontal cortex in the macaque. It differs somewhat from that of area 24b defined as a component of cingulate cortex ( Vogt-2012 ).