The term allocortex refers to one of two types of cerebral cortex defined on the basis of cytoarchitecture and fetal development. The other is neocortex. Allocortex does not pass through a prenatal phase of six-layered structure and has three or four layers in the mature brain ( Schiebler-1999 ). Allocortex has three subtypes: paleocortex, archicortex and periallocortex. This definition differs from that in some older sources, which excluded the main olfactory bulb and the accessory main olfactory bulb ( Carpenter-1983 ).