The term area 24a of Carmichael refers to a portion of the anterior cingulate gyrus that is defined on the basis of internal structure in the macaque. Located largely in the cortical bank of the callosal sulcus as it curves around the genu of the corpus callosum, it is one of three components of area 24o in the macaque as defined in Carmichael-1994. The others are area 24b of Carmichael and area 24c of Carmichael. This definition differs from that of area a24 as defined by Glasser-2016 and Vogt-2012 in that it extends beyond anterior cingulate cortex into midcingulate cortex, areas designated parts of area 24' by those authors.