The term archicortex refers to a composite substructure of the limbic lobe defined on the basis of dissection and internal structure. It is a C-shaped structure consisting of multiple gray matter substructures. In the human and, the macaque, the hippocampal complex (HPC), which lies horizontal in the lower limb of the limbic lobe, narrows posteriorly to become the fasciolar gyrus (FSG). The FSG curves around the splenium of the corpus callosum and narrows further to become the supracallosal gyrus (SCG). The SCG continues on the dorsal surface of the body of the corpus callosum and ventrally around the genu of the corpus callosum to become the paraterminal gyrus ( Stephan-1975 ). In the human, the archicortex constitutes 3.5% of the surface area of the cerebral cortex ( Zilles-1990 ). In the rodent, the substructures are the same except that the subiculum, a key component of the HPC in the primate is not assigned to the HPC equivalent, the hippocampal region. Instead it is considered part of the retrohippocampal region. Also, the FSG, SCG and PTG equivalents, i.e., fasciola cinerea and induseum griseum, are not topologically separate structures in the rodent but are embedded successively in the posterior parahippocampal cortex, retrosplenial area, anterior cingulate area, and cerebral cortex abutting the septal nuclei ( Swanson-2004 ). Updated 23 May, 2024.